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Non-abelian color dielectric - towards the effective model of the low
energy QCD: Lattice motivated triplet color scalar field theory is analyzed. We consider
non-minimal as well as covariant derivative coupling with SU(2) gauge fields.
Field configurations generated by external electric sources are presented.
Moreover non-Abelian magnetic monopoles are found. Dependence on the spatial
coordinates in the obtained solutions is identical as in the usual Abelian
case. We show also that after a decomposition of the fields a modified
Faddeev-Niemi action can be obtained. It contains explicit O(3) symmetry
breaking term parameterized by the condensate of an isoscalar field. Due to
that Goldstone bosons observed in the original Faddeev-Niemi model are removed. | hep-ph |
Lambda(1520) photoproduciton off the proton target with Regge
contributions: We investigate the Lambda(1520,3/2^-)=Lambda* photoproduction off the proton
target with the Regge contributions to go beyond the resonance region, in
addition to the tree-level Born terms consisting of the s, t, and u channels,
and contact term. For this purpose, the Reggeized propagators for the K and K*
exchanges in the t channel are employed in a gauge-invariant manner. We also
take into account the contribution from a nucleon resonance D_{13}(2030). We
compute the angular and energy dependences of the production process, including
polarization observables, such as the photon-beam asymmetry and the
polarization-transfer coefficients, resulting in good qualitative agreement
with current experimental data. It turns out that the Regge contributions are
necessary to explain the high-energy data beyond E_{gamma}~4 GeV especially for
the angular dependences in the forward-scattering region. On the contrary, the
polarization observables are insensitive to the Regge contributions due to the
contact-term dominance and gauge invariance. We also compute the K^{-}-angle
distribution function in the Gottfried-Jackson frame, using the
polarization-transfer coefficients in the z direction. It shows nontrivial
theta and E_{gamma} dependences in the forward-scattering region. | hep-ph |
Precision Theory of Electroweak Interactions: As a part of the celebration of 50 years of the Standard Model of particle
physics, I present a brief history of the precision theory of electroweak
interactions. I emphasize in particular the theoretical preparations for the
LEP program and the prediction of m_t and m_h from the electroweak precision
data. [to appear in the proceedings of the SM@50 Symposium, Case Western
Reserve University, June 1-4, 2018] | hep-ph |
Bounds on TeV Seesaw Models from LHC Higgs Data: We derive bounds on the Dirac Yukawa couplings of the neutrinos in seesaw
models using the recent Large Hadron Collider (LHC) data on Higgs decays for
the case where the Standard Model singlet heavy leptons needed for the seesaw
mechanism have masses in the 100 GeV range. Such scenarios with large Yukawa
couplings are natural in Inverse Seesaw models since the small neutrino mass
owes its origin to a small Majorana mass of a new set of singlet fermions.
Large Yukawas with sub-TeV mass right-handed neutrinos are also possible for
certain textures in Type-I seesaw models, so that the above bounds also apply
to them. We find that the current Higgs data from the LHC can put bounds on
both electron- and muon-type Yukawa couplings of order 10^{-2}. | hep-ph |
Delicate interplay between the D0-D*0, rho0-J/psi, and omega-J/psi
channels in the X(3872) resonance: The nature of the X(3872) enhancement is analysed in the framework of the
Resonance-Spectrum Expansion, by studying it as a regular $J^{PC}=1^{++}$
charmonium state, though strongly influenced and shifted by open-charm decay
channels. The observed but Okubo-Zweig-Iizuka-forbidden $\rho^0 J/\psi$ and
$\omega J/\psi$ channels are coupled as well, but effectively smeared out by
using complex $\rho^0$ and $\omega$ masses, in order to account for their
physical widths, followed by a rigorous algebraic procedure to restore
unitarity. A very delicate interplay between the $D^0 D^{*0}$, $\rho^0 J/\psi$,
and $\omega J/\psi$ channels is observed. The data clearly suggest that the
X(3872) is a very narrow axial-vector $c\bar{c}$ resonance, with a pole at or
slightly below the $D^0D^{*0}$ threshold. | hep-ph |
High-p_T Pion Quenching versus anti+Baryon Enhancement in
Nucleus-Nucleus Collisions: Jet quenching of quarks and gluons in central A+A collisions suppresses the
high-p_T meson production and exposes novel baryon dynamics that we attribute
to (gluonic) baryon junctions. This mechanism predicts baryon enhancement in a
finite moderate-p_T window that decreases with increasing impact parameter. We
also extend recent calculations of the transverse momentum behavior of p/pi^+
and p-bar/pi^- to other baryon species and show that a similar pattern is
expected for the K^-/Lambda and K^+/bar{Lambda} ratios. Within the framework of
the model constant p-bar/p and bar{Lambda}/Lambda ratios are found in central
Au+Au collisions at RHIC energies up to p_T ~= 4 - 5 GeV. | hep-ph |
High-energy neutrino deeply inelastic scattering cross sections from 100
GeV to 1000 EeV: We present a state-of-the-art prediction for cross sections of neutrino
deeply inelastic scattering (DIS) from nucleon at high neutrino energies,
$E_\nu$, from 100 GeV to 1000 EeV ($10^{12}$ GeV). Our calculations are based
on the latest CT18 NNLO parton distribution functions (PDFs) and their
associated uncertainties. In order to make predictions for the highest
energies, we extrapolate the PDFs to small $x$ according to several procedures
and assumptions, thus affecting the uncertainties at ultra-high $E_\nu$; we
quantify the uncertainties corresponding to these choices. Similarly, we
quantify the uncertainties introduced by the nuclear corrections which are
required to evaluate neutrino-nuclear cross sections for neutrino telescopes.
These results can be applied to currently-running astrophysical neutrino
observatories, such as IceCube, as well as various future experiments which
have been proposed. | hep-ph |
A proposal for improving the hadronization of QCD currents in TAUOLA: After overviewing the general features of semileptonic decays of the tau
lepton, I will recall the most widely used model for them, namely that of
Kuhn-Santamaria (KS), and I will explain the subsequent works that were done
along these lines and that are implemented in the TAUOLA library for analysing
tau decays. After that, I will move to the description of our project that aims
to achieve a theory as close as possible to QCD for the considered decays. I
conclude by emphasizing the importance of the implementation of our work in
TAUOLA. | hep-ph |
The $ΔS=1$ Effective Hamiltonian Including Next-to-Leading Order
QCD and QED Corrections: In this paper we present a calculation of the $\Delta S=1$ effective weak
Hamiltonian including next-to-leading order QCD and QED corrections. At a scale
$\mu$ of the order of few GeV, the Wilson coefficients of the operators are
given in terms of the renormalization group evolution matrix and of the
coefficients computed at a large scale $\sim M_W$. The expression of the
evolution matrix is derived from the two-loop anomalous dimension matrix which
governs the mixing of the relevant current-current and penguin operators,
renormalized in some given regularization scheme. We have computed the
anomalous dimension matrix up to and including order $\alphas^2$ and $\alphae
\alphas$ in two different renormalization schemes, NDR and HV, with consistent
results. We give many details on the calculation of the anomalous dimension
matrix at two loops, on the determination of the Wilson coefficients at the
scale $M_W$ and of their evolution from $M_W$ to $\mu$. We also discuss the
dependence of the Wilson coefficients/operators on the regularization scheme. | hep-ph |
Neutral pion decay in dense skyrmion matter: We study the density dependence of the decay $\pi^0\to \gamma \gamma$ using
the Skyrme Lagrangian to describe simultaneously both the matter background and
mesonic fluctuations. Pion properties such as mass and decay constant are
modified by the medium. This leads to large suppression at high density of both
photo-production from the neutral pion and the reverse process. The in-medium
effective charge of $\pi^{\pm}$ are also discussed in the same framework. | hep-ph |
One-Loop N Gluon Amplitudes with Maximal Helicity Violation via
Collinear Limits: We present a conjecture for the $n$-gluon one-loop amplitudes with maximal
helicity violation. The conjecture emerges from the powerful requirement that
the amplitudes have the correct behavior in the collinear limits of external
momenta. One implication is that the corresponding amplitudes where three or
more gluon legs are replaced by photons vanish for $n>4$. | hep-ph |
Heavy-flavor effects in soft gluon resummation for electroweak boson
production at hadron colliders: We evaluate the impact of heavy-quark masses on transverse momentum
distributions of W, Z, and supersymmetric neutral Higgs bosons at the Tevatron
and LHC. The masses of charm and bottom quarks act as non-negligible momentum
scales at small transverse momentum, and affect resummation of soft and
collinear radiation. We point out inconsistencies in the treatment of
heavy-flavor channels at small transverse momentum in massless factorization
schemes, and formulate small transverse momentum resummation in a general-mass
