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Nuclear Force from Monte Carlo Simulations of Lattice Quantum
Chromodynamics: The nuclear force acting between protons and neutrons is studied in the Monte
Carlo simulations of the fundamental theory of the strong interaction, the
quantum chromodynamics defined on the hypercubic space-time lattice. After a
brief summary of the empirical nucleon-nucleon (NN) potentials which can fit
the NN scattering experiments in high precision, we outline the basic
formulation to derive the potential between the extended objects such as the
nucleons composed of quarks. The equal-time Bethe-Salpeter amplitude is a key
ingredient for defining the NN potential on the lattice. We show the results of
the numerical simulations on a $32^4$ lattice with the lattice spacing $a
\simeq 0.137 $fm (lattice volume (4.4 fm)$^4$) in the quenched approximation.
The calculation was carried out using the massively parallel computer Blue
Gene/L at KEK. We found that the calculated NN potential at low energy has
basic features expected from the empirical NN potentials; attraction at long
and medium distances and the repulsive core at short distance. Various future
directions along this line of research are also summarized. | hep-ph |
Single Spin Asymmetry in Inclusive Pion Production, Collins Effect and
the String Model (revised version): We calculated the single spin asymmetry in the inclusive pion production in
the fragmentation region of transversely polarized proton-proton collisions. We
generated the asymmetry at the level of fragmentation function (Collins effect)
by the Lund coloured string mechanism. We compared our results to the presently
available experimental data. We obtained a qualitative agreement with the data
after assuming that the transverse polarizations of the $u$ and the $d$ quarks
in the proton are +1 and -1, respectively, at x_B = 1. | hep-ph |
Can the X(3872) be a 1^{++} four-quark state?: We use QCD spectral sum rules to test the nature of the meson X(3872),
assumed to be an exotic four-quark (c\bar{c}q\bar{q}) state with J^{PC}=1^{++}.
For definiteness, we work with the current proposed recently by Maiani et al
[1], at leading order in \alpha_s, consider the contributions of higher
dimension condensates and keep terms which are linear in the light quark mass
m_q. We find M_X=(3925+- 127) MeV which is compatible, within the errors, with
he experimental candidate X(3872), while the SU(3) breaking-terms lead to an
unusual mass-splitting M_{X^{s}}-M_X=- (61+-30) MeV. The mass-difference
between the neutral states due to isospin violation of about (2.6-3.9) MeV is
much smaller than the value (8+-3) MeV proposed in [1]. For the b-quark, we
predict M_{X_b}= (10144+-106) MeV for the X_b(b\bar{b}q \bar{q}), which is much
below the {\bar B}B* threshold in contrast to the {\bar B}B* molecule
prediction [2], and for the X_b^s(b\bar{b}s \bar{s}), a mass-splitting
M_{X^s_{b}}-M_{X_b}=-(121+-182) MeV. Our analysis also indicates that the
mass-splitting between the ground state and the radial excitation of about
(225~250) MeV is much smaller than in the case of ordinary mesons and is
(within the errors) flavour-independent. We also extract the decay constants,
analogous to f_\pi, of such mesons, which are useful for further studies of
their leptonic and hadronic decay widths. The uncertainties of our estimates
are mainly due to the ones from the c and b quark masses. | hep-ph |
First Lattice QCD Study of the Sigma -> n Axial and Vector Form Factors
with SU(3) Breaking Corrections: We present the first quenched lattice QCD study of the form factors relevant
for the hyperon semileptonic decay Sigma -> n l nu. The momentum dependence of
both axial and vector form factors is investigated and the values of all the
form factors at zero-momentum transfer are presented. Following the same
strategy already applied to the decay K0 -> pi- l nu, the SU(3)-breaking
corrections to the vector form factor at zero-momentum transfer, f1(0), are
determined with great statistical accuracy in the regime of the simulated quark
masses, which correspond to pion masses above ~ 0.7 GeV. Besides f1(0) also the
axial to vector ratio g1(0) / f1(0), which is relevant for the extraction of
the CKM matrix element Vus, is determined with significant accuracy. Due to the
heavy masses involved, a polynomial extrapolation, which does not include the
effects of meson loops, is performed down to the physical quark masses,
obtaining f1(0) = -0.948 +/- 0.029 and g1(0) / f1(0) = -0.287 +/- 0.052, where
the uncertainties do not include the quenching effect. Adding a recent
next-to-leading order determination of chiral loops, calculated within the
Heavy Baryon Chiral Perturbation Theory in the approximation of neglecting the
decuplet contribution, we obtain f1(0) = -0.988 +/- 0.029(lattice) +/-
0.040(HBChPT). Our findings indicate that SU(3)-breaking corrections are
moderate on both f1(0) and g1(0). They also favor the experimental scenario in
which the weak electricity form factor, g2(0), is large and positive, and
correspondingly the value of |g1(0) / f1(0)| is reduced with respect to the one
obtained with the conventional assumption g2(q**2) = 0 based on exact SU(3)
symmetry. | hep-ph |
Eta-eta' mixing from V->Pgamma and J/psi->VP decays: The $\eta$-$\eta^\prime$ pseudoscalar mixing angle and the gluonium content
of the $\eta^\prime$ meson are deduced from an updated phenomenological
analysis of $V\to P\gamma$ and $J/\psi\to VP$ decays. In absence of gluonium,
the value of the mixing angle in the quark-flavour basis is found to be
$\phi_P=(41.5\pm 1.2)^\circ$ from $V\to P\gamma$ and $\phi_P=(40.5\pm
2.4)^\circ$ from $J/\psi\to VP$. In presence of gluonium, the values for the
mixing angle and the gluonic content of the $\eta^\prime$ wave function are
$\phi_P=(41.4\pm 1.3)^\circ$ and $Z^2_{\eta^\prime}=0.04\pm 0.09$ from $V\to
P\gamma$ and $\phi_P=(44.5\pm 4.3)^\circ$ and $Z^2_{\eta^\prime}=0.28\pm 0.21$
from $J/\psi\to VP$, respectively. | hep-ph |
Neutrino Mass from Triplet and Doublet Scalars at the TeV Scale: If the minimal standard model of particle interactions is extended to include
a scalar triplet with lepton number $L=-2$ and a scalar doublet with $L=-1$,
neutrino masses $m_\nu \sim \mu_{12}^4 v^2/M^5 \sim 10^{-2}$ eV is possible,
where $v \sim 10^2$ GeV is the electroweak symmetry breaking scale, $M \sim 1$
TeV is the typical mass of the new scalars, and $\mu_{12} \sim 1$ GeV is a soft
lepton-number-violating parameter. | hep-ph |
QCD Corrections to Flavor Changing Neutral Coupling Mediated Rare Top
Quark Decays: Recently we have presented an analysis of flavor changing neutral coupling
mediated radiative top quark decays at next-to-leading order in QCD. In the
present paper we provide the details of the calculation of QCD corrections to
t-> q gamma and t-> q Z decays within the effective theory approach including
operator mixing. In particular, we calculate virtual matrix element corrections
and the corresponding bremsstrahlung contributions. In the case of t-> q gamma
we study the effects of kinematic cuts on the extracted branching ratios.
Analytical formulae are given at all stages of the calculation. We find that
the t-> q gamma decay can be used to probe also the effective operators
mediating t-> q g processes, since these can naturally contribute 10% or more
to the radiative decay, given typical experimental cuts on the decay kinematics
at hadron colliders. Conversely, we argue that any positive experimental signal
of the t-> q g process would indicate a natural lower bound on t-> q gamma
decay rate. | hep-ph |
Learning to Identify Semi-Visible Jets: We train a network to identify jets with fractional dark decay (semi-visible
jets) using the pattern of their low-level jet constituents, and explore the
nature of the information used by the network by mapping it to a space of jet
substructure observables. Semi-visible jets arise from dark matter particles
which decay into a mixture of dark sector (invisible) and Standard Model
(visible) particles. Such objects are challenging to identify due to the
complex nature of jets and the alignment of the momentum imbalance from the
dark particles with the jet axis, but such jets do not yet benefit from the
construction of dedicated theoretically-motivated jet substructure observables.
A deep network operating on jet constituents is used as a probe of the
available information and indicates that classification power not captured by
current high-level observables arises primarily from low-$p_\textrm{T}$ jet
constituents. | hep-ph |
An alternative heavy Higgs mass limit: After commenting on the present value of the Higgs particle mass from
radiative corrections, we explore the phenomenological implications of an
alternative, non-perturbative renormