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Right-Chiral Sneutrino LSP in mSUGRA: Event characteristics of NLSP at
the LHC: We study a supersymmetric scenario where the lighter tau-sneutrino is the
lightest supersymmetric particle, while the lighter stau-state is the next
lightest. Such a scenario can be motivated within the framework of minimal
supergravity, with just the addition of a right-chiral neutrino superfield.
Such a spectrum leads to rather unusual signals of supersymmetry, showing
stable tracks of the stau in the muon chambers. We study the event
characteristics of the long-lived staus at the LHC and demonstrate that the
stau tracks can be distinguished from the muonic ones through proper kinematic
cuts which also enable one to remove all standard model backgrounds. | hep-ph |
Higgs Production and Decay via $e^+e^-\rightarrow Z^0 H^0 \rightarrow
b\bar bW^+W^-$ and Irreducible Backgrounds at the Next Linear Collider: The complete matrix element for $e^+e^-\ar b\bar bW^+W^-$ has been computed
at tree--level and applied to $Z^0H^0$ production followed by $Z^0\ar b\bar b$
and $H^0\ar W^+W^-$, keeping into account all irreducible backgrounds, which
are dominated by \ttb production, at the Next Linear Colliders. We find that,
depending on the center of mass energies and on the search strategies, this
channel can be useful for the study of the parameters of the Standard Model
Higgs boson over the most part of the heavy mass range. | hep-ph |
Evolution of transverse-momentum-dependent densities: We discuss different operator definitions of the transverse-momentum
dependent (TMD) parton densities from the point of view of their
renormalization-group (RG) properties and UV evolution. We also consider the
structure of the gauge links (Wilson lines) in these operator definitions and
examine the role of the soft factor in the factorization formula within the TMD
approach to semi-inclusive processes. | hep-ph |
Pair production of doubly heavy baryons: We analytically calculate the total and differential cross sections for the
pair production of doubly heavy baryons in the framework of diquark model. The
processes of electron-positron and quark-antiquark annihilations are
considered. The fractions of doubly heavy baryons in the yields of heavy quarks
are evaluated numerically. | hep-ph |
Current-Target Correlations as a Probe of Delta_G/G in Polarized Deep
Inelastic Scattering: The measurement of the polarized gluon distribution function Delta_G/G using
current-target correlations in the Breit frame of deep inelastic scattering is
proposed. The approach is illustrated using a Monte Carlo simulation of
polarized $ep$-collisions for HERA energies. | hep-ph |
Effects of non-standard interaction on microscopic black holes from
ultra-high energy neutrinos: If the universe has more than 4-dimensions, the TeV scale gravity theories
predict formation of microscopic black holes due to interaction of ultra high
energy neutrinos coming from some extragalactic origin with the nucleons
present in the Earth's atmosphere. The decay of these black holes can generate
high multiplicity events which can be detected through neutrino telescopes.
Ultra high energy neutrinos can also produce events without the formation of
black holes which can be distinguished from the black hole events depending on
their topological structure. In this work we study the effects of non-standard
interaction on the production of these shower events. We find that new physics
has inconsequential impact on the number of events produced through the
generation of black holes. For events produced without the formation of black
holes, new physics can only provide a marginal deviation. Therefore a large
enhancement in the number of shower events over the standard model prediction
can provide unambiguous signatures of TeV scale gravity in the form of
microscopic black hole production. | hep-ph |
Cosmological Axion and Quark Nugget Dark Matter Model: We study a dark matter (DM) model offering a very natural explanation of two
(naively unrelated) problems in cosmology: the observed relation $\Omega_{\rm
DM}\sim\Omega_{\rm visible}$ and the observed asymmetry between matter and
antimatter in the Universe, known as the "baryogenesis" problem. In this
framework, both types of matter (dark and visible) have the same QCD origin,
form at the same QCD epoch, and both proportional to one and the same
dimensional parameter of the system, $\Lambda_{\rm QCD}$, which explains how
these two, naively distinct, problems could be intimately related, and could be
solved simultaneously within the same framework. More specifically, the DM in
this model is composed by two different ingredients: the (well- studied) DM
axions and (less-studied) the quark nuggets made of matter or antimatter. The
focus of the present work is the quantitative analysis of the relation between
these two distinct components contributing to the dark sector of the theory
determined by $\Omega_{\rm DM}\equiv [\Omega_{\rm DM}(\rm nuggets)+ \Omega_{\rm
DM}(\rm axion)]$. We argue that the nugget's DM component always traces the
visible matter density, i.e. $\Omega_{\rm DM}(\rm nuggets)\sim\Omega_{\rm
visible}$ and this feature is not sensitive to the parameters of the system
such as the axion mass $m_a$ or the misalignment angle $\theta_0$. It should be
contrasted with conventional axion production mechanism due to the misalignment
when $\Omega_{\rm DM}(\rm axion)$ is highly sensitive to the axion mass $m_a$
and the initial misalignment angle $\theta_0$. We also discuss the constraints
on this model related to the inflationary scale $H_I$, non-observation of the
isocurvature perturbations, $r_T < 0.12$, and also, varies axions search
experiments. | hep-ph |
The 14 TeV LHC Takes Aim at SUSY: A No-Scale Supergravity Model for LHC
Run 2: The Supergravity model named No-Scale ${\cal F}$-$SU(5)$, which is based upon
the flipped $SU$(5) Grand Unified Theory (GUT) with additional TeV-scale
vector-like flippon multiplets, has been partially probed during the LHC Run 1
at 7-8 TeV, though the majority of its model space remains viable and should be
accessible by the 13-14 TeV LHC during Run 2. The model framework possesses the
rather unique capacity to provide a light CP-even Higgs boson mass in the
favored 124-126 GeV window while simultaneously retaining a testably light
supersymmetry (SUSY) spectrum. We summarize the outlook for No-Scale ${\cal
F}$-$SU(5)$ at the 13-14 TeV LHC and review a promising methodology for the
discrimination of its long-chain cascade decay signature. We further show that
proportional dependence of all model scales upon the unified gaugino mass
$M_{1/2}$ minimizes electroweak fine-tuning, allowing the $Z$-boson mass $M_Z$
to be expressed as an explicit function of $M_{1/2}$, $M_Z^2 = M_Z^2
(M_{1/2}^2)$, with implicit dependence upon a dimensionless ratio $c$ of the
supersymmetric Higgs mixing parameter $\mu$ and $M_{1/2}$. Finally, we
elucidate an empirical connection between recent scalar tensor measurements and
No-Scale Supergravity cosmological models that mimic the Starobinsky model of
inflation. | hep-ph |
Dark top partner: Composite Higgs models with extended symmetries can feature mesonic dark
matter candidates. In fundamental CHMs, the origin of dark parity can be
explained in the UV theory. Combined with top partial compositeness, this leads
to non-chiral Yukawa interaction connecting mesonic DM with one dark top
partner and one SM top. We examine the DM phenomenology in SU(6)/SO(6) and
SU(6)/Sp(6) CHMs with the presence of dark top partners. Phenomenological
constraints require the mass of top partner in even parity to be of the
multi-TeV order. | hep-ph |
Precision measurements of IVB parameters and bounds on new physics: The main purpose of this thesis is to discuss the impact of electroweak
precision measurements on the present knowledge of particle physics, both in
the framework of the Standard Model and of its most straightforward extensions.
