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The Inverse Seesaw in Conformal Electro-Weak Symmetry Breaking and
Phenomenological Consequences: We study the inverse seesaw mechanism for neutrino masses and
phenomenological consequences in the context of conformal electro-weak symmetry
breaking. The main difference to the usual case is that all explicit fermion
mass terms including Majorana masses for neutrinos are forbidden. All fermion
mass terms arise therefore from vacuum expectation values of suitable scalars
times some Yukawa couplings. This leads to interesting consequences for model
building, neutrino mass phenomenology and the Dark Matter abundance. In the
context of the inverse seesaw we find a favoured scenario with heavy
pseudo-Dirac sterile neutrinos at the TeV scale, which in the conformal
framework conspire with the electro-weak scale to generate keV scale warm Dark
Matter. The mass scale relations provide naturally the correct relic abundance
due to a freeze-in mechanism. We demonstrate also how conformal symmetry
decouples the right-handed neutrino mass scale and effective lepton number
violation. We find that lepton flavour violating processes can be well within
the reach of modern experiments. Furthermore, interesting decay signatures are
expected at the LHC. | hep-ph |
Determination of Fundamental Supersymmetry Parameters from Chargino
Production at Lepii: If accessible at LEP II, chargino production is likely to be one of the few
available supersymmetric signals for many years. We consider the prospects for
the determination of fundamental supersymmetry parameters in such a scenario.
The study is complicated by the dependence of observables on a large number of
these parameters. We propose a straightforward procedure for disentangling
these dependences and demonstrate its effectiveness by presenting a number of
case studies at representative points in parameter space. Working in the
context of the minimal supersymmetric standard model, we find that chargino
production by itself is a fairly sensitive probe of the supersymmetry-breaking
sector. For significant regions of parameter space, it is possible to test the
gaugino mass unification hypothesis and to measure the gaugino contents of the
charginos and neutralinos, thereby testing the predictions of grand unification
and the viability of the lightest supersymmetric particle as a dark matter
candidate. For much of the parameter space, it is also possible to set limits
on the mass of the electron sneutrino, which provide a valuable guide for
future particle searches. | hep-ph |
Perturbative heavy quarkonium spectrum at
next-to-next-to-next-to-leading order: We compute the energy levels of some of the lower-lying heavy quarkonium
states perturbatively up to O(alpha_s^5*m) and O(alpha_s^5*m*log[alpha_s]).
Stability of the predictions depends crucially on the unknown 4-loop pole-MSbar
mass relation. We discuss the current status of the predictions with respect to
the observed bottomonium spectrum. | hep-ph |
Measuring the skewness dependency of Generalized Parton Distributions: Generalized Parton Distributions (GPDs) have emerged over the 1990s as a
powerful concept and tool to study nucleon structure. They provide nucleon
tomography from the correlation between transverse position and longitudinal
momentum of partons. The Double Deeply Virtual Compton Scattering (DDVCS)
process consists of the Deeply Virtual Compton Scattering (DVCS) process with a
virtual photon in the final state eventually generating a lepton pair, which
can be either an electron-positron or a muon-antimuon pair. The virtuality of
the final time-like photon can be measured and varied, thus providing an extra
lever arm and allowing one to measure the GPDs for the initial and transferred
momentum dependences independently. This unique feature of DDVCS is of
relevance, among others, for the determination of the distribution of nuclear
forces which is accessed through the skewness dependency of GPDs. This
proceeding discusses the feasibility and merits of a DDVCS experiment in the
context of JLab 12 GeV based on model-predicted pseudo-data and the capability
of extraction of Compton Form Factors based on a fitter algorithm. | hep-ph |
Color flux-tube nature of the states $T_{cs}(2900)$ and
$T^a_{c\bar{s}}(2900)$: Inspired by the states $T_{cs0}(2900)^0$, $T_{cs1}(2900)^0$,
$T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$ reported by the
LHCb Collaboration, we carry out a systematical investigation on the properties
of the ground and $P$-wave states $[cs][\bar{u}\bar{d}]$ and
$[cu][\bar{s}\bar{d}]$ with various spin, isospin or $U$-spin, and color
combinations in a multiquark color flux-tube model. Matching our results with
the spin-parity and mass of the states $T_{cs0}(2900)^0$ and $T_{cs1}(2900)^0$,
we can describe them as the compact states $[cs][\bar{u}\bar{d}]$ with
$I(J^{P})=1(0^+)$ and $0(1^-)$ in the model, respectively. The ground state
$T_{cs0}(2900)^0$ is mainly made of strongly overlapped an axial-vector
$[cs]_{\bar{\mathbf{3}}_c}$ and an axial-vector
$[\bar{u}\bar{d}]_{\mathbf{3}_c}$. The $P$-wave state $T_{cs1}(2900)^0$ is
dominantly consisted of a gradually separated scalar or axial vector
$[cs]_{\bar{\mathbf{3}}_c}$ and a scalar $[\bar{u}\bar{d}]_{\mathbf{3}_c}$ in
the shape of a dumbbell. Supposing the states $T^a_{c\bar{s}0}(2900)^{0}$ and
$T^a_{c\bar{s}0}(2900)^{++}$ belong to the same isospin triplet, the mass of
the state $\left [[cu]_{\bar{\mathbf{3}}_c}[\bar{s}\bar{d}]_
{\mathbf{3}_c}\right ]_{\mathbf{1}_c}$ with symmetrical $U$-spin and $J^P=0^+$
is highly consistent with that of the states $T^a_{c\bar{s}0}(2900)^{0}$ and
$T^a_{c\bar{s}0}(2900)^{++}$ in the model. After coupling two color
configurations, the state $[cu][\bar{s}\bar{d}]$ is slightly lighter than the
states $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$. In
addition, we also discuss the properties of other states in the model. | hep-ph |
$b\to s γ$ Decay in the Two Higgs Doublet Model: QCD corrections to $b \to s \gamma$ decay in the two Higgs doublet model are
calculated from the energy scale of top quark to that of bottom. The
constraints on the two Higgs doublet model from the new experimental bounds of
$b\to s\gamma$ by CLEO and the latest top quark mass by CDF and D0 are
reanalyzed. It shows that the constraints become more stringent than that of
the earlier analysis, i.e. a bigger region of the parameter space of the model
is ruled out. | hep-ph |
Extra dimensions, orthopositronium decay, and stellar cooling: In a class of extra dimensional models with a warped metric and a single
brane the photon can be localized on the brane by gravity only. An intriguing
feature of these models is the possibility of the photon escaping into the
extra dimensions. The search for this effect has motivated the present round of
precision orthopositronium decay experiments. We point out that in this
framework a photon in plasma should be metastable. We consider the
astrophysical consequences of this observation, in particular, what it implies
for the plasmon decay rate in globular cluster stars and for the core-collapse
supernova cooling rate. The resulting bounds on the model parameter exceed the
possible reach of orthopositronium experiments by many orders of magnitude. | hep-ph |
Effects of random matter density fluctuations on the neutrino
oscillation transition probabilities in the Earth: In this paper, we investigate the effects of random fluctuations of the Earth
matter density for long baselines on the neutrino oscillation transition
probabilities. We especially identify relevant parameters characterizing the
matter density noise and calculate their effects by averaging over statistical
ensembles of a large number of matter density profiles. For energies and
baselines appropriate to neutrino factories, absolute errors on the relevant
appearance probabilities are at the level of $|\Delta P_{\alpha \beta}| \sim
10^{-4}$ (with perhaps $|\Delta P_{\mu e}|/P_{\mu e} \sim 1%$ for neutrinos),
whereby a modest improvement in understanding of the geophysical data should
render such effects unimportant. | hep-ph |
Two-loop corrections to the Higgs trilinear coupling in BSM models with
classical scale invariance: Classical scale invariance (CSI) is an attractive concept for BSM model
building, explaining the apparent alignment of the Higgs sector and potentially
relating to the hierarchy problem. Furthermore, a particularly interesting
feature is that the Higgs trilinear coupling $\lambda_{hhh}$ is universally
predicted at one loop in CSI models, and deviates by 67% from its (tree-level)
SM prediction. This result is however modified at two loops, and we review in
these proceedings our calculation of leading two-loop corrections to
$\lambda_{hhh}$ in models with classical scale invariance, taking as an example
a CSI scenario of a Two-Higgs-Doublet Model. We find that the inclusion of
two-loop effects allows distinguishing different scenarios with CSI, although
the requirement of reproducing the known 125-GeV Higgs-boson mass severely
restricts the allowed values of $\lambda_{hhh}$. | hep-ph |
Treating the b quark distribution function with reliable uncertainties: The parton distribution function for a b quark in the B meson (called the
shape function) plays an important role in the analysis of the B -> X_s gamma
and B -> X_u l nu data, and gives one of the dominant uncertainties in the
determination of |Vub|. We introduce a new framework to treat the shape
function, which consistently incorporates its renormalization group evolution
and all constraints on its shape and moments in any short distance mass scheme.
