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Unparticle physics in diphoton production at the CERN LHC: We have considered the di-photon production with unparticle at LHC. The
contributions of spin-0 and spin-2 unparticle to the di-photon production are
studied in the invariant mass and other kinematical distributions, along with
their dependencies on the model dependent parameters. The signal corresponding
to the unparticle is significant for moderate coupling constant values. | hep-ph |
CutLHCO: A Consumer-Level Tool for Implementing Generic Collider Data
Selection Cuts in the Search for New Physics: A new computer program named CutLHCO is introduced, whose function is the
implementation of generic data selection cuts on collider event specification
files in the standardized .lhco format. This software is intended to fill an
open market niche for a lightweight yet flexible "consumer-level" alternative
to the ROOT data analysis framework. The primary envisioned application is as a
filter on output produced by the PGS4 and DELPHES detector simulations, which
are themselves lightweight alternatives to the GEANT4 based solutions favored
by the large LHC experiments. All process control instructions are provided via
a compact and powerful card file input syntax that efficiently facilitates the
reasonable approximation of most event selection strategies and specialized
discovery statistics commonly employed by the CMS and ATLAS collaborations. The
structure, function, invocation and usage of the most recent CutLHCO 2.0
program version are documented thoroughly, including a detailed deconstruction
of several example card file specifications. The associated software is
simultaneously being made available for free public download. | hep-ph |
Extended Dark Matter EFT: Conventional approaches to describe dark matter phenomenology at collider and
(in)direct detection experiments in the form of dark matter effective field
theory or simplified models suffer in general from drawbacks regarding validity
at high energies and/or generality, limiting their applicability. In order to
avoid these shortcomings, we propose a hybrid framework in the form of an
effective theory, including, however, both the dark matter states and a
mediator connecting the former to the Standard Model fields. Since the
mediation can be realized through rather light new dynamical fields allowing
for non-negligible collider signals in missing energy searches, the framework
remains valid for the phenomenologically interesting parameter region, while
retaining correlations dictated by gauge symmetry. Moreover, a richer
new-physics sector can be consistently included via higher-dimensional
operators. Interestingly, for fermionic and scalar dark matter with a
(pseudo-)scalar mediator, the leading effects originate from dimension-five
operators, allowing to capture them with a rather small set of new couplings.
We finally examine the correlations between constraints from reproducing the
correct relic density, direct-detection experiments, and mono-jet and
Higgs+missing energy signatures at the LHC. | hep-ph |
CP Violation in the Neutral Higgs Sector of a Non-minimal Supersymmetric
Standard Model with Multiple Higgs Singlets: The possibility of CP violation is studied in the Higgs sector of a
supersymmetric standard model with multiple Higgs singlets. The tree-level
Lagrangian in this model is assumed to conserve the CP symmetry. We find that
CP violation is viable in this model at the one-loop level, in an explicit way,
if the radiative corrections from the third generation of quarks and squarks
are taken into account. In the presence of explicit CP violation, at the
one-loop level, the upper bound on the mass of the lightest neutral Higgs boson
and the productions of the neutral Higgs bosons via the Higgsstrahlung process
in high-energy $e^+e^-$ collisions are calculated. We find that the upper bound
on the mass of the lightest neutral Higgs boson increases as the number of
Higgs singlets increases in a regulated manner. The production cross sections
of the neutral Higgs bosons also show a reasonable increasing behavior with
respect to the number of Higgs singlets. | hep-ph |
Spontaneous CP Violation in the Next-to-Minimal Supersymmetric Standard
Model Revisited: We re-examine spontaneous CP violation at the tree level in the context of
the next-to-minimal supersymmetric standard model (NMSSM) with two Higgs
doublets and a gauge singlet field. We analyse the most general Higgs potential
without a discrete Z_3 symmetry, and derive an upper bound on the mass of the
lightest neutral Higgs boson consistent with present experimental data. We
investigate, in particular, its dependence on the admixture and CP-violating
phase of the gauge singlet field, as well as on tan(beta). To assess the
viability of the spontaneous CP violation scenario, we estimate epsilon_K by
applying the mass insertion approximation. We find that a non-trivial flavour
structure in the soft-breaking A terms is required to account for the observed
CP violation in the neutral kaon sector. Furthermore, combining the
minimisation conditions for spontaneous CP violation with the constraints
coming from K0-K0bar mixing, we find that the upper bound on the lightest
Higgs-boson mass becomes stronger. We also point out that the electric dipole
moments of electron and neutron are a serious challenge for SUSY models with
spontaneous CP violation. | hep-ph |
A role of parton charges and masses in the exclusive photon-photon
production of meson pairs: The exclusive photon-photon production of the $K$-meson pairs has been
analyzed within the partonic model of QCD for the kinematical conditions of
BELLE experiment. The cross section dependences on partonic masses, charges,
and a shape of $K$-meson wave function have been studied for the process under
discussion. | hep-ph |
$ν$ Electroweak Baryogenesis: We investigate if the CP violation necessary for successful electroweak
baryogenesis may be sourced by the neutrino Yukawa couplings. In particular, we
consider an electroweak scale Seesaw realisation with sizeable Yukawas where
the new neutrino singlets form (pseudo)-Dirac pairs. We find that flavour
effects critically impact the final asymmetry obtained and that, taking them
into account, the observed value may be obtained in some regions of the
parameter space. This source of CP violation naturally avoids the strong
constraints from electric dipole moments and links the origin of the baryon
asymmetry of the Universe with the mechanism underlying neutrino masses.
Interestingly, the mixing of the active and heavy neutrinos needs to be
sizeable and could be probed at the LHC or future collider experiments. | hep-ph |
When does the Schwinger Preheating Occur?: When the inflaton couples to photons and amplifies electric fields, charged
particles produced via the Schwinger effect can dominate the universe after
inflation, which is dubbed as the Schwinger preheating. Using the hydrodynamic
approach for the Boltzmann equation, we numerically study two cases, the
Starobinsky inflation model with the kinetic coupling and the anisotropic
inflation model. The Schwinger preheating is not observed in the latter model
but occurs for a sufficiently large inflaton-photon coupling in the first
model. We analytically address its condition and derive a general attractor
solution of the electric fields. The occurrence of the Schwinger preheating in
the first model is determined by whether the electric fields enter the
attractor solution during inflation or not. | hep-ph |
Comparison of improved TMD and CGC frameworks in forward quark dijet
production: For studying small-$x$ gluon saturation in forward dijet production in
high-energy dilute-dense collisions, the improved TMD (ITMD) factorization
formula was recently proposed. In the Color Glass Condensate (CGC) framework,
it represents the leading term of an expansion in inverse powers of the hard
scale. It contains the leading-twist TMD factorization formula relevant for
small gluon's transverse momentum $k_t$, but also incorporates an all-order
resummation of kinematical twists, resulting in a proper matching to
high-energy factorization at large $k_t$. In this paper, we evaluate the
accuracy of the ITMD formula quantitatively, for the case of quark dijet
production in high-energy proton-proton($p+p$) and proton-nucleus ($p+A$)
collisions at LHC energies. We do so by comparing the quark-antiquark azimuthal
angle $\Delta\phi$ distribution to that obtained with the CGC formula. For a
dijet with each quark momentum $p_t$ much larger than the target saturation
scale, $Q_s$, the ITMD formula is a good approximation to the CGC formula in a
wide range of azimuthal angle. It becomes less accurate as the jet $p_t$'s are
lowered, as expected, due to the presence of genuine higher-twists
contributions in the CGC framework, which represent multi-body scattering
effects absent in the ITMD formula. We find that, as the hard jet momenta are
lowered, the accuracy of ITMD start by deteriorating at small angles, in the
high-energy-factorization regime, while in the TMD regime near
$\Delta\phi=\pi$, very low values of $p_t$ are needed to see differences
between the CGC and the ITMD formula. In addition, the genuine twists
corrections to ITMD become visible for higher values of $p_t$ in $p+A$
collisions, compared to $p+p$ collisions, signaling that they are enhanced by
the target saturation scale. | hep-ph |
Transverse momentum spectra of D and B mesons in hadron collisions at
high energies: Transverse momentum spectra of charmed and beauty mesons produced in
proton-proton and proton-antiproton collisions at high energies are analyzed
within the modified quark-gluon string model (QGSM) including the internal
motion of quarks in colliding hadrons. It is shown that this approach can
describe rather satisfactorily the experimental data at not large values of the
transverse momentum where the NLO QCD calculation has a big uncertainty. We
also show that using both the QGSM and the NLO QCD one can describe these data
in a wide region of transverse momenta and give some predictions for the future
LHC experiments. | hep-ph |
AROMA 2.2 - A Monte Carlo Generator for Heavy Flavour Events in $ep$
Collisions: A program to simulate the production of heavy quarks through the boson-gluon
fusion process in $e^{\pm}p$ collisions is presented. The full electro\-weak
structure of the electron--gluon interaction is taken into account as well as
the masses of the produced heavy quarks. Higher order QCD radiation is treated
using initial and final state parton showers, and hadronization is performed
using the Lund string model. Physics and programming aspects are described in
this manual. | hep-ph |
The Sigma Meson and Chiral Transition in Hot and Dense Matter: It is pointed out that the hadron spectroscopy should be a study of the
structure of the QCD vacuum, low-energy elementary excitations on top of which
are hadrons. Concentrating on the dynamical breaking of the chiral symmetry in
the QCD vacuum, we emphasize the importance to clarify what is going on with