variable flavor number factorization scheme. The improved treatment of the
quark mass dependence leads to non-negligible effects in precision measurements
of the W boson mass at the LHC, and may cause observable modifications in
production of Higgs bosons and other particles in heavy-quark scattering. | hep-ph |
Beam polarization effects on top-pair production at the ILC: Full one-loop electroweak-corrections for an $e^-e^+\rightarrow t \bar{t}$
process associated with sequential $t\rightarrow b \mu\nu_\mu$ decay are
discussed. At the one-loop level, the spin-polarization effects of the initial
electron and positron beams are included in the total and differential cross
sections. A narrow-width approximation is used to treat the top-quark
production and decay while including full spin correlations between them. We
observed that the radiative corrections due to the weak interaction have a
large polarization dependence on both the total and differential cross
sections. Therefore, experimental observables that depend on angular
distributions such as the forward-backward asymmetry of the top production
angle must be treated carefully including radiative corrections. We also
observed that the energy distribution of bottom quarks is majorly affected by
the radiative corrections. | hep-ph |
Electroweak Physics at HERA: Introduction and Summary: A high luminosity upgrade of HERA will allow the measurement of standard
model parameters and the neutral current couplings of quarks. These results
will have to be consistent with other precision measurements or indicate traces
of new physics. The analysis of $W$ production will complement future results
of LEP 2 and the Tevatron. We summarize the main results and conclusions
obtained by the working group on Electroweak Physics concerning the potential
of future experimentation at HERA. | hep-ph |
New light on WW scattering at the LHC with W jet tagging: After the recent discovery of a 125 GeV Higgs-like particle at the Large
Hadron Collider (LHC), it is crucial to examine its role in unitarizing high
energy W_LW_L scattering, which may reveal its possible deviation from a
Standard Model Higgs. We perform an updated study on WW scattering in the
semileptonic channel at the LHC, improved by the recently developed W jet
tagging method. The resultant statistical significance of a
Strongly-Interacting Light Higgs (SILH) model is about 20% larger than that
based on the conventionally "gold-plated" dileptonic channel, while 200% more
signal events are retained. This allows the discovery of an SILH model if the
signal strength is 100% (10%) of a pure Higgsless model, using about 40 (3000)
fb^{-1} data at the 14 TeV LHC. Meanwhile, the excellent sensitivity to the
anomalous Higgs-W boson coupling makes semileptonic WW scattering an important
complement to precision measurements at the Higgs resonance. | hep-ph |
Probing Majorana neutrinos in rare K and D, D_s, B, B_c meson decays: We study lepton number violating decays of charged K, D, D_s, B and B_c
mesons of the form M^+\to {M'}^-\ell^+\ell^+, induced by the existence of
Majorana neutrinos. These processes provide information complementary to
neutrinoless double nuclear beta decays, and are sensitive to neutrino masses
and lepton mixing. We explore neutrino mass ranges m_N from below 1 eV to
several hundred GeV. We find that in many cases the branching ratios are
prohibitively small, however in the intermediate range m_\pi < m_N < m_{B_c},
in specific channels and for specific neutrino masses, the branching ratios can
be at the reach of high luminosity experiments like those at the LHC-b and
future Super flavor-factories, and can provide bounds on the lepton mixing
parameters. | hep-ph |
Structures of Neutrino Flavor Mixing Matrix and Neutrino Oscillations at
CHORUS and NOMAD: We have studied structures of the neutrino flavor mixing matrix focusing on
the neutrino oscillations at CHORUS and NOMAD as well as the one at LSND(or
KARMEN). We have assumed two typical neutrino mass hierarchies $m_3\simeq
m_2\gg m_1$ and $m_3\gg m_2\gg m_1({\rm or}\simeq m_1)$. Taking into account
the see-saw mechanism of neutrino masses, the reasonable neutrino flavor mixing
patterns have been discussed. The observation of the neutrino oscillation at
CHORUS and NOMAD presents us the important constraint for the structure of the
neutrino flavor mixing matrix. The atomospheric neutrino anomaly has been
discussed in relation to the CHORUS and NOMAD experiments. | hep-ph |
An analysis of Precision Electroweak Measurements: Summer 98 Update: We update our analysis of precision electroweak measurements using the latest
data announced at Moriond, March 1998. Possible oblique corrections from new
physics are parametrized using the STU formalism of Ref.[1], and non-oblique
corrections to the Zbb vertex are parametrized using the xi_b zeta_b formalism
of Ref.[2]. The implications of the analysis on minimal SU(5) grand unification
is discussed. | hep-ph |
Progress in the Theory of the Electroweak Phase Transition: Recent progress in the theory of the electroweak phase transition is
discussed. For the Higgs boson mass smaller than the masses of W and Z bosons,
the phase transition is of the first order. However, its strength is
approximately 2/3 times less than what follows from the one-loop approximation.
This rules out baryogenesis in the minimal version of the electroweak theory
with light Higgs bosons. The possibility of the strongly first order phase
transition in the theory with superheavy Higgs bosons is considered.
We show that if the Yang-Mills field at high temperature acquires a magnetic
mass $\sim g^2 T$, then no linear terms appear in the effective potential in
all orders of perturbation theory and the symmetry in gauge theories at high
temperatures is actually restored. Even though the last statement was never
questioned by most of the authors, it was extremely difficult to come to a
reliable conclusion about it due to the infrared problem in thermodynamics of
non-Abelian gauge fields.
The phase transition occurs due to production and expansion of critical
bubbles. A general analytic expression for the probability of the bubble
formation is obtained, which may be used for study of tunneling in a wide class
of theories. | hep-ph |
Reconciling the nonrelativistic QCD prediction and the $J/ψ\to
3γ$ data: It has been a long-standing problem that the rare electromagnetic decay
process $J/\psi\to 3\gamma$ is plagued with both large and negative radiative
and relativistic corrections. To date it remains futile to make a definite
prediction to confront with the branching fraction of $J/\psi\to 3\gamma$
recently measured by the \textsf{CLEO-c} and \textsf{BESIII} Collaborations. In
this work, we investigate the joint perturbative and relativistic correction
(i.e. the ${\mathcal O}(\alpha_s v^2)$ correction, where $v$ denotes the
characteristic velocity of the charm quark inside the $J/\psi$) for this decay
process, which turns out to be very significant. After incorporating the
contribution from this new ingredient, with the reasonable choice of the input
parameters, we are able to account for the measured decay rates in a
satisfactory degree. | hep-ph |
MSSM Constraints from Higgs Boson Searches: The LEP era has brought immense progress in searches for Higgs bosons over
the last 12 years which will guide searches at future colliders. The evolution
of the Higgs boson mass limits are reviewed with the focus on results from
general parameter scans in the Minimal Supersymmetric extension of the Standard
Model (MSSM) in contrast to the so-called benchmark limits. The hint for a
Standard Model (SM) Higgs boson of 115.6 GeV can also be interpreted as a
preference for a Higgs boson of that mass in the MSSM. Further small data
excesses allow the hypothesis that the neutral Higgs bosons of the MSSM all
have masses between 90 and 116 GeV. | hep-ph |
Classical Gluon Production Amplitude for Nucleus-Nucleus Collisions:
First Saturation Correction in the Projectile: We calculate the classical single-gluon production amplitude in
nucleus-nucleus collisions including the first saturation correction in one of
the nuclei (the projectile) while keeping multiple-rescattering (saturation)
corrections to all orders in the other nucleus (the target). In our
approximation only two nucleons interact in the projectile nucleus: the
single-gluon production amplitude we calculate is order-g^3 and is
leading-order in the atomic number of the projectile, while resumming all
order-one saturation corrections in the target nucleus. Our result is the first
step towards obtaining an analytic expression for the first projectile
saturation correction to the gluon production cross section in nucleus-nucleus
collisions. | hep-ph |
The Simplest Models of Radiative Neutrino Mass: Excluding Simplified Zee
Models and Beyond: The complexity of radiative neutrino-mass models can be judged by: (i)
whether they require the imposition of ad hoc symmetries, (ii) the number of
new multiplets they introduce, and (iii) the number of arbitrary parameters
that appear. Adopting the view that the imposition of arbitrary new symmetries
is the least appealing approach, the simplest models have two new multiplets
and a minimal number of new parameters. With this in mind, we search for the
simplest models of radiative neutrino mass. We are lead to two new models,
containing a real scalar triplet and a charged scalar doublet (respectively),
in addition to the charged singlet scalar considered by Zee [h^+\sim(1,1,2)].