At the same time it allows a reliable treatment of the uncertainties. We
develop an expansion in a suitable complete set of orthonormal basis functions,
which provides a procedure for systematically controlling the uncertainties due
to the unknown functional form of the shape function. This is a significant
improvement over fits to model functions. Given any model for the shape
function, our construction gives an orthonormal basis in which the model occurs
as the first term, and corrections to it can be studied. We introduce a new
short distance scheme, the "invisible scheme", for the kinetic energy matrix
element, lambda_1. We obtain closed form results for the differential rates
that incorporate perturbative corrections and a summations of logarithms at any
order in perturbation theory, and present results using known
next-to-next-to-leading order expressions. The experimental implementation of
our framework is straightforward. | hep-ph |
Neutrino Oscillations in Finite Time Path Out-of-Equilibrium Thermal
Field Theory: We demonstrate that the Finite-Time-Path Field Theory is an adequate tool for
calculating neutrino oscillations. We apply this theory using a mass-mixing
Lagrangian which involves the correct Dirac spin and chirality structure and a
Pontecorvo-Maki-Nakagawa-Sakata (PMNS)-like mixing matrix. The model is exactly
solvable. The Dyson-Schwinger equations transform propagators of the input free
(massless) flavor neutrinos into a linear combination of oscillating (massive)
neutrinos. The results are consistent with the predictions of the PMNS matrix
while allowing for extrapolation to early times. | hep-ph |
The Rare Top Decays $t \to b W^+ Z$ and $t \to c W^+ W^-$: The large value of the top quark mass implies that the rare top decays $t
\rightarrow b W^+ Z, s W^+ Z$ and $d W^+ Z$, and $t \rightarrow c W^+ W^-$ and
$u W^+ W^-$, are kinematically allowed decays so long as $m_t \ge m_W + m_Z +
m_{d_i} \approx 171.5 GeV + m_{d_i}$ or $m_t \ge 2m_W + m_{u,c} \approx 160.6
GeV + m_{u,c}$, respectively. The partial decay widths for these decay modes
are calculated in the standard model. The partial widths depend sensitively on
the precise value of the top quark mass. The branching ratio for $t\rightarrow
b W^+ Z$ is as much as $2 \times 10^{-5}$ for $m_t = 200 GeV$, and could be
observable at LHC. The rare decay modes $t \rightarrow c W^+ W^-$ and $u W^+
W^-$ are highly GIM-suppressed, and thus provide a means for testing the GIM
mechanism for three generations of quarks in the u, c, t sector. | hep-ph |
Gluon-Meson Duality in the Mean Field Approximation: In a gauge-fixed language gluon-meson duality can be described as the Higgs
mechanism for ``spontaneous symmetry breaking'' of color. We present a mean
field computation which suggests that this phenomenon is plausible in QCD. One
obtains realistic masses of the light mesons and baryons. | hep-ph |
Facets of chiral perturbation theory: Chiral perturbation theory is the effective field theory of the Standard
Model at low energies. After a short introduction and overview, I discuss three
topics where the chiral approach leads to a deeper understanding of low-energy
hadron physics: radiative kaon decays, carbogenesis in stellar nucleosynthesis
and the interplay of chiral perturbation theory and lattice QCD. | hep-ph |
Hidden Mass Hierarchy in QCD: We discuss implications of the recent measurements of the non-Abelian action
density associated with the monopoles condensed in the confining phase of
gluodynamics. The radius of the monopole determined in terms of the action was
found to be small numerically. As far as the condensation of the monopoles is
described in terms of a scalar field, a fine tuning is then implied. In other
words, a hierarchy exists between the self energy of the monopole and the
temperature of the confinement-deconfinement phase transition. The ratio of the
two scales is no less than a factor of 10. Moreover, we argue that the
hierarchy scale can well eventually extend to a few hundred GeV on the
ultraviolet side. The corresponding phenomenology is discussed, mostly within
the polymer picture of the monopole condensation. | hep-ph |
Asymmetry of Strange Sea in Nucleons: Based on the finite-temperature field theory, we evaluate the medium effects
in nucleon which can induce an asymmetry between quarks and antiquarks of the
strange sea. The short-distance effects determined by the weak interaction can
give rise to $\delta m\equiv \Delta m_s-\Delta m_{\bar s}$ where $\Delta
m_{s(\bar s)}$ is the medium-induced mass of strange quark by a few KeV at
most, but the long-distance effects by strong interaction are sizable. Our
numerical results show that there exists an obvious mass difference between
strange and anti-strange quarks, as large as 10-100 MeV. | hep-ph |
Pileup and Underlying Event Mitigation with Iterative Constituent
Subtraction: The hard-scatter processes in hadronic collisions are often largely
contaminated with soft background coming from pileup in proton-proton
collisions, or underlying event in heavy-ion collisions. This paper presents a
new background subtraction method for jets and event observables (such as
missing transverse energy) which is based on the previously published
Constituent Subtraction algorithm. The new subtraction method, called Iterative
Constituent Subtraction, applies event-wide implementation of Constituent
Subtraction iteratively in order to fully equilibrate the background
subtraction across the entire event. Besides documenting the new method, we
provide guidelines for setting the free parameters of the subtraction
algorithm. Using particle-level simulation, we provide a comparison of
Iterative Constituent Subtraction with several existing methods from which we
conclude that the new method has a significant potential to improve the
background mitigation in both proton-proton and heavy-ion collisions. | hep-ph |
Divergences in anomalous dimension matrices of quarks at three loops:
Explanation and simple solution: Three-loop counterterms for the Standard Model (SM) revealed that the matrix
of anomalous dimensions ($\gamma$) of quarks is divergent in the $d \to 4$
limit unless a carefully chosen non-Hermitian square-root of $Z$ matrix is used
in the textbook formula for $\gamma$. Here, an alternative prescription is
given, which expresses $\gamma$ and $\beta$ functions directly in terms of
counterterms (instead of $\sqrt{Z}$ and conventional `bare couplings') and
produces finite results. In the SM, this prescription $automatically$
reproduces results obtained previously by adjusting $\sqrt{Z}$. | hep-ph |
Peak shifts due to $B^{(*)}-\bar{B}^{(*)}$ rescattering in
$Υ(5S)$ dipion transitions: We study the energy distributions of dipion transitions $\Upsilon(5S)$ to
$\Upsilon(1S,2S,3S)\pi^+\pi^-$ in the final state rescattering model. Since the
$\Upsilon(5S)$ is well above the open bottom thresholds, the dipion transitions
are expected to mainly proceed through the real processes $\Upsilon(5S)\to
B^{(*)}\bar{B}^{(*)}$ and $B^{(*)}\bar{B}^{(*)}\to
\Upsilon(1S,2S,3S)\pi^+\pi^-$. We find that the energy distributions of
$\Upsilon(1S,2S,3S)\pi^+\pi^-$ markedly differ from that of $\Upsilon(5S)\to
B^{(*)}\bar{B}^{(*)}$. In particular, the resonance peak will be pushed up by
about 7-20 MeV for these dipion transitions relative to the main hadronic decay
modes. These predictions can be used to test the final state rescattering
mechanism in hadronic transitions for heavy quarkonia above the open flavor
thresholds. | hep-ph |
Quark Model, Nonperturbative Wave Functions, the QCD Sum Rules and
Instantons: The main subject of these lectures is the Nonperturbative Wave Functions. We
describe some nonperturbative methods (like QCD sum rules, dispersion
relations, duality etc) in order to study this object. We also consider some
applications of the obtained results, such as form factors, inclusive
amplitudes and diffractive electroproduction. Finally, we discuss the instanton
liquid model which may help us to understand the success of the constituent
quark model. | hep-ph |
WIMP Dark Matter in a Well-Tempered Regime: A case study on
Singlet-Doublets Fermionic WIMP: Serious searches for the weakly interacting massive particle (WIMP) have now
begun. In this context, the most important questions that need to be addressed
are: "To what extent can we constrain the WIMP models in the future?" and "What
will then be the remaining unexplored regions in the WIMP parameter space for
each of these models?" In our quest to answer these questions, we classify WIMP
in terms of quantum number and study each case adopting minimality as a guiding
principle. As a first step, we study one of the simple cases of the minimal
composition in the well-tempered fermionic WIMP regime, namely the
singlet-doublets WIMP model. We consider all available constraints from direct
and indirect searches and also the predicted constraints coming from the near
future and the future experiments. We thus obtain the current status, the near
future prospects and the future prospects of this model in all its generality.