mesons in the $I=J=0$-channel, i.e., the sigma meson channel, because it is
connected to the quantum fluctuations of the chiral order parameter. After
summarizing the significance of the sigma meson in QCD and low-energy hadron
phenomenology, we give a review on some theoretical and experimental effort to
try to reveal the possible restoration of chiral symmetry in hot and dense
nuclear matter including heavy nuclei. | hep-ph |
Searching for Scalar Ultralight Dark Matter with Optical Fibers: We consider optical fibers as detectors for scalar ultralight dark matter
(UDM) and propose using a fiber-based interferometer to search for scalar UDM
with particle mass in the range $10^{-17} - 10^{-13}$ eV/$c^2$ $\left(10^{-3}-
10 \text{ Hz}\right)$. Composed of a solid core and a hollow core fiber, the
proposed detector would be sensitive to relative oscillations in the fibers'
refractive indices due to scalar UDM-induced modulations in the fine-structure
constant $\alpha$. We predict that, implementing detector arrays or cryogenic
cooling, the proposed optical fiber-based scalar UDM search has the potential
to reach new regions of the parameter space. Such a search would be
particularly well-suited to probe for a Solar halo of dark matter with a
sensitivity exceeding that of previous DM searches over the particle mass range
$7\times 10^{-17} - 2\times 10^{-14}$ eV/$c^2$. | hep-ph |
Accurate decay-constant ratios $f_{B^*}/f_B$ and $f_{B_s^*}/f_{B_s}$
from Borel QCD sum rules: We present our analysis of the decay constants of the beauty vector mesons
$B^*$ and $B^*_s$ within the framework of dispersive sum rules for the
two-point correlator of vector currents in QCD. While the decay constants of
the vector mesons $f_{B^*}$ and $f_{B_s^*}$ $-$ similar to the decay constants
of the pseudoscalar mesons $f_B$ and $f_{B_s}$ $-$ individually have large
uncertainties induced by theory parameters not known with a satisfactory
precision, these uncertainties almost entirely cancel out in the ratios of
vector over pseudoscalar decay constants. These ratios may be thus predicted
with very high accuracy due to the good control over the systematic
uncertainties of the decay constants gained upon application of our
hadron-parameter extraction algorithm. Our final results read
$f_{B^*}/f_B=0.944\pm0.011_{\rm OPE}\pm0.018_{\rm syst}$ and
$f_{B_s^*}/f_{B_s}=0.947\pm0.023_{\rm OPE}\pm0.020_{\rm syst}$. Thus, both
$f_{B^*}/f_B$ and $f_{B_s^*}/f_{B_s}$ are less than unity at 2.5$\sigma$ and
2$\sigma$ level, respectively. | hep-ph |
A Parametrization for $K^+\to π^+π^- e^+ν$: We discuss various models and Chiral Perturbation Theory results for the
$K_{l4}$ form factors $F$ and $G$. We check in how much a simple
parametrization with a few parameters can be used to extract information from
experiment. | hep-ph |
Electromagnetic Properties of the SU(3) Octet Baryons in the
semibosonized Nambu--Jona-Lasinio Model: The electromagnetic properties of the SU(3) octet baryons are investigated in
the semibosonized SU(3) Nambu--Jona-Lasinio model.The rotational $1/N_c$ and
strange quark mass corrections in linear order are taken into account. It turns
out that the model is in good agreement with the experimental data. | hep-ph |
Higgsino Dark Matter or Not: Role of Disappearing Track Searches at the
LHC and Future Colliders: Higgsino in supersymmetric standard models is known to be a promising
candidate for dark matter in the Universe. Its phenomenological property is
strongly affected by the gaugino fraction in the Higgsino-like state. If this
is sizable, in other words, if gaugino masses are less than ${\cal O}(10)$ TeV,
we may probe the Higgsino dark matter in future non-accelerator experiments
such as dark matter direct searches and measurements of electric dipole
moments. On the other hand, if gauginos are much heavier, then it is hard to
search for Higgsino in these experiments. In this case, due to a lack of
gaugino components, the mass difference between the neutral and charged
Higgsinos is uniquely determined by electroweak interactions to be around $350$
MeV, which makes the heavier charged state rather long-lived, with a decay
length of about $1$ cm. In this letter, we argue that a charged particle with a
flight length of ${\cal O}(1)$ cm can be probed in disappearing-track searches
if we require only two hits in the pixel detector. Even in this case, we can
reduce background events with the help of the displaced-vertex reconstruction
technique. We study the prospects of this search strategy at the LHC and future
colliders for the Higgsino dark matter scenario. It is found that an almost
pure Higgsino is indeed within the reach of the future $33$ TeV collider
experiments. We then discuss that the interplay among collider and
non-accelerator experiments plays a crucial role in testing the Higgsino dark
matter scenarios. Our strategy for disappearing-track searches can also enlarge
the discovery potential of pure wino dark matter as well as other
electroweak-charged dark matter candidates. | hep-ph |
Is the tri-bimaximal mixing accidental?: The Tri-bimaximal (TBM) mixing is not accidental if structures of the
corresponding leptonic mass matrices follow immediately from certain (residual
or broken) flavor symmetry. We develop a simple formalism which allows one to
analyze effects of deviations of the lepton mixing from TBM on structure of the
neutrino mass matrix and on underlying flavor symmetry. We show that possible
deviations from the TBM mixing can lead to strong modifications of the mass
matrix and strong violation of the TBM mass relations. As a result, the mass
matrix may have an "anarchical" structure with random values of elements or it
may have some symmetry which differs from the TBM symmetry. Interesting
examples include matrices with texture zeros, matrices with certain "flavor
alignment" as well as hierarchical matrices with a two-component structure,
where the dominant and sub-dominant contributions have different symmetries.
This opens up new approaches to understand the lepton mixing. | hep-ph |
Pion mass dependence of the electromagnetic form factors of singly heavy
baryons: We study the electromagnetic form factors of the lowest-lying singly heavy
baryons with spin 1/2 within the framework of the chiral quark-soliton model,
focusing on the comparison with recent lattice data. To compare the present
results quantitatively with the lattice data, it is essential to treat the pion
mass as a variable parameter, i.e., to employ the unphysical values of the pion
mass, which are used in lattice calculations. While the results with the
physical value of the pion mass fall off faster than those from the lattice
calculations as the momentum transfer increases, the extrapolated results with
larger pion masses get closer to the lattice data. | hep-ph |
Stability constraint for spin equation of state: A generalized Frenkel condition is proposed for use in spin hydrodynamics to
relate the spin density and spin polarization (or spin chemical potential)
tensors. It allows for independent treatment of electric- and magnetic-like
components of the spin density tensor, which helps to fulfill the stability
conditions recently derived in the literature. The generalized Frenkel
condition extrapolates between the original Frenkel condition, where only the
magnetic-like part of the spin tensor is present, and the case where the spin
density tensor is directly proportional to the spin polarization tensor. We
also demonstrate that our approach is supported by the result of a microscopic
calculation. | hep-ph |
Searching for supersymmetry in rare B decays: We quantify the ability of B-Factories to observe supersymmetric
contributions to the rare decays B -> X_s \gamma and B -> X_s l+ l-. A global
fit to the Wilson coefficients which contribute to these decays is performed
from Monte Carlo generated data on B(B -> X_s \gamma) and the kinematic
distributions associated with the final state lepton pair in B -> X_s l+ l-.
This fit is then compared to supersymmetric predictions. Evaluation of the
Wilson coefficients is carried out with several different patterns of the
superpartner spectrum. We find that the B-Factories will be able to probe
regions of the SUSY parameter space not accessible to LEPII, the Tevatron, and
perhaps the LHC. We also employ the recent NLO calculation of the matrix
elements for B -> X_s \gamma and find the bound mH+ > 300 GeV in
two-Higgs-doublet models using present data. | hep-ph |
Accessing quark helicity in $e^+e^-$ and SIDIS via dihadron correlations: The correlation between the longitudinal polarization of a fragmenting quark
and the transverse momenta of the produced hadrons was predicted over two
decades ago. Nevertheless, experimental searches in the electron-positron
annihilation process, both through the so-called jet handedness measurements by
the {\tt SLD} Collaboration and more recently via the measurements of the
azimuthal asymmetry containing the helicity-dependent dihadron fragmentation
function (DiFF) by the $\textrm{BELLE}$ Collaboration, did not yield a signal.
We will first discuss our recent explanation of the zero result at
$\textrm{BELLE}$, and the two new methods for accessing the helicity-dependent
DiFFs both in the electron-positron annihilation experiments, and in the
semi-inclusive deep inelastic scattering (SIDIS) experiments with a
longitudinally polarized target. We will also for the first time describe yet
another, new method for accessing the helicity-dependent DiFFs in SIDIS using
polarized beam asymmetry. Finally, we will present a new Monte Carlo
calculation of the specific Fourier moments of the helicity-dependent DiFF
entering in to the new asymmetries, performed within the extended quark-jet
model, and compare the results to those for the interference DiFF. | hep-ph |
Application of the QCD light cone sum rule to tetraquarks: the strong
vertices $X_bX_bρ$ and $X_cX_cρ$: The full version of QCD light-cone sum rule method is applied to tetraquarks
containing a single heavy $b$ or $c$ quark. To this end, investigations of the
strong vertices $X_{b}X_{b}\rho$ and $X_{c}X_{c}\rho$ are performed, where
$X_b=[su][\bar b\bar d]$ and $X_c=[su][\bar c\bar d]$ are the exotic states
built of four quarks of different flavors. The strong coupling constants
$G_{X_{b}X_{b}\rho}$ and $G_{X_{c}X_{c}\rho}$ corresponding to these vertices
are found using the $\rho$-meson leading and higher-twist distribution
amplitudes. In the calculations $X_{b}$ and $X_{c}$ are treated as scalar bound
states of a diquark and antidiquark. | hep-ph |
Confinement and chiral symmetry crossovers: We study the QCD phase diagram, in particular we study the critical points of
the two main QCD phase transitions, confinement and chiral symmetry breaking.
Confinement drives chiral symmetry breaking, and, due to the finite quark mass,
at small density both transitions are a crossover, while they are a first or
second order phase transition in large density. We study the QCD phase diagram
with a quark potential model including both confinement and chiral symmetry.