The new models are essentially simplified versions of the Zee model and appear
to be \emph{the simplest} models of radiative neutrino mass. However, these
models are only of pedagogical interest; despite successfully generating
nonzero masses, present-day data is sufficient to rule them out. The lessons
learned from these models also enable one to exclude a more general class of
radiative models. Moving beyond the minimal cases, we find a new model of
two-loop masses that employs the charged doublet \Phi\sim(1,2,3) and the
doubly-charged scalar k^{++}\sim(1,1,4). | hep-ph |
Curvature Perturbation from Supersymmetric Flat Directions: We show that a contribution to the total curvature perturbation may be due to
the presence of flat directions in supersymmetric models. It is generated at
the first os- cillation of the flat direction condensate when the latter
relaxes to the minimum of its potential after the end of inflation. We also
point out that, if the contribution to the total curvature perturbation from
supersymmetric flat direction is the dominant one, then a significant level of
non-Gaussianity in the cosmological perturbation is also naturally expected. | hep-ph |
QCD correction to gluino decay to $t\bar{t}\tildeχ^0_1$ in the MSSM: We calculate the complete next-to-leading order QCD corrections to the
three-body decay of gluino into top-pair associated with a lightest neutralino
in the minimal supersymmetric standard model. We obtain that the LO and NLO QCD
corrected decay widths of $\tilde{g} \to t \bar{t} \tilde{\chi}_1^0$ at the
${\rm SPS 6}$ benchmark point are $0.1490 GeV$ and 0.1069 GeV respectively, and
the relative correction is -28.2%. We investigate the dependence of the QCD
correction to $\tilde{g} \to t \bar{t} \tilde{\chi}_1^0$ on $\tan\beta$ and the
masses of gluino, scalar top quarks and the lightest neutralino around the
${\rm SPS6}$ benchmark point, separately. We find that the NLO QCD corrections
suppress the LO decay width, and the absolute relative correction can exceed
30% in some parameter space. Therefore, the QCD corrections to the three-body
decay $\tilde{g} \to t\bar{t}\tilde{\chi}^0_1$ should be taken into account for
the precise experimental measurement at future colliders. Moreover, we study
the distributions of the top-pair invariant mass ($M_{t\bar t}$) and the
missing energy ($E^{miss}$), and find that the line shapes of the LO
distributions of $M_{t\bar t}$ and $E^{miss}$ are not obviously distorted by
the NLO QCD corrections. | hep-ph |
Consistency of Gauged Two Higgs Doublet Model: Gauge Sector: We study the constraints on the new parameters in the gauge sector of gauged
two Higgs doublet model using the electroweak precision test data collected
from the Large Electron Positron Collider (LEP) at and off the Z-pole as well
as the current Drell-Yan and high-mass dilepton resonance data from the Large
Hadron Collider (LHC). Impacts on the new parameters by the projected
sensitivities of various electroweak observables at the Circular Electron
Positron Collider (CEPC) proposed to be built in China are also discussed. We
also clarify why the St\"{u}eckelberg mass $M_Y$ for the hypercharge $U(1)_Y$
is set to be zero in the model by showing that it would otherwise lead to the
violation of the standard charge assignments for the elementary quarks and
leptons. | hep-ph |
Wandzura-Wilczek approximation for the twist-3 DVCS amplitude: We present a derivation of Wandzura-Wilczek (WW) like relations for skewed
parton distributions. It is demonstrated for photon-pion scattering that the
skewed twist-3 parton distributions contributing to the DVCS amplitude have
discontinuities at the points $x=\pm\xi$ in the WW approximation. This may lead
to a violation of factorisation for the twist-3 DVCS amplitude with transverse
polarization of the virtual photon. We show, however, that the contribution of
the divergencies to the scattering of a transversely polarized virtual photon
affects DVCS observables only at order $1/Q^2$ and can be neglected at twist-3
accuracy. For the scattering of a longitudinally polarized photon the twist-3
amplitude is free of such divergencies. | hep-ph |
New effective treatment of the light-front nonvalence contribution in
timelike exclusive processes: We discuss a necessary nonvalence contribution in timelike exclusive
processes. Following a Schwinger-Dyson type of approach, we relate the
nonvalence contribution to an ordinary light-front wave function that has been
extensively tested in the spacelike exclusive processes. A complicate four-body
energy denominator is exactly cancelled in summing the light-front time-ordered
amplitudes. Applying our method to $K_{\ell3}$ and $D^0\to K^- \ell^+ \nu_l$
where a rather substantial nonvalence contribution is expected, we find not
only an improvement in comparing with the experimental data but also a
covariance(i.e. frame-independence) of existing light-front constituent quark
model. | hep-ph |
Relic neutrino asymmetries and big bang nucleosynthesis in a four
neutrino model: Oscillations between ordinary and sterile neutrinos can generate large
neutrino asymmetries in the early universe. These asymmetries can significantly
affect big bang nucleosynthesis (BBN) through modification of nuclear reaction
rates. We study this phenomenon within a model consisting of the three ordinary
neutrinos plus one sterile neutrino that can be motivated by the neutrino
anomalies and the dark matter problem. We calculate how the lepton asymmetries
produced evolve at temperatures where they impact on BBN. The effect of the
asymmetries on primordial helium production is determined, leading to an
effective number of neutrino flavours during BBN of either about 2.7 or 3.1
depending on the sign of the lepton asymmetry. | hep-ph |
Gauge dependence of the quark gap equation: an exploratory study: We study the gauge dependence of the quark propagator in quantum
chromodynamics by solving the gap equation with a nonperturbative quark-gluon
vertex which is constrained by longitudinal and transverse Slavnov-Taylor
identities, the discrete charge conjugation and parity symmetries and which is
free of kinematic singularities in the limit of equal incoming and outgoing
quark momenta. We employ gluon propagators in renormalizable $R_\xi$ gauges
obtained in lattice QCD studies. We report the dependence of the
nonperturbative quark propagator on the gauge parameter, in particular we
observe an increase, proportional to the gauge-fixing parameter, of the mass
function in the infrared domain, whereas the wave renormalization decreases
within the range $0 \leq \xi \leq 1$ considered here. The chiral quark
condensate reveals a mild gauge dependence in the region of $\xi$ investigated.
We comment on how to build and improve upon this exploratory study in future in
conjunction with generalized gauge covariance relations for QCD. | hep-ph |
The LPM Effect in sequential bremsstrahlung: $1/N_c^2$ corrections: An important question concerning in-medium high-energy parton showers in a
quark-gluon plasma or other QCD medium is whether consecutive splittings of the
partons in a given shower can be treated as quantum mechanically independent,
or whether the formation times for two consecutive splittings instead have
significant overlap. Various previous calculations of the effect of overlapping
formation times have either (i) restricted attention to a soft bremsstrahlung
limit, or else (ii) used the large-$N_c$ limit (where $N_c{=}3$ is the number
of quark colors). In this paper, we make a first study of the accuracy of the
large-$N_c$ limit used by those calculations of overlap effects that avoid a
soft bremsstrahlung approximation. Specifically, we calculate the $1/N_c^2$
correction to previous $N_c{=}\infty$ results for overlap $g \to gg \to ggg$ of
two consecutive gluon splittings $g \to gg$. At order $1/N_c^2$, there is
interesting and non-trivial color dynamics that must be accounted for during
the overlap of the formation times. | hep-ph |
Forward Compton Scattering, using Real Analytic Amplitudes: We analyze forward Compton scattering, using real analytic amplitudes. By
fitting the total \gamma p scattering cross section data in the high energy
region 5 GeV < \sqrt s < 20 GeV, using a cross section rising as \ln^2 s, we
calculate \rho_{\gamma p}, the ratio of the real to the imaginary portion of
the the forward Compton scattering amplitude, and compare this to \rho_{nn},
the ratio of the even portions of the pp and p-bar p forward scattering
amplitudes. We find that the two \rho-values are, within errors, the same in
the c.m.s. energy region 5 GeV < \sqrt s < 200 GeV, as predicted by a
factorization theorem of Block and Kadailov. | hep-ph |
The production of the doubly charmed baryon in deeply inelastic $ep$
scattering at the Large Hadron Electron Collider: In this paper, we carry out a detailed study on the production of the doubly
charmed baryon in deeply inelastic $ep$ scattering (DIS) for $Q^2\in[2,
100]~\textrm{GeV}^2$, at the Large Hadron Electron Collider (LHeC) with
$E_e=60(140)$ GeV and $E_p=7000$ GeV. To exclude the contributions from the
diffractive productions and the $b$ hadron decays, we impose the kinematic cuts
$0.3<z<0.9$, and $p_{t,\textrm{baryon}}^{\star2}>1~\textrm{GeV}^2$ in the
center-of-mass (CM) frame of $\gamma^{*}p$. Based on the designed LHeC
luminosity, by detecting the decay channel $\Xi^{+}_{cc}(\Xi^{++}_{cc}) \to
\Lambda_c^{+}$ with the subsequent decay $\Lambda_c^{+} \to pK^{-}\pi^{+}$, we
predict that about 1880 (2700) $\Xi^{+}_{cc}$ events and 3750 (5400)
$\Xi^{++}_{cc}$ events can be accumulated per year, which signifies the
prospect of observing them via the DIS at the forthcoming LHeC. In addition, we
also predict the distributions of a rich variety of physical observables in the
laboratory frame and the $\gamma^{*}p$ CM frame, including $Q^2$, $p_t^{2}$,
$Y$(rapidity), $p_t^{\star2}$, $Y^{\star}$, $W$, and $z$ distributions,
respectively, which can provide helpful references for studying the doubly
charmed baryon. In conclusion, we think that in addition to the LHC, the LHeC
is also a helpful platform for studying the properties of the doubly charmed
baryon. | hep-ph |
Master Integrals for Inclusive Weak Decays of Heavy Flavours at
Next-to-Leading Order: We present analytical results for master integrals emerging in the
computation of differential rates for inclusive weak decays of heavy flavors at
next-to-leading order (NLO) in QCD. As an immediate physical application, these
master integrals allow for a calculation of the spectra of the leptonic
invariant mass in inclusive semileptonic decays in the framework of the heavy
quark expansion, including the NLO QCD corrections to power suppressed terms. | hep-ph |
Elastic and transition form factors of light pseudoscalar mesons from
QCD sum rules: We revisit $F_\pi(Q^2)$ and $F_{P\gamma}(Q^2)$, $P=\pi,\eta,\eta'$, making
use of the local-duality (LD) version of QCD sum rules. We give arguments, that
the LD sum rule provides reliable predictions for these form factors at $Q^2
\ge 5-6$ GeV$^2$, the accuracy of the method increasing with $Q^2$ in this
region. For the pion elastic form factor, the well-measured data at small $Q^2$
give a hint that the LD limit may be reached already at relatively low values
of momentum transfers, $Q^2\approx 4-8$ GeV$^2$; we therefore conclude that
large deviations from LD in the region $Q^2=20-50$ GeV$^2$ seem very unlikely.