In Chapter 1 we give a general overview of the electroweak sector of the SM and
of SUSY phenomenology. In Chapter 2 we deal with different definitions of the
electroweak mixing angle, with particular attention to the relation between the
phenomenological angle $\theta$ and the MS parameter $\hat\theta$. In Chapter 3
we use results found in the previous chapter to discuss in detail how both the
decoupling and the non-decoupling approach to the running of coupling constants
in the MS scheme produce the same numerical value of $m_{GUT}$, despite of the
different initial conditions. In Chapter 4 we derive simple analytical formulas
for the contribution of a chargino almost degenerate with the lightest
neutralino to electroweak observables, showing that in the case of wino
domination the study of oblique corrections allows a concrete improvement of
experimental bounds on chargino mass. Finally, in Chapter 5 we consider the
possibility of extra fermion generations, proving that they are strongly
disfavoured by the present experimental data if all particles are heavier that
Z-boson, while for the specific case of the extra neutrino around 50 GeV in
mass (still allowed by experimental data) the quality of the fit is not worse
than the SM. | hep-ph |
Search for neutrinoless double beta decay with enriched 76Ge in Gran
Sasso 1990-2003: The results of the HEIDELBERG-MOSCOW experiment which searches with 11 kg of
enriched 76Ge for double beta decay in the GRAN Sasso underground laboratory
are presented for the full running period August 1990 - May 2003. The duty
cycle of the experiment was ~80%, the collected statistics is 71.7 kg y. The
background achieved in the energy region of the Q value for double beta decay
is 0.11 events/ kg y keV. The two-neutrino accompanied half-life is determined
on the basis of more than 100 000 events. The confidence level for the
neutrinoless signal has been improved to 4.2 sigma. | hep-ph |
Sum-rule constraints on possible diphoton resonances at LHC: The study of the forward scattering amplitude $V(k,\lambda) V(k'\lambda')\to
V(k,\lambda) V(k',\lambda')$ of real massless gauge bosons $V$, e.g. photons or
gluons, leads to a sum-rule that can be used to investigate beyond the Standard
Model signals at LHC in the $\gamma\gamma$ channel. The sum-rule only relies on
general properties such as analyticity, unitarity and crossing. We use the now
buried 750 GeV diphoton resonance as a case of study to exemplify the
constraints that the forward sum-rule requires to any new physics candidate. In
the case of a large $\gamma\gamma$ or $gg$ partial width, of the order of 10
GeV in our 750 GeV analysis, one finds that an infinite tower of states with
spin $J_R=2$ and higher must be ultimately incorporated to the beyond Standard
Model theory in order to fulfill the sum-rule. We expect these techniques may
be useful in next diphoton searches at LHC and future colliders. | hep-ph |
Little Higgs Model Discrimination at the LHC and ILC: We propose a means to discriminate between the two basic variants of Little
Higgs models, the Product Group and Simple Group models, at the next generation
of colliders. It relies on a special coupling of light pseudoscalar particles
present in Little Higgs models, the pseudoaxions, to the Z and the Higgs boson,
which is present only in Simple Group models. We discuss the collider
phenomenology of the pseudoaxion in the presence of such a coupling at the LHC,
where resonant production and decay of either the Higgs or the pseudoaxion
induced by that coupling can be observed for much of parameter space. The full
allowed range of parameters, including regions where the observability is
limited at the LHC, is covered by a future ILC, where double scalar production
would be a golden channel to look for. | hep-ph |
Muon transverse polarization in the $K_{l2γ}$ decay in SM: The muon transverse polarization in the $K^+ \to \mu^+ \nu \gamma$ process
induced by the electromagnetic final state interaction is calculated in the
framework of Standard Model. It is shown that one loop contributions lead to a
nonvanihing muon transverse polarization. The value of the muon transverse
polarization averaged over the kinematical region of $E_\gamma \geq 20$ MeV is
equal to $5.63 \times 10^{-4}$. | hep-ph |
Lifetime of quasiparticles in hot gauge theories: The perturbative calculation of the lifetime of charged excitations in
ultrarelativistic plasmas is plagued with infrared divergences which are not
eliminated by the screening corrections. The physical processes responsible for
these divergences are the collisions involving the exchange of longwavelength,
quasistatic, magnetic gluons (or photons), which are not screened by plasma
effects. In QED, the leading divergences can be resummed in a non-perturbative
treatement based on a generalization of the Bloch-Nordsieck model at finite
temperature. The resulting expression of the fermion propagator is free of
infrared problems, and exhibits a ``non-exponential'' damping at large times:
$S_R(t)\sim exp {-\alpha T t ln\omega_pt}$, where $\omega_p=eT/3$ is the plasma
frequency and $\alpha=e^2/4\pi$. | hep-ph |
Coulomb-Nuclear Interference:the Latest Modification: We argue that the account of Coulomb-nuclear interference (CNI) in the
differential cross-section of elastic $ pp $ scattering may be easily treated
without introduction of intermediate IR regularization ("photon mass"). We also
indicate that the parametrization used earlier misses some terms of the second
order in $ \alpha $ while it contains a superfluous term of the first order. | hep-ph |
Higgs Radiation off Top Quarks at the Tevatron and the LHC: Higgs bosons can be searched for in the channels $p\bar p/pp\to t\bar tH+X$
at the Tevatron and the LHC. We have calculated the QCD corrections to these
processes in the Standard Model at next-to-leading order. The higher-order
corrections reduce the renormalization and factorization scale dependence
considerably and stabilize the theoretical predictions for the cross sections.
At the central scale $\mu=(2m_t+M_H)/2$ the properly defined $K$ factors are
slightly below unity for the Tevatron ($K \sim 0.8$) and slightly above unity
for the LHC ($K \sim 1.2$). | hep-ph |
A Linear Sigma Model with Three Flavors and Vector and Axial-Vector
Mesons: We outline the extension of the globally chirally invariant Nf = 2 linear
sigma model with vector and axial-vector degrees of freedom to Nf=3. We present
preliminary results concerning the scalar meson masses. | hep-ph |
Dark Photon Dark Matter from Cosmic Strings and Gravitational Wave
Background: Dark photon dark matter may be produced by the cosmic strings in association
with the dark U(1) gauge symmetry breaking. We perform three-dimensional
lattice simulations of the Abelian-Higgs model and follow the evolution of
cosmic strings. In particular, we simulate the case of (very) light vector
boson and find that such vector bosons are efficiently produced by the collapse
of small loops while the production is inefficient in the case of heavy vector
boson. We calculate the spectrum of the gravitational wave background produced
by the cosmic string loops for the light vector boson case and find
characteristic features in the spectrum, which can serve as a probe of the dark
photon dark matter scenario. In particular, we find that the current
ground-based detectors may be sensitive to such gravitational wave signals and
also on-going/future pulsar timing observations give stringent constraint on
the dark photon dark matter scenario. | hep-ph |
$πK$ sum rules and the SU(3) chiral expansion: A recently proposed set of sum rules, based on the pion-Kaon scattering
amplitudes and their crossing-symmetric conjugates are analysed in detail. A
key role is played by the $l=0$ $\pi\pi\to K\overline K$ amplitude which
requires an extrapolation to be performed. It is shown how this is tightly
constrained from analyticity, chiral counting and the available experimental
data, and its stability is tested. A re-evaluation of the $O(p^4)$ chiral
couplings $L_1$, $L_2$, $L_3$ is obtained, as well as a new evaluation of the
large $N_c$ suppressed coupling $L_4$. | hep-ph |
Proposed Tests of CPT Symmetry Using D Mesons: Parameters describing CPT violation are extracted from a variety of rate
asymmetries in the neutral-$D$ system. The precision to which these parameters
could be measured in present and planned machines is examined. | hep-ph |
Low scale quantum gravity in gauge-Higgs unified models: We consider the scale at which gravity becomes strong in linearized General
Relativity coupled to the gauge-Higgs unified(GHU) model. We also discuss the
unitarity of S-matrix in the same framework. The Kaluza-Klein(KK) gauge bosons,
KK scalars and KK fermions in the GHU models can drastically change the strong
gravity scale and the unitarity violation scale. In particular we consider two
models GHU_SM and GHU_MSSM which have the zero modes corresponding to the
particle content of the Standard Model and the Minimal Supersymmetric Standard
Model, respectively. We find that the strong gravity scale could be lowered as
much as 10^13 (10^14) GeV in the GHU_SM (GHU_MSSM) for one extra dimension
taking 1 TeV as the compactification scale. It is also shown that these scales
are proportional to the inverse of the number of extra dimensions d. In the
d=10 case, they could be lowered up to 10^5 GeV for both models. We also find
that the maximum compactification scales of extra dimensions quickly converge
into one special scale M_O near Planck scale or equivalently into one common
radius R_0 irrespectively of d as the number of zero modes increases. It may
mean that all extra dimensions emerge with the same radius near Planck scale.
In addition, it is shown that the supersymmetry can help to remove the
discordance between the strong gravity scale and the unitarity violation scale. | hep-ph |
Transverse momentum distributions of valence quark in light and heavy
vector mesons: We study the leading-twist time-reversal even transverse momentum dependent
parton distribution functions (TMDs) of light and heavy vector mesons, i.e.,
the $\rho$, $J/\psi$ and $\Upsilon$. We employ the leading Fock-state light
front wave functions (LF-LFWFs) of $\rho$ and $J/\psi$ from our recent study,
and supplement with $\Upsilon$'s LF-LFWFs. These LF-LFWFs are extracted from
dynamically solved Bethe-Salpeter wave functions. The vector meson TMDs are
then studied with the light front overlap representation at leading Fock-state.