This formalism, in the Coulomb gauge hamiltonian formalism of QCD, is presently
the only one able to microscopically include both a quark-antiquark confining
potential and a vacuum condensate of quark-antiquark pairs. This model is able
to address all the excited hadrons, and chiral symmetry breaking, at the same
token. Our order parameters are the Polyakov loop and the quark mass gap. The
confining potential is extracted from the Lattice QCD data of the Bielefeld
group. We address how the quark masses affect the critical point location in
the phase diagram. | hep-ph |
Gravitational and higher-order form factors of the pion in chiral quark
models: The gravitational form factor of the pion is evaluated in two chiral quark
models and confronted to the recent full-QCD lattice data. We find good
agreement for the case of the Spectral Quark Model, which builds in the
vector-meson dominance for the charge form factor. We derive a simple relation
between the gravitational and electromagnetic form factors, holding in the
considered quark models in the chiral limit. The relation implies that the
gravitational mean squared radius is half the electromagnetic one. We also
analyze higher-order quark generalized form factors of the pion, related to
higher moments in the symmetric Bjorken X-variable of the generalized parton
distribution functions, and discuss their perturbative QCD evolution, needed to
relate the quark-model predictions to the lattice data. The values of the
higher-order quark form factors at t=0, computed on the lattice, also agree
with our quark model results within the statistical and method uncertainties. | hep-ph |
Enhancement of dilepton production rate and electric conductivity around
QCD critical point: We investigate whether the soft mode that becomes massless at the QCD
critical point (CP) causes an enhancement of the dilepton production rate (DPR)
and the electric conductivity around the CP through the modification of the
photon self-energy. The modification is described by the so-called
Aslamazov-Larkin, Maki-Thompson and density of states terms, which have been
taken into account in our previous study on the DPR near the
color-superconducting phase transition, with a replacement of the diquark modes
with the soft mode of the QCD CP. We show that the coupling of photons with the
soft modes brings about an enhancement of the DPR in the low invariant-mass
region and the conductivity near the CP, which would be observable in the
relativistic heavy-ion collisions. | hep-ph |
Charged lepton flavor violation searches in the charmonium system: An invited research highlight article on Charged lepton flavor violation
searches in the charmonium system. | hep-ph |
Impact of theoretical uncertainties on model parameter reconstruction
from GW signals sourced by cosmological phase transitions: Different computational techniques for cosmological phase transition
parameters can impact the Gravitational Wave (GW) spectra predicted in a given
particle physics model. To scrutinize the importance of this effect, we perform
large-scale parameter scans of the dynamical real-singlet extended Standard
Model using three perturbative approximations for the effective potential: the
$\overline{\rm MS}$ and on-shell schemes at leading order, and
three-dimensional thermal effective theory (3D EFT) at next-to-leading order.
While predictions of GW amplitudes are typically unreliable in the absence of
higher-order corrections, we show that the reconstructed model parameter spaces
are robust up to a few percent in uncertainty. While 3D EFT is accurate from
one loop order, theoretical uncertainties of reconstructed model parameters,
using four-dimensional standard techniques, remain dominant over the
experimental ones even for signals merely strong enough to claim a detection by
LISA. | hep-ph |
NLO QCD corrections to pp -> ttbb+X via quark anti-quark annihilation: The process pp -> top anti-top bottom anti-bottom + X represents a very
important background reaction to searches at the LHC, in particular to top
anti-top H production where the Higgs boson decays into a bottom anti-bottom
pair. A successful analysis of top anti-top H at the LHC requires the knowledge
of direct top anti-top bottom anti-bottom production at NLO in QCD. We take the
first step in this direction upon calculating the NLO QCD corrections to the
subprocess initiated by quark anti-quark annihilation. | hep-ph |
Hadronization from color interactions: A quark coalescence model is presented based on semi-relativistic molecular
dynamics with color interactions among quarks taken into account and applied to
$pp$ collisions to study the effects of this model. A phenomenological
potential with two tunable parameters is introduced to describe the color
interactions between quarks and antiquarks. The interactions drive the process
of hadronization and finally make them form different color neutral clusters,
which can be identified as hadrons based on some criteria. A Monte Carlo
generator, PYTHIA is used to generate the quarks in the initial state of
hadronization, and different values of tunable parameters are used to study
their effects on the final state distributions and correlations. Baryon to
meson ratios, transverse momentum spectra, pseudorapidity distributions and
forward-backward multiplicity correlations of hadrons produced in the
hadronization process from this model with different parameters are compared
with those from PYTHIA. | hep-ph |
The midpoint between dipole and parton showers: We present a new parton-shower algorithm. Borrowing from the basic ideas of
dipole cascades, the evolution variable is judiciously chosen as the transverse
momentum in the soft limit. This leads to a very simple analytic structure of
the evolution. A weighting algorithm is implemented, that allows to
consistently treat potentially negative values of the splitting functions and
the parton distributions. We provide two independent, publicly available
implementations for the two event generators Pythia and Sherpa. | hep-ph |
Phenomenological Approach to Multiple Particle Production: We formulate empirically the rapidity density distribution of produced
particles in multiple particle production. The assumed mechanism is that the
produced particles are emitted isotropically from several emitting centers,
located on the rapidity axis. The formula includes five adjustable parameters,
which are to be determined by the experimental data of (pseudo-)rapidity
density distributions and transverse momentum distributions at various
energies. It is a distinguished difference of the present rapidity density
distribution from those of other models that the particle production is
suppressed strongly in the forward region. We discuss multiplicity and
inelasticity at high energies, the pseudo-rapidity density distribution at LHC
energy and some speculations, based on the present formulation. | hep-ph |
Electroweak couplings and LHC constraints on alternative $Z^{\prime}$
models in $E_6$: We report the most general expression for the chiral charges of a $Z'$ gauge
boson coming from an $E_6$ unification model, as a function of the electroweak
parameters and the charges of the $U(1)$ factors in the chain of subgroups.
These charges are valid for an arbitrary Higgs sector and only depend on the
branching rules of the $E_6$ fundamental representation and the corresponding
rules for the fermionic representations of their subgroups. By assuming $E_6$
unification, the renormalization group equations~(RGE) allow us to calculate
the electroweak parameters at low energies for most of the chains of subgroups
in $E_6$. From RGE and unitary conditions, we show that at low energies there
must be a mixing between the gauge boson of the standard model hypercharge and
the $Z'$. From this, it is possible to delimit the preferred region in the
parameter space for a breaking pattern in $E_6$. In general, without
unification, it is not viable to determine this region; however, for some
models and under certain assumptions, it is possible to limit the corresponding
parameter space. By using the most recent upper limits on the cross-section of
extra gauge vector bosons $Z'$ decaying into dileptons from the ATLAS data at
13~TeV with accumulated luminosities of 36.1~fb$^{-1}$ and 13.3~fb$^{-1}$, we
report the 95$\%$ C.L. lower limits on the $Z'$ mass for the typical $E_6$
benchmark models. We also show the contours in the 95\% C.L. of the $Z'$ mass
bounds for the entire parameter space of $E_6$. | hep-ph |
Is Radiative Electroweak Symmetry Breaking Consistent with a 125 GeV
Higgs Mass?: The mechanism of radiative electroweak symmetry breaking occurs through loop
corrections, and unlike conventional symmetry breaking where the Higgs mass is
a parameter, the radiatively-generated Higgs mass is dynamically predicted.
Pade approximations and an averaging method are developed to extend the Higgs
mass predictions in radiative electroweak symmetry breaking from five- to
nine-loop order in the scalar sector of the Standard Model, resulting in an
upper bound on the Higgs mass of 141 GeV. The mass predictions are
well-described by a geometric series behaviour, converging to an asymptotic
Higgs mass of 124 GeV consistent with the recent ATLAS/CMS observations.
Similarly, we find that the Higgs self-coupling converges to $\lambda=0.23$,
which is significantly larger than its conventional symmetry breaking
counterpart for a 124 GeV Higgs mass. In addition to this significant
enhancement of the Higgs self-coupling and $HH\rightarrow HH$ scattering, we
find that Higgs decays to gauge bosons are unaltered and the scattering
processes $W_{L}^{+}W_{L}^{+}\rightarrow HH$, $Z_{L}Z_{L}\rightarrow HH$ are
also enhanced, providing signals to distinguish conventional and radiative
electroweak symmetry breaking mechanisms. | hep-ph |
Possible Interpretations of $D_{sJ}^+(2632)$ If It Really Exists: We analyze various possible interpretations of the narrow state
$D_{sJ}^+(2632)$ observed by SELEX Collaboration recently, which lies above
threshold and has abnormal decay pattern. These interpretations include: (1)
several versions of tetraquarks; (2) conventional $c\bar s$ meson such as the
first radial excitation of $D_s(2112)$ with abnormally large SU(3) symmetry
breaking; (3) conventional $c\bar s$ meson with abnormally large $\eta_1$
coupling; (4) heavy hybrid meson. We discuss the physical implications of each
interpretation. For example, if the existence of $D_{sJ}^+(2632)$ is confirmed
as the first radial excitation of $D_s(2112)$ by other experiments, it will be
helpful to look for (1) its SU(3) flavor partners $D_{J}^{0,+}(2530)$; (2) its
B-meson analogues $B_{J}^{0,+}(5840), B_{sJ}^+(5940)$; (3) S-wave two pion
decay modes. | hep-ph |
Mixing at 1-loop in a SU(2)_L gauge theory of weak interactions: Flavor mixing is scrutinized at 1-loop in a SU(2)_L gauge theory of massive
fermions. The main issue is to cope with kinetic-like, momentum (p^2) dependent
effective interactions that arise at this order. They spoil the unitarity of
the connection between flavor and mass states, which potentially alters the
standard Cabibbo-Kobayashi-Maskawa (CKM) phenomenology by giving rise, in
particular, to extra flavor changing neutral currents (FCNC). We explore the
conservative requirement that these should be suppressed, which yields
relations between the CKM angles, the fermion and $W$ masses, and a
renormalization scale $\mu$. For two generations, two solutions arise: either
the mixing angle of the fermion pair the closer to degeneracy is close to
maximal while, inversely, the mass and flavor states of the other pair are
quasi-aligned, or mixing angles in both sectors are very small. For three
generations, all mixing angles of neutrinos are predicted to be large
(theta_{23}, close to maximal, is the largest) and the smallness of their mass
differences induces mass-flavor quasi-alignment for all charged leptons. The
hadronic sector differs in that the top quark is twice as heavy as the W. The
situation is, there, bleaker, as all angles come out too large, but,
nevertheless, encouraging, because theta_{12} decreases as the top mass
increases. Whether other super-heavy fermions could drag it down to realistic
values stays an open issue, together with the role of higher order corrections.