The data on the ($\eta,\eta')\to\gamma\gamma^*$ form factors meet the
expectations from the LD model. However, the {\sc BaBar} results for the
$\pi^0\to\gamma\gamma^*$ form factor imply a violation of LD growing with $Q^2$
even at $Q^2\approx 40$ GeV$^2$, at odds with the $\eta,\eta'$ case and with
the general properties expected for the LD sum rule. | hep-ph |
Higher Twist Distribution Amplitudes of the Nucleon in QCD: We present the first systematic study of higher-twist light-cone distribution
amplitudes of the nucleon in QCD. We find that the valence three-quark state is
described at small transverse separations by eight independent distribution
amplitudes. One of them is leading twist-3, three distributions are twist-4 and
twist-5, respectively, and one is twist-6. A complete set of distribution
amplitudes is constructed, which satisfies equations of motion and constraints
that follow from conformal expansion. Nonperturbative input parameters are
estimated from QCD sum rules. | hep-ph |
Baryon number non-conservation as Peccei-Quinn mechanism: Baryon number is an accidental symmetry in the standard model, while
Peccei-Quinn symmetry is hypothetical symmetry which is introduced to solve the
strong CP problem. We study the possible connections between Peccei-Quinn
symmetry and baryon number symmetry. In this framework, an axion is identified
as the Nambu-Goldstone boson of baryon number violation. As a result,
characteristic baryon number violating processes are predicted. We developed
the general method to determine the baryon number and lepton number of new
scalar in the axion model. | hep-ph |
The Electroweak Phase Transition at $m_H \simeq m_W$: We study the finite temperature electroweak transition with non-perturbative
lattice Monte Carlo simulations. We find that it is of first order, at least
for Higgs masses up to 80 GeV. The critical temperature of the phase transition
is found to be smaller than that determined by a 2-loop renormalization group
improved effective potential. The jump of the order parameter at the critical
temperature is considerably larger than the perturbative value. By comparing
lattice data and perturbation theory, we demonstrate that the latter, for the
computation of the vacuum expectation value of the Higgs field $v(T)$ in the
broken phase at given temperature, converges quite well, provided $v(T)/T>1$.
An upper bound on the Higgs mass necessary for electroweak baryogenesis in the
light of the lattice data is briefly discussed. | hep-ph |
Higgs-gauge unification without tadpoles: In orbifold gauge theories localized tadpoles can be radiatively generated at
the fixed points where U(1) subgroups are conserved. If the Standard Model
Higgs fields are identified with internal components of the bulk gauge fields
(Higgs-gauge unification) in the presence of these tadpoles the Higgs mass
becomes sensitive to the UV cutoff and electroweak symmetry breaking is
spoiled. We find the general conditions, based on symmetry arguments, for the
absence/presence of localized tadpoles in models with an arbitrary number of
dimensions D. We show that in the class of orbifold compactifications based on
T^{D-4}/Z_N (D even, N>2) tadpoles are always allowed, while on T^{D-4}/\mathbb
Z_2 (arbitrary D) with fermions in arbitrary representations of the bulk gauge
group tadpoles can only appear in D=6 dimensions. We explicitly check this with
one- and two-loops calculations | hep-ph |
Scalar field couplings to quadratic curvature and decay into gravitons: Any field, even if it lives in a completely hidden sector, interacts with the
visible sector at least via the gravitational interaction. In this paper, we
show that a scalar field in such a hidden sector generically couples to the
quadratic curvature via dimension five operators, i.e., $\phi R^2$, $\phi
R^{\mu\nu} R_{\mu\nu}$, $\phi R_{\mu\nu\rho\sigma} R^{\mu\nu\rho\sigma}$, $\phi
R_{\mu\nu\rho\sigma} \tilde R^{\mu\nu\rho\sigma}$, because they can emerge if
there exist particles heavier than it. We derive these scalar couplings to the
quadratic curvature by integrating out heavy particles in a systematic manner.
Such couplings are of phenomenological interest since some of them induce the
scalar decay into the graviton pair. We point out that the decay of a scalar
field can produce a substantial amount of the stochastic cosmic graviton
background at high frequency since the suppression scale of these operators is
given by the mass of heavy particles not by the Planck scale. The resultant
graviton spectrum is computed in some concrete models. | hep-ph |
Search for Physics Beyond the Standard Model: We survey some recent ideas and progress in looking for particle physics
beyond the Standard Model, connected by the theme of Supersymmetry (SUSY). We
review the success of SUSY-GUT models, the expected experimental signatures and
present limits on SUSY partner particles, and Higgs phenomenology in the
minimal SUSY model. | hep-ph |
Probing the QCD Equation of State: We propose a novel quasiparticle interpretation of the equation of state of
deconfined QCD at finite temperature. Using appropriate thermal masses, we
introduce a phenomenological parametrisation of the onset of confinement in the
vicinity of the phase transition. Lattice results of bulk thermodynamic
quantities are well reproduced, the extension to small quark chemical potential
is also successful. We then apply the model to dilepton production and charm
suppression in ultrarelativistic heavy-ion collisions. | hep-ph |
The High Density Parton Dynamics from Eikonal and Dipole Pictures: In this contribution we discuss distinct approaches for the high density QCD
(hdQCD) and the demonstration of the equivalence between the AGL approach and
the K approach is presented. Our conclusion is that the AGL equation is a good
candidate for an unitarized evolution equation at high densities in the DLA
limit. | hep-ph |
Approximate degeneracy of heavy-light mesons with the same $L$: Careful observation of the experimental spectra of heavy-light mesons tells
us that heavy-light mesons with the same angular momentum $L$ are almost
degenerate. The estimate is given how much this degeneracy is broken in our
relativistic potential model, and it is analytically shown that expectation
values of a commutator between the lowest order Hamiltonian and ${\vec L}^{~2}$
are of the order of $1/m_Q$ with a heavy quark mass $m_Q$. It turns out that
nonrelativistic approximation of heavy quark system has a rotational symmetry
and hence degeneracy among states with the same $L$. This feature can be tested
by measuring higher orbitally and radially excited heavy-light meson spectra
for $D/D_s/B/B_s$ in LHCb and forthcoming BelleII. | hep-ph |
Atlas of solar hidden photon emission: Hidden photons, gauge bosons of a U(1) symmetry of a hidden sector, can
constitute the dark matter of the universe and a smoking gun for large volume
compactifications of string theory. In the sub-eV mass range, a possible
discovery experiment consists on searching the copious flux of these particles
emitted from the Sun in a helioscope setup \`a la Sikivie. In this paper, we
compute the flux of transversely polarised HPs from the Sun, a necessary
ingredient for interpreting such experiments. We provide a detailed exposition
of photon-HP oscillations in inhomogenous media, with special focus on
resonance oscillations, which play a leading role in many cases. The region of
the Sun emitting HPs resonantly is a thin spherical shell for which we justify
an averaged-emission formula and which implies a distinctive morphology of the
angular distribution of HPs on Earth in many cases. Low mass HPs with energies
in the visible and IR have resonances very close to the photosphere where the
solar plasma is not fully ionised and requires building a detailed model of
solar refraction and absorption. We present results for a broad range of HP
masses (from 0-1 keV) and energies (from the IR to the X-ray range), the most
complete atlas of solar HP emission to date. | hep-ph |
Twist expansion of the nucleon structure functions, F2 and FL, in the
DGLAP improved saturation model: Higher twist effects in the deeply inelastic scattering are studied. We start
with a short review of the theoretical results on higher twists in QCD. Within
the saturation model we perform a twist analysis of the nucleon structure
functions FT and FL at small value of the Bjorken variable x. The parameters of
the model are fitted to the HERA F2 data, and we derive a prediction for the
longitudinal structure function FL. We conclude that for FL the higher twist
corrections are sizable whereas for F2 = FT + FL there is a nearly complete
cancellation of twist-4 corrections in FT and FL. We discuss a few consequences
for future LHC measurements. | hep-ph |
Hadron production in non linear relativistic mean field models: By using a parametrization of the non-linear Walecka model which takes into
account the binding energy of different hyperons, we present a study of
particle production yields measured in central Au-Au collision at RHIC. Two
sets of different hyperon-meson coupling constants are employed in obtaining
the hadron production and chemical freeze-out parameters. These quantities show
a weak dependence on the used hyperon-meson couplings. Results are in good
overall accordance with experimental data. We have found that the repulsion
among the baryons is quite small and, through a preliminary analysis of the
effective mesonic masses, we suggest a way to improve the fittings. | hep-ph |
The ttbar threshold at a muon collider: The beam energy spread is a major issue in future attempts to study the
$t\overline{t}$ threshold at $e^+e^-$ colliders. Muon colliders are expected to
naturally have narrow band beams making them an ideal place to study the
excitation curve. We present the parameter determinations that are possible
from measuring the total cross section near threshold at a $\mu ^+\mu ^-$
collider. | hep-ph |
Hadron Resonance Gas Model with Induced Surface Tension: Here we present a physically transparent generalization of the multicomponent
Van der Waals equation of state in the grand canonical ensemble. For the
one-component case the third and fourth virial coefficients are calculated
analytically. It is shown that an adjustment of a single model parameter allows
us to reproduce the third and fourth virial coefficients of the gas of hard