We find that in the future, this model will be constrained almost solely by the
future direct dark matter detection experiments (as compared to the weaker
indirect and collider constraints) and the cosmological (relic density)
constraints and will hence be gradually pushed to the corner of the
coannihilation region, if no WIMP signal is detected. Future lepton colliders
will then be useful in exploring this region not constrained by any other
experiments. | hep-ph |
${\mathcal O}(α_s)$ corrections to $e^+e^-\rightarrow
J/ψ+η_{c2}(χ_{c1}^\prime)$ at $B$ factories: We investigate the ${\cal O}(\alpha_s)$ correction to $e^+e^-\to
J/\psi+\eta_{c2}$ in the NRQCD factorization approach. A detailed comparative
study between $e^+e^-\to J/\psi+\eta_{c2}$ and $e^+e^-\to
J/\psi+\chi^\prime_{c1}$ at $B$ factory energy is also carried out. After
incorporating the ${\cal O}(\alpha_s)$ correction, we predict the cross section
for the former process to be around 0.3 fb, while that of the latter about 6
times greater. The outgoing $J/\psi$ is found to be dominantly
transversely-polarized in the former process, while longitudinally-polarized in
the latter. These features may provide valuable guidance for the future
experiment to examine the ${}^3P_1$ or ${}^1D_2$ charmonium option of the
X(3872) meson through the exclusive double-charmonium production processes. The
observation potential of $e^+e^-\to J/\psi+\chi^\prime_{c1}$ looks bright for
the current data sample of the \textsc{Belle} experiment, provided that the
$\chi^\prime_{c1}$ is indeed the narrow X(3872) state. In the appendix, we also
identify the coefficients of the double logarithms of form $\ln^2(s/m_c^2)$
associated with all the relevant next-to-leading order Feynman diagrams, for
the helicity-suppressed double-charmonium production channels $e^+ e^- \to
J/\psi+ \eta_{c2}(\eta_c,\chi_{c0,1,2})$. | hep-ph |
Baryogenesis from L-violating Higgs-doublet decay in the density-matrix
formalism: We compute in the density-matrix formalism the baryon asymmetry generated by
the decay of the Higgs doublet into a right-handed (RH) neutrino and a Standard
Model lepton. The emphasis is put on the baryon asymmetry produced by the total
lepton-number violating decay. From the derivation of the corresponding
evolution equations, and from their integration, we find that this contribution
is fully relevant for large parts of the parameter space. This confirms the
results found recently in the CP-violating decay formalism with thermal
corrections and shows in particular that the lepton-number violating processes
are important not only for high-scale leptogenesis but also when the
RH-neutrino masses are in the GeV range. For large values of the Yukawa
couplings, we also find that the strong washout is generically much milder for
this total lepton-number violating part than for the usual RH-neutrino
oscillation flavour part. | hep-ph |
Bs to mu mu gamma from Bs to mu mu: The Bs to mu mu gamma decay offers sensitivity to a wider set of effective
operators than its non-radiative counterpart Bs to mu mu, and a set that is
interesting in the light of present-day discrepancies in flavour data. On the
other hand, the direct measurement of the Bs to mu mu gamma decay poses
challenges with respect to the Bs to mu mu one. We present a novel strategy to
search for Bs to mu mu gamma decays in the very event sample selected for Bs to
mu mu searches. The method consists in extracting the Bs to mu mu gamma
spectrum as a "contamination" to the Bs to mu mu one, as the signal window for
the latter is extended downward with respect to the peak region. We provide
arguments for the actual practicability of the method already on Run-2 data of
the LHC. | hep-ph |
Correlation femtoscopy of small systems: The basic principles of the correlation femtoscopy, including its
correspondence to the Hanbury Brown and Twiss intensity interferometry, are
re-examined. The main subject of the paper is an analysis of the correlation
femtoscopy when the source size is as small as the order of the uncertainty
limit. It is about 1 fm for the current high energy experiments. Then the
standard femtoscopy model of random sources is inapplicable. The uncertainty
principle leads to the partial indistinguishability and coherence of closely
located emitters that affect the observed femtoscopy scales. In thermal systems
the role of corresponding coherent length is taken by the thermal de Broglie
wavelength that also defines the size of a single emitter. The formalism of
partially coherent phases in the amplitudes of closely located individual
emitters is used for the quantitative analysis. The general approach is
illustrated analytically for the case of the Gaussian approximation for
emitting sources. A reduction of the interferometry radii and a suppression of
the Bose-Einstein correlation functions for small sources due to the
uncertainty principle are found. There is a positive correlation between the
source size and the intercept of the correlation function. The peculiarities of
the non-femtoscopic correlations caused by minijets and fluctuations of the
initial states of the systems formed in $pp$ and $e^+e^-$ collisions are also
analyzed. The factorization property for the contributions of femtoscopic and
non-femtoscopic correlations into complete correlation function is observed in
numerical calculations in a wide range of the model parameters. | hep-ph |
Dirac Neutrinos and Hybrid Inflation from String Theory: We consider a possible scenario for the generation of Dirac neutrino masses
motivated by Type I string theory. The smallness of the neutrino Yukawa
couplings is explained by an anisotropic compactification with one
compactification radius larger than the others. In addition to this we utilise
small Yukawa couplings to develop strong links between the origin of neutrino
masses and the physics driving inflation. We construct a minimal model which
simultaneously accommodates small Dirac neutrino masses leading to bi-large
lepton mixing as well as an inflationary solution to the strong CP and to the
$\mu$ problem. | hep-ph |
RGE, the naturalness problem and the understanding of the Higgs mass
term: The naturalness problem might be studied on the complex two dimensional plane
with the technique of dimensional regularization(DREG). The Renormalization
group equation(RGE) of the Higgs mass on the plane suggests the Higgs mass
approaches zero at ultraviolate (UV) scale, the scale can be Planck scale when
the top quark pole mass $M_{t}=168$ GeV. The real issue of the naturalness
problem in the sense of Wilsonian renormalization group method is not about
quadratic divergences but the rescaling effect. The Higgs mass can be
considered to be one composed mass. All terms in the lagrangian in this
scenario are marginal terms and no relevant terms are left, thus no rescaling
effect to cause the naturalness problem anymore. RGE of the vacuum expectation
value (VEV) in the Landau gauge up to two-loop order is studied.
Scale-dependent behavior of the composed Higgs mass shows that we can have one
tiny Higgs mass at high energy scale, even around the Planck scale, when
$M_{t}\leq170.7$ GeV. | hep-ph |
Parton densities and structure functions at next-to-next-to-leading
order and beyond: We summarize recent results on the evolution of unpolarized parton densities
and deep-inelastic structure functions in massless perturbative QCD. Due to
last year's extension of the integer-moment calculations of the three-loop
splitting functions, the NNLO evolution of the parton distributions can now be
performed reliably at momentum fractions x >= 10^-4, facilitating a
considerably improved theoretical accuracy of their extraction from data on
deep-inelastic scattering. The NNLO corrections are not dominated, at relevant
values of x, by their leading small-x terms. At large x the splitting-function
series converges very rapidly, hence, employing results on the three-loop
coefficient functions, the structure functions can be analysed at N^3LO for x >
10^-2. The resulting values for alpha_s do not significantly change beyond
NNLO, their renormalization scale dependence reaches about +-1% at N^3LO. | hep-ph |
Unitarity and Fermion Mass Generatation: Some years ago Appelquist and Chanowitz considered the scattering of
fermion--anti-fermion into a pair of longitudinal gauge bosons. Their
calculation established that unitarity implies that the physics giving mass to
a quark of mass $m_f$ must be below a mass scale of $16 \pi v^2 / m_f$ ($v=246$
GeV). This bound is a bit difficult to interpret, because the unitarity of
gauge boson scattering requires in any case that there be new physics, such as
a Higgs boson, with a mass lighter than this. This paper re-examines the
Appelquist-Chanowitz bound in order to clarify its meaning. This work uses toy
models with a singlet Higgs boson to unitarize gauge boson scattering, and
considers other possibilities for the new physics affecting the fermion mass.
This new physics has the effect of changing the Higgs
boson--fermion--anti-fermion coupling. New physics cannot significantly alter
this coupling unless it is substantially lighter than the Appelquist-Chanowitz
bound. | hep-ph |
Effect of finite volume on thermodynamics of quark-hadron matter: The effects of a finite system volume on thermodynamic quantities, such as
the pressure, energy density, specific heat, speed of sound, conserved charge
susceptibilities and correlations, in hot and dense strongly interacting matter
are studied within the parity-doublet Chiral Mean Field (CMF) model.
Such an investigation is motivated by relativistic heavy-ion collisions,
which create a blob of hot QCD matter of a finite volume, consisting of
strongly interacting hadrons and potentially deconfined quarks and gluons.
The effect of the finite volume of the system is incorporated by introducing
a lower momentum cut-offs in the momentum integrals appearing in the model, the
numerical value of the momentum cut-off being related to the de Broglie
wavelength of the given particle species.
It is found that some of these quantities show a significant volume
dependence, in particular those sensitive to pion degrees of freedom, and the
crossover transition is generally observed to become smoother in finite volume.
These findings are relevant for the effective equation of state used in fluid
dynamical simulations of heavy-ion collisions and efforts to extract the freeze
out properties of heavy-ion collisions with susceptibilities involving electric
charge and strangeness. | hep-ph |
Twisted particles in heavy-ion collisions: The importance of production of twisted (vortex) particles in heavy-ion
collisions is analyzed. Free twisted particles can possess giant intrinsic
orbital angular momenta. Twisted particles are spatially localized and can be
rather ubiquitous in laboratories and nature. Twisted photons have nonzero
effective masses. Charged twisted particles can be recognized by their
dynamics, magnetic moments, and specific effects in external fields. | hep-ph |
Neutrino Masses and Absence of Flavor Changing Interactions in the 2HDM
from Gauge Principles: We propose several Two Higgs Doublet Models with the addition of an Abelian
gauge group which free the usual framework from flavor changing neutral
interactions and explain neutrino masses through the seesaw mechanism. We
discuss the kinetic and mass-mixing gripping phenomenology which encompass
several constraints coming from atomic parity violation, the muon anomalous
magnetic moment, rare meson decays, Higgs physics, LEP precision data,
neutrino-electron scattering, low energy accelerators and LHC probes. | hep-ph |
Open-source QCD analysis of nuclear parton distribution functions at NLO
and NNLO: We present new sets of nuclear parton distribution functions (nPDFs) at
next-to-leading order (NLO) and next-to-next-to-leading order (NNLO). Our
analyses are based on deeply inelastic scattering data with charged-lepton and
neutrino beams on nuclear targets. In addition, a set of proton baseline PDFs
is fitted within the same framework with the same theoretical assumptions. The
results of this global QCD analysis are compared to existing nPDF sets and to
the fitted cross sections. Also, the uncertainties resulting from the limited
constraining power of the included experimental data are presented. The
published work is based on an open-source tool, xFitter, which has been
modified to be applicable also for a nuclear PDF analysis. The required
extensions of the code are discussed as well. | hep-ph |
The Elusiveness of Infrared Critical Exponents in Landau Gauge
Yang--Mills Theories: We solve a truncated system of coupled Dyson-Schwinger equations for the
gluon and ghost propagators in SU($N_c$) Yang-Mills theories in Faddeev-Popov
quantization on a four-torus. This compact space-time manifold provides an
efficient mean to solve the gluon and ghost Dyson-Schwinger equations without
any angular approximations. We verify that analytically two power-like
solutions in the very far infrared seem possible. However, only one of these
solutions can be matched to a numerical solution for non-vanishing momenta. For
a bare ghost-gluon vertex this implies that the gluon propagator is only weakly
infrared vanishing, $D_{gl}(k^2) \propto (k^2)^{2\kappa -1}$, $\kappa \approx
0.595$, and the ghost propagator is infrared singular, $D_{gh}(k^2) \propto
(k^2)^{-\kappa -1}$. For non-vanishing momenta our solutions are in agreement
with the results of recent SU(2) Monte-Carlo lattice calculations. The running
coupling possesses an infrared fixed point. We obtain $\alpha(0) = 8.92/N_c$
for all gauge groups SU($N_c$). Above one GeV the running coupling rapidly
approaches its perturbative form. | hep-ph |
Self-consistent Gaussian model of nonperturbative QCD vacuum: We show that the minimal Gaussian model of nonlocal vacuum quark and
quark-gluon condensates in QCD generates the non-transversity of vector current
correlators. We suggest the improved Gaussian model of the nonperturbative QCD
vacuum, which respects QCD equations of motion and minimizes the revealed
gauge-invariance breakdown. We obtain the refined values of pion distribution
amplitude (DA) conformal moments using the improved QCD vacuum model and
construct the allowed region for Gegenbauer coefficients a_2 and a_4 of the
pion DA. | hep-ph |
Implementing inverse seesaw mechanism in SU(3)xSU(4)xU(1) gauge models: Generating appropriate tiny neutrino masses via inverse seesaw mechanism
within the framework of a particular SU(3)xSU(4)xU(1) gauge model is the main
outcome of this letter. It is achieved by simply adding three singlet exotic
Majorana neutrinos to the usual ones included in the three lepton quadruplet
representations. The theoretical device of treating gauge models with high
symmetries is the general method by Cotaescu. It provides us with a unique free
parameter (a) to be tuned in order to get a realistic mass spectrum for the
gauge bosons and charged fermions in the model. The overall breaking scale can
be set around 1-10 TeV so its phenomenology is quite testable at present
facilities. | hep-ph |
Can supercooling explain the HBT puzzle?: Possible hadronization of supercooled QGP, created in heavy ion collisions at
RHIC and SPS, is discussed within a Bjorken hydrodynamic model. Such a
hadronization is expected to be a very fast shock-like process, what, if
hadronization coincides or shortly followed by freeze out, could explain a part
of the HBT puzzle, i.e. the flash-like particle emission
($R_{out}/R_{side}\approx 1$). HBT data also show that the expansion time
before freeze out is very short ($\sim 6-10 fm/c$). In this work we discuss
question of supercooled QGP and the timescale of the reaction. | hep-ph |
R-parity violating anomaly mediated supersymmetry breaking: We propose a new scenario that solves the slepton negative mass squared
problem of the minimal supersymmetric standard model with anomaly mediated
supersymmetry breaking. The solution is achieved by including three trilinear
R-parity violating operators in the superpotential. The soft supersymmetry
breaking terms satisfy renormalisation group invariant relations in terms of
supersymmetric couplings and the overall supersymmetry breaking mass scale.