The same type of counterterms that turned off the 4th order static corrections
to the quark electric dipole moment are, here too, needed, in particular to
stabilize quantum corrections to mixing angles. | hep-ph |
NLO Monte-Carlo approach in 1 or 2 jets Photoproduction: We present a method for calculating the photoproduction of jets at HERA based
on Next to Leading Logarithm QCD calculations. It is implemented in a
Monte-Carlo generator which allows us to easily compute any infra-red safe
cross sections for 1 or 2 jet observables using various jet reconstruction
algorithms. We focus on the possibility of extracting the gluon contents of the
photon and of the proton from present and future H1 and ZEUS data. | hep-ph |
SU(3) Mixing for Excited Mesons: The SU(3)-flavor symmetry breaking and the quark-antiquark annihilation
mechanism are taken into account for describing the singlet-octet mixing for
several nonets assigned by Particle Data Group(PDG). This task is approached
with the mass matrix formalism. | hep-ph |
Impact of nonextensivity on the transport coefficients of a magnetized
hot and dense QCD matter: We have studied the impact of the nonextensivity on the transport
coefficients related to charge and heat in thermal QCD. For this purpose, the
electrical ($\sigma_{\rm el}$), Hall ($\sigma_{\rm H}$), thermal ($\kappa$) and
Hall-type thermal ($\kappa_{\rm H}$) conductivities are determined using the
kinetic theory approach in association with the nonextensive Tsallis
statistical mechanism. The effect of nonextensivity is encoded in the
nonextensive Tsallis distribution function, where the deviation of the
parameter $q$ from 1 signifies the degree of nonextensivity in the concerned
system. The thermal and electrical conductivities are found to increase with
the introduction of nonextensivity, which means that the deviation of the
medium from thermal equilibrium enhances both charge and heat transports. With
the magnetic field, the deviations of $\sigma_{\rm el}$, $\sigma_{\rm H}$,
$\kappa$ and $\kappa_{\rm H}$ from their respective equilibrated values
increase, whereas these deviations decrease with the chemical potential. We
have also studied how the extent of the nonextensivity modulates the longevity
of magnetic field. Present work is further extended to the study of some
observables associated with the aforesaid transport phenomena, such as the
Knudsen number and the elliptic flow within the nonextensive Tsallis framework. | hep-ph |
(beta beta)_{0 nu}-decay: a possible test of the nuclear matrix element
calculations: The existing calculations of the nuclear matrix elements of the neutrinoless
double beta-decay differ by about a factor three. This uncertainty prevents
quantative interpretation of the results of experiments searching for this
process. We suggest here that the observation of the neutrinoless double
beta-decay of several nuclei in future experiments of could allow to test
different calculations of the nuclear matrix elements through the direct
comparison of them with the experimental data. | hep-ph |
Status of the NLO Corrections to the Photon Impact Factor: We present the status of the programme of calculating the next-to-leading
order corrections to the virtual photon impact factor. In particular, we
discuss new results for the transversely polarized photon. We briefly outline
the definition of infrared finite terms and the subtraction of the leading
logarithmic parts. | hep-ph |
Decays of the neutral Higgs bosons into SM fermions and gauge bosons in
the $\mathcal{CP}$-violating NMSSM: The Next-to-Minimal Supersymmetric Standard Model (NMSSM) offers a rich
framework embedding physics beyond the Standard Model as well as consistent
interpretations of the results about the Higgs signal detected at the LHC. We
investigate the decays of neutral Higgs states into Standard Model (SM)
fermions and gauge bosons. We perform full one-loop calculations of the decay
widths and include leading higher-order QCD corrections. We first discuss the
technical aspects of our approach, before confronting our predictions to those
of existing public tools, performing a numerical analysis and discussing the
remaining theoretical uncertainties. In particular, we find that the decay
widths of doublet-dominated heavy Higgs bosons into electroweak gauge bosons
are dominated by the radiative corrections, so that the tree-level
approximations that are often employed in phenomenological analyses fail.
Finally, we focus on the phenomenological properties of a mostly singlet-like
state with a mass below the one at $125\,$GeV, a scenario that appears commonly
within the NMSSM. In fact, the possible existence of a singlet-dominated state
in the mass range around or just below $100\,$GeV would have interesting
phenomenological implications. Such a scenario could provide an interpretation
for both the $2.3\sigma$ local excess observed at LEP in the $e^+e^-\to Z(H\to
b\bar{b})$ searches at $\sim 98\,$GeV and for the local excess in the diphoton
searches recently reported by CMS in this mass range, while at the same time it
would reduce the "Little Hierarchy" problem. | hep-ph |
The renormalization group analysis of the large lepton flavor mixing and
the neutrino mass: The Superkamiokande experiment suggests the large flavor mixing between nu_mu
and nu_tau. We show that the mixing angle receives significant corrections from
the renormalization group equation (RGE) when both the second and the third
generation neutrino masses are larger than O(0.1eV). This means that the mixing
angle must be small at the decoupling scale of right-handed neutrinos in the
model containing a sterile neutrino nu_s with the mass spectrum of m_nu_s =
m_nu_e << m_nu_mu = m_nu_tau. | hep-ph |
Perturbative QCD description of jet data from LHC Run-I and Tevatron
Run-II: We present a systematic comparison of jet predictions at the LHC and the
Tevatron, with accuracy up to next-to-next-to-leading order (NNLO). The exact
computation at NNLO is completed for the gluons-only channel, so we compare the
exact predictions for this channel with an approximate prediction based on
threshold resummation, in order to determine the regions where this
approximation is reliable at NNLO. The kinematic regions used in this study are
identical to the experimental setup used by recently published jet data from
the ATLAS and CMS experiments at the LHC, and CDF and D0 experiments at the
Tevatron. We study the effect of choosing different renormalisation and
factorisation scales for the NNLO exact prediction and as an exercise assess
their impact on a PDF fit including these corrections. Finally we provide
numerical values of the NNLO k-factors relevant for the LHC and Tevatron
experiments. | hep-ph |
Decoupling Theoretical Uncertainties from Measurements of the Higgs
Boson: We develop a technique to present Higgs coupling measurements, which decouple
the poorly defined theoretical uncertainties associated to inclusive and
exclusive cross section predictions. The technique simplifies the combination
of multiple measurements and can be used in a more general setting. We
illustrate the approach with toy LHC Higgs coupling measurements and a
collection of new physics models. | hep-ph |
Precision test of a Fermion mass texture: Texture zeros in the quark Yukawa matrices generally lead to precise and
simple expressions for CKM matrix elements in terms of ratios of quark masses.
Using the new data on $b-$decays we test a particularly promising texture zero
solution and show that it is at best approximate. We analyse the approximate
texture zero structure and show it is consistent with experiment. We
investigate the implications for the CKM unitarity triangle, measurements at
$BaBar$ and $BELLE$ as well as for the theories which invoke family symmetries. | hep-ph |
Uncertainties of predictions from parton distribution functions II: the
Hessian method: We develop a general method to quantify the uncertainties of parton
distribution functions and their physical predictions, with emphasis on
incorporating all relevant experimental constraints. The method uses the
Hessian formalism to study an effective chi-squared function that quantifies
the fit between theory and experiment. Key ingredients are a recently developed
iterative procedure to calculate the Hessian matrix in the difficult global
analysis environment, and the use of parameters defined as components along
appropriately normalized eigenvectors. The result is a set of 2d Eigenvector
Basis parton distributions (where d=16 is the number of parton parameters) from
which the uncertainty on any physical quantity due to the uncertainty in parton
distributions can be calculated. We illustrate the method by applying it to
calculate uncertainties of gluon and quark distribution functions, W boson
rapidity distributions, and the correlation between W and Z production cross
sections. | hep-ph |
Thermodynamic inconsistency in quasiparticle model - a revisit: Widely studied quasiparticle models for quark gluon plasma is revisited here
to understand the statistical mechanics and thermodynamics of the system. We
investigate the statistical mechanics and thermodynamics inconsistencies
involved in these models and their consequences in the observables.
Quasiparticle model is a phenomenological model with few parameters and by
adjusting them all models fit the results of lattice gauge simulation of gluon
plasma \cite{bo.1}. However, after fixing 2 of the 3 parameters of the model by
physical arguments, only one quasiparticle model, which is consistent with both
statistical mechanics and thermodynamics, fits the Bielefeld lattice data
\cite{bo.1}. The same model also fits the recent lattice results of
Wuppertal-Budapest group \cite{fo.1}, which deals with precision SU(3)
thermodynamics for a large temperature range, reasonably well. | hep-ph |
Unstable Gravitino Dark Matter and Neutrino Flux: The gravitino is a promising supersymmetric dark matter candidate which does
not require exact R-parity conservation. In fact, even with some small R-parity
breaking, gravitinos are sufficiently long-lived to constitute the dark matter
of the Universe, while yielding a cosmological scenario consistent with
primordial nucleosynthesis and the high reheating temperature required for
thermal leptogenesis. In this paper, we compute the neutrino flux from direct
gravitino decay and gauge boson fragmentation in a simple scenario with
bilinear R-parity breaking. Our choice of parameters is motivated by a proposed
interpretation of anomalies in the extragalactic gamma-ray spectrum and the
positron fraction in terms of gravitino dark matter decay. We find that the
generated neutrino flux is compatible with present measurements. We also
discuss the possibility of detecting these neutrinos in present and future
experiments and conclude that it is a challenging task. However, if detected,
this distinctive signal might bring significant support to the scenario of
gravitinos as decaying dark matter. | hep-ph |
Higgs boson decays into γγ and Zγ in the MSSM and
BLSSM: We calculate Higgs decay rates into {\gamma}{\gamma} and Z{\gamma} in the
Minimal Supersymmetric Standard Model (MSSM) and (B-L) Supersymmetric Standard
Model (BLSSM) by allowing for contributions from light staus and charginos. We
show that sizable departures are possible from the SM predictions for the 125
GeV state and that they are testable during run 2 at the Large Hadron Collider.