All the obtained TMDs are non-vanishing and evolve with current quark mass, in
particular the tensor polarized TMDs $f_{1LT}$ and $f_{1TT}$ which undergo a
sign flip. The $\rho$ TMDs are compared with other model studies and agreement
is found, aside from $f_{1LT}$ and $f_{1TT}$. Finally, the collinear PDFs of
vector mesons are studied. The $\rho$'s valence PDFs $f_{1,v}(x)$ and
$g_{1L,v}(x)$ are evolved to the scale of 2.4 GeV, with their first three
moments compared to lattice QCD prediction. The qualitative behavior of tensor
polarized PDF $f_{1LL}(x)$ in $\rho$ at large $x$ is also discussed. | hep-ph |
The Friedberg-Lee model at finite temperature and density: The Friedberg-Lee model is studied at finite temperature and density. By
using the finite temperature field theory, the effective potential of the
Friedberg-Lee model and the bag constant $B(T)$ and $B(T,\mu)$ have been
calculated at different temperatures and densities. It is shown that there is a
critical temperature $T_{C}\simeq 106.6 \mathrm{MeV}$ when $\mu=0 \mathrm{MeV}$
and a critical chemical potential $\mu \simeq 223.1 \mathrm{MeV}$ for fixing
the temperature at $T=50 \mathrm{MeV}$. We also calculate the soliton solutions
of the Friedberg-Lee model at finite temperature and density. It turns out that
when $T\leq T_{C}$ (or $\mu \leq \mu_C$), there is a bag constant $B(T)$ (or
$B(T,\mu)$) and the soliton solutions are stable. However, when $T>T_{C}$ (or
$\mu>\mu_C$) the bag constant $B(T)=0 \mathrm{MeV}$ (or $B(T,\mu)=0
\mathrm{MeV}$) and there is no soliton solution anymore, therefore, the
confinement of quarks disappears quickly. | hep-ph |
Anomalous $Z'$ effects in the WW channel at NLC: We consider the virtual signals of a $Z'$ of very general type in the process
$e^+e^-\to W^+W^-$ at a future linear collider (NLC). We show that possible
deviations from the SM predictions in this channel are related to similar
deviations in the purely leptonic one in a way that is only characteristic of
this $Z'$ model, and not in general of possible competitor models with
anomalous gauge couplings. | hep-ph |
Mass-degenerate Higgs bosons at 125 GeV in the Two-Higgs-Doublet Model: The analysis of the Higgs boson data by the ATLAS and CMS Collaborations
appears to exhibit an excess of h --> gamma\gamma events above the Standard
Model (SM) expectations; whereas no significant excess is observed in h --> ZZ*
--> {four lepton} events, albeit with large statistical uncertainty due to the
small data sample. These results (assuming they persist with further data)
could be explained by a pair of nearly mass-degenerate scalars, one of which is
a SM-like Higgs boson and the other is a scalar with suppressed couplings to
W+W- and ZZ. In the two Higgs doublet model, the observed \gamma\gamma and ZZ*
--> {four lepton} data can be reproduced by an approximately degenerate CP-even
(h) and CP-odd (A) Higgs boson for values of \sin(\beta-\alpha) near unity and
0.7 < \tan\beta < 1. An enhanced \gamma\gamma signal can also arise in cases
where m_h ~ m_H, m_H ~ m_A, or m_h ~ m_H ~ m_A. Since the ZZ* --> {four lepton}
signal derives primarily from a SM-like Higgs boson whereas the \gamma\gamma
signal receives contributions from two (or more) nearly mass-degenerate states,
one would expect a slightly different invariant mass peak in the ZZ* --> {four
lepton} and \gamma\gamma channels. The phenomenological consequences of such
models can be tested with additional Higgs data that will be collected at the
LHC in the near future. | hep-ph |
BEACH 2014 Theory Summary: I summarize key aspects of the quest for physics beyond the Standard Model in
flavour physics as discussed at the BEACH 2014 conference in Birmingham. | hep-ph |
Probing the lightest new gauge boson $B_H$ in the littlest Higgs model
via the processes $γγ\to f\bar{f}B_H$ at the ILC: The neutral gauge boson $B_H$ with the mass of hundreds GeV, is the lightest
particle predicted by the littlest Higgs(LH) model, and such particle should be
the first signal of the LH model at the planed ILC if it exists indeed. In this
paper, we study some processes of the $B_H$ production associated with the
fermion pair at the ILC, i.e., $\gamma\gamma\to f\bar{f}B_{H}$. The studies
show that the most promising processes to detect $B_H$ among $\gamma\gamma\to
f\bar{f}B_{H}$ are $\gamma\gamma\to l'^+l'^-B_{H}(l'=e,\mu)$, and they can
produce the sufficient signals in most parameter space preferred by the
electroweak precision data at the ILC. On the other hand, the signal produced
via the certain $B_H$ decay modes is typical and such signal can be easily
identified from the SM background. Therefore, $B_H$, the lightest gauge boson
in the LH model would be detectable at the photon collider realized at the ILC. | hep-ph |
Uncovering the Root of LEFT in SMEFT: At energies below the electroweak scale, baryon number $B$ and lepton number
$L$ violating processes are of significant importance in identifying the nature
of UV extensions of the Standard Model. The imprint of UV theories on
low-energy measurements can be calculated to a high accuracy using the
theoretical framework of the Low Energy Effective Theory (LEFT). Using $B,\; L$
and the operators' dimensions as classifying characteristics, we construct a
network connecting operator classes of the LEFT with the Standard Model
Effective Theory (SMEFT). Following the links of this network, the contact
interactions described by the effective operators of LEFT can be unambiguously
embedded into those of SMEFT, which enables us to constrain the possible
realisations of UV theories. In turn, this can help to prioritise low energy
measurements with the aim of comprehensively testing all classes of LEFT and
SMEFT operators. | hep-ph |
Delta I=1/2 and epsilon'/epsilon in Large-Nc QCD: We present new results for the matrix elements of the Q_6 and Q_4 penguin
operators, evaluated in a large-Nc approach which incorporates important
O(N_c^2\frac{n_f}{N_c}) unfactorized contributions. Our approach shows analytic
matching between short- and long-distance scale dependences within dimensional
renormalization schemes, such as MS-bar. Numerically, we find that there is a
large positive contribution to the Delta I =1/2 matrix element of Q_6 and hence
to the direct CP-violation parameter epsilon'/epsilon. We also present results
for the Delta I = 1/2 rule in K -> pi pi amplitudes, which incorporate the
related and important ``eye-diagram'' contributions of O(N_c^2\frac{1}{N_c})
from the Q_2 operator (i.e. the penguin-like contraction). The results lead to
an enhancement of the Delta I = 1/2 effective coupling. The origin of the large
unfactorized contributions which we find is discussed in terms of the relevant
scales of the problem. | hep-ph |
An improvement of the Moliere-Fano multiple scattering theory: In the framework of unitary Glauber approximation for particle-atom
scattering, we develop the general formalism of the Moliere-Fano multiple
scattering theory (M-F theory) on the basis of reconstruction of the
generalized optical theorem in it. We present rigorous relations between some
exact and first-order parameters of the Moliere multiple scattering theory,
instead of the approximate one obtained in the original paper by Moliere. We
consider the relative unitarity corrections and the Coulomb corrections to the
quantities of the M-F theory. Also, we examine their Z dependence in the range
of nuclear charge, from Z=4 to Z=92. Additionally, we show the difference
between our results and those of Moliere over this Z range. | hep-ph |
Generalized Dirac-Pauli equation and spin light of neutrino in
magnetized matter: We consider propagation of a massive neutrino in matter within the quantum
approach based on the two equations for the neutrino field: the first one is
the Dirac-Pauli equation for a massive neutrino in an external magnetic field
generalized on the inclusion of effects of the background matter; the second
one is the modified Dirac equation derived directly from the neutrino-matter
interaction Lagrangian. On the basis of these two equations the quantum theory
of a neutrino moving in the background matter is developed (the exact solutions
of these equations are found and classified over the neutrino spin states, the
corresponding energy spectra are also derived). Using these solutions we study
within the quantum approach the spin light of neutrino ($SL\nu$) in matter with
the effect of a longitudinal magnetic field being also incorporated. In
particular, the $SL\nu$ radiation rate and total power are derived. The use of
the generalized Dirac-Pauli equation also enables us to consider the $SL\nu$ in
matter polarized under the influence of strong magnetic field. | hep-ph |
A semi-analytic method to compute Feynman integrals applied to four-loop
corrections to the $\overline{\rm MS}$-pole quark mass relation: We describe a method to numerically compute multi-loop integrals, depending
on one dimensionless parameter $x$ and the dimension $d$, in the whole
kinematic range of $x$. The method is based on differential equations, which,
however, do not require any special form, and series expansions around singular
and regular points. This method provides results well suited for fast numerical
evaluation and sufficiently precise for phenomenological applications. We apply
the approach to four-loop on-shell integrals and compute the coefficient
function of eight colour structures in the relation between the mass of a heavy
quark defined in the $\overline{\rm MS}$ and the on-shell scheme allowing for a
second non-zero quark mass. We also obtain analytic results for these eight
coefficient functions in terms of harmonic polylogarithms and iterated
integrals. This allows for a validation of the numerical accuracy. | hep-ph |
Diquarks and antiquarks in exotics: a menage a trois and a menage a
quatre: A menage a trois is very different from an ordinary family. Similarly, exotic
hadrons with both qq and qbar q pairs have important color-space correlations
that are completely absent in ordinary mesons and baryons. The presence of both
types of pairs requires attention to the basic QCD physics that the q qbar
interaction is much stronger than the qq interaction. This new physics in
multiquark systems produces color structures totally different from those of
normal hadrons, for example the ud system is utterly unlike the ud diquark in
the uds Lambda baryon. The color-space correlations produce unusual
experimental properties in tetraquarks with heavy quark pairs which may be
relevant for newly discovered mesons like the X(3872) resonance. Tetraquark
masses can be below the two-meson threshold for sufficiently high quark masses.
A simple model calculation shows the b q bbar ubar and b q cbar qbar
tetraquarks below the B Bbar and B Dbar thresholds. Some of these states have
exotic electric charge and their decays might have striking signatures
involving monoenergetic photons and/or pions. | hep-ph |
Spatial densities of momentum and forces in spin-one hadrons: Densities associated with the energy-momentum tensor are calculated for
spin-one targets. These calculations are done in a light front formalism, which
accounts for relativistic effects due to boosts and allows for arbitrary
spatial localization of the target. These densities include the distribution of
momentum, angular momentum, and pressures over a two-dimensional plane
transverse to the light front. Results are obtained for both longitudinally and
transversely polarized targets, and the formalism is tailored to allow the
possibility of massless targets. The momentum density and pressure
distributions are calculated for a deuteron target in a light cone convolution
model, with which the properties of this model (such as helicity dependence of
the densities) is illustrated. | hep-ph |
Non-Hermitian Perturbations to the Fritzsch Textures of Lepton and Quark
Mass Matrices: We show that non-Hermitian and nearest-neighbor-interacting perturbations to
the Fritzsch textures of lepton and quark mass matrices can make both of them
fit current experimental data very well. In particular, we obtain \theta_{23}
\simeq 45^\circ for the atmospheric neutrino mixing angle and predict
\theta_{13} \simeq 3^\circ to 6^\circ for the smallest neutrino mixing angle
when the perturbations in the lepton sector are at the 20% level. The same
level of perturbations is required in the quark sector, where the Jarlskog
invariant of CP violation is about 3.7 \times 10^{-5}. In comparison, the
strength of leptonic CP violation is possible to reach about 1.5 \times 10^{-2}
in neutrino oscillations. | hep-ph |
NLO Corrections to Heavy Quark Production with Polarized Beams: We present a calculation of the NLO QCD corrections to heavy flavor
photoproduction with longitudinally polarized beams. We apply our results to
study the spin asymmetry for total charm quark production which will be used
for a first direct determination of Delta g by the COMPASS experiment. We also
briefly discuss the main theoretical uncertainties inherent in this
calculation. | hep-ph |
Probing wrong-sign Yukawa couplings at the LHC and a future linear
collider: We consider the two-Higgs-doublet model as a framework in which to evaluate
the viability of scenarios in which the sign of the coupling of the observed
Higgs boson to down-type fermions (in particular, $b$-quark pairs) is opposite
to that of the Standard Model (SM), while at the same time all other tree-level
couplings are close to the SM values. We show that, whereas such a scenario is
consistent with current LHC observations, both future running at the LHC and a
future $e^+ e^-$ linear collider could determine the sign of the Higgs coupling
to $b$-quark pairs. Discrimination is possible for two reasons. First, the
interference between the $b$-quark and the $t$-quark loop contributions to the
$ggh$ coupling changes sign. Second, the charged-Higgs loop contribution to the
$\gamma \gamma h$ coupling is large and fairly constant up to the largest
charged-Higgs mass allowed by tree-level unitarity bounds when the $b$-quark
Yukawa coupling has the opposite sign from that of the SM (the change in sign
of the interference terms between the $b$-quark loop and the $W$ and $t$ loops
having negligible impact). | hep-ph |
Strongly interacting matter from holographic QCD model: We introduce the 5-dimension dynamical holographic QCD model, which is
constructed in the graviton-dilaton-scalar framework with the dilaton
background field $\Phi$ and the scalar field $X$ responsible for the
gluodynamics and chiral dynamics, respectively. We review our results on the
hadron spectra including the glueball and light meson spectra, QCD phase
transitions and transport properties in the framework of the dynamical
holographic QCD model. | hep-ph |
Twist-4 Matrix Elements of the Nucleon from Recent DIS Data at CERN and
SLAC: We analyse the recent precision measurements of the lepton-hadron deep
inelastic scattering at CERN and SLAC to extract model independent constraints
among the nucleon matrix elements of the twist-4 operators. We also study a
parameterization of these matrix elements and point out the possibility that
the matrix elements of the quark-gluon mixed operator has a negative value of
the order of $- (400 \pm 100\ {\rm MeV})^2$ at 5 GeV$^2$ renormalization scale. | hep-ph |
Holographic Picture of Heavy Vector Meson Melting: The fraction of heavy vector mesons produced in a heavy ion collision, as
compared to a proton proton collision, serves as an important indication of the
formation of a thermal medium, the quark gluon plasma. This sort of analysis
strongly depends on understanding the thermal effects of a medium like the
plasma on the states of heavy mesons. In particular, it is crucial to know the
temperature ranges where they undergo a thermal dissociation, or melting.
AdS/QCD models are know to provide an important tool for the calculation of
hadronic masses, but in general are not consistent with the observation that
decay constants of heavy vector mesons decrease with excitation level. It has
recently been shown that this problem can be overcome using a soft wall
background and introducing an extra energy parameter, through the calculation
of correlation functions at a finite position of anti-de Sitter space. This
approach leads to the evaluation of masses and decay constants of S wave
quarkonium states with just one flavor dependent and one flavor independent
parameters. Here we extend this more realistic model to finite temperatures and
analyse the thermal behavior of the states $1S, 2S$ and $ 3S$ of bottomonium
and charmonium. The corresponding spectral function exhibits a consistent
picture for the melting of the states where, for each flavor, the higher
excitations melt at lower temperatures. We estimate for these six states, the
energy ranges in which the heavy vector mesons undergo a transition from a well
defined peak in the spectral function to complete melting in the thermal
medium. A very clear distinction between the heavy flavors emerges, with
bottomonium state $\Upsilon (1S)$ surviving deconfinemet transition at
temperatures much larger than the critical deconfinement temperature of the
medium. | hep-ph |
Running Flavor Number and Asymptotic Freedom in the Normal Phase of QED: In the normal phase (where no dynamical fermion mass generation occurs) of
the D-dimensional quantum electrodynamics with $N_f$ flavors of fermions, we
derive an integral equation which should be satisfied by (the inverse of) the
wave function renormalization of the fermion in the Landau gauge. For this we
use the inverse Landau-Khalatnikov transformation connecting the nonlocal gauge
with the Landau gauge. This leads to a similar equation for the running flavor
number in the framework of the $1/N_f$ resumed Schwinger-Dyson equation.
Solving the equation analytically and numerically, we study the infrared
behavior and the critical exponent of the 3-dimensional QED (QED$_3$). This
confirms that the flavor number in QED$_3$ runs according to the $\beta$
function which is consistent with the asymptotic freedom as that in
4-dimensional QCD. | hep-ph |
Quantitative Study of Geometrical Scaling in Deep Inelastic Scattering
at HERA: We propose a method to assess the quality of geometrical scaling in Deep
Inelastic Scattering and apply it to the combined HERA data on $\gamma^{\ast}p$
cross-section. Using two different approaches based on Bjorken $x$ binning and
binning in $\gamma^{\ast}p$ scattering energy $W$, we show that geometrical
scaling in variable $\tau\sim Q^{2} x^{\lambda}$ works well up to Bjorken $x$'s
0.1. The corresponding value of exponent $\lambda$ is 0.32 -- 0.34. | hep-ph |
Bounds on the Higgs-Boson Mass in the Presence of Non-Standard
Interactions: The triviality and vacuum stability bounds on the Higgs-boson mass are
revisited in the presence of new interactions parameterized in a
model-independent way by an effective lagrangian. When the scale of new physics
is below 50 TeV the triviality bound is unchanged but the stability lower bound
is increased by 40-60 GeV. Should the Higgs-boson mass be close to its current
lower experimental limit, this leads to the possibility of new physics at the
scale of a few TeV, even for modest values of the effective lagrangian
parameters. | hep-ph |
The New Pentaquarks in the Diquark Model: Pentaquark baryons are a natural expectation of an extended picture of
hadrons where quarks and diquarks are the fundamental units. The parity/mass
pattern observed, when compared to that of exotic mesons, appears as the
footprint of a compact five-quark structure. What has been learned from the
X,Y,Z phenomenology informs about the newly found pentaquark structure and
suggests further experimental tests and directions to be explored. | hep-ph |
Heavy-Quark Mass and Heavy-Meson Decay Constants from QCD Sum Rules: We present a sum-rule extraction of heavy-meson decay constants from the
two-point correlator of heavy-light pseudoscalar currents. Our main concern is
to control the uncertainties of the decay constants, induced by both input QCD
parameters and limited accuracy of the sum-rule method. Gaining this control is
possible by applying our novel procedure for the extraction of hadron
observables utilizing Borel-parameter-depending dual thresholds. For the
charmed mesons, we obtain f_D = 206.2 \pm 7.3 (OPE) \pm 5.1 (syst) MeV and
f_{D_s} = 245.3 \pm 15.7 (OPE) \pm 4.5 (syst) MeV. For the beauty mesons, the
decay constants prove to be extremely sensitive to the exact value of the
b-quark MS-bar mass m_b(m_b). Matching our sum-rule prediction for f_B to the
lattice findings, the very accurate b-mass value m_b(m_b) = 4.245 \pm 0.025 GeV
is found, which yields f_B = 193.4 \pm 12.3 (OPE) \pm 4.3 (syst) MeV and
f_{B_s} = 232.5 \pm 18.6 (OPE) \pm 2.4 (syst) MeV. | hep-ph |
A Consistent Scenario for B to PS Decays: We consider B to PS decays where P stands for pseudoscalar and S for a heavy
(~1500 MeV) scalar meson. We achieve agreement with available experimental data
-- which includes a two orders of magnitude hierarchy -- assuming the scalars
mesons are two quark states. The contribution of the dipolar penguin operator
O_{11} is quantified. | hep-ph |
Structure of the sigma meson and the softening: We study the structure of the sigma meson, the lowest-lying resonance of the
pi pi scattering in the scalar-isoscalar channel, through the softening
phenomena associated with the partial restoration of chiral symmetry. We build
dynamical chiral models to describe the pi pi scattering amplitude, in which
the sigma meson is described either as the chiral partner of the pion or as the
dynamically generated resonance through the pi pi attraction. It is shown that
the internal structure is reflected in the softening phenomena; the softening
pattern of the dynamically generated sigma meson is qualitatively different
from the behavior of the chiral partner of the pion. On the other hand, in the
symmetry restoration limit, the dynamically generated sigma meson behaves
similarly to the chiral partner. | hep-ph |
Search for muon-philic new light gauge boson at Belle II: Motivated by the long-lasting $3.5\sigma$ discrepancy in the anomalous
magnetic moment of muon, we consider a new muon-specific force mediated by a
light gauge boson, $X$, with mass $m_X < 2m_\mu$ and the coupling constant $g_X
\sim (10^{-4}, 10^{-3})$. We show that the Belle~II experiment has a robust
chance to probe such a light boson in $e^+ e^- \to \mu^+ \mu^- + X$ channel and
cover the most interesting parameter space explaining the discrepancy with the
planned target luminosity, $\int dt \ {\cal L}=50~{\rm ab^{-1}}$. The clean
signal of muon-pair plus missing energy at Belle II can be a smoking gun for
the new gauge boson. We expect that the (invisibly decaying) muon-philic light
($m_X \leq 2 m_\mu$) gauge boson can be probed down to $g_X \geq 1.5 \times
10^{-4} \ (4.6 \times 10^{-4}, \ 2.3 \times 10^{-4})$ for 50 (1, 10)
ab${}^{-1}$ search. | hep-ph |
Selected Topics in Rapidity Gap Physics: This talk will review selected topics in rapidity gap physics. In particular
I will discuss diffractive jet production and the possibility of searching for
the higgs boson using diffraction at the LHC; the dipole picture of diffraction
and saturation; and those processes where a large momentum is transferred
across the rapidity gap, for which there has been recent progress both
experimentally and theoretically. | hep-ph |
On the Higher Moments of Particle Multiplicity, Chemical Freeze-Out and
QCD Critical Endpoint: We calculate the first six non-normalized moments of particle multiplicity
within the framework of the hadron resonance gas model. In terms of the lower
order moments and corresponding correlation functions, general expressions of
higher order moments are derived. Thermal evolution of the first four
normalized moments and their products (ratios) are studied at different
chemical potentials {\mu}, so that it is possible to evaluate them at chemical
freeze out curve. It is found that a non-monotonic behavior, reflecting the
dynamical fluctuation and strong correlation of particles starts to appear from
the normalized third order moment. We introduce novel conditions for describing
the chemical freeze out curve. Although the hadron resonance gas model does not
contain any information on the criticality related to the chiral dynamics and
singularity in some physical observables, we are able find out the location of
the QCD critical endpoint at $\mu\sim 350 $MeV and temperature $T \sim 162
$MeV. | hep-ph |
TMD evolution of the Sivers asymmetry: The energy scale dependence of the Sivers asymmetry in semi-inclusive deep
inelastic scattering is studied numerically within the framework of TMD
factorization that was put forward in 2011. The comparison to previous results
in the literature shows that the treatment of next-to-leading logarithmic
effects is important for the fall-off of the Sivers asymmetry with energy in
the measurable regime. The TMD factorization based approach indicates that the
peak of the Sivers asymmetry falls off with energy scale Q to good
approximation as 1/Q^{0.7}, somewhat faster than found previously based on the
first TMD factorization expressions by Collins and Soper in 1981. It is found
that the peak of the asymmetry moves rather slowly towards higher transverse
momentum values as $Q$ increases, which may be due to the absence of
perturbative tails of the TMDs in the presented treatments. We conclude that
the behavior of the peak of the asymmetry as a function of energy {\it and}
transverse momentum allows for valuable tests of the TMD formalism and the
considered approximations. To confront the TMD approach with experiment, high
energy experimental data from an Electron-Ion Collider is required. | hep-ph |
Mass and CKM Matrices of Quarks and Leptons, the Leptonic CP-phase in
neutrino oscillations: A general approach for construction of quark and lepton mass matrices is
formulated. The hierarchy of quarks and charged leptons ("electrons") is large,
it leads using the experimental values of mixing angles to the hierarchical
mass matrix slightly deviating from one's suggested earlier by Stech and
including naturally the CP-phase.
The same method based on the rotation of generation numbers in the diagonal
mass matrix is used in the electron-neutrino sector of theory, where neutrino
mass matrix is determined by the Majorano see-saw approach. The hierarchy of
neutrino masses, much smaller than for quarks, was used including all existing
(even preliminary) experimental data on neutrinos mixing.
The leptonic mass matrix found in this way includes not known value of the
leptonic CP-phase. It leads to a large $\nu_\mu \nu_\tau$ oscillations and
suppresses the $\nu_e\nu_\tau$ and also $\nu_e \nu_\mu$ oscillations. The
explicit expressions for the probabilities of neutrino oscillation were
obtained in order to specify the role of leptonic CP-phase. The value of time
reversal effect (proportional to $\sin\delta'$) was found to be small $\sim
1%$. However, a dependence of the values of $\nu_e \nu_\mu, \nu_e \nu_\tau$
transition probabilities, averaged over oscillations, on the leptonic CP-phase
has found to be not small - of order of tens percent. | hep-ph |
Ratios of Fluctuation Observables in the Search for the QCD Critical
Point: The QCD critical point can be found in heavy ion collision experiments via
the non-monotonic behavior of many fluctuation observables as a function of the
collision energy. The event-by-event fluctuations of various particle
multiplicities are enhanced in those collisions that freeze out near the
critical point. Higher, non-Gaussian, moments of the event-by-event
distributions of such observables are particularly sensitive to critical
fluctuations, since their magnitude depends on the critical correlation length
to a high power. We present quantitative estimates of the contribution of
critical fluctuations to the third and fourth moments of the pion and proton,
as well as estimates of various measures of pion-proton correlations, all as a
function of the same five non-universal parameters. We show how to use
nontrivial but parameter independent ratios among these more than a dozen
fluctuation observables to discover the critical point. We also construct
ratios that, if the critical point is found, can be used to overconstrain the
values of the non-universal parameters. | hep-ph |
Probing feebly interacting dark matter with monojet searches: Dark matter may consist of feebly interacting massive particles (FIMPs) that
never thermalized with the cosmic plasma. Their relic density is achieved via
freeze-in for a wide range of masses, significantly expanding the model space
that can be tested compared to other production mechanisms. However, testing
the tiny couplings required by freeze-in is challenging. We show that FIMPs can
be probed by LHC searches for new physics in mono-jet events with large missing
energy. We study a $Z'$ portal model in which gluon annihilation produces FIMPs
in the early universe and today at colliders. Monojet searches by LHC Run 3
might discover new physics accounted for by FIMPs with mass in the MeV-TeV
range. | hep-ph |
Pentaquark Magnetic Moments In Different Models: We calculate the magnetic moments of the pentaquark states from different
models and compare our results with predictions of other groups. | hep-ph |
Fermion dispersion in axion medium: The interaction of a fermion with the dense axion medium is investigated for
the purpose of finding an axion medium effect on the fermion dispersion. It is
shown that axion medium influence on the fermion dispersion under astrophysical
conditions is negligible small if the correct Lagrangian of the axion-fermion
interaction is used. | hep-ph |
Cerenkov radiation by neutrinos in a supernova core: Neutrinos with a magnetic dipole moment propagating in a medium with a
velocity larger than the phase velocity of light emit photons by the Cerenkov
process. The Cerenkov radiation is a helicity flip process via which a
left-handed neutrino in a supernova core may change into a sterile right-handed
one and free-stream out of the core. Assuming that the luminosity of such
sterile right-handed neutrinos is less than $10^{53}$ ergs/sec gives an upper
bound on the neutrino magnetic dipole moment $\mu_\nu < 0.2 \times 10^{-13}
\mu_B$. This is two orders of magnitude more stringent than the previously
established bounds on $\mu_\nu$ from considerations of supernova cooling rate
by right-handed neutrinos. | hep-ph |
The same-sign top probe for baryon number violation at the LHC: Despite strong experimental evidences for their conservation at low energies,
the baryon $B$ and lepton $L$ numbers are not expected to be absolute
symmetries. Already violated in the Standard Model (SM) by non-perturbative
effects (tiny at low temperatures and energies) and not justified by any
fundamental principle, $B$ and $L$ appear naturally violated in beyond the
Standard Model (BSM) scenarios, e.g. in supersymmetry (SUSY). The fact that any
violation remained unobserved at low energies can nonetheless be explained,
without pushing the associated characteristic sale beyond the TeV, by using SM
flavour symmetries implemented BSM thanks to the Minimal Flavour Violation
(MFV) prescription. Violation effects could therefore be observable at the LHC.
Same-sign (anti-)tops, sometimes leading to a distinctive predominance of
negatively charged lepton pairs over positively charged ones, is a clean
signature that is for instance generically present in R-parity violating
supersymmetry. | hep-ph |
Sphaleron portal baryogenesis: Nontrivial topological vacua of non-Abelian gauge symmetry $SU(3)\times
SU(2)_{L}$ of the Standard Model play an important role in baryogenesis. In
particular, the baryon (and lepton) number violation from $SU(2)_{L}$ sphaleron
is a crucial ingredient for baryogenesis at weak scale or higher. In this work,
we point out that generically, a baryon asymmetry is induced by an asymmetry
generated in the new sector through strong $SU(3)$ and/or weak $SU(2)_{L}$
sphaleron portals and vice versa. In the standard radiation-dominated early
Universe, due to phenomenological constraints, the sphaleron portal
baryogenesis has to take place at cosmic temperature $T\gtrsim10^{6}-10^{8}$
GeV together with a $(B-L)$-violating source. As an example, we show an
explicit model where strong sphaleron portal baryogenesis occurs at the scale
of Peccei-Quinn breaking to solve the strong CP problem and this coincides
nicely with the scale where the Weinberg operator responsible for Majorana
neutrino mass is in equilibrium. | hep-ph |
Flavor Changing Supersymmetry Interactions in a Supernova: We consider for the first time R-parity violating interactions of the Minimal
Standard Supersymmetric Model involving neutrinos and quarks (``flavor changing
neutral currents'', FCNC's) in the infall stage of stellar collapse. Our
considerations extend to other kinds of flavor changing neutrino reactions as
well. We examine non-forward neutrino scattering processes on heavy nuclei and
free nucleons in the supernova core. This investigation has led to four
principal original discoveries/products: (1) first calculation of neutrino
flavor changing cross sections for spin one half (e.g. free nucleon) and spin
zero nuclear targets; (2) discovery of nuclear mass number squared (A squared)
coherent amplification of neutrino-quark FCNC's; (3) analysis of FCNC-induced
alteration of electron capture and weak/nuclear equilibrium in the collapsing
core; and (4) generalization of the calculated cross sections (mentioned in 1)
for the case of hot heavy nuclei to be used in collapse/supernova and neutrino
transport simulations. The scattering processes that we consider allow electron
neutrinos to change flavor during core collapse, thereby opening holes in the
electron neutrino sea, which allows electron capture to proceed and results in
a lower core electron fraction. A lower electron fraction implies a lower
homologous core mass, a lower shock energy, and a greater nuclear
photo-disintegration burden for the shock. In addition, unlike the standard
supernova model, the core now could have net muon and/or tau lepton numbers.