Flavour changing neutral currents can be naturally highly suppressed. A
specific model predicts tan beta=4.2+/-1.0. Excluding sleptons, the
supersymmetric particle spectrum then depends upon two remaining free
parameters. In the case of the R-parity violating couplings set at their
quasi-fixed points at a supersymmetric GUT scale, the whole sparticle spectrum
approximately depends upon only one free parameter. Imposing experimental
limits leads to a constrained and distinctive phenomenology. The lightest
CP-even Higgs of mass m_h=118 GeV would be seen at the Tevatron. All sparticles
and heavy Higgs would evade detection except for the lightest charginos and
neutralinos, whose distinctive leptonic decays would be seen at the LHC. | hep-ph |
On the Hadronic light-by-light contribution to the muon $g-2$: This talk is about the hadronic light-by-light contribution to the muon
anomalous magnetic moment, mainly our old work but including some newer results
as well. It concentrates on the model calculations. Most attention is paid to
pseudo-scalar exchange and the pion loop contribution. Scalar, $a_1$-exchange
and other contributions are shortly discussed as well. For the $\pi^0$-exchange
a possible large cancellation between connected and disconnected diagrams is
expected. | hep-ph |
$A_0$ condensation, Nielsen's identity and effective potential of order
parameter: In high temperature SU(2) gluodynamics, the condensation of the zero
component gauge field potential A_0 =const and its gauge-fixing dependence are
investigated. A_0 is mutually related with Polyakov's loop <L>. The two-loop
effective potential W(A_0,xi) is recalculated in the background relativistic
R_xi gauge. It depends on the parameter xi, has a nontrivial minimum and
satisfies Nielsen's identity. These signs mean gauge invariance of the
condensation phenomenon.
Following the idea of Belyaev, we express W(A_0,xi) in terms of <L>. The
obtained effective potential of order parameter differs from that derived by
this author. It is independent of xi and has a nontrivial minimum position.
Hence the A_0 condensation follows. We show that the equation relating A_0 and
(A_0)|_(classical) coincides with the special characteristic orbit in the
(A)$-plain along which the W(A_0,xi) is xi-independent. In this way the link
between these two gauge invariant descriptions is established. The minimum
value of the Polyakov loop is calculated. Comparison with results of other
authors is given. | hep-ph |
Some results from the NA27 Data: The self-affine analysis and erraticity analysis of pseudorapidity gaps are
performed for the data of 400GeV/$c$ pp collisions. The self-affine analysis
has been shown to exhibit a better scaling behavior. The self-affine
multifractal dimensions and multifractal spectrum have been obtained. The
simulated results using FRITIOF program can not reproduce the scaling behavior.
The analysis of event-to-event fluctuations has been performed. The increase of
event-space moments $C_{p,q}(M)$ with decreasing phase-space scale is dominated
by the statistical fluctuations. The erraticity analysis based on measuring the
pseudorapidity gaps is also performed. The entropy-like quantities $S_q$ and
$\Sigma_q$ deviate from 1 significantly, implying that both of them are useful
to serve as effective measures of erraticity in multiparticle production. The
ln${S_q}$ versus $q$ has a quite linear behavior, but the ln${\Sigma_q}$ versus
$q$ has only an approximate linear behavior. The FRITIOF simulated results
follow the same scaling behavior, but the deviations from the experimental data
are rather large. | hep-ph |
Theory of heavy quark energy loss: We briefly review some of the models and theoretical schemes established to
describe heavy quark quenching in ultrarelativistic heavy ions collisions. Some
lessons are derived from RHIC and early LHC data, especially as for the
contraints they impose on those models. | hep-ph |
Anomalies in charged-current $B$ decays: This paper reviews the recent progresses of the flavor and collider searches
that can probe New Physics effects responsible for the current discrepancy in
the lepton flavor universality ratio of $R_{D^{(*)}}$ between the experimental
measurements and SM values. | hep-ph |
Pseudoscalar Meson Decay Constants and Couplings, the Witten-Veneziano
Formula beyond large N_c, and the Topological Susceptibility: The QCD formulae for the radiative decays $\eta,\eta'\to\c\c$, and the
corresponding Dashen--Gell-Mann--Oakes--Renner relations, differ from
conventional PCAC results due to the gluonic $U(1)_A$ axial anomaly. This
introduces a critical dependence on the gluon topological susceptibility. In
this paper, we revisit our earlier theoretical analysis of radiative
pseudoscalar decays and the DGMOR relations and extract explicit experimental
values for the decay constants. This is our main result. The flavour singlet
DGMOR relation is the generalisation of the Witten-Veneziano formula beyond
large $N_c$, so we are able to give a quantitative assessment of the
realisation of the $1/N_c$ expansion in the $U(1)_A$ sector of QCD.