spheres with small deviations from their exact values. A thorough comparison of
the compressibility factor and speed of sound of the developed model with the
one and two component Carnahan-Starling equation of state is made. It is shown
that the model with the induced surface tension is able to reproduce the
results of the Carnahan-Starling equation of state up to the packing fractions
0.2-0.22 at which the usual Van der Waals equation of state is inapplicable. At
higher packing fractions the developed equation of state is softer than the gas
of hard spheres and, hence, it breaks causality in the domain where the
hadronic description is expected to be inapplicable. Using this equation of
state we develop an entirely new hadron resonance gas model and apply it to a
description of the hadron yield ratios measured at AGS, SPS, RHIC and ALICE
energies of nuclear collisions. The achieved quality of the fit per degree of
freedom is about 1.08. We confirm that the strangeness enhancement factor has a
peak at low AGS energies, while at and above the highest SPS energy of
collisions the chemical equilibrium of strangeness is observed. We argue that
the chemical equilibrium of strangeness, i.e. $\gamma_s \simeq 1$, observed
above the center of mass collision energy 4.3 GeV may be related to the
hadronization of quark gluon bags which have the Hagedorn mass spectrum, and,
hence, it may be a new signal for the onset of deconfinement. | hep-ph |
Nongauge antisymmetric-tensor bosons mediating interactions in the
hidden sector: In a recent work, we have constructed a model of hidden sector of the
Universe, consisting of sterile spin-1/2 Dirac fermions ("sterinos"), sterile
spin-0 bosons ("sterons") conjectured to get spontaneously nonzero vacuum
expectation value, and also of conventional photons assumed to participate both
in the hidden and Standard-Model sectors (after the electroweak symmetry is
spontaneously broken by the Standard-Model Higgs mechanism). This provides a
"photonic portal" to the hidden sector as an alternative to the popular "Higgs
portal". Moreover, we have proposed to stop the proliferation of new kinds of
gauge bosons as sterile mediators of nongravitational interactions in the
hidden sector, introducing instead nongauge mediating bosons described by an
antisymmetric-tensor field (of dimension one), whose sources are given not only
by sterino-antisterino pairs, but also by steron-photon pairs. Then,
conventional photons display, beside the familiar gauge coupling to the
Standard-Model electric current, a new nongauge weak coupling of sterile
antisymmetric-tensor bosons to steron-photon pairs, where photons are described
by the gauge-invariant electromagnetic field F_{\mu \nu}. The new mediators are
unstable, decaying, for instance, into electron-positron pairs. When
interacting in pairs, they can annihilate simply into two photons. The
corresponding cross-section is calculated. | hep-ph |
Probing neutrino masses with future galaxy redshift surveys: We perform a new study of future sensitivities of galaxy redshift surveys to
the free-streaming effect caused by neutrino masses, adding the information on
cosmological parameters from measurements of primary anisotropies of the cosmic
microwave background (CMB). Our reference cosmological scenario has nine
parameters and three different neutrino masses, with a hierarchy imposed by
oscillation experiments. Within the present decade, the combination of the
Sloan Digital Sky Survey (SDSS) and CMB data from the PLANCK experiment will
have a 2-sigma detection threshold on the total neutrino mass close to 0.2 eV.
This estimate is robust against the inclusion of extra free parameters in the
reference cosmological model. On a longer term, the next generation of
experiments may reach values of order sum m_nu = 0.1 eV at 2-sigma, or better
if a galaxy redshift survey significantly larger than SDSS is completed. We
also discuss how the small changes on the free-streaming scales in the normal
and inverted hierarchy schemes are translated into the expected errors from
future cosmological data. | hep-ph |
Searching for a New Source(s) of T-Violation in Spin Dependent Total
Cross Section Measurements: We first re-prove with a more complete method that the the minimum standard
model, with the inclusion of the CKM-matrix, requires the T-odd/P-odd total
cross section of two spin-1/2 particles to vanish in all orders\cite{gxu}. Then
we study the contribution to T-odd/P-odd total scattering cross sections from
various channels within the Higgs sector, and optimize conditions for possible
experimental measurements of these effects. These studies show that such
contributions can appear at tree level, and that the spin dependent cross
section asymmetry is measurable if the lightest Higgs paarticle is not too
massive, {\it e.g.} $m_H \sim 200 GeV$, and if suitable reaction channels and
beam energies and luminosities are chosen. | hep-ph |
Studies of the ambient light of deep Baikal waters with Baikal-GVD: The Baikal-GVD neutrino detector is a deep-underwater neutrino telescope
under construction and recently after the winter 2023 deployment it consists of
3456 optical modules attached on 96 vertical strings. This 3-dimensional array
of photo-sensors allows to observe ambient light in the vicinity of the
Baikal-GVD telescope that is associated mostly with water luminescence. Results
on time and space variations of the luminescent activity are reviewed based on
data collected in 2018-2022. | hep-ph |
Right-handed current contributions in B -> K pi decays: We reexamine the right-handed current effects in $b \to s$ transitions in
nonmanifest left-right models. Using the effective Hamiltonian approach
including all possible low-energy operators, we obtain especially the B \to K
\pi decay amplitudes including annihilation contributions, and investigate the
right-handed current contributions to CP asymmetries in $B \to K \pi$ decays.
Taking into account the constraints from global analysis of muon decay
measurements, |V_{ub}| measurements in inclusive and exclusive B decays, and
$B_s^0-\bar{B_s^0}$ mixing measurements, we find the allowed regions of new
physics parameters satisfying the current experimental data. | hep-ph |
Detecting Tau Neutrino Oscillations at PeV Energies: It is suggested that a large deep underocean (or ice) neutrino detector,
given the presence of significant numbers of neutrinos in the PeV energy range
as predicted by various models of Active Galactic Nuclei, can make unique
measurements of the properties of neutrinos. It will be possible to observe the
existence of the tau neutrino, measure its mixing with other flavors, in fact
test the mixing pattern for all three flavors based upon the mixing parameters
suggested by the atmospheric and solar neutrino data, and measure the tau
neutrino cross section. The key signature is the charged current tau neutrino
interaction, which produces a double cascade, one at either end of a lightly
radiating track. At a few PeV these cascades would be separated by roughly 100
m, and thus be easily resolvable in next generation DUMAND-like detectors.
First examples might be found in detectors presently under construction. Future
applications are precise neutrino astronomy and earth tomography. This paper is
an expanded version of hep-ph/9405296, for publication. | hep-ph |
Gravitational Instabilities of the Cosmic Neutrino Background with
Non-zero Lepton Number: We argue that a cosmic neutrino background that carries non-zero lepton
charge develops gravitational instabilities. Fundamentally, these instabilities
are related to the mixed gravity-lepton number anomaly. We have explicitly
computed the gravitational Chern-Simons term which is generated
quantum-mechanically in the effective action in the presence of a lepton number
asymmetric neutrino background. The induced Chern-Simons term has a twofold
effect: (i) gravitational waves propagating in such a neutrino background
exhibit birefringent behaviour leading to an enhancement/suppression of the
gravitational wave amplitudes depending on the polarisation, where the
magnitude of this effect is related to the size of the lepton asymmetry; (ii)
Negative energy graviton modes are induced in the high frequency regime, which
leads to very fast vacuum decay producing, e.g., positive energy photons and
negative energy gravitons. From the constraint on the present radiation energy
density, we obtain an interesting bound on the lepton asymmetry of the
universe. | hep-ph |
$β$-function for topologically massive gluons: We calculate the quantum corrections to the two-point function of four
dimensional topologically massive non-Abelian vector fields at one loop order
for $SU(N)$ gauge theory in Feynman-'t Hooft gauge. We calculate the beta
function of the gauge coupling constant and find that the theory becomes
asymptotically free faster than pure $SU(N)$ gauge theory. | hep-ph |
Electroweak Physics: We review the prospects for studies in electroweak physics at the LHC. | hep-ph |
Status of Constraints on Supersymmetry: A short summary of constraints on the parameter space of supersymmetric
models is given. Experimental limits from high energy colliders, electroweak
precision data, flavor and Higgs physics, and cosmology are considered. The
main focus is on the MSSM with conserved R- and CP-parity and minimal flavor
violation, but more general scenarios and extended models will also be
discussed briefly. | hep-ph |
A novel left-right symmetric model: A novel gauge model which has a spontaneously broken parity symmetry is
constructed. The model has only 2 parameters beyond those of the standard
model. Some of the unusual implications of the model are discussed. | hep-ph |
Hard inclusive production and a violation of the factorization theorem: A new mechanism for hard inclusive production, which leads to a violation of
the factorization theorem, is suggested. The mechanism is illustrated by a
detailed discussion of Higgs meson production in high energy deutron-deutron
scattering. Numerical estimates for the effect are given for high energy hadron
(nucleus) scattering. | hep-ph |
Exact formulae for Higgs production through e gamma --> e H in the
non-linear R_ξgauge: We study the production of the SM Higgs boson (H^0) at future e gamma
colliders, through the reaction e gamma --> e H^0. The amplitude is evaluated
using the non-linear R_\xi gauge, which greatly simplifies the calculation.