These effects could be significant even for supersymmetric couplings below
current experimental bounds. | hep-ph |
Radiation reaction and limiting acceleration: We investigate the strong acceleration properties of the radiation reaction
force and identify a new and promising limiting acceleration feature in the
Eliezer-Ford-O'Connell model; in the strong field regime, for many field
configurations, we find an upper limit to acceleration resulting in a bound to
the rate of radiation emission. If this model applies, strongly accelerated
particles are losing energy at a much slower pace than predicted by the usual
radiation reaction benchmark, the Landau-Lifshitz equation, which certainly
cannot be used in this regime. We explore examples involving various "constant"
electromagnetic field configurations and study particle motion in a light plane
wave as well as in a material medium. | hep-ph |
Comment on "Chiral symmetry and the intrinsic structure of the nucleon"-
by D.B.Leinweber,A.W.Thomas and R.D.Young: Some remarks are presented on a recent paper (Leinweber,Thomas and Young,
Phys.Rev.Lett. 86, 5011, 2001). In particular a statement of the above paper on
the fact that the ratio between the magnetic moments of proton and neutron
should remain constant at -3/2, independent of the change of the quark mass is
discussed on the basis of the general parameterization. | hep-ph |
Supersymmetric Models in Light of Improved Higgs Mass Calculations: We discuss the parameter spaces of supersymmetry (SUSY) scenarios taking into
account the improved Higgs-mass prediction provided by FeynHiggs 2.14.1. Among
other improvements, this prediction incorporates three-loop
renormalization-group effects and two-loop threshold corrections, and can
accommodate three separate mass scales: m_{\tilde q} (for squarks), m_{\tilde
g} (for gluinos) and m_{\tilde\chi} (for electroweakinos). Furthermore, it
contains an improved treatment of the DRbar scalar top parameters avoiding
problems with the conversion to on-shell parameters, that yields more accurate
results for large SUSY-breaking scales. We first consider the CMSSM, in which
the soft SUSY-breaking parameters m_0 and m_{1/2} are universal at the GUT
scale, and then sub-GUT models in which universality is imposed at some lower
scale. In both cases, we consider the constraints from the Higgs-boson mass M_h
in the bulk of the (m_0, m_{1/2}) plane and also along stop coannihilation
strips where sparticle masses may extend into the multi-TeV range. We then
consider the minimal anomaly-mediated SUSY-breaking (mAMSB) scenario, in which
large sparticle masses are generic. In all these scenarios the substantial
improvements between the calculations of M_h in FeynHiggs 2.14.1 and FeynHiggs
2.10.0, which was used in an earlier study, change significantly the preferred
portions of the models' parameter spaces. Finally, we consider the pMSSM11, in
which sparticle masses may be significantly smaller and we find only small
changes in the preferred regions of parameter space. | hep-ph |
The Suppression of Neutralino Annihilation into Zh: The Indirect Detection of neutralino Dark Matter is most promising through
annihilation channels producing a hard energy spectrum for the detected
particles, such as the neutralino annihilation into $Zh$. A cancellation
however makes this particular annihilation channel generically subdominant in
the huge parameter space of supersymmetric models. This cancellation requires
non-trivial relations between neutralino mixings and masses, which we derive
from gauge independence and unitarity of the MSSM. To show how the cancellation
overshoots leaving only a subdominant result, we use a perturbative expansion
in powers of the electroweak/supersymmetry breaking ratio $m_{Z}/m_{\chi}$. | hep-ph |
The rare decays of D mesons: The flavor changing transitions in the c->u gamma, c->u gamma gamma and c->u
l+ l- offer the possibility to search for new physics in the charm sector. We
investigate dominant decay mechanisms in the radiative decays D->V gamma,
D->P(V) l+ l-, D->gamma gamma and we discuss chances to see physics beyond the
standard model in these decays. In addition, we analyze Cabibbo allowed D->K pi
gamma decays with nonresonant K pi, and we probe the role of light vector
mesons in these decays. | hep-ph |
The high-energy radiation pattern from BFKLex with double-log collinear
contributions: We study high-energy jet production in the multi-Regge limit making use of
the Monte Carlo event generator BFKLex which includes collinear improvements in
the form of double-log contributions as presented in [1]. Making use of the
anti-kt jet algorithm in the FastJet implementation, we present results for the
average transverse momentum and azimuthal angle of the produced jets when two
tagged forward/backward jets are present in the final state. We also introduce
a new observable which accounts for the average rapidity separation among
subsequent emissions. Results are presented, for comparison, at leading order
and next-to-leading order, with the resummation of collinear double logs
proposed in [2]. | hep-ph |
Charmless hadronic $B_c \to VA, AA$ decays in the perturbative QCD
approach: In this work, we calculate the branching ratios (BRs) and the polarization
fractions of sixty two charmless two-body $B_c$ meson decays into final states
involving one vector and one axial-vector meson ($VA$) or two axial-vector
mesons($AA$) within the framework of perturbative QCD (pQCD) approach
systematically, where $A$ is either a $^3P_1$ or $^1P_1$ axial-vector meson.
All considered decay channels can only occur through the annihilation
topologies in the standard model. Based on the perturbative calculations and
phenomenological analysis, we find the following results: (i) the CP-averaged
BRs of the considered sixty two $B_c$ decays are in the range of $10^{-5}$ to
$10^{-9}$; (ii) since the behavior for $^1P_1$ meson is much different from
that of $^3P_1$ meson, the BRs of $B_c \to A(^1P_1) (V, A(^1P_1))$ decays are
generally larger than that of $B_c \to A(^3P_1) (V, A(^3P_1))$ decays in the
pQCD approach; (iii) many considered decays modes, such as $B_c\to a_1(1260)^+
\omega$, $b_1(1235) \rho$, etc, have sizable BRs within the reach of the LHCb
experiments; (iv) the longitudinal polarization fractions of most considered
decays are large and play the dominant role; (v) the pQCD predictions for
several decays involving mixtures of $^3P_1$ and/or $^1P_1$ mesons are highly
sensitive to the values of the mixing angles, which will be tested by the
ongoing LHC and forthcoming Super-B experiments; (vi) the CP-violating
asymmetries of these considered $B_c$ decays are absent in the standard model
because only one type tree operator is involved. | hep-ph |
Shooting String Holography of Jet Quenching at RHIC and LHC: We derive a new formula for jet energy loss using finite endpoint momentum
shooting strings initial conditions in SYM plasmas to overcome the difficulties
of previous falling string holographic scenarios. We apply the new formula to
compute the nuclear modification factor RAA and the elliptic flow parameter v2
of light hadrons at RHIC and LHC. We show furthermore that Gauss-Bonnet
quadratic curvature corrections to the AdS5 geometry improve the agreement with
the recent data. | hep-ph |
Non-linear evolution in QCD at high-energy beyond leading order: The next-to-leading order (NLO) Balitsky-Kovchegov (BK) equation describing
the high-energy evolution of the scattering between a dilute projectile and a
dense target suffers from instabilities unless it is supplemented by a proper
resummation of the radiative corrections enhanced by (anti-)collinear
logarithms. Earlier studies have shown that if one expresses the evolution in
terms of the rapidity of the dilute projectile, the dominant anti-collinear
contributions can be resummed to all orders. However, in applications to
physics, the results must be re-expressed in terms of the rapidity of the dense
target. We show that although they lead to stable evolution equations,
resummations expressed in the rapidity of the dilute projectile show a strong,
unwanted, scheme dependence when their results are translated in terms of the
target rapidity. Instead, in this paper, we work directly in the rapidity of
the dense target where anti-collinear contributions are absent but where new,
collinear, instabilities arise. These are milder since disfavoured by the
typical BK evolution. We propose several prescriptions for resumming these new
double logarithms and find only little scheme dependence. The resummed
equations are non-local in rapidity and can be extended to full NLO accuracy. | hep-ph |
Branching Fractions and Direct CP Violation in Charmless Three-body
Decays of B Mesons: Charmless three-body decays of B mesons is studied using a simple model based
on the framework of the factorization approach. Hadronic three-body decays
receive both resonant and nonresonant contributions. Dominant nonresonant
contributions to tree-dominated three-body decays arise from the $b\to u$ tree
transition which can be evaluated using heavy meson chiral perturbation theory
valid in the soft meson limit. For penguin-dominated decays, nonresonant
signals come mainly from the penguin amplitude governed by the matrix elements
of scalar densities $<M_1M_2|\bar q_1 q_2|0>$. We use the measurements of $\bar
B^0\to K_SK_SK_S$ to constrain the nonresonant component of $<K\bar K|\bar
ss|0>$. The intermediate vector meson contributions to three-body decays are
identified through the vector current, while the scalar meson resonances are
mainly associated with the scalar density. While the calculated direct CP
violation in $B^-\to K^+K^-K^-$ and $B^-\to \pi^+\pi^-\pi^-$ decays agrees well
with experiment in both magnitude and sign, the predicted CP asymmetries in
$B^-\to \pi^- K^+K^-$ and $B^-\to K^-\pi^+\pi^-$ are wrong in signs when
confronted with experiment. It has been conjectured recently that a possible
resolution to this CP puzzle may rely on final-state rescattering of
$\pi^+\pi^-$ and $K^+K^-$. Assuming a large strong phase associated with the
matrix element $<K\pi|\bar sq|0>$ arising from some sort of power corrections,
we fit it to the data of $K^-\pi^+\pi^-$ and find a correct sign for $\pi^-
K^+K^-$. | hep-ph |
A Three-Flavor Chiral Effective Model with Four Baryonic Multiplets
within the Mirror Assignment: In the case of three quark flavors, (pseudo)scalar diquarks transform as
antiquarks under chiral transformations. We construct four spin-1/2 baryonic
multiplets from left- and right-handed quarks as well as left- and right-handed
diquarks. The fact that two of these multiplets transform in a "mirror" way
allows for chirally invariant mass terms. We then embed these baryonic
multiplets into the Lagrangian of the so-called extended Linear Sigma Model,
which features (pseudo)scalar and (axial-)vector mesons, as well as glueballs.