Applications to other aspects of $\eta'$ physics, including the relation with
the first moment sum rule for the polarised photon structure function $g_1^\c$,
are highlighted. The $U(1)_A$ Goldberger-Treiman relation is extended to
accommodate SU(3) flavour breaking and the implications of a more precise
measurement of the $\eta$ and $\eta'$-nucleon couplings are discussed. A
comparison with the existing literature on pseudoscalar meson decay constants
using large-$N_c$ chiral Lagrangians is also made. | hep-ph |
The KLN Theorem and Soft Radiation in Gauge Theories: Abelian Case: We present a covariant formulation of the Kinoshita, Lee, Nauenberg (KLN)
theorem for processes involving the radiation of soft particles. The role of
the disconnected diagrams is explored and a rearrangement of the perturbation
theory is performed such that the purely disconnected diagrams are factored
out. The remaining effect of the disconnected diagrams results in a simple
modification of the usual Feynman rules for the S-matrix elements. As an
application, we show that when combined with the Low theorem, this leads to a
proof of the absense of the $1/Q$ corrections to inclusive processes (like the
Drell-Yan process). In this paper the abelian case is discussed to all orders
in the coupling. | hep-ph |
Baryon Number, Lepton Number, and Operator Dimension in the Standard
Model: We prove that for a given operator in the Standard Model (SM) with baryon
number B and lepton number L, that the operator's dimension is even (odd) if
(B-L)/2 is even (odd). Consequently, this establishes the veracity of
statements that were long observed or expected to be true, but not proven,
e.g., operators with B-L=0 are of even dimension, B-L must be an even number,
etc. These results remain true even if the SM is augmented by any number of
right-handed neutrinos with L=1. | hep-ph |
High-Energy Proton-Proton Forward Scattering and Derivative Analyticity
Relations: We present the results of several parametrizations to two different ensemble
of data on $pp$ total cross sections $\sigma_{tot}^{pp}$ at the highest
center-of-mass energies (including cosmic-ray information). The results are
statistically consistent with two distinct scenarios at high energies. From one
ensemble the prediction for the LHC ($\sqrt s = 14$ TeV) is $\sigma_{tot}^{pp}
= 113 \pm 5$ mb and from the other, $\sigma_{tot}^{pp}=140 \pm 7$ mb. From each
parametrization, and making use of derivative analyticity relations (DAR), we
determine $\rho(s)$ (ratio between the forward real and imaginary parts of the
elastic scattering amplitude). A discussion on the optimization of the DAR in
terms of a free parameter is also presented.In all cases good descriptions of
the experimental data are obtained. | hep-ph |
Light scalar mesons and charmless hadronic $B_c \to SP, SV$ decays in
the perturbative QCD approach: In this work, based on the assumption of two-quark structure of the scalars,
the charmless hadronic $B_c \to SP, SV$ decays(here, $S$, $P$, and $V$ denote
the light scalar, pseudoscalar, and vector mesons, respectively) are
investigated by employing the perturbative QCD(pQCD) factorization
approach.From our numerical evaluations and phenomenological analysis, we find
that (a) the pQCD predictions for the {\it CP}-averaged branching ratios(BRs)
of the considered $B_c$ decays vary in the range of $10^{-5}$ to $10^{-8}$,
which will be tested in the ongoing LHCb and forthcoming Super-B experiments,
while the {\it CP}-violating asymmetries for these modes are absent naturally
in the standard model because only one type tree operator is involved; %% (b)
analogous to $B \to K^* \eta^{(\prime)}$ decays, $Br(B_c \to \kappa^+ \eta)
\sim 5 \times Br(B_c \to \kappa^+ \eta^\prime)$ in the pQCD approach, which can
be understood by the constructive and destructive interference between the
$\eta_q$ and $\eta_s$ contributions to the $B_c \to \kappa^+ \eta$ and $B_c \to
\kappa^+ \eta^\prime$ decays, however, $Br(B_c \to K_0^*(1430) \eta)$ is
approximately equal to $Br(B_c \to K_0^*(1430) \eta')$ in both scenarios
because the factorizable contributions from $\eta_s$ term play the dominant
role in the considered two channels; %% (c) if $a_0(980)$ and $\kappa$ are the
$q\bar q$ bound states, the pQCD predicted BRs for $B_c \to a_0(980) (\pi,
\rho)$ and $B_c \to \kappa K^{(*)}$ decays will be in the range of $10^{-6}
\sim 10^{-5}$, which are within the reach of the LHCb experiments and could be
measured in the near future; and %% (d) for the $a_0(1450)$ and $K_0^*(1430)$
channels, the BRs for $B_c \to a_0(1450) (\pi, \rho)$ and $B_c \to K_0^*(1430)
K^{(*)}$ modes in the pQCD approach are found to be $(5 \sim 47) \times
10^{-6}$ and $(0.7 \sim 36) \times 10^{-6}$, respectively. | hep-ph |
The Mueller-Tang jet impact factor at NLO from the high energy effective
action: We report on recent progress in the evaluation of next-to-leading order
observables using Lipatov's QCD high energy effective action. In this
contribution we focus on the determination of the real part of the
next-to-leading order corrections to the Mueller-Tang impact factor which is
the only missing element for a complete NLO BFKL description of quark induced
dijet events with a rapidity gap. | hep-ph |
Spectroscopy of Exotic Hadrons Formed from Dynamical Diquarks: The dynamical diquark picture asserts that exotic hadrons can be formed from
widely separated colored diquark or triquark components. We use the
Born-Oppenheimer (BO) approximation to study the spectrum of states thus
constructed, both in the basis of diquark spins and in the basis of heavy
quark-antiquark spins. We develop a compact notation for naming these states,
and use the results of lattice simulations for hybrid mesons to predict the
lowest expected BO potentials for both tetraquarks and pentaquarks. We then
compare to the set of exotic candidates with experimentally determined quantum
numbers, and find that all of them can be accommodated. Once decay modes are
also considered, one can develop selection rules of both exact ($J^{PC}$
conservation) and approximate (within the context of the BO approximation)
types and test their effectiveness. We find that the most appealing way to
satisfy both sets of selection rules requires including additional low-lying BO
potentials, a hypothesis that can be checked on the lattice. | hep-ph |
Higgs Inflation, Reheating and Gravitino Production in No-Scale
Supersymmetric GUTs: We extend our previous study of supersymmetric Higgs inflation in the context
of no-scale supergravity and grand unification, to include models based on the
flipped SU(5) and the Pati-Salam group. Like the previous SU(5) GUT model,
these yield a class of inflation models whose inflation predictions interpolate
between those of the quadratic chaotic inflation and Starobinsky-like
inflation, while avoiding tension with proton decay limits. We further analyse
the reheating process in these models, and derive the number of e-folds, which
is independent of the reheating temperature. We derive the corresponding
predictions for the scalar tilt and the tensor-to-scalar ratio in cosmic
microwave background perturbations, as well as discussing the gravitino
production following inflation. | hep-ph |
Impact of Electroweak Corrections on Neutral Higgs Boson Decays in
Extended Higgs Sectors: Precision predictions play an important role in the search for indirect New
Physics effects in the Higgs sector itself. For the electroweak (EW)
corrections of the Higgs bosons in extended Higgs sectors several
renormalization schemes have been worked out that provide
gauge-parameter-independent relations between the input parameters and the
computed observables. Our recently published program codes 2HDECAY and
ewN2HDECAY allow for the computation of the EW corrections to the Higgs decay
widths and branching ratios of the Two-Higgs-Doublet Model (2HDM) and the
Next-to-Minimal-2HDM (N2HDM) for different renormalization schemes of the
scalar mixing angles. In this paper, we present a comprehensive and complete
overview over the relative size of the EW corrections to the branching ratios
of the 2HDM and N2HDM neutral Higgs bosons for different applied
renormalization schemes. We quantify the size of the EW corrections of Standard
Model(SM)- and non-SM-like Higgs bosons and moreover also identify
renormalization schemes that are well-behaved and do not induce unnaturally
large corrections. We furthermore pin down decays and parameter regions that
feature large EW corrections and need further treatment in order to improve the
predictions. Our study sets the scene for future work in the computation of
higher-order corrections to the decays of non-minimal Higgs sectors. | hep-ph |
Lepton flavor-violating transitions in effective field theory and
gluonic operators: Lepton flavor-violating processes offer interesting possibilities to probe
new physics at multi-TeV scale. We discuss those in the framework of effective
field theory, emphasizing the role of gluonic operators. Those operators are
obtained by integrating out heavy quarks that are kinematically inaccessible at
the scale where low-energy experiments take place and make those experiments
sensitive to the couplings of lepton flavor changing neutral currents to heavy
quarks. We discuss constraints on the Wilson coefficients of those operators
from the muon conversion $\mu^- + (A,Z) \to e^- + (A,Z)$ and from lepton
flavor-violating tau decays with one or two hadrons in the final state, e.g.
$\tau \to \ell \ \eta^{(\prime)}$ and $\tau \to \ell \ \pi^+\pi^-$ with $\ell =
\mu, e$. To illustrate the results we discuss explicit examples of constraining
parameters of leptoquark models. | hep-ph |
Open charm effects in the explanation of the long-standing "$ρπ$
puzzle": A detailed analysis of the open charm effects on the decays of
$J/\psi(\psi^\prime)\to VP$ is presented, where $V$ stands for light vector
meson and $P$ for light pseudoscalar meson. These are the channels that the
so-called "12% rule" of perturbative QCD (pQCD) is obviously violated.
Nevertheless, they are also the channels that violate the pQCD helicity
selection rule (HSR) at leading order. In this work, we put constraints on the
electromagnetic (EM) contribution, short-distance contribution from the
$c\bar{c}$ annihilation at the wavefunction origin, and long-distance
contribution from the open charm threshold effects on these two decays. We show
that interferences among these amplitudes, in particular, the destructive
interferences between the short-distance and long-distance strong amplitudes
play a key role to evade the HSR and cause the significant deviations from the
pQCD expected "12% rule". | hep-ph |
A fresh look at the generalized parton distributions of light
pseudoscalar mesons: We present a symmetry-preserving scheme to derive the pion and kaon
generalized parton distributions (GPDs) in Euclidean space. The key to
maintaining crucial symmetries under this approach is the treatment of the
scattering amplitude, such that it contains both the traditional leading-order
contributions and the scalar/vector pole contribution automatically, the latter
being necessary to ensure the soft-pion theorem. The GPD is extracted
analytically via the uniqueness and definition of the Mellin moments and we
find that it naturally matches the double distribution; consequently, the