Furthermore, we illustrate how a second light scalar Higgs signal in either or
both these decay modes can be accessed at the CERN machine rather promptly
within the BLSSM, a possibility instead precluded to the MSSM owing to the much
larger mass of its heavy scalar state. | hep-ph |
Q-ball Metamorphosis: Flat directions in the minimal supersymmetric standard model are known to
deform into non-topological solitons, Q-balls, which generally possess both
baryon and lepton asymmetries. We investigate how Q-balls evolve if some of the
constituent fields of the flat direction decay into light species. It is found
that the Q-balls takes a new configuration whose energy per charge slightly
increases due to the decay. Specifically, we show that all the stable Q-balls
eventually transform into pure B-balls via the decay into neutrinos. | hep-ph |
Nuclear effects in the proton-deuteron Drell-Yan process: We compute the nuclear corrections to the proton-deuteron Drell-Yan cross
section for inclusive dilepton production, which, when combined with the
proton-proton cross section, is used to determine the flavor asymmetry in the
proton sea, dbar - ubar. In addition to nuclear smearing corrections that are
known to be important at large values of the nucleon's parton momentum fraction
x_N, we also consider dynamical off-shell nucleon corrections associated with
the modifications of the bound nucleon structure inside the deuteron, which we
find to be significant at intermediate and large x_N values. We also provide
estimates of the nuclear corrections at kinematics corresponding to existing
and planned Drell-Yan experiments at Fermilab and J-PARC which aim to determine
the dbar/ubar ratio for x < 0.6. | hep-ph |
A review of neutrino decoupling from the early universe to the current
universe: We review the distortions of spectra of relic neutrinos due to the
interactions with electrons, positrons, and neutrinos in the early universe. We
solve integro-differential kinetic equations for the neutrino density matrix,
including vacuum three-flavor neutrino oscillations, oscillations in electron
and positron background, a collision term and finite temperature corrections to
electron mass and electromagnetic plasma up to the next-to-leading order
$\mathcal{O}(e^3)$. After that, we estimate the effects of the spectral
distortions in neutrino decoupling on the number density and energy density of
the Cosmic Neutrino Background (C$\nu$B) in the current universe, and discuss
the implications of these effects on the capture rates in direct detection of
the C$\nu$B on tritium, with emphasis on the PTOLEMY-type experiment. In
addition, we find a precise value of the effective number of neutrinos, $N_{\rm
eff}=3.044$. However, QED corrections to weak interaction rates at order
$\mathcal{O}(e^2 G_F^2)$ and forward scattering of neutrinos via their
self-interactions have not been precisely taken into account in the whole
literature so far. Recent studies suggest that these neglections might induce
uncertainties of $\pm(10^{-3} - 10^{-4})$ in $N_{\rm eff}$. | hep-ph |
An extended Higgs sector for neutrino mass, dark matter and baryon
asymmetry: In this talk, we discuss a TeV scale model which would explain neutrino
oscillation, dark matter, and baryon asymmetry of the Universe simultaneously
by the dynamics of the extended Higgs sector and TeV-scale right-handed
neutrinos. By the imposed exact $Z_2$ symmetry, tiny neutrino masses are
generated at the three loop level, and the stability of the dark matter
candidate, an additional singlet scalar field, is guaranteed. The extra Higgs
doublet is introduced not only for neutrino masses but also for successful
electroweak baryogenesis. The model provides various discriminative predictions
in Higgs phenomenology, which can be tested at the Large Hadron Collider and
the International Linear Collider. | hep-ph |
3-3-1 exotic quark search at CERN LEPII-LHC: The 3-3-1 electroweak model is the simplest chiral extension of the standard
model which predicts single and double charged bileptons and exotic quarks
carrying -4/3 and 5/3 units of the positron charge. In this paper we study the
possibilities of the production and decay of one of these exotic quarks at CERN
LEPII-LHC collider. For typical vector bilepton, exotic quark masses and mixing
angles we obtained between 20 and 750 events per year. Angular distributions
are also presented. | hep-ph |
Theoretical investigations on the Y(4260) being an hybrid meson: The new recently experiments at the B-factories yield a renewed interest in
the charm and charmonium spectroscopy. New intriguing states have been
observed, which appear to be non-conventional mesons, such as X(3862) and
Y(4260) and request more theoretical investigations. We will explore the
possibility for the Y(4260) to be a c-cbar-g hybrid meson. Using the
quark-gluon constituent model, we exclude its existence as QE-hybrid meson, and
as mixing of c-cbar-g hybrid with conventional c-cbar meson. We find the only
interpretation as GE-hybrid, decaying in D_(1)-Dbar channels. Then more
experimental studies are needed to confirm the existence of this resonance and
to give its properties. | hep-ph |
The Heavy Quark Expansion for the Charm Quark: We show that one can re-arrange the Heavy Quark Expansion for inclusive weak
decays of charmed hadrons in such a way that the resulting expansion is an
expansion in $\Lambda_{\rm QCD} / m_c$ and $\alpha_s (m_c)$ with order-one
coefficients. Unlike in the case of the bottom quark, the leading term includes
not only the contribution of the free-quark decay, but also a tower of terms
related to matrix elements of four quark operators. | hep-ph |
Reach of the CERN LHC for the Minimal Anomaly-Mediated SUSY Breaking
Model: We examine the reach of the CERN LHC pp collider for supersymmetric models
where the dominant contribution to soft SUSY breaking parameters arises from
the superconformal anomaly. In the simplest viable anomaly mediated SUSY
breaking (AMSB) model, tachyonic slepton squared masses are made positive by
adding a universal contribution m_0^2 to all scalars. We use the event
generator ISAJET to generate AMSB signal events as a function of model
parameter space. Assuming an integrated luminosity of 10 fb-1, the LHC can
reach to values of $m_{\tg}\sim 2.3$ TeV for low values of $m_0$, where the
dilepton plus jets plus E_T(missing) channel offers the best reach. For large
$m_0$, the best signature is typically 0 or 1 isolated lepton plus jets plus
E_T(missing); in this case the reach is typically diminished to values of
$m_{\tg}\sim 1.3$ TeV. The presence of terminating tracks in a subset of signal
events could serve to verify the presence of a long lived lightest chargino
which is generic in the minimal AMSB model. | hep-ph |
One-loop Weak Dipole Form Factors and Weak Dipole Moments of Heavy
Fermions: The one-loop weak-magnetic and weak-electric dipole form factors of heavy
fermions in a generic model are derived. Numerical predictions for the $\tau$
lepton and $b$ quark Weak Anomalous Magnetic and Electric Dipole Moments (AWMDM
and WEDM) in the SM and MSSM are reviewed. The MSSM contribution to the $\tau$
($b$) AWMDM could be, in the high $\tan\beta$ scenario, four (thirty) times
larger than the Electroweak SM one, but still a factor five below the QCD
contribution (in the $b$ case). More interesting is the CP-odd sector where the
contribution to the $\tau$ ($b$) WEDM in the MSSM could be up to twelve orders
of magnitude larger than in the SM. | hep-ph |
Gauge Dependence of Lower Bounds on the Higgs Mass Derived from
Electroweak Vacuum Stability Constraints: We examine the gauge dependence of lower bounds on the Higgs mass obtained
from the requirement that the electroweak vacuum be the global minimum of the
effective potential. We study a simple model, the spontaneously-broken Abelian
Higgs model coupled to a chiral quark doublet in a two-parameter gauge and
demonstrate that the lower bounds on the Higgs mass obtained in this model are
dependent on the choice of gauge parameters. We discuss the significance of
this result for calculations in the Standard Model. | hep-ph |
Zee and Zee-Babu mechanisms in the minimal 331 model: We show that the minimal 3-3-1 model cannot accommodate the neutrino masses
at tree level using present experimental data. Nevertheless, a modified Zee and
the Zee-Babu mechanisms for generating neutrino masses at 1-loop and 2-loop,
respectively, are automatically implemented in the minimal 3-3-1 model, without
introducing new degrees of freedom to the model. We also present a systematic
method for finding solutions to the leptonic sector masses and mixing. As a
case study, we accommodate the charged and neutral leptons masses and the PMNS
matrix in the 1-loop modified Zee mechanism contained in the minimal 3-3-1
model. | hep-ph |
Troubles with the Minimal SU(5) Supergravity Model: We show that within the framework of the minimal $SU(5)$ supergravity model,
radiatively-induced electroweak symmetry breaking and presently available
experimental lower bounds on nucleon decay, impose severe constraints on the
available parameter space of the model which correspond to fine-tuning of the
model parameters of over two orders of magnitude. Furthermore, a
straightforward calculation of the cosmic relic density of neutralinos ($\chi$)
gives $\Omega_\chi h^2\gg1$ for most of the allowed parameter space in this
model, although small regions may still be cosmologically acceptable. We
finally discuss how the {\it no-scale flipped $SU(5)$ supergravity model}
avoids naturally the above troubles and thus constitutes a good candidate for
the low-energy effective supergravity model. | hep-ph |
Bounds on heavy Majorana neutrinos in type-I seesaw and implications for
collider searches: The neutrino masses and flavor mixings, which are missing in the Standard
Model (SM), can be naturally incorporated in the type-I seesaw extension of the
SM with heavy Majorana neutrinos being singlet under the SM gauge group. If the
heavy Majorana neutrinos are around the electroweak scale and their mixings
with the SM neutrinos are sizable, they can be produced at high energy
colliders, leaving characteristic signatures with lepton-number violations.
Employing the general parametrization for the neutrino Dirac mass matrix in the
minimal seesaw scenario, we perform a parameter scan and identify allowed
regions to satisfy a variety of experimental constraints from the neutrino
oscillation data, the electroweak precision measurements and the lepton-flavor
violating processes. We find that the resultant mixing parameters between the
heavy neutrinos and the SM neutrinos are more severely constrained than those
obtained from the current search for heavy Majorana neutrinos at the LHC. Such
parameter regions can be explored at the High-Luminosity LHC and a 100 TeV
pp-collider in the future. | hep-ph |
Energy Momentum Tensor Correlators in Improved Holographic QCD: In this thesis, we study the physics of the quark gluon plasma (QGP) using
holographic methods borrowed from string theory. We start our discussion by
motivating the use of such machinery, explaining how recent experimental
results from the LHC and RHIC colliders suggests that the created QGP should be
described as a strongly coupled liquid with small but nonvanishing bulk and
shear viscosities. We argue that holographic dualities are a very efficient
framework for studying transport properties in such a medium.
Next, we introduce the underlying physics behind all holographic dualities,
the AdS/CFT correspondence, and then motivate the necessity of implementing
conformal invariance breaking in them. After this, we present the
phenomenologically most successful holographic model of the strong interactions
- Improved Holographic QCD (IHQCD).