Complete analytical expressions for the amplitudes are presented, which include
the contributions from 1-loop triangles "gamma gamma^* H^0" and "gamma Z^* H^0"
as well as the W- and Z-boxes with their related $eeH^0$ triangle graphs. The
resulting cross section for this mechanism indicates that it could be used to
detect the Higgs signal and to test its properties. | hep-ph |
Slepton pair production at the LHC in NLO+NLL with resummation-improved
parton densities: Novel PDFs taking into account resummation-improved matrix elements, albeit
only in the fit of a reduced data set, allow for consistent NLO+NLL
calculations of slepton pair production at the LHC. We apply a factorisation
method to this process that minimises the effect of the data set reduction,
avoids the problem of outlier replicas in the NNPDF method for PDF
uncertainties and preserves the reduction of the scale uncertainty. For Run II
of the LHC, left-handed selectron/smuon, right-handed and maximally mixed stau
production, we confirm that the consistent use of threshold-improved PDFs
partially compensates the resummation contributions in the matrix elements.
Together with the reduction of the scale uncertainty at NLO+NLL, the described
method further increases the reliability of slepton pair production cross
sections at the LHC. | hep-ph |
Gauge Coupling Unification in Gauge-Higgs Grand Unification: We discuss renormalization group equations for gauge coupling constants in
gauge-Higgs grand unification on five-dimensional Randall-Sundrum warped space.
We show that all the four-dimensional Standard Model gauge coupling constants
are asymptotically free and are effectively unified in $SO(11)$ gauge-Higgs
grand unified theories on 5D Randall-Sundrum warped space. | hep-ph |
μ-τSymmetry and Maximal CP Violation: We argue the possibility that a real part of a flavor neutrino mass matrix
only respects a mu-tau symmetry. This possibility is shown to be extended to
more general case with a phase parameter \theta, where the mu-tau symmetric
part has a phase of \theta/2. This texture shows maximal CP violation and no
Majorana CP violation. | hep-ph |
Low-Scale Leptogenesis and the Domain Wall Problem in Models with
Discrete Flavor Symmetries: We propose a new mechanism for leptogenesis, which is naturally realized in
some models with a flavor symmetry based on the discrete group A_4, where the
symmetry breaking parameter also controls the Majorana masses for the heavy
right handed (RH) neutrinos. During the early universe, for T>TeV, part of the
symmetry is restored, due to finite temperature contributions, and the RH
neutrinos remain massless and can be produced in thermal equilibrium even at
temperatures well below the most conservative gravitino bounds. Below this
temperature the phase transition occurs and they become massive, decaying out
of equilibrium and producing the necessary lepton asymmetry. Unless the
symmetry is broken explicitly by Planck-suppressed terms, the domain walls
generated by the symmetry breaking survive till the quark-hadron phase
transition, where they disappear due to a small energy splitting between
different vacua caused by the QCD anomaly. | hep-ph |
Overview of Neutrino Mixing Models and Ways to Differentiate among Them: An overview of neutrino-mixing models is presented with emphasis on the types
of horizontal flavor and vertical family symmetries that have been invoked.
Distributions for the mixing angles of many models are displayed. Ways to
differentiate among the models and to narrow the list of viable models are
discussed. | hep-ph |
Hadronic Final States in DIS at NNLO QCD with Parton Showers: We present a parton-shower matched NNLO QCD calculation for hadronic final
state production in Deep Inelastic Scattering. The computation is based on the
UNLOPS method and is implemented in the publicly available event generation
framework SHERPA. Results are compared to measurements performed by the H1
collaboration. | hep-ph |
Searches for Decays of New Particles in the DUNE Multi-Purpose Near
Detector: One proposed component of the upcoming Deep Underground Neutrino Experiment
(DUNE) near detector complex is a multi-purpose, magnetized, gaseous argon time
projection chamber: the Multi-Purpose Detector (MPD). We explore the
new-physics potential of the MPD, focusing on scenarios in which the MPD is
significantly more sensitive to new physics than a liquid argon detector,
specifically searches for semi-long-lived particles that are produced in/near
the beam target and decay in the MPD. The specific physics possibilities
studied are searches for dark vector bosons mixing kinetically with the
Standard Model hypercharge group, leptophilic vector bosons, dark scalars
mixing with the Standard Model Higgs boson, and heavy neutral leptons that mix
with the Standard Model neutrinos. We demonstrate that the MPD can extend
existing bounds in most of these scenarios. We illustrate how the ability of
the MPD to measure the momentum and charge of the final state particles leads
to these bounds. | hep-ph |
Enhanced Higgs Mass in a Gaugino Mediation Model without the Polonyi
Problem: We consider a SUSY breaking scenario without the Polonyi problem. To solve
the problem, the enhanced couplings of the Polonyi field to an inflaton, gauge
kinetic functions and itself are assumed. As a result, a gaugino mediated SUSY
breaking occurs. In this scenario, the Higgs boson mass becomes consistent with
the recently observed value of the Higgs-like boson (i.e., m_h ~= 125 GeV) for
the gluino mass about 4TeV, which is, however, out of the reach of the LHC
experiment. We show that the trilinear coupling of the scalar top is
automatically enhanced by the presence of the extra matters. With such extra
matters, the Higgs mass as large as 125 GeV can be realized with the gluino
mass of 1-2 TeV which is within the reach of the LHC experiment. In our
scenario, the gravitino is the lightest SUSY particle and the candidate for
dark matter, and the Wino, Bino, and sleptons are in a range from 200 GeV to
700 GeV. | hep-ph |
Mass Spectra of $D$, $D_s$ Mesons using Dirac formalism with martin-like
confinement potential: We have calculated mass spectra of $D$, $D_s$ mesons using Dirac formalism
with Martin-like potential in Potential model. | hep-ph |
Matter Effects on Long Baseline Neutrino Oscillation Experiments: We calculate matter effects on neutrino oscillations relevant for long
baseline neutrino oscillation experiments. In particular, we compare the
results obtained with simplifying approximations for the density profile in the
Earth versus results obtained with actual density profiles. We study the
dependence of the oscillation signals on both $E/\Delta m^2_{atm.}$ and on the
angles in the leptonic mixing matrix. The results show quantitatively how
matter effects can cause significant changes in the oscillation signals,
relative to vacuum oscillations and can be useful in amplifying these signals
and helping one to obtain measurements of mixing parameters and the magnitude
and sign of $\Delta m^2$. | hep-ph |
On the Nature of X(4260): We study the property of $X(4260)$ resonance by re-analyzing all experimental
data available, especially the $e^+e^- \rightarrow
J/\psi\,\pi^+\pi^-,\,\,\,\omega\chi_{c0}$ cross section data. The final state
interactions of the $\pi\pi$, $K\bar K$ couple channel system are also taken
into account. A sizable coupling between the $X(4260)$ and $\omega\chi_{c0}$ is
found. The inclusion of the $\omega\chi_{c0}$ data indicates a small value of
$\Gamma_{e^+e^-}=23.30\pm 3.55$eV. | hep-ph |
Muon conversion to electron in nuclei within the BLMSSM: In a supersymmetric extension of the standard model with local gauged baryon
and lepton numbers (BLMSSM), there are new sources for lepton flavor violation,
because the right-handed neutrinos, new gauginos and Higgs are introduced. We
investigate muon conversion to electron in nuclei within the BLMSSM in detail.