Reducing the Lagrangian to the two-flavor case, we obtain four doublets of
nucleonic states. These mix to produce four experimentally observed states with
definite parity: the positive-parity nucleon $N(939)$ and Roper resonance
$N(1440)$, as well as the negative-parity resonances $N(1535)$ and $N(1650)$.
We determine the parameters of the nucleonic part of the Lagrangian from a fit
to masses and decay properties of the aforementioned states. Studying the limit
of vanishing quark condensate, we conclude that $N(939)$ and $N(1535)$, as well
as $N(1440)$ and $N(1650)$ form pairs of chiral partners. | hep-ph |
Two-loop Calculation of Higgs Mass in Gauge-Higgs Unification: 5D
Massless QED Compactified on S^1: We calculate the quantum corrections to the mass of the zero mode of the
fifth component of the gauge field at two-loop level in a five dimensional
massless QED compactified on S^1. We discuss in detail how the divergences are
exactly canceled and the mass becomes finite. The key ingredients to obtain the
result are the five dimensional gauge invariance and the Ward-Takahashi
identity. We also evaluate the finite part of corrections. | hep-ph |
Baryon deceleration by strong chromofields in ultrarelativistic nuclear
collisions: It is assumed that strong chromofields are generated at early stages of
ultrarelativistic heavy-ion collisions which give rise to a collective
deceleration of net baryons from colliding nuclei. We have solved classical
equations of motion for baryonic slabs under the action of a time-dependent
longitudinal chromoelectric field. It is demonstrated that the slab final
rapidities are rather sensitive to the strength and decay time of the
chromofield as well as to the back reaction of the produced partonic plasma.
The net-baryon rapidity loss of about 2 units, found for most central Au-Au
collisions at RHIC, can be explained by the action of chromofields with the
initial energy density of about 50 GeV/fm^3. Predictions for the baryon
stopping at the LHC are made. | hep-ph |
LHC diboson excesses as an evidence for a heavy WW resonance: Recently reported diboson excesses at LHC are interpreted to be connected
with heavy $WW$ resonance with weak isotopic spin 2. The resonance appears due
to the wouldbe anomalous triple interaction of the weak bosons, which is
defined by well-known coupling constant $\lambda$. We obtain estimates for the
effect, which qualitatively agree with ATLAS data. Effects are predicted in
inclusive production of $W^+W^+, W^+ (Z,\gamma), W^+ W^-, (Z,\gamma)
(Z,\gamma), W^- (Z,\gamma), W^-W^-$ resonances with $M_R \simeq 2\,TeV$, which
could be reliably checked at the upgraded LHC with $\sqrt{s}\,=\,13 TeV$. In
the framework of an approach to the spontaneous generation of of the triple
anomalous interaction its coupling constant is estimated to be $\lambda =
-\,0.017\pm 0.005$ in an agreement with existing restrictions. | hep-ph |
Anomalous Gauge Interactions of the Higgs Boson: Precision Constraints
and Weak Boson Scatterings: Interaction of Higgs scalar (H) with weak gauge bosons (V=W,Z) is the {\it
key} to understand electroweak symmetry breaking (EWSB) mechanism. New physics
effects in the HVV interactions, as predicted by models of compositeness,
supersymmetry and extra dimensions, can be formulated as anomalous couplings
via a generic effective Lagrangian. We first show that the existing electroweak
precision data already impose nontrivial indirect constraints on the anomalous
HVV couplings. Then, we systematically study VV --> VV scatterings in the TeV
region, via Gold-plated pure leptonic decay modes of the weak bosons. We
demonstrate that, even for a light Higgs boson in the mass range 115GeV < m_H <
300GeV, this process can directly probe the anomalous HVV interactions at the
LHC with an integrated luminosity of 300fb^{-1}, which further supports the
``No-Lose'' theorem for the LHC to uncover the EWSB mechanism. Comparisons with
the constraints from measuring the cross section of VH associate production and
the Higgs boson decay width are also given. | hep-ph |
WPHACT 1.0 - A program for $WW$, Higgs and 4 fermion physics at $e^+
e^-$ colliders: WPHACT (W W and Higgs Physics with PHACT) is a MC program and unweighted
event generator which computes all Standard Model processes with four fermion
in the final state at $e^+ e^-$ colliders. It is based on an helicity amplitude
method which allows precise and fast evaluations of the matrix elements both
for massless and massive fermions. Fermion masses for $b$ quarks are exactly
taken into account. QED initial state and Coulomb corrections are evaluated,
while QCD final state corrections are included in an approximate formulation.
Cuts can be easily introduced and distributions for any variable at parton
level can be implemented. The contributions to the processes of neutral
Standard Model or Susy Higgs can be included. Anomalous couplings effects for
the triple coupling can be computed. An interface to hadronization is provided
and Jetset can be directly called from the program. | hep-ph |
Light mesons production at the Tevatron to next-to-leading order: Inclusive production of light mesons ($\pi^0$, $\eta$, $\pi^{\pm}$, $K^{\pm}$
) at the Tevatron is considered in QCD to next-to-leading order in the
formalism of fragmentation functions. We present various distributions of
phenomenological interest, along with a new set of $K$ mesons fragmentation
functions. | hep-ph |
Improving the Effective Potential, Multi-Mass Problem and Modified
Mass-Dependent Scheme: We present a new procedure for improving the effective potential by using
renormalization group equation (RGE) in the presence of several mass scales. We
propose a modification of the mass-dependent (MD) renormalization scheme, MDbar
scheme, so that the scalar mass parameter runs at most logarithmically on the
one hand and the decoupling of heavy particles is naturally incorporated in the
RGE's on the other. Thanks to these properties, the procedure in MDbar scheme
turns out to be very simple compared with the regionwise procedure in MSbar
scheme proposed previously. The relation with other schemes is also discussed
both analytically and numerically. | hep-ph |
A quark model analysis of the Sivers function: We develop a formalism to evaluate the Sivers function. The approach is well
suited for calculations which use constituent quark models to describe the
structure of the nucleon. A non-relativistic reduction of the scheme is
performed and applied to the Isgur-Karl model of hadron structure. The results
obtained are consistent with a sizable Sivers effect and the signs for the u
and d flavor contributions turn out to be opposite. This pattern is in
agreement with the one found analyzing, in the same model, the impact parameter
dependent generalized parton distributions. The Burkardt Sum Rule turns out to
be fulfilled to a large extent. We estimate the QCD evolution of our results
from the momentum scale of the model to the experimental one and obtain
reasonable agreement with the available data. | hep-ph |
Searching for Ultralight Dark Matter Conversion in Solar Corona using
Low Frequency Array Data: Ultralight dark photons and axions are well-motivated hypothetical dark
matter candidates. Both dark photon dark matter and axion dark matter can
resonantly convert into electromagnetic waves in the solar corona when their
mass is equal to the solar plasma frequency. The resultant electromagnetic
waves appear as monochromatic signals within the radio-frequency range with an
energy equal to the dark matter mass, which can be detected via radio
telescopes for solar observations. Here we show our search for converted
monochromatic signals in the observational data collected by the
high-sensitivity Low Frequency Array (LOFAR) telescope and establish an upper
limit on the kinetic mixing coupling between dark photon dark matter and
photon, which can reach values as low as $10^{-13}$ within the frequency range
of $30-80$ MHz. This limit represents an improvement of approximately one order
of magnitude better than the existing constraint from the cosmic microwave
background observation. Additionally, we derive an upper limit on the
axion-photon coupling within the same frequency range, which is better than the
constraints from Light-Shining-through-a-Wall experiments while not exceeding
the CERN Axion Solar Telescope (CAST) experiment or other astrophysical bounds. | hep-ph |
Production of Isolated Photons in Deep Inelastic Scattering: We present here the predictions obtained from a calculation of the inclusive
isolated photon production cross section in deep inelastic scattering. The
results are compared with the cross section measurement of the ZEUS
collaboration and found in good agreement with all aspects of it. Furthermore,
a way of measuring the quark-to-photon fragmention function in DIS is also
briefly outlined. | hep-ph |
Soft-Wall Stabilization: We propose a general class of five-dimensional soft-wall models with AdS
metric near the ultraviolet brane and four-dimensional Poincar\'e invariance,
where the infrared scale is determined dynamically. A large UV/IR hierarchy can
be generated without any fine-tuning, thus solving the electroweak/Planck scale
hierarchy problem. Generically, the spectrum of fluctuations is discrete with a
level spacing (mass gap) provided by the inverse length of the wall, similar to
RS1 models with Standard Model fields propagating in the bulk. Moreover two
particularly interesting cases arise. They can describe: (a) a theory with a
continuous spectrum above the mass gap which can model unparticles
corresponding to operators of a CFT where the conformal symmetry is broken by a
mass gap, and; (b) a theory with a discrete spectrum provided by linear Regge
trajectories as in AdS/QCD models. | hep-ph |
A model of non-perturbative gluon emission in an initial state parton
shower: We consider a model of transverse momentum production in which
non-perturbative smearing takes place throughout the perturbative evolution, by
a simple modification to an initial state parton shower algorithm. Using this
as the important non-perturbative ingredient, we get a good fit to data over a
wide range of energy. Combining it with the non-perturbative masses and cutoffs
that are a feature of conventional parton showers also leads to a reasonable
fit. We discuss the extrapolation to the LHC. | hep-ph |
CP violation in $B \to φK$ decay and anomalous right-handed top
quark couplings: We explore the CP violation in $B \to \phi K$ decay processes in the presence
of the anomalous right-handed $\bar{t}sW$ and $\bar{t}bW$ couplings. The
complex anomalous top coupling can be a source of the new CP violation and lead
to a deviation of the observed weak phase in $B \to \phi K$ decays, which takes
account for the present disagreement of the observed $\sin 2 \beta$ between $B
\to J/\psi K$ and $B \to \phi K$ decays. The direct CP violation is also
predicted. | hep-ph |
Analyticity Properties and Unitarity Constraints of Heavy Meson Form
Factors: We derive new bounds on the b-number form factor $F(q^2)$ of the B meson.