Working within IHQCD, we next move on to calculate energy momentum tensor
correlators in the bulk and shear channels of large-Nc Yang-Mills theory. In
the shear channel, we confront our results with those derived in strongly
coupled N=4 Super Yang-Mills theory as well as weakly interacting ordinary
Yang-Mills theory. Close to the critical temperature of the deconfinement
transition, we observe significant effects of conformal invariance breaking. In
the bulk channel, where the conformal result is trivial, we make comparisons
with both perturbative and lattice QCD. We observe that lattice data seem to
favor our holographic prediction over the perturbative one over a wide range of
temperatures. | hep-ph |
A comprehensive study on the semileptonic decay of heavy flavor mesons: The semileptonic decay of heavy flavor mesons offers a clean environment for
extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, which
describes the CP-violating and flavor changing process in the Standard Model.
The involved form factors where the dynamical information is encoded play an
essential role in achieving any conclusive statement. That is, the knowledge of
the form factors should be under good control, requiring one to examine more
observables in addition to the branching fraction. In this paper, we provide
the mean value and the $q^2$-dependent shape for further observables
[differential decay distribution ($d\Gamma/dq^2$), forward-backward asymmetry
($\mathcal{A}_{FB}^l$), longitudinal ($P_L^l$) and transverse ($P_T^l$)
polarization of a charged lepton, longitudinal polarization of a vector meson
in the final state ($F_L^l(V)$), leptonic convexity parameter ($C_F^l$), and
trigonometric moments ($W_i^l$) in the decay of $D_{(s)}$ and $B_{(s)}$ to $P/V
l^+ \nu_l$ ($l=e$, $\mu$ or $\tau$)], based on the predictions of the relevant
form factors from the covariant light-front quark model. $P$ and $V$ denote the
pseudoscalar and vector meson, respectively. As a comparison, we find a good
agreement with the results from the covariant confining quark model and the
relativistic quark model in the literature. As it has been observed that the
$P_L^l$ and $F_L^l(V)$ are crucial quantities to discriminate various New
Physics models, the reexamination of these observables from a different method
is also essential and necessary. | hep-ph |
The tau lepton Monte Carlo Event Generation -- imprinting New Physics
models with exotic scalar or vector states into simulation samples: The Monte Carlo for lepton pair production andtau decays consist of KKMC for
lepton pair production, tauola for tau lepton decays and photos for radiative
corrections in decays.
An effort for adaptation of the system for precision data being collected at
the Belle II experiment included simulation of additional light lepton pairs.
Extension to processes where lepton pair is produced through narrow resonances,
like dark photon or dark scalar phi resonances, was straight forward.
Modified programs versions are available in stand-alone format from gitlab
repository or through the basf2 system of Belle II software. It was explained
recently during the International Workshop on Tau Lepton Physics September,
2021, Bloomington IN. Now we concentrate on simulations for phi resonance, a
hypothetical object which could be responsible for anomalous moment g-2 in
Z-\tau-\tau interactions through virtual contributions. | hep-ph |
Possible Suppression of Resonant Signals for Split-UED by Mixing at the
LHC?: The mixing of the imaginary parts of the transition amplitudes of nearby
resonances via the breakdown of the Breit-Wigner approximation has been shown
to lead to potentially large modifications in the signal rates for new physics
at colliders. In the case of suppression, this effect may be significant enough
to lead to some new physics signatures being initially missed in searches at,
e.g., the LHC. Here we explore the influence of this `width mixing' on the
production of the nearly degenerate, level-2 Kaluza-Klein (KK) neutral gauge
bosons present in Split-UED. We demonstrate that in this particular case large
cross section modifications in the resonance region are necessarily absent and
explain why this is so based on the group theoretical structure of the SM. | hep-ph |
Electrodynamics with Lorentz-violating operators of arbitrary dimension: The behavior of photons in the presence of Lorentz and CPT violation is
studied. Allowing for operators of arbitrary mass dimension, we classify all
gauge-invariant Lorentz- and CPT-violating terms in the quadratic Lagrange
density associated with the effective photon propagator. The covariant
dispersion relation is obtained, and conditions for birefringence are
discussed. We provide a complete characterization of the coefficients for
Lorentz violation for all mass dimensions via a decomposition using
spin-weighted spherical harmonics. The resulting nine independent sets of
spherical coefficients control birefringence, dispersion, and anisotropy. We
discuss the restriction of the general theory to various special models,
including among others the minimal Standard-Model Extension, the isotropic
limit, the case of vacuum propagation, the nonbirefringent limit, and the
vacuum-orthogonal model. The transformation of the spherical coefficients for
Lorentz violation between the laboratory frame and the standard Sun-centered
frame is provided. We apply the results to various astrophysical observations
and laboratory experiments. Astrophysical searches of relevance include studies
of birefringence and of dispersion. We use polarimetric and dispersive data
from gamma-ray bursts to set constraints on coefficients for Lorentz violation
involving operators of dimensions four through nine, and we describe the mixing
of polarizations induced by Lorentz and CPT violation in the cosmic-microwave
background. Laboratory searches of interest include cavity experiments. We
present the theory for searches with cavities, derive the experiment-dependent
factors for coefficients in the vacuum-orthogonal model, and predict the
corresponding frequency shift for a circular-cylindrical cavity. | hep-ph |
Annihilating Asymmetric Dark Matter: The relic abundance of particle and antiparticle dark matter (DM) need not be
vastly different in thermal asymmetric dark matter (ADM) models. By considering
the effect of a primordial asymmetry on the thermal Boltzmann evolution of
coupled DM and anti-DM, we derive the requisite annihilation cross section.
This is used in conjunction with CMB and Fermi-LAT gamma-ray data to impose a
limit on the number density of anti-DM particles surviving thermal freeze-out.
When the extended gamma-ray emission from the Galactic Center is reanalyzed in
a thermal ADM framework, we find that annihilation into $\tau$ leptons prefer
anti-DM number densities 1-4$\%$ that of DM while the $b$-quark channel prefers
50-100$\%$. | hep-ph |
Anti-B --> X(s) gamma in two universal extra dimensions: We calculate the leading order corrections to the anti-B --> X(s) gamma decay
in the standard model with two large flat universal extra dimensions. We find
that the contributions involving the exchange of Kaluza-Klein modes of the
physical scalar field a^+-_(kl) depend logarithmically on the ultraviolet
cut-off scale Lambda. We emphasize that all flavor-changing neutral current
transitions suffer from this problem. Although the ultraviolet sensitivity
weakens the lower bound on the inverse compactification radius 1/R that follows
from anti-B --> X(s) gamma, the constraint remains stronger than any other
available direct measurement. After performing a careful study of the potential
impact of cut-off and higher-order effects, we find 1/R > 650 GeV at 95%
confidence level if errors are combined in quadrature. Our limit is at variance
with the parameter region 1/R <~ 600 GeV preferred by dark matter constraints. | hep-ph |
Large mixing, family structure, and dominant block in the neutrino mass
matrix: A possible connection between the flavour structure of the charged fermions
and the large $\nu_\mu-\nu_\tau$ mixing motivates an ansatz for the neutrino
mass matrix with a dominant block. We distinguish between a general form and
the specific forms of the ansatz, and concentrate on the cases of
phenomenological interest. The general form can incorporate an observable
amount of CP violation in the leptonic sector. Only specific forms can
incorporate the Mikheyev-Smirnov-Wolfenstein solutions for solar neutrinos,
with small or large mixing angles. Other specific variants explain the Los
Alamos neutrino anomaly, or provide a two-neutrino hot dark matter component. | hep-ph |
Semi-inclusive production of spin-3/2 hadrons in deep inelastic
scattering: We investigate the production of spin-3/2 hadrons in semi-inclusive deep
inelastic lepton-nucleon scatterings. The complete differential cross section
is derived through the kinematic analysis and expressed in terms of 288
structure functions, corresponding to all polarization configurations and
azimuthal modulations. For an unpolarized lepton beam, half of the 192
structure functions have nonzero leading order contributions in the parton
model, among which 42 are from rank-3 tensor polarized fragmentation functions
of the hadron. For a polarized lepton beam, one third of the 96 structure
functions contribute at the leading order and 14 of them are from rank-3 tensor
polarized fragmentation functions. In addition to the formalism, we perform a
model estimation of the spin transfer to a $S_{hLLL}$ polarized hadron and
sizable asymmetry is expected. Therefore, these newly defined observables for
the production of a spin-3/2 hadron in semi-inclusive deep inelastic scattering
process can be explored in future experiments to understand nucleon spin
structures and spin-dependent fragmentation functions. | hep-ph |
A sum rule for elastic scattering: A sum rule is derived for elastic scattering of hadrons at high energies
which is in good agreement with experimental data on $p\bar{p}$ available upto
the maximum energy $\sqrt{s} = 2 TeV$. Physically, our sum rule reflects the
way unitarity correlates and limits how large the elastic amplitude can be as a
function of energy to how fast it decreases as a function of the momentum
transfer. The universality of our result is justified through our earlier
result on equipartition of quark and glue momenta obtained from the virial
theorem for massless quarks and the Wilson conjecture | hep-ph |
Are CP Violating Effects in the Standard Model Really Tiny?: We derive an effective action of the bosonic sector of the Standard Model by
integrating out the fermionic degrees of freedom in the worldline approach. The
CP violation due to the complex phase in the CKM matrix gives rise to
CP-violating operators in the effective action. We calculate the prefactor of
the appropriate next-to-leading order operators and give general estimates of
CP violation in the bosonic sector of the Standard Model. In particular, we
show that the effective CP violation for weak gauge fields is not suppressed by
the Yukawa couplings of the light quarks and is much larger than the bound
given by the Jarlskog determinant. | hep-ph |
Diagnosis of Supersymmetry Breaking Mediation Schemes by Mass
Reconstruction at the LHC: If supersymmetry is discovered at the LHC, the next question will be the
determination of the underlying model. While this may be challenging or even
intractable, a more optimistic question is whether we can understand the main
contours of any particular paradigm of the mediation of supersymmetry breaking.