The numerical results indicate that the $\mu \rightarrow e $ conversion rates
in nuclei within the BLMSSM can reach the experimental upper bound, which may
be detected in the future experiments. | hep-ph |
Next-to-leading order QCD corrections to the top quark decay via
model-independent FCNC couplings: D0 and CDF collaborations at the Fermilab Tevatron have searched for
non-standard-model single top-quark production and set upper limits on the
anomalous top quark flavor-changing neutral current (FCNC) couplings
$\kappa^g_{tc}/\Lambda$ and $\kappa^g_{tu}/\Lambda$ using the measurement of
total cross section calculated at the next-to-leading order (NLO) in QCD. In
this Letter, we report on the effect of anomalous FCNC couplings to various
decay branching ratios of the top quark, calculated at the NLO. This result is
not only mandatory for a consistent treatment of both the top quark production
and decay via FCNC couplings by D0 and CDF at the Tevatron but is also
important for the study of ATLAS and CMS sensitivity to these anomalous
couplings at the CERN LHC. We find that the NLO corrections to the partial
decay widths of the three decay channels $ t\to q + g$, $ t\to q + \gamma$ and
$ t\to q + Z$ are at the order of 10% in magnitude and modify their branching
ratios by about 20%, 0.4% and 2%, respectively, as compared to their leading
order predictions. | hep-ph |
Curvature and thermal corrections in tree-level CPT-Violating
Leptogenesis: In a model for leptogenesis based on spontaneous breaking of Lorentz and CPT
symmetry [1-3], we examine the consistency of using the approximation of
plane-wave solutions for a free spin-(1/2) Dirac (or Majorana) fermion field
propagating in a Friedmann-Lemaitre-Robertson-Walker space time augmented with
a cosmic time-dependent (or, equivalently, a temperature-dependent) Kalb-Ramond
(KR) background. For the range of parameters relevant for leptogenesis, our
analysis fully justifies the use of plane-wave solutions in our study of
leptogenesis with Boltzmann equations; any corrections induced by
space-time-curvature are negligible. We also elaborate further on how the
lepton asymmetry is communicated to the Baryon sector. We demonstrate that the
KR background (KRB) does not contribute to the anomaly equations that determine
the baryon asymmetry a) through an explicit evaluation of a triangle Feynman
graph and b) indirectly, on topological grounds, by identifying the KRB as
torsion (in the effective string-inspired low energy gravitational field
theory). | hep-ph |
Empirical regularities in the $x$--dependence of nuclear J/Psi
suppression: The measured ratios $R(x,A_1/A_2)$ for $J/\Psi$, $\Psi'$ and $\mu^+\mu^-$
production on two different targets $A_1, A_2$ as a function of the fractional
momentum $x$ of the final state are well fit with a very simple functional form
having three adjustable parameters. An empirical relation is found between the
three parameters of the fit. The deduced $J/\Psi$ absorption cross sections
$\sigma_{abs}$ cluster around two values of which only $\sigma_{abs} = 5.8 \pm
0.2$ mb seems acceptable. | hep-ph |
Chromomagnetic dipole moment of the top quark in the Bestest Little
Higgs model: We calculate the chromomagnetic dipole moment of the top quark,
$\hat{\mu}_t$, in the context of the Bestest Little Higgs model. This extension
of the Standard Model aims to solve the hierarchy problem without fine tuning,
by introducing one-loop corrections to the Higgs boson mass through heavy top
quark partners and heavy gauge bosons. We found that the largest resulting
value for the chromomagnetic is $\hat{\mu}_t\sim 10^{-5}$ and the lowest is
around $10^{-6}$, mainly due to the Higgs boson of the Standard Model, which
couples to both the top quark of the Standard Model and its heavy partners.
Also, we present a wide variety of new Feynman rules involved in our
calculation. | hep-ph |
Contribution of the elastic radiative tail to the deep inelastic muon
scattering on heavy targets: Improvement of the radiative correction scheme for the deep inelastic
scattering on the heavy targets is discussed. Arguments that the contribution
of the radiative tail from the elastic peak should be calculated without use of
the Born approximation in the case of the heavy target scattering are
presented. The semianalytical approach based on the classical solution of the
old bremsstrahlung problem is shortly described. The numerical results for the
new correction factor are presented for the scattering on tin and lead. | hep-ph |
On-shell renormalisation constants including two different nonzero
masses: We present results for the effect of a second massive quark in the relation
between the pole and the minimal subtracted quark mass at the three loop level.
We also consider the analogous effect for the wave function renormalisation
constant. Some technical details of the calculation are given. Our result is
phenomenologically relevant for the bottom quark including virtual charm
effects. | hep-ph |
Color path-integral Monte Carlo simulations of quark-gluon plasma: Thermodynamic properties of a strongly coupled quark-gluon plasma (QGP) of
constituent quasiparticles are studied by a color path-integral Monte Carlo
simulations (CPIMC). For our simulations we have presented QGP partition
function in the form of color path integral with new relativistic measure
instead of Gaussian one used in Feynman and Wiener path integrals. For
integration over color variable we have also developed procedure of sampling
color variables according to the group SU(3) Haar measure. It is shown that
this method is able to reproduce the available quantum lattice chromodynamics
(QCD) data. | hep-ph |
Primordial Lepton Oscillations and Baryogenesis: The baryon asymmetry of the Universe should have been produced after the
inflation era. We consider the possibility that the asymmetry is generated by
the flavor oscillations in the reheating process after inflation, so that the
baryon asymmetry is realized already at the beginning of the radiation
dominated era. In the seesaw model, we show that the propagators of the
left-handed leptons generically have flavor mixings in the thermal background,
that can generate flavor-dependent lepton asymmetry through the $CP$ violation
in the oscillation phenomena. The flavor dependent rates for the wash-out
process can leave the net asymmetry today. | hep-ph |
External-leg corrections as an origin of large logarithms: Obtaining precise theoretical predictions for both production and decay
processes of heavy new particles is of great importance to constrain the
allowed parameter spaces of Beyond-the-Standard-Model (BSM) theories, and to
properly assess the sensitivity for discoveries and for discriminating between
different possible BSM scenarios. In this context, it is well known that large
logarithmic corrections can appear in the presence of widely separated mass
scales. We point out the existence of a new type of possible large,
Sudakov-like, logarithms in external-leg corrections of heavy scalars. To the
difference of usual Sudakov logarithms, these can furthermore potentially be
enhanced by large trilinear couplings. Such large logarithms are associated
with infrared singularities and we review several techniques to address these
at one loop. In addition to this discussion, we also present the derivation of
the two-loop corrections containing this type of large logarithms, pointing out
in this context the importance of adopting an on-shell renormalisation scheme.
Finally, we illustrate our calculations and examine the possible magnitude of
these corrections for a simple scalar toy model as well as for decay processes
involving heavy stop quarks in the Minimal Supersymmetric Standard Model and a
heavy Higgs boson in the Next-to-Two-Higgs-Doublet Model. | hep-ph |
The 2HD+a model for a combined explanation of the possible excesses in
the CDF $\mathbf{M_W}$ measurement and $\mathbf{(g-2)_μ}$ with Dark Matter: The new measurement of the $W$ boson mass performed by the CDF experiment at
the Tevatron shows a significant deviation not only with the expectation in the
Standard Model but also with other precision measurements performed at LEP, the
Tevatron and the LHC. We nevertheless take this new measurement at face value
and interpret it as an effect of new physics. We particularly try to link it
with other possible anomalies such as the recent muon $g-2$ and consider a
scenario that addresses some shortcomings of the Standard Model. We show that a
model with two doublets and a light pseudoscalar Higgs fields, supplemented by
a stable isosinglet fermion, can simultaneously explain the possible $M_W$ and
$(g-2)_\mu$ anomalies and accounts for the weakly interacting massive particle
that could be responsible of the dark matter in the universe. | hep-ph |
Weak decays of doubly heavy baryons: decays to system of $π$ mesons: In the presented article we consider exclusive weak decays of doubly heavy
baryons with spin $J=1/2$ with production of leptonic pair or a set of light
mesons. Using QCD factorization theorem and spectral functions approach we
obtain theoretical predictions for the partial probabilities of these decays
and distributions over various kinematic variables. According to the obtaining
results partial probabilities of some of researched decays are large enough to
be observed experimentally. | hep-ph |
Light-cone distribution amplitudes of light mesons with QED effects: We discuss the generalization of the leading-twist light-cone distribution
amplitude for light mesons including QED effects. This generalization was
introduced to describe virtual collinear photon exchanges above the
strong-interaction scale $\Lambda_{\rm QCD}$ in the factorization of QED
effects in non-leptonic $B$-meson decays. In this paper we study the
renormalization group evolution of this non-perturbative function. For charged
mesons, in particular, this exhibits qualitative differences with respect to
the well-known scale evolution in QCD only, especially regarding the
endpoint-behaviour. We analytically solve the evolution equation to first order
in the electromagnetic coupling $\alpha_{\rm em}$, which resums large
logarithms in QCD on top of a fixed-order expansion in $\alpha_{\rm em}$. We
further provide numerical estimates for QED corrections to Gegenbauer
coefficients as well as inverse moments relevant to (QED-generalized)
factorization theorems for hard exclusive processes. | hep-ph |
Towards a determination of the tau lepton dipole moments: The tau anomalous magnetic moment (a_tau) and electric dipole moment (d_tau)
have not yet been observed. The present bounds on their values are of order
10^-2 and 10^-17 e*cm, respectively. We propose to measure a_tau with a
precision of O(10^-3) or better and improve the existing limits on d_tau using
precise tau- -> l- nu_tau \bar{nu}_l gamma (l=e or mu) data from
high-luminosity B factories. A detailed feasibility study of this method is
underway. | hep-ph |
Geometry of gauge links in operator definitions of transverse-momentum
dependent PDFs: A comparative view: Different approaches to the problem of a gauge-invariant operator definition
of transverse-momentum dependent parton densities (TMDs) are reviewed and
compared from the point of view of their compatibility with the operator
definition of collinear (integrated) parton distribution functions. In
particular, geometry of the longitudinal and transverse gauge links (Wilson
lines) both in unsubtracted quark TMDs and in the associate soft factors is
addressed. A possible connection between different operator definitions is also
discussed. | hep-ph |
Exclusive nonleptonic decays of B mesons: The energetic exclusive two-body nonleptonic decays of B mesons are
investigated in the framework of the relativistic quark model within the
factorization approximation. The heavy quark expansion is used for the
calculation of form factors. The obtained results are in agrement with
available experimental data. | hep-ph |
Distinctive nuclear signatures of low-energy atmospheric neutrinos: New probes of neutrino mixing are needed to advance precision studies. One
promising direction is via the detection of low-energy atmospheric neutrinos
(below a few hundred MeV), to which a variety of near-term experiments will
have much-improved sensitivity. Here we focus on probing these neutrinos
through distinctive nuclear signatures of exclusive neutrino-carbon
interactions -- those that lead to detectable nuclear-decay signals with low
backgrounds -- in both neutral-current and charged-current channels. The
neutral-current signature is a line at 15.11 MeV and the charged-current
signatures are two- or three-fold coincidences with delayed decays. We
calculate the prospects for identifying such events in the Jiangmen Underground
Neutrino Observatory (JUNO), a large-scale liquid-scintillator detector. A
five-year exposure would yield about 16 neutral-current events (all flavors)
and about 16 charged-current events (mostly from $\nu_e + \bar{\nu}_e$, with
some from $\nu_\mu + \bar{\nu}_\mu$), and thus roughly 25\% uncertainties on
each of their rates. Our results show the potential of JUNO to make the first
identified measurement of sub-100 MeV atmospheric neutrinos. They also are a
step towards multi-detector studies of low-energy atmospheric neutrinos, with
the goal of identifying additional distinctive nuclear signatures for carbon
and other targets. | hep-ph |
Charged Particle Fluctuations as a Signal of the Dynamics of Heavy Ion
Processes: Comparing proposed quantities to analyze charged particle fluctuations in
heavy ion experiments we find the dispersion of the charges in a central
rapidity box as best suited. Various energies and different nuclear sizes were
considered in an explicit Dual-Parton-Model calculation using the DPMJET code.
A definite deviation from predictions of recently considered statistical models
was obtained. Hence the charged particle fluctuations should provide a clear
signal of the dynamics of heavy ion processes. They should allow to directly
measure the degree of thermalization in a quantitative way. | hep-ph |
Particle-accelerator constraints on isotropic modifications of the speed
of light: The absence of vacuum Cherenkov radiation for 104.5 GeV electrons and
positrons at LEP combined with the observed stability of 300 GeV photons at the
Tevatron constrains deviations of the speed of light relative to the maximal
attainable speed of electrons. Within the Standard-Model Extension (SME), the
limit $-5.8\times10^{-12} \leq \tilde{\kappa}_{\rm tr}-{4/3}c_e^{00} \leq
1.2\times10^{-11}$ is extracted, which sharpens previous bounds by more than 3
orders of magnitude. The potential for further refinements of this limit with
terrestrial experiments and astrophysical observations is discussed. | hep-ph |
Beyond Low-Gribov theorem for high energy interactions of scalar and
gauge particles: We obtain a generalization of the Low theorem for non-Abelian boson emission
in collision of scalar and gauge vector particles and its extension to high
energy collisions for small transverse momenta of produced particles. We
demonstrate that in the case of particles with spin the direct extension the
Low formula to high energy is in contradiction with the correct amplitude
factorization behavior. Consideration of different kinematical regions and use
of methods of dual models allows us to separate contributions of intermediate
excited states and standard spin corrections in the Low formulae. We show that
the amplitude factorization occurs at high energy due to the contribution of
the intermediate states which is additional to the gluon production amplitude
for the scalar particle collision. | hep-ph |
Analytic representations of two-loop scattering amplitudes with internal
masses: We highlight the latest developments in computing higher-order scattering
amplitudes with massive internal propagators. The contributing Feynman
integrals often lead to special classes of functions, for example, functions
associated with elliptic curves. With the presence of more scales in the
amplitudes, it becomes imperative to have a better understanding of the
contributing Feynman integrals and using current cutting-edge technologies to
tackle the growth in analytic and algebraic complexities. In particular, we
start with discussing two-loop scattering amplitudes for top-quark pair
production and conclude with motivating important steps towards obtaining
next-to-next-to leading-order corrections for five-point processes. | hep-ph |
Constraining Light Mediators via Detection of Coherent Elastic Solar
Neutrino Nucleus Scattering: Dark matter (DM) direct detection experiments are entering the multiple-ton
era and will be sensitive to the coherent elastic neutrino nucleus scattering
(CE$\nu$NS) of solar neutrinos, enabling the possibility to explore
contributions from new physics with light mediators at the low energy range. In
this paper we consider light mediator models (scalar, vector and axial vector)
and the corresponding contributions to the solar neutrino CE$\nu$NS process.
Motivated by the current status of new generation of DM direct detection
experiments and the future plan, we study the sensitivity of light mediators in
DM direct detection experiments of different nuclear targets and detector
techniques. The constraints from the latest $^8$B solar neutrino measurements
of XENON-1T are also derived. Finally, We show that the solar neutrino
CE$\nu$NS process can provide stringent limitation on the $ L_{\mu}-L_{\tau} $
model with the vector mediator mass below 100 MeV, covering the viable
parameter space of the solution to the $ (g-2)_{\mu}$ anomaly. | hep-ph |
QCD Analysis of the Polarized Deep-Inelastic World Data: The results of a recent next-to-leading order QCD analysis of the world data
on polarized deep inelastic scattering are reported. New parameterizations are
derived for the quark and gluon distributions, accounting for the massive
Wilson coefficient for the charm quarks, and the value of $\alpha_s(M_z^2)$ is
determined with correlated errors. We obtain $\alpha_s^{\rm NLO}(M_Z^2)= 0.1132
{array}{l} + 0.0056 -0.0095 {array}$. Limits on potential higher twist
contributions to the structure function $g_1(x,Q^2)$ are derived. We also
compare to the results obtained by other groups. | hep-ph |
HiggsSignals: Confronting arbitrary Higgs sectors with measurements at
the Tevatron and the LHC: HiggsSignals is a Fortran90 computer code that allows to test the
compatibility of Higgs sector predictions against Higgs rates and masses
measured at the LHC or the Tevatron. Arbitrary models with any number of Higgs
bosons can be investigated using a model-independent input scheme based on
HiggsBounds. The test is based on the calculation of a chi-squared measure from
the predictions and the measured Higgs rates and masses, with the ability of
fully taking into account systematics and correlations for the signal rate
predictions, luminosity and Higgs mass predictions. It features two
complementary methods for the test. First, the peak-centered method, in which
each observable is defined by a Higgs signal rate measured at a specific
hypothetical Higgs mass, corresponding to a tentative Higgs signal. Second, the
mass-centered method, where the test is evaluated by comparing the signal rate
measurement to the theory prediction at the Higgs mass predicted by the model.
The program allows for the simultaneous use of both methods, which is useful in
testing models with multiple Higgs bosons. The code automatically combines the
signal rates of multiple Higgs bosons if their signals cannot be resolved by
the experimental analysis. We compare results obtained with HiggsSignals to
official ATLAS and CMS results for various examples of Higgs property
determinations and find very good agreement. A few examples of HiggsSignals
applications are provided, going beyond the scenarios investigated by the LHC
collaborations. For models with more than one Higgs boson we recommend to use
HiggsSignals and HiggsBounds in parallel to exploit the full constraining power
of Higgs search exclusion limits and the measurements of the signal seen at
around 125.5 GeV. | hep-ph |
Hybrid textures in minimal seesaw mass matrices: In the context of minimal seesaw framework, we study the implications of
Dirac and Majorana mass matrices in which two rigid properties coexist, namely,
equalities among mass matrix elements and texture zeros. In the first part of
the study, we discuss general possibilities of the Dirac and Majorana mass
matrices for neutrinos with such hybrid structures. We then classify the mass
matrices into realistic textures which are compatible with global neutrino
oscillation data and unrealistic ones which do not comply with the data. Among
the large number of general possibilities, we find that only 6 patterns are
consistent with the observations at the level of the most minimal number of
free parameters. These solutions have only 2 adjustable parameters, so that all
the mixing angles can be described in terms of the two mass differences or pure
numbers. We analyze these textures in detail and discuss their impacts for
future neutrino experiments and for leptogenesis. | hep-ph |
Boosted Dark Matter at the Deep Underground Neutrino Experiment: We investigate the detection prospects of a non-standard dark sector in the
context of boosted dark matter. We consider a scenario where two stable
particles have a large mass difference and the heavier particle accounts for
most of dark matter in our current universe. The heavier candidate is assumed
to have no interaction with the standard model particles at tree-level, hence
evading existing constraints. Although subdominant, the lighter dark matter
particles are efficiently produced via pair-annihilation of the heavier ones in
the center of the Galaxy or the Sun. The large Lorentz boost enables detection
of the non-minimal dark sector in large volume terrestrial experiments via
exchange of a light dark photon with electrons or nuclei. Various experiments
designed for neutrino physics and proton decay are examined in detail,
including Super-K and Hyper-K. In this study, we focus on the sensitivity of
the far detector at the Deep Underground Neutrino Experiment for boosted dark
matter produced in the center of the Sun, and compare our findings with recent
results for boosted dark matter produced in the galactic center. | hep-ph |
Heavy-quark contributions to the ratio F_L/F_2 at low x: We study the heavy-quark contribution to the proton structure functions
F_2^i(x,Q^2) and F_L^i(x,Q^2), with i=c,b, for small values of Bjorken's x
variable at next-to-lading order and provide compact formulas for their ratios
R_i=F_L^i/F_2^i that are useful to extract F_2^i(x,Q^2) from measurements of
the doubly differential cross section of inclusive deep-inelastic scattering at
DESY HERA. Our approach naturally explains why R_i is approximately independent
of x and the details of the parton distributions in the small-x regime. | hep-ph |
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