polynomiality condition and sum rules are satisfied. The present scheme thus
paves the way for the extraction of the GPD in Euclidean space using the
Dyson-Schwinger equation framework or similar continuum approaches. | hep-ph |
Precision tools and models to narrow in on the 750 GeV diphoton
resonance: The hints for a new resonance at 750 GeV from ATLAS and CMS have triggered a
significant amount of attention. Since the simplest extensions of the standard
model cannot accommodate the observation, many alternatives have been
considered to explain the excess. Here we focus on several proposed
renormalisable weakly-coupled models and revisit results given in the
literature. We point out that physically important subtleties are often missed
or neglected. To facilitate the study of the excess we have created a
collection of 40 model files, selected from recent literature, for the
Mathematica package SARAH. With SARAH one can generate files to perform
numerical studies using the tailor-made spectrum generators FlexibleSUSY and
SPheno. These have been extended to automatically include crucial higher order
corrections to the diphoton and digluon decay rates for both CP-even and CP-odd
scalars. Additionally, we have extended the UFO and CalcHep interfaces of
SARAH, to pass the precise information about the effective vertices from the
spectrum generator to a Monte-Carlo tool. Finally, as an example to demonstrate
the power of the entire setup, we present a new supersymmetric model that
accommodates the diphoton excess, explicitly demonstrating how a large width
can be obtained. We explicitly show several steps in detail to elucidate the
use of these public tools in the precision study of this model. | hep-ph |
Tau Portal Dark Matter models at the LHC: Motivated by the Galactic Center gamma-ray excess in the Fermi-LAT data, we
study the signatures of a class of tau portal dark matter (DM) models where DM
particles preferentially couple to tau leptons at the LHC. We consider the
constraints from the DM direct detection and investigate the sensitivity of the
LHC to di-tau plus missing energy signatures. We find that the LHC with a high
luminosity of 3000 fb$^{-1}$ can test the tau portal DM models with fermionic
mediators in the mass range of $120\sim450$ GeV. | hep-ph |
NLO QCD Corrections to $B_c$-to-Charmonium Form Factors: The $B_c(^1S_0)$ meson to S-wave Charmonia transition form factors are
calculated in next-to-leading order(NLO) accuracy of Quantum
Chromodynamics(QCD). Our results indicate that the higher order corrections to
these form factors are remarkable, and hence are important to the
phenomenological study of the corresponding processes. For the convenience of
comparison and use, the relevant expressions in asymptotic form at the limit of
$m_c\rightarrow0$ for the radiative corrections are presented. | hep-ph |
Nucleon sea and the five-quark components: We generalize the approach of Brodsky {\it et al.} for the intrinsic charm
quark distribution in the nucleons to the light-quark sector involving
intrinsic $\bar u, \bar d, s$ and $\bar s$ sea quarks. We compare the
calculations with the existing $\bar d - \bar u$, $s + \bar s$, and $\bar u +
\bar d - s -\bar s$ data. The good agreement between the theory and the data is
interpreted as evidence for the existence of the intrinsic light-quark sea in
the nucleons. The probabilities for the $|uudu\bar{u}>$, $|uudd\bar{d}>$ and
$|uuds\bar{s}>$ Fock states are also extracted. | hep-ph |
Optimizing the pulse shape for Schwinger pair production: Recent studies of the dynamically assisted Schwinger effect have shown that
particle production is significantly enhanced by a proper choice of the
electric field. We demonstrate that optimal control theory provides a
systematic means of modifying the pulse shape in order to maximize the particle
yield. We employ the quantum kinetic framework and derive the relevant optimal
control equations. By means of simple examples we discuss several important
issues of the optimization procedure such as constraints, initial conditions or
scaling. By relating our findings to established results we demonstrate that
the particle yield is systematically maximized by this procedure. | hep-ph |
A Symmetry Approach to CP Violation: One of the greatest challenges for particle physics in the 1990's is
understanding the broken symmetry of CP violation. It is now almost 30 years
since the discovery in 1964 of the $K_{L} \rightarrow 2\pi$ decay. What has
happened since? Why has there been no significant new experimental input in
this long period? The original $K_{L} \rightarrow 2\pi$ decay experiment is
described by two parameters $\epsilon$ and $\epsilon'$. Today $\epsilon \approx
$ its 1964 value while $\epsilon'$ still consistent with zero, and there is no
new evidence for CP violation outside the kaon system. Why is it so hard to
find CP violation? How can B Physics Help? We present a symmetry approach to
these questions. | hep-ph |
The anomalous dimension of spin-1/2 baryons in many flavors QCD: The anomalous dimension of spin-1/2 baryon operators in QCD is derived at
leading 1/Nf order using the minimal subtraction scheme. A residual ambiguity,
originating from the presence of evanescent operators in dimensional
regularization, is parametrized by a function of the renormalized coupling. Our
result is shown to agree with previous 2 and 3 loop calculations performed in
two different renormalization schemes. | hep-ph |
On Equations for the Multi-quark Bound States in Nambu--Jona-Lasinio
Model: In present report we review some preliminary results of investigation of
higher orders of mean-field expansion for Nambu--Jona-Lasinio model. We discuss
first results of investigation of next-to-next-to-leading order of mean-field
expansion equations for four-quark and three-quark Green functions. We have
considered equations for Green functions of Nambu--Jona-Lasinio model in
mean-field expansion up to third order. | hep-ph |
The Reach of LHC (CMS) for Models with Effective Supersymmetry and
Nonuniversal Gaugino Masses: We investigate squark and gluino pair production at LHC (CMS) with subsequent
decays into quarks, leptons and LSP in models with effective supersymmetry
where third generation of squarks is relatively light while the first two
generations of squarks are heavy. We consider the general case of nonuniversal
gaugino masses. Visibility of signal by an excess over SM background in $(n
\geq 2)jets + (m \geq 0)leptons + E^{miss}_T$ events depends rather strongly on
the relation between LSP, second neutralino, gluino and squark masses and it
decreases with the increase of LSP mass. | hep-ph |
Phase-shift analysis of low-energy $π^{\pm}p$ elastic-scattering data: Using electromagnetic corrections previously calculated by means of a
potential model, we have made a phase-shift analysis of the $\pi^\pm p$
elastic-scattering data up to a pion laboratory kinetic energy of 100 MeV. The
hadronic interaction was assumed to be isospin invariant. We found that it was
possible to obtain self-consistent databases by removing very few measurements.
A pion-nucleon model was fitted to the elastic-scattering database obtained
after the removal of the outliers. The model-parameter values showed an
impressive stability when the database was subjected to different criteria for
the rejection of experiments. Our result for the pseudovector $\pi N N$
coupling constant (in the standard form) is $0.0733 \pm 0.0014$. The six
hadronic phase shifts up to 100 MeV are given in tabulated form. We also give
the values of the s-wave scattering lengths and the p-wave scattering volumes.
Big differences in the s-wave part of the interaction were observed when
comparing our hadronic phase shifts with those of the current GWU solution. We
demonstrate that the hadronic phase shifts obtained from the analysis of the
elastic-scattering data cannot reproduce the measurements of the $\pi^- p$
charge-exchange reaction, thus corroborating past evidence that the hadronic
interaction violates isospin invariance. Assuming the validity of the result
obtained within the framework of chiral perturbation theory, that the mass
difference between the $u$- and the $d$-quark has only a very small effect on
the isospin invariance of the purely hadronic interaction, the
isospin-invariance violation revealed by the data must arise from the fact that
we are dealing with a hadronic interaction which still contains residual
effects of electromagnetic origin. | hep-ph |
Double Lepton Polarization Forward--Backward Asymmetries in B \rar
K^\ast \ell^+ \ell^- Decay in the SM4: This study examines the influence of the fourth generation quarks on the
double lepton polarizations forward--backward asymmetries in B \rar K^\ast
\ell^+ \ell^- decay. We obtain that for both (muon, tau) channels the magnitude
and the sign of the differential forward--backward asymmetries and the
magnitude of the average forward--backward asymmetries are quite sensitive to
the 4th generation quarks mass and mixing parameters. It can serve as a good
tool to search for new physics effects, precisely, to search for the fourth
generation quarks(t', b') via its indirect manifestations in the loop diagrams. | hep-ph |
Gauge Extensions of Supersymmetric Models and Hidden Valleys: Supersymmetric models with extended group structure beyond the standard model
are revisited in the framework of general gauge mediation. Sum rules for
sfermion masses are shown to depend genuinely on the group structure, which can
serve as important probes for specific models. The left-right model and models
with extra U(1) are worked out for illustrations. If the couplings of extra
gauge groups are small, supersymmetric hidden valleys of the scale 10-100 GeV
can be naturally constructed in companion of a TeV-scale supersymmetric visible
sector. | hep-ph |
Fermion Mixings in SU(9) Family Unification: In an SU(9) model of gauged family unification, we propose an explanation for
why angles observed in the lepton flavor ({\it PMNS}) mixing matrix are
significantly larger than those measured for any analagous quark flavor ({\it
KM}) mixing angle. It is directly related to a see-saw mechanism that we assume
to be responsible for the generation of neutrino masses. Our model is more
constrained and therefore even more predictive than a model previously proposed
by Barr. | hep-ph |
Tadpole contribution to magnetic photon-graviton conversion: Photon-graviton conversion in a magnetic field is a process that is usually
studied at tree level, but the one-loop corrections due to scalars and spinors
have also been calculated. Differently from the tree-level process, at one-loop
one finds the amplitude to depend on the photon polarization, leading to
dichroism. However, previous calculations overlooked a tadpole contribution of
the type that was considered to be vanishing in QED for decades but erroneously
so, as shown by H. Gies and one of the authors in 2016. Here we compute this
missing diagram in closed form, and show that it does not contribute to
dichroism. | hep-ph |
Accumulating Evidence for the Associated Production of a New Higgs Boson
at the Large Hadron Collider: In the last decades, the Standard Model (SM) of particle physics has been
extensively tested and confirmed, with the announced discovery of the Higgs