The determination of superpartner masses through endpoint measurements of
kinematic observables arising from cascade decays is a powerful diagnostic
tool. In particular, the determination of the gaugino sector has the potential
to discriminate between certain mediation schemes (not all schemes, and not
between different UV realizations of a given scheme). We reconstruct gaugino
masses, choosing a model where anomaly contributions to supersymmetry breaking
are important (KKLT compactification), and find the gaugino unification scale.
Moreover, reconstruction of other superpartner masses allows us to solve for
the parameters defining the UV model. The analysis is performed in the stop and
stau coannihilation regions where the lightest neutralinos are mainly gauginos,
to additionally satisfy dark matter constraints. We thus develop observables to
determine stau and stop masses to verify that the coannihilation mechanism is
indeed operational, and solve for the relic density. | hep-ph |
Electron Mass Operator in a Strong Magnetic Field and Dynamical Chiral
Symmetry Breaking: The electron mass operator in a strong magnetic field is calculated. The
contribution of higher Landau levels of virtual electrons, along with the
ground Landau level, is shown to be essential in the leading log approximation.
The effect of the electron dynamical mass generation by a magnetic field is
investigated. In a model with N charged fermions, it is shown that some
critical number N_{cr} exists for any value of the electromagnetic coupling
constant alpha, such that the fermion dynamical mass is generated with a
doublet splitting for N < N_{cr}, and the dynamical mass does not arise at all
for N > N_{cr}, thus leaving the chiral symmetry unbroken. | hep-ph |
Three-Loop Effective Potential of O(N) $φ^4$ Theory: The three-loop effective potential of the massless O(N) $\phi^4$ theory is
calculated analytically using techniques of dimensional regularization. We see
a complete agreement between our result and Jackiw's result obtained only up to
two-loop order using a different regularization (cutoff regularization) method,
but the same renormalization conditions. For an easy check of the mutual
cancellation of all the dangerous pole terms in each loop order, we give the
$\epsilon$-expanded loop integrals in full detail. | hep-ph |
Towards a consistent AdS/QCD dictionary: This note focuses on the large-N behaviour of the Hard Wall model of QCD and
clarifies the AdS/QCD dictionary formulated on the basis of the AdS/CFT
correspondence. It is shown how short-distance studies performed in the
framework of the AdS/QCD Soft Wall model allow one to determine unambiguously
the chiral symmetry breaking function in the Hard Wall model. Especially, the
different forms of the field/operator prescription are emphasized. The large-N
behaviour of the Hard Wall model is then checked considering the vector and
gravitational form factors of the pion in the chiral limit. | hep-ph |
Inclusive hadronic distributions at small x: After giving their general expressions valid at all x, double differential
1-particle inclusive distribution inside a quark and a gluon jet produced in a
hard process, together with the inclusive kt distribution, are given at small x
in the Modified Leading Logarithmic Approximation (MLLA), as functions of the
transverse momentum kt of the outgoing hadron. | hep-ph |
Matching of Fracture Functions for SIDIS in Target Fragmentation Region: In the target fragmentation region of Semi-Inclusive Deep Inelastic
Scattering, the diffractively produced hadron has small transverse momentum. If
it is at order of $\Lambda_{QCD}$, it prevents to make predictions with the
standard collinear factorization. However, in this case, differential
cross-sections can be predicted by the factorization with fracture functions,
diffractive parton distributions. If the transverse momentum is much larger
than $\Lambda_{QCD}$ but much smaller than $Q$ which is the virtuality of the
virtual photon, both factorizations apply. In this case, fracture functions can
be factorized with collinear parton distributions and fragmentation functions.
We study the factorization up to twist-3 level and obtain gauge invariant
results. They will be helpful for modeling fracture functions and useful for
resummation of large logarithm of the transverse momentum appearing in
collinear factorization. | hep-ph |
Isolating a light Higgs boson from the di-photon background at the LHC: We compute the QCD corrections to the gluon fusion subprocess gg to gamma
gamma, which forms an important component of the background to the search for a
light Higgs boson at the LHC. We study the dependence of the improved pp to
gamma gamma X background calculation on the factorization and renormalization
scales, on various choices for photon isolation cuts, and on the rapidities of
the photons. We also investigate ways to enhance the statistical significance
of the Higgs signal in the di-photon channel. | hep-ph |
SMEFT interpretation of $Δ$F = 2 transitions: A model-independent anatomy of $\Delta F= 2$ transitions in the context of
the Weak Effective Theory (WET) below the electroweak scale (EW) and the
Standard Model Effective Field Theory (SMEFT) above the EW scale is discussed.
Two master formulae for the BSM contribution of the mixing amplitude $M_{12}$,
in terms of Wilson coefficients are presented. The coefficients entering these
formulae contain all the information below the EW scale and the NP scale
$\Lambda$, respectively. The renormalization group evolution from the top-quark
Yukawa coupling has the largest impact on the result. The obtained expressions
depend on whether the down-basis or the up-basis for SMEFT operators is
considered. | hep-ph |
Confinement of Fermions in Tachyon Matter at Finite Temperature: We study a phenomenological model that mimics the characteristics of QCD
theory at finite temperature. The model involves fermions coupled with a
modified Abelian gauge field in a tachyon matter. It reproduces some important
QCD features such as, confinement, deconfinement, chiral symmetry and
quark-gluon-plasma (QGP) phase transitions. The study may shed light on both
light and heavy quark potentials and their string tensions. Flux-tube and
Cornell potentials are developed depending on the regime under consideration.
Other confining properties such as scalar glueball mass, gluon mass,
glueball-meson mixing states, gluon and chiral condensates are exploited as
well. The study is focused on two possible regimes, the ultraviolet (UV) and
the infrared (IR) regimes. | hep-ph |
Light $q\bar{q}$ Resonances: Spectrum and Decays: I give a brief introduction to light $q\bar{q}$ resonances. The properties of
$q\bar{q}$ states are discussed in the context of the constituent quark model,
including predictions for mass and partial decay widths. Problems and puzzles
in the meson spectrum are pointed out with an emphasis on how an 8+ GeV photon
beam can address these. I also point out some areas where I believe theoretical
study would be useful. | hep-ph |
Chiral density waves in quarkyonic matter: We study the phase diagram of strongly interacting matter including the
inhomogeneous phase of Chiral Density Waves (CDW) within the Polyakov loop
extended Nambu-Jona-Lasinio (PNJL) model. We discuss the phase structure taking
into account density and flavour dependence of the Polyakov loop potential
parameter and temperature dependence of the four-point coupling constant of the
NJL model. It is shown that the CDW phase exists and that can be interpreted as
a special realisation of quarkyonic matter. This fact is of particular interest
because the existence of homogeneous quarkyonic matter is strongly constrained.
This also indicates that the study of inhomogeneous phases at finite
temperatures and baryon densities are of special importance. | hep-ph |
Light Scalars and the KOTO Anomaly: The KOTO experiment recently presented a significant excess of events in
their search for the rare SM process $K_L \to \pi^0\nu\bar{\nu}$, well above
both Standard Model signal and background predictions. We show that this excess
may be due to weakly-coupled scalars that are produced from Kaon decays and
escape KOTO undetected. We study two concrete realizations, the minimal Higgs
portal and a hadrophilic scalar model, and demonstrate that they can explain
the observed events while satisfying bounds from other flavor and beam-dump
experiments. Hadronic beam-dump experiments provide particularly interesting
constraints on these types of models, and we discuss in detail the normally
underestimated uncertainties associated with them. The simplicity of the models
which can explain the excess, and their possible relations with interesting UV
constructions, provides strong theoretical motivation for a new physics
interpretation of the KOTO data. | hep-ph |
Studying the Higgs Potential at the e+e- Linear Collider: The determination of the shape of the Higgs potential is needed to complete
the investigation of the Higgs profile and to obtain a direct experimental
proof of the mechanism of electro-weak symmetry breaking. This can be achieved,
at a linear collider, by determining the Higgs triple self-coupling g_HHH in
the processes e+e--> HHZ and HHnunu and, possibly, the quartic coupling. This
paper summarises the results of a study of the expected accuracies on the
determination of g_HHH at a TeV-class LC and at a multi-TeV LC. The statistical
dilution arising from contributions not sensitive to the triple Higgs vertex,
can be reduced by means of variables sensitive to the kinematics and the spin
properties of the reactions. | hep-ph |
An analysis of f_0-sigma mixing in light cone QCD sum rules: We investigate f_0-sigma mixing in the framework of light cone QCD sum rules
and by employing the experimental results about the decay widths and the masses
of these scalar mesons we estimate the scalar mixing angle by using sigma meson
data and f_0 meson data. The two values we thus obtain of the scalar mixing
angle are not entirely consistent with each other, possibly indicating that the
structure of these mesons cannot be simple quark-antiquark states. | hep-ph |
Pinching phenomenon: Central feature in out of equilibrium thermal field
theories: We continue to study out of equilibrium TFT with switching on the interaction
occurring at finite time. We exploit the concept of projected function (PF) and
Wigner transform of projected function (WTPF). WTPF's are bare propagators,
one-loop self-energies, retarded and advanced components of the resummed
propagator. Among WTPF's convolution product is very simple, one does not need
gradient expansion. However, WTPF's are completely determined by their infinite
time limit and, thus, cannot be the carriers of relaxation phenomena.
Furthermore, we observe that the functions capable of carrying relaxation
phenomena (non-WTPF) emerge in the mixed ("ill-defined") products of retarded
and advanced propagators and self-energies. In particular, only non-WTPF's
contribute to time variation of equal-time Green functions (particle number,
etc.); contributions from WTPF will be constant in time. As these are generated
in mixed products, the pinching phenomenon is being promoted from an obstacle
to the central feature of out of equilibrium TFT. We analyze the pinching
phenomenon. In the case of naive pinching we reproduce known results. In
Schwinger-Dyson equations the Keldysh component of self-energy is well defined
even for multiple self-energy insertion contributions. We calaculate explicitly
single self-energy contribution to Keldysh component of propagator which
generates nontrivial time dependence. For photon production from QCD plasma
(finite-lifetime effect) our approximate analytic results agree with the
results by S. -Y. Wang and D. Boyanovsky obtained within dynamical
renormalisation group approach. | hep-ph |
Charged Lepton Flavor Violation at the High-Energy Colliders: Neutrino
Mass Relevant Particles: We summarize the potential charged lepton flavor violation (LFV) from
neutrino mass relevant models, for instance the seesaw mechanisms. In
particular, we study, in a model-dependent way, the LFV signals at the
high-energy hadron and lepton colliders originating from the beyond standard
model (BSM) neutral scalar $H$, doubly charged scalar $H^{\pm\pm}$, heavy
neutrino $N$, heavy $W_R$ boson, and the $Z'$ boson. For the neutral scalar,
doubly charged scalar and $Z'$ boson, the LFV signals originate from the
(effective) LFV couplings of these particles to the charged leptons, while for
the heavy neutrino $N$ and $W_R$ boson, the LFV effects are from flavor mixing
in the neutrino sector. We consider current limits on these BSM particles and
estimate their prospects at future high-energy hadron and lepton colliders. | hep-ph |
Sea contribution to the charge radii and quadrupole moment of
$J^P=\frac{1}{2}^+, \frac{3}{2}^+$ baryons: An operator formalism is used on the wavefunction of baryons to compute their
charge radii and quadrupole moments. Total anti-symmetric wavefunction in spin,
color and flavor space is framed for $J^P=\frac{1}{2}^+$ nucleons and
$J^P=\frac{3}{2}^+$ hyperons. To understand the importance of sea, statistical
model is used in conjugation with the detailed balance principle. Within the
statistical approach, the importance of sea with quarks and gluons are studied
using the relevant probabilities that are associated with spin, flavor, and
color space. The present work also focuses on individual contributions of
valence and sea which contains terms of scalar, vector and tensor sea. The
obtained results are in agreement with available theories and few experimental
outcomes. Our computed results may provide important information for upcoming
experimental findings. | hep-ph |
The renormalization group and quark number fluctuations in the Polyakov
loop extended quark-meson model at finite baryon density: Thermodynamics and the phase structure of the Polyakov loop-extended two
flavors chiral quark--meson (PQM) model is explored beyond the mean-field
approximation. The analysis of the PQM model is based on the functional
renormalization group (FRG) method. We formulate and solve the renormalization
group flow equation for the scale-dependent thermodynamic potential in the
presence of the gluonic background field at finite temperature and density. We
determine the phase diagram of the PQM model in the FRG approach and discuss
its modification in comparison with the one obtained under the mean-field
approximation. We focus on properties of the net-quark number density
fluctuations as well as their higher moments and discuss the influence of
non-perturbative effects on their properties near the chiral crossover
transition. We show, that with an increasing net-quark number density the
higher order moments exhibit a peculiar structure near the phase transition. We
also consider ratios of different moments of the net-quark number density and
discuss their role as probes of deconfinement and chiral phase transitions. | hep-ph |
Singlet scalars as Higgs imposters at the Large Hadron Collider: An electroweak singlet scalar can couple to pairs of vector bosons through
loop-induced dimension five operators. Compared to a Standard Model Higgs
boson, the singlet decay widths in the diphotons and Z gamma channels are
generically enhanced, while decays into massive final states like WW and ZZ are
kinematically disfavored. The overall event rates into gamma gamma and Z gamma
can exceed the Standard Model expectations by orders of magnitude. Such a
singlet may appear as a resonant signal in the gamma gamma and Z gamma
channels, even with a mass above the WW kinematic threshold. | hep-ph |
A road to an elementary particle physics model with no Higgs -- II: This is the second of two companion papers in which we continue developing
the construction of an elementary particle model with no Higgs. Here we show
that the recently identified non-perturbative field-theoretical feature,
alternative to the Higgs mechanism and capable of giving masses to quarks,
Tera-quarks and $W$, can also provide mass to leptons and Tera-leptons when the
model is extended to include, besides strong, Tera-strong and weak
interactions, also hypercharge. In the present approach elementary fermion
masses are not free parameters but are determined by the dynamics of the
theory. We derive parametric formulae for elementary particle masses from which
we can ``predict'' the order of magnitude of the scale of the new
Tera-interaction and get crude numerical estimates for mass ratios in fair
agreement with phenomenology. The interest of considering elementary particle
models endowed with this kind of non-perturbative mass generation mechanism is
that they allow solving some of the conceptual problems of the present
formulation of the Standard Model, namely origin of the electroweak scale and
naturalness. | hep-ph |
J/P=1/2+, J/P=3/2+ masses in statistical model: The mass formulae for the baryon octet and decuplet are calculated. These
formulae are function of constituent quark masses and spin spin interaction
terms for the quarks inside the baryons. The coefficients in the mass formulae
is estimated by the statistical model for J/P=1/2+, J/P=3/2+, incorporating the
contributions from \sea" containing uu; dd; ss pairs and gluons . The measured
masses are presented and found to be matching good with some of the
experimental and theoretical data. | hep-ph |
Leptoquark effects on $b \to s ν\barν$ and $B \to K l^+ l^-$
decay processes: We study the rare semileptonic decays of $B$ mesons induced by $b \to s \nu
\bar{\nu}$ as well as $b \to s l^+ l^-$ transitions in the scalar leptoquark
model where the leptoquarks transform as $(3,2,7/6)$ and $(3,2,1/6)$ under the
standard model gauge group. The leptoquark parameter space is constrained using
the most recent experimental results on ${\rm Br}(B_s \rightarrow \mu^+ \mu^-)$
and ${\rm Br}(B_d \to X_s \mu^+ \mu^-)$ processes. Considering only the baryon
number conserving leptoquark interactions, we estimate the branching ratios for
the exclusive $\bar{B} \rightarrow \bar{K}^{(*)} \nu \bar{\nu}$ and inclusive
$B \rightarrow X_s \nu \bar{\nu}$ decay processes by using the constraint
parameters. We also obtain the low recoil (large lepton invariant mass, i.e.,
$q^2 \sim m^2_b$) predictions for the angular distribution of $\bar B
\rightarrow \bar{K} l^+ l^-$ process and several other observables including
the flat term and lepton flavour non-universality factor in this model. | hep-ph |
Drell-Yan hadron tensor: contour gauge and gluon propagator: We consider the gauge invariant Drell-Yan hadron tensor which includes the
standard and non-standard diagram contributions. The non-standard diagram
contribution is appeared owing to the complexity of the twist three
$B^V(x_1,x_2)$-function where the gluon pole manifests. We use the contour
gauge conception which allows us to fix easily the spurious uncertainties in
the gluon propagator. The contour gauge condition is generated by the
corresponding Wilson lines in both the standard and non-standard diagrams. We
demonstrate the substantial role of the non-standard diagram for forming of the
relevant contour in the Wilson path-ordered exponential that leads to the
spurious singularity fixing. | hep-ph |
Shift Symmetry and Higgs Inflation in Supergravity with Observable
Gravitational Waves: We demonstrate how to realize within supergravity a novel chaotic-type
inflationary scenario driven by the radial parts of a conjugate pair of Higgs
superfields causing the spontaneous breaking of a grand unified gauge symmetry
at a scale assuming the value of the supersymmetric grand unification scale.
The superpotential is uniquely determined at the renormalizable level by the
gauge symmetry and a continuous R symmetry. We select two types of Kahler
potentials, which respect these symmetries as well as an approximate shift
symmetry. In particular, they include in a logarithm a dominant shift-symmetric
term proportional to a parameter c- together with a small term violating this
symmetry and characterized by a parameter c+. In both cases, imposing a lower
bound on c-, inflation can be attained with subplanckian values of the original
inflaton, while the corresponding effective theory respects perturbative
unitarity for r+-=c+/c-<1. These inflationary models do not lead to
overproduction of cosmic defects, are largely independent of the one-loop
radiative corrections and accommodate, for natural values of r+-, observable
gravitational waves consistently with all the current observational data. The
inflaton mass is mostly confined in the range (3.7-8.1)x10^10 GeV. | hep-ph |
Global analysis of the Sivers functions at NLO+NNLL in QCD: We perform global fit to the quark Sivers function within the transverse
momentum dependent (TMD) factorization formalism in QCD. We simultaneously fit
Sivers asymmetry data from Semi-Inclusive Deep Inelastic Scattering (SIDIS) at
COMPASS, HERMES, and JLab, from Drell-Yan lepton pair production at COMPASS,
and from $W/Z$ boson at RHIC. This extraction is performed at next-to-leading
order (NLO) and next-to-next-to leading logarithmic (NNLL) accuracy. We find
excellent agreement between our extracted asymmetry and the experimental data
for SIDIS and Drell-Yan lepton pair production, while tension arises when
trying to describe the spin asymmetries of $W/Z$ bosons at RHIC. We carefully
assess the situation, and we study in details the impact of the RHIC data and
their implications through different ways of performing the fit. In addition,
we find that the quality of the description of $W/Z$ vector boson asymmetry
data could be strongly sensitive to the DGLAP evolution of Qiu-Sterman
function, besides the usual TMD evolution. We present discussion on this and
the implications for measurements of the transverse-spin asymmetries at the
future Electron Ion Collider. | hep-ph |
Insights from the Interplay of K -> pi nu anti-nu and epsilon_K on the
New Physics Flavour Structure: In certain new physics (NP) models, such as the Littlest Higgs model with
T-parity, a strict correlation between the K_L -> pi0 nu anti-nu and K+ -> pi+
nu anti-nu branching ratios has been observed, allowing essentially only for
two branches of possible points, while in other NP frameworks, such as the
general MSSM or warped extra dimensional models, no visible correlation
appears. We analyse the origin of the correlation in question and show it to be
a direct consequence of the stringent experimental constraint on epsilon_K,
provided that the NP enters with comparable strength and a universal weak phase
in both Delta S = 2 and Delta S = 1 transitions. This happens in many NP
scenarios with either only SM operators, or where the NP induces exclusively
right-handed currents while the left-right Delta S = 2 operators are absent. On
the other hand, if the NP phases in Delta S = 2 and Delta S = 1 processes are
uncorrelated, epsilon_K has no power to put constraints on the K -> pi nu
anti-nu system. The latter appears in particular in those NP models where K^0 -
anti-K^0 mixing receives contributions from the chirally enhanced left-right
operators. We discuss the stability of the correlation in question against
small deviations from the assumption of universal Delta S = 2 and Delta S = 1
weak phases, and in the presence of non-negligible NP contributions to
epsilon_K. | hep-ph |
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