(Revised version of hep-ph/9306214). | hep-ph |
Impact of axions on the Cassiopea A neutron star cooling: The observed anomalous steady decrease in surface temperature of the
supernova remnant Cassiopeia A (Cas A), which was reported about ten years ago,
has generated much debate. Several exotic cooling scenarios have been proposed
using non-standard assumptions about the physics and evolution of this neutron
star (NS). At present, significant corrections have been made to the
observational data, which make it possible to numerically simulate the Cas A NS
cooling process in the framework of the scenario of minimal neutrino cooling.
If there is an additional source of cooling, such as axion emission, the
steepness of the Cas A NS surface temperature drop will increase with the
growth of the axion-nucleon interaction strength. This makes it possible to
limit the minimum value of the axion decay constant $f_a$ using the condition
that the NS surface temperature should be within the 99% confidence interval
obtained from the observational data. Two types of axion models are considered:
the Kim-Shifman-Weinstein-Zakharov -- KSVZ model and the
Dean-Fischler-Srednitsky-Zhitnitsky --DFSZ model. The above criterion gives a
lower limit on the axion decay constant, $f_a>3\times 10^7$ GeV and
$f_a>4.5\times 10^8$ GeV for KSVZ and DFSZ axions, respectively. | hep-ph |
Effective theories with maximal analyticity: In this paper (second in the series) we study the properties of tree-level
binary amplitudes of the infinite-component effective field theory of strong
interaction obeying the requirements of quark-hadron duality and maximal
analyticity. In contrast to the previous paper, here we derive the results
following from less restrictive --- Regge-like --- boundedness conditions. We
develop the technique of Cauchy's forms in two variables and show the
string-like structure of a theory. Next, we derive the full set of bootstrap
constraints for the resonance parameters in (\pi,K) system. Numerical test
shows: (1) those constraints are consistent with data on well established
vector resonances; (2) two light broad resonances -- sigma- and kappa-mesons --
are needed to saturate sum rules following from Chiral symmetry and
analyticity. As a by-product we obtain expressions for the parameters of Chiral
expansions and give corresponding estimates. | hep-ph |
Color transparency in deeply inelastic diffraction: We suggest a simple physical picture for the diffractive parton distributions
that appear in diffractive deeply inelastic scattering. In this picture,
partons impinging on the proton can have any transverse separation, but only
when the separation is small can they penetrate the proton without breaking it
up. By comparing the predictions from this picture with the diffractive data
from HERA, we determine rough values for the small separations that dominate
the diffraction process. | hep-ph |
A $L_μ- L_τ$ theory of Higgs flavor violation and $(g-2)_μ$: Several experiments reported hints for the violation of lepton flavor or
lepton flavor universality in processes involving muons. Most prominently,
there is the hint for a non-zero rate of the flavor violating Higgs decay $h
\to \tau\mu$ at the LHC, as well as the hint for lepton flavor universality
violation in rare $B$ meson decays at LHCb. In addition, also the long standing
discrepancy in the anomalous magnetic moment of the muon motivates new physics
connected to muons. A symmetry which violates lepton flavor universality, is
$L_\mu-L_\tau$: the difference of muon-number and tau-number. We show that
adding vector-like fermions to a $L_\mu-L_\tau$ theory generates naturally an
effect in the anomalous magnetic moment of the muon and $h\to\tau\mu$, while
effects in other $\tau \to \mu$ transitions are systematically suppressed by
symmetry arguments. We find that if $L_\mu-L_\tau$ is gauged it is possible to
also accommodate the discrepant $b\to s\mu\mu$ data while predicting a
$\tau\to3\mu$ and a modified $h\to\mu\mu$ rate within reach of upcoming
experiments. | hep-ph |
Probing new physics with high-multiplicity events: UHE neutrinos at
air-shower detector arrays: Semi-classical processes such as production and decay of electroweak
sphaleron in the Standard Model and also microscopic black hole in low scale
gravity scenario typically involve large number of particles in final states.
These large multiplicities can be distinctively seen in collisions of
Ultra-high-energy (UHE) neutrinos with $E_\nu \geq 10^9~\text{GeV}$ and
nucleons in the atmosphere of the Earth. Focusing on air-shower detector array
experiments including Telescope Array Experiment (TA), Pierre-Auger Observatory
(Auger), we propose strategic ways to discover and analyze such events. | hep-ph |
The non-perturbative constraint on sea quarks --the strange sea quarks
in the nucleon and the soft pion contribution at high energy--: The mean charge sum rule for the light sea quarks in the nucleon which holds
under the same theoretical footing as the modified Gottfried sum rule shows
that a usual parameterization of the strange sea quark distribution
underestimate its contribution in the small $x$ region. We give a discussion of
the soft pion contribution at high energy as a possible explanation of the
saturation of the sum rule and show that it naturally explains why the strange
sea quark is suppressed in the region above $x \sim 0.01$ while it becomes
abundant below it. | hep-ph |
Minimal gauge inflation: We consider a gauge inflation model in the simplest orbifold M4 x S1/Z2 with
the minimal non-Abelian SU(2) hidden sector gauge symmetry. The inflaton
potential is fully radiatively generated solely by gauge self-interactions.
Following the virtue of gauge inflation idea, the inflaton, a part of the five
dimensional gauge boson, is automatically protected by the gauge symmetry and
its potential is stable against quantum corrections. We show that the model
perfectly fits the recent cosmological observations, including the recent WMAP
5-year data, in a wide range of the model parameters. In the perturbative
regime of gauge interactions (g_{4D} <= 1/(2pi R M_P)) with the moderately
compactified radius (10 <= R M_P <= 100) the anticipated magnitude of the
curvature perturbation power spectrum and the value of the corresponding
spectral index are in perfect agreement with the recent observations. The model
also predicts a large fraction of the gravitational waves, negligible
non-Gaussianity, and high enough reheating temperature. | hep-ph |
Separate seesaw and its applications to dark matter and baryogenesis: We propose a new seesaw model in an extra-dimensional setup where only
right-handed neutrinos are bulk fields. In the model, localizations of an
extra-dimensional wave function and brane Majorana mass of the right-handed
neutrinos can be different among each generation of the right-handed neutrinos.
The setup can lead to different suppression factor dependences of effective
right-handed neutrino masses and neutrino Yukawa couplings for each generation.
It is shown that the resultant mass spectra of the right-handed neutrinos and
neutrino Yukawa couplings are favored in models of neutrino dark matter with
baryogenesis. | hep-ph |
Heavy baryon spectroscopy: Masses of heavy baryons are calculated in the relativistic quark-diquark
picture. Obtained results are in good agreement with available experimental
data including recent measurements by the LHCb Collaboration. Possible quantum
numbers of excited heavy baryon states are discussed. | hep-ph |
Analytic Study of Small Scale Structure on Cosmic Strings: The properties of string networks at scales well below the horizon are poorly
understood, but they enter critically into many observables. We argue that in
some regimes, stretching will be the only relevant process governing the
evolution. In this case, the string two-point function is determined up to
normalization: the fractal dimension approaches one at short distance, but the
rate of approach is characterized by an exponent that plays an essential role
in network properties. The smoothness at short distance implies, for example,
that cosmic string lensing images are little distorted. We then add in loop
production as a perturbation and find that it diverges at small scales. This
need not invalidate the stretching model, since the loop production occurs in
localized regions, but it implies a complicated fragmentation process. Our
ability to model this process is limited, but we argue that loop production
peaks a few orders of magnitude below the horizon scale, without the inclusion
of gravitational radiation. We find agreement with some features of
simulations, and interesting discrepancies that must be resolved by future
work. | hep-ph |
Exclusive hadronic tau decays as probes of non-SM interactions: We perform a global analysis of exclusive hadronic tau decays into one and
two mesons using the low-energy limit of the Standard Model Effective Field
Theory up to dimension six, assuming left-handed neutrinos. A controlled
theoretical input on the Standard Model hadronic form factors, based on chiral
symmetry, dispersion relations, data and asymptotic QCD properties, has allowed
us to set bounds on the New Physics effective couplings using the present
experimental data. Our results highlight the importance of semileptonic $\tau$
decays in complementing the traditional low-energy probes, such nuclear $\beta$
decays or semileptonic pion and kaon decays, and the high-energy measurements
at LHC scales. This makes yet another reason for considering hadronic tau
decays as golden modes at Belle-II. | hep-ph |
HARD PROBES OF DENSE MATTER: Direct probes for the QGP must be hard enough to resolve sub-hadronic scales
($\ll \la^{-1}$) and distinguish confined and deconfined media. This can be
achieved by fast colour charges (jets) and heavy quark resonances (quarkonia).
After a general survey, we study quarkonia as confinement probe and show in
particular that confined matter is transparent, deconfined matter opaque to
\J's. | hep-ph |
Pauli-Villars Regularization in a Discrete Light-Cone Model: Pauli-Villars regularization is successfully applied to nonperturbative
calculations in a (3+1)-dimensional light-cone model. Numerical results
obtained with discretized light-cone quantization compare favorably with the
analytic solution. | hep-ph |
pi(-)p atom in ChPT: strong energy-level shift: The general formula of the pi(-)p atom strong energy-level shift in the 1s
state is derived in the next-to-leading order in the isospin breaking, and in
all orders in chiral expansion. Isospin-breaking corrections to the level shift
are explicitly evaluated at order p^2 in ChPT. The results clearly demonstrate
the necessity to critically reaccess the values of the piN scattering lengths,
extracted from the energy-level shift measurement by means of the potential
model-based theoretical analysis. | hep-ph |
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