boson in 2012 being the last missing puzzle piece. Even though since then the
search for new particles and interactions has been further intensified, the
experiments ATLAS and CMS at the Large Hadron Collider (LHC) at CERN did not
find evidence for the direct production of a new state. However, in recent
years deviations between LHC data and SM predictions in multiple observables
involving two or more leptons (electrons or muons) have emerged, the so-called
``multi-lepton anomalies'', pointing towards the existence of a beyond the SM
Higgs boson $S$. While from these measurements its mass cannot be exactly
determined, it is estimated to lay in the range between $130\,$GeV and
$160\,$GeV. Motivated by this observation, we perform a search for signatures
of $S$, by using existing CMS and ATLAS analyses. Combining channels involving
the associate productions of SM gauge bosons ($\gamma\gamma$ and $Z\gamma$), we
find that a simplified model with a new scalar with $m_S= 151.5\,$GeV is
preferred over the SM hypothesis by 4.3$\sigma$ (3.9$\sigma$) locally
(globally). On the face of it, this provides a good indication for the
existence of a new scalar resonance $S$ decaying into photons, in association
with missing energy and allows for a connection to the long-standing problem of
Dark Matter. Furthermore, because $S$ is always produced together with other
particles, we postulate the existence of a second new (heavier) Higgs boson $H$
that decays into $S$ and propose novel searches to discover this particle,
which can be performed by ATLAS and CMS. | hep-ph |
Flavour Physics in an SO(10) Grand Unified Model: Grand unified theories open the possibility to transfer the neutrino mixing
matrix U_PMNS to the quark sector. This is accomplished in a controlled way in
a supersymmetric grand-unified model proposed by Chang, Masiero and Murayama
(CMM model) where the atmospheric neutrino mixing angle induces large new b ->
s and tau -> mu transitions. Relating the supersymmetric low-energy parameters
to seven new parameters a_0, m_0^2, m_tilde{g}, D, xi, tan beta and arg(mu) of
this SO(10) model, we perform a correlated study of several flavour-changing
neutral current (FCNC) processes. The CMM model can serve as an alternative
benchmark scenario to the popular constraint MSSM. | hep-ph |
Selected topics on tau physics: The B Factories have generated a large amount of new results on the tau
lepton. The present status of some selected topics on tau physics is presented:
charged-current universality tests, bounds on lepton-flavour violation, the
determination of alpha_s from the inclusive tau hadronic width, and the
measurement of |V_{us}| through the Cabibbo-suppressed decays of the tau
lepton. | hep-ph |
Scattering amplitudes for e^+e^- --> 3 jets at next-to-next-to-leading
order QCD: We present the calculation of the fermionic contribution to the QCD two-loop
amplitude for e^+e^- --> q qbar g. | hep-ph |
Critical QCD in Nuclear Collisions: A detailed study of correlated scalars, produced in collisions of nuclei and
associated with the $\sigma$-field fluctuations, $(\delta \sigma)^2= < \sigma^2
>$, at the QCD critical point (critical fluctuations), is performed on the
basis of a critical event generator (Critical Monte-Carlo) developed in our
previous work. The aim of this analysis is to reveal suitable observables of
critical QCD in the multiparticle environment of simulated events and select
appropriate signatures of the critical point, associated with new and strong
effects in nuclear collisions. | hep-ph |
A lower bound on the Longitudinal Structure Function at small x from a
self-similarity based model of Proton: Self-similarity based model of proton structure function at small \textit{x}
was reported in the literature sometime back. The phenomenological validity of
the model is in the kinematical region $ 6.2\, \times \, 10^{-7} \leq x \leq
10^{-2}$ and $ 0.045 \leq Q^{2} \leq 120 \, \mathrm{GeV^{2}} $. We use momentum
sum rule to pin down the corresponding self-similarity based gluon distribution
function valid in the same kinematical region. The model is then used to
compute bound on the longitudinal structure function $F_{L}\left(x,Q^{2}
\right)$ for Altarelli-Martinelli equation in QCD and is compared with the
recent HERA data. | hep-ph |
Bounding Lorentz Violation at Particle Colliders By Tracking the Motion
of Charged Particles: In the presence of Lorentz violation, the motion of a charged particle in a
magnetic field is distorted. By measuring the eccentricities of particles'
elliptical orbits and studying how those eccentricities vary with the absolute
orientation of the laboratory, it is possible to constrain the
Lorentz-violating c_JK parameters. For each observed species, this method can
provide constraints on four linear combinations of coefficients for which, in
some species, there are presently no two-sided bounds. | hep-ph |
Application of High Quality Antiproton Beam with Momentum Ranging from 1
GeV/c to 15 GeV/c to Study Charmonium and Charmed Hybrids: The elaborate analysis of spectrum of charmonium states and charmed hybrids
in the mass region over DD-threshold is given. The combined approach based on
the potential model and relativistic spherical symmetric top model for decay
products has been proposed. The experimental data from different collaborations
were analyzed. Especial attention was given to the new states with the hidden
charm discovered recently. Eight of these states may be interpreted as higher
laying radial excited charmoniumstates. Butmuchmore data on different decay
modes are needed for deeper analysis. These data can be derived directly from
the experiments using high quality antiproton beam with the momentum ranging
from 1 GeV/c to 15 GeV/c (PANDA experiment at FAIR). | hep-ph |
Deep learning for the R-parity violating supersymmetry searches at the
LHC: Supersymmetry with hadronic R-parity violation in which the lightest
neutralino decays into three quarks is still weakly constrained. This work aims
to further improve the current search for this scenario by the boosted decision
tree method with additional information from jet substructure. In particular,
we find a deep neural network turns out to perform well in characterizing the
neutralino jet substructure. We first construct a Convolutional Neutral Network
(CNN) which is capable of tagging the neutralino jet in any signal process by
using the idea of jet image. When applied to pure jet samples, such a CNN
outperforms the N-subjettiness variable by a factor of a few in tagging
efficiency. Moreover, we find the method, which combines the CNN output and jet
invariant mass, can perform better and is applicable to a wider range of
neutralino mass than the CNN alone. Finally, the ATLAS search for the signal of
gluino pair production with subsequent decay $\tilde{g} \to q q
\tilde{\chi}^0_1 (\to q q q)$ is recasted as an application. In contrast to the
pure sample, the heavy contamination among jets in this complex final state
renders the discriminating powers of the CNN and N-subjettiness similar. By
analyzing the jets substructure in events which pass the ATLAS cuts with our
CNN method, the exclusion limit on gluino mass can be pushed up by $\sim200$
GeV for neutralino mass $\sim 100$ GeV. | hep-ph |
QCD string and the Lorentz nature of confinement: We address the question of the Lorentz nature of the effective long-range
interquark interaction generated by the QCD string with quarks at the ends.
Studying the Dyson-Schwinger equation for a heavy-light quark-antiquark system,
we demonstrate explicitly how a Lorentz-scalar interaction appears in the
Diraclike equation for the light quark, as a consequence of chiral symmetry
breaking. We argue that the effective interquark interaction in the Hamiltonian
of the QCD string with quarks at the ends stems from this effective scalar
interaction. | hep-ph |
Challenges and Opportunities for the Next Generation of Photon
Regeneration Experiments: Photon regeneration experiments searching for signatures of oscillations of
photons into hypothetical very weakly interacting ultra-light particles, such
as axions, axion-like and hidden-sector particles, have improved their
sensitivity considerably in recent years. Important progress in laser and
detector technology as well as recycling of available magnets from accelerators
may allow a big further step in sensitivity such that, for the first time,
laser light shining through a wall experiments will explore territory in
parameter space that has not been excluded yet by astrophysics and cosmology.
We review these challenges and opportunities for the next generation
experiments. | hep-ph |
The Infrared Behavior of One-Loop Gluon Amplitudes at
Next-to-Next-to-Leading Order: For the case of $n$-jet production at next-to-next-to-leading order in the
QCD coupling, in the infrared divergent corners of phase space where particles
are collinear or soft, one must evaluate $(n+1)$-parton final-state one-loop
amplitudes through $\Ord(\eps^2)$, where $\eps$ is the dimensional
regularization parameter. For the case of gluons, we present to all orders in
$\eps$ the required universal functions which describe the behavior of one-loop
amplitudes in the soft and collinear regions of phase space. An explicit
example is discussed for three-parton production in multi-Regge kinematics that
has applications to the next-to-leading logarithmic corrections to the BFKL
equation. | hep-ph |
Physics of heavy neutrinos: Theoretical and experimental situation in physics of heavy neutrinos
$(M_N>M_Z)$ is briefly presented. Various experimental bounds on heavy neutrino
masses and mixings are shortly reviewed. Special attention is paid to
possibility of detecting heavy neutrinos in future lepton linear colliders. | hep-ph |
Small Shear Viscosity of a Quark-Gluon Plasma Implies Strong Jet
Quenching: We derive an expression relating the transport parameter $\hat{q}$ and the
shear viscosity $\eta$ of a weakly coupled quark-gluon plasma. A deviation from
this relation can be regarded as a quantitative measure of ``strong coupling''
of the medium. The ratio $T^3/\hat{q}$, where $T$ is the temperature, is a more
broadly valid measure of the coupling strength of the medium than $\eta/s$,
where $s$ denotes the entropy density. Different estimates of $\hat{q}$ derived
from existing RHIC data are shown to imply radically different structures of
the produced matter. | hep-ph |
Determination of the spectroscopic parameters of beauty-partners of
$T_{cc}$ from QCD: Motivated by the recent discovery of a new tetra-quark $T_{cc}^+$ state with
two charm quarks and two light quarks by LHCb collaboration, we calculate the
spectroscopic parameters, namely, the mass and residues of beauty partners of
$T_{cc}^+$ within QCD sum rules by using hadronic molecular $BB^*$ picture. The
obtained results are compared with the predictions of different approaches in
the literature. | hep-ph |
First extraction of the scalar proton dynamical polarizabilities from
real Compton scattering data: We present the first attempt to extract the scalar dipole dynamical
polarizabilities from proton real Compton scattering data below pion-production
threshold. The theoretical framework combines dispersion relations technique,
low-energy expansion and multipole decomposition of the scattering amplitudes.
The results are obtained with statistical tools that have never been applied so
far to Compton scattering data and are crucial to overcome problems inherent to
the analysis of the available data set. | hep-ph |
Test for Lorentz and CPT Violation with the MiniBooNE Low-Energy Excess: The MiniBooNE experiment is a $\nu_\mu\to\nu_e$ and $\bar\nu_\mu\to\bar\nu_e$
appearance neutrino oscillation experiment at Fermilab. The neutrino mode
oscillation analysis shows an excess of $\nu_e$ candidate events in the
low-energy region. These events are analyzed under the SME formalism, utilizing
the short baseline approximation. The preliminary result shows the time
independent solution is favored. The relationship with the SME parameters
extracted from the LSND experiment is discussed. The systematic error analysis
and antineutrino mode analysis are outlined. | hep-ph |
Study of kaon structure using the light-cone quark model: We investigate the various distributions explaining multi-dimensional
structure of kaon at the level of its constituents ($u$ and $\bar{s}$) using
the light-cone quark model. The overlap form of wavefunctions associated with
the light-cone quark model is adopted for the calculations. The generalized
parton distributions(GPDs)of $u$ and $\bar{s}$ quarks are presented for the
case when the momentum transfer in the longitudinal direction is non-zero. The
dependence of kaon GPDs is studied in terms of variation of quark longitudinal
momentum fraction, momentum transfer in longitudinal direction and total
momentum transfer to the final state of hadron. The transverse impact-parameter
dependent GPDs are also studied by taking the Fourier transformation of general
GPDs. Further, the quantum phase-space distributions; Wigner distributions are
studied for the case of unpolarized, longitudinally-polarized and
transversely-polarized parton in an unpolarized kaon. The Wigner distributions
are analysed in the transverse impact-parameter plane, the transverse momentum
plane and the mixed plane. Further, to get a complete picture of kaon in terms
of its valence quarks, the variation of longitudinal momentum fraction carried
by quark and antiquark in the generalized transverse momentum-dependent parton
distributions (GTMDs) is studied for different values of transverse quark and
antiquark momentum $({\bf k}_\perp)$ as well as for different values of
momentum transferred to the kaon in transverse direction $({\bf
\Delta}_\perp)$. This has been done for zero as well as non-zero skewedness
representing respectively the absence and presence of momentum transfer to the
final state of kaon in longitudinal direction. Furthermore, the possible
spin-orbit correlation for $u$ and $\bar{s}$ in kaon is elaborated in context
of Wigner distributions and GTMDs. | hep-ph |
Nuclear Structure Functions at Small x in Multiple Scattering Approaches: A simple model for nuclear structure functions in the region of small $x$ and
small and moderate $Q^2$, is presented. It is a parameter-free extension, in
the Glauber-Gribov approach to nuclear collisions, of a saturation model for
the nucleon. A reasonable agreement with experimental data on ratios of nuclear
structure functions is obtained. The unintegrated gluon distribution and the
behavior of the saturation scale which result from this model are discussed. | hep-ph |
A Susy Phase Transition as Central Engine: For several decades the energy source powering supernovae and gamma ray
bursts has been a troubling mystery. Many articles on these phenomena have been
content to model the consequences of an unknown "central engine" depositing a
large amount of energy in a small region. In the case of supernovae this is
somewhat unsettling since the type 1a supernovae are assumed to be
"standardizable candles" from which important information concerning the dark
energy can be derived. It should be expected that a more detailed understanding
of supernovae dynamics could lead to a reduction of the errors in this
relationship. Similarly, the current state of the standard model theory of
gamma ray bursts, which in some cases have been associated with supernovae, has
conceptual gaps not only in the central engine but also in the mechanism for
jet collimation and the lack of baryon loading. We discuss here the
Supersymmetric (susy) phase transition model for the central engine. | hep-ph |
Stops in R-parity Breaking Model for High-$Q^2$ Events at HERA: We investigate an event excess in the reaction $e^+p \to e^+ X$ with large
$x$ and high $Q^2$ observed at HERA and show that the events could naturally be
interpreted as a signature of the production of the scalar top quarks (stops)
in a supersymmetric model with $R$-parity breaking interactions. The HERA
events are characterized by the broad mass distribution and in fact it can be
simulated by our specific scenario if we consider almost degenerate two mass
eigenstates $\tilde{t_1}$ and $\tilde{t_2}$ of the stops. | hep-ph |
Heavy Quark State Production In p-p Collisions: We estimate the relative probabilities of $\Psi'(2S)$ to $J/\Psi$ production
at BNL-RHIC and $\Upsilon(nS)$ production at the LHC and Fermilab in p-p
collisions, using our recent theory of mixed heavy quark hybrids, in which the
$\Psi'(2S)$ and $\Upsilon(3S)$ mesons have approximately equal normal
$q\bar{q}$ and hybrid $q\bar{q}g$ components. | hep-ph |
Vector-scalar mixing to all orders, for an arbitrary gauge model in the
generic linear gauge: I give explicit fromulae for full propagators of vector and scalar fields in
a generic spin-1 gauge model quantized in an arbitrary linear covariant gauge.
The propagators, expressed in terms of all-order one-particle-irreducible
correlation functions, have a remarkably simple form because of constraints
originating from Slavnov-Taylor identities of Becchi-Rouet-Stora symmetry. I
also determine the behavior of the propagators in the neighborhood of the
poles, and give a simple prescription for the coefficients that generalize (to
the case with an arbitrary vector-scalar mixing) the standard
$\sqrt{\mathcal{Z}}$ factors of Lehmann, Symanzik and Zimmermann. So obtained
generalized $\sqrt{\mathcal{Z}}$ factors, are indispensable to the correct
extraction of physical amplitudes from the amputated correlation functions in
the presence of mixing. The standard $R_\xi$ guauges form a particularly
important subclass of gauges considered in this paper. While the tree-level
vector-scalar mixing is, by construction, absent in $R_\xi$ gauges, it
unavoidably reappears at higher orders. Therefore the prescription for the
generalized $\sqrt{\mathcal{Z}}$ factors given in this paper is directly
relevant for the extraction of amplitudes in $R_\xi$ gauges. | hep-ph |
Benchmarking LHC searches for light 2HDM+$\boldsymbol{a}$ pseudoscalars: Using two suitable benchmark scenarios that satisfy the experimental
constraints on the total decay width of the $125 \, {\rm GeV}$ Higgs boson, we
determine the bounds on light CP-odd spin-0 states in the 2HDM+$a$ model that
arise from existing LHC searches. Our work represents the first thorough study
that considers the parameter space with $m_a \lesssim 100 \, {\rm GeV}$ and
should prove useful for 2HDM+$a$ interpretations of future ATLAS, CMS and LHCb
searches for pseudoscalars with masses below the electroweak scale. | hep-ph |
Report of Working Group on Electromagnetic Corrections: The talks delivered by M. Knecht, H. Neufeld, V.E. Lyubovitskij, A. Rusetsky
and J. Soto during the session of the working group of electromagnetic
corrections to hadronic processes at the Eight International Symposium MENU99,
cover a wide range of problems. In particular, those include: construction of
the effective Lagrangians that then are used for the evaluation of
electromagnetic corrections to the decays of K mesons; evaluation of some of
the low-energy constants in these Lagrangians, using sum rules and the
large-N_c arguments; complete calculations of electromagnetic corrections to
the pi pi scattering amplitude at O(e^2p^2); the general theory of
electromagnetic bound states of hadrons in the Standard Model. | hep-ph |
Physics with near detectors at a neutrino factory: We discuss the impact of near detectors at a neutrino factory both on
standard oscillation and non-standard interaction measurements. Our systematics
treatment includes cross section errors, flux errors, and background
uncertainties, and our near detector fluxes include the geometry of the
neutrino source and the detector. Instead of a specific detector concept, we
introduce qualitatively different classes of near detectors with different
characteristics, such as near detectors catching the whole neutrino flux (near
detector limit) versus near detectors observing a spectrum similar to that of
the far detector (far detector limit). We include the low energy neutrino
factory in the discussion. We illustrate for which measurements near detectors
are required, discuss how many are needed, and what the role of the flux
monitoring is. For instance, we demonstrate that near detectors are mandatory
for the leading atmospheric parameter measurements if the neutrino factory has
only one baseline, whereas systematical errors partially cancel if the neutrino
factory complex includes the magic baseline. Finally, near detectors with
nu_tau detection are shown to be useful for non-standard interactions. | hep-ph |
Spectrum for Heavy Quankonia and Mixture of the Relevant Wave Functions
within the Framework of Bethe-Salpeter Equation: Considering the fact that some excited states of the heavy quarkonia
(charmonium and bottomonium) still missing in experimental observations and
potential applications of the relevant wave functions of the bound states, we
re-analyze the spectrum and the relevant wave functions of the heavy quarkonia
within the framework of Bethe-Salpeter (B.S.) equation with a proper
QCD-inspired kernel. Such a kernel for the heavy quarkonia, relating to
potential of non-relativistic quark model, is instantaneous, so we call the
corresponding B.S. equation as BS-In equation throughout the paper.
Particularly, a new way to solve the B.S. equation, which is different from the
traditional ones, is proposed here, and with it not only the known spectrum for
the heavy quarkonia is re-generated, but also an important issue is brought in,
i.e., the obtained solutions of the equation `automatically' include the
'fine', 'hyperfine' splittings and the wave function mixture, such as $S-D$
wave mixing in $J^{PC}=1^{--}$ states, $P-F$ wave mixing in $J^{PC}=2^{++}$
states for charmonium and bottomonium etc. It is pointed out that the best
place to test the wave mixture probably is at $Z$-factory ($e^+e^-$ collider
running at $Z$-boson pole with extremely high luminosity). | hep-ph |
Non linear evolution: revisiting the solution in the saturation region: In this paper we revisit the problem of the solution to Balitsky-Kovchegov
equation deeply in the saturation domain. We find that solution has the form of
Levin-Tuchin solution but it depends on variable $\bar{z} = \ln(r^2 Q^2_s) +
\mbox{Const}$ and the value of $\mbox{Const}$ is calculated in this paper. We
propose the solution for full BFKL kernel at large $z$ in the entire kinematic
region that satisfies the McLerram-Venugopalan initial condition | hep-ph |
Probing the neutrino mass matrix in next generation neutrino oscillation
experiments: We review the current status of the neutrino mass and mixing parameters
needed to reconstruct the neutrino mass matrix. A comparative study of the
precision in the measurement of oscillation parameters expected from the next
generation solar, atmospheric, reactor and accelerator based experiments is
presented. We discuss the potential of $0\nu\beta\beta$ experiments in
determining the neutrino mass hierarchy and the importance of a better
$\theta_{12}$ measurement for it. | hep-ph |
Multi-jet Production in Hadron Collisions: The advent of high-energy hadron colliders necessitates efficient and
accurate computation of multi-jet production processes, both as QCD processes
in their own right and as backgrounds for other physics. The algorithm that
performs these tasks and a brief numerical study of multi-jet processes are
presented. | hep-ph |
Soft spin correlations in final-state parton showers: We introduce a simple procedure that resolves the long-standing question of
how to account for single-logarithmic spin-correlation effects in parton
showers not just in the collinear limit, but also in the soft wide-angle limit,
at leading colour. We discuss its implementation in the context of the
PanScales family of parton showers, where it complements our earlier treatment
of the purely collinear spin correlations. Comparisons to fixed-order matrix
elements help validate our approach up to third order in the strong coupling,
and an appendix demonstrates the small size of residual subleading-colour
effects. To help probe wide-angle soft spin correlation effects, we introduce a
new declustering-based non-global spin-sensitive observable, the first of its
kind. Our showers provide a reference for its single-logarithmic resummation.
The work in this paper represents the last step required for final-state
massless showers to satisfy the broad PanScales next-to-leading logarithmic
accuracy goals. | hep-ph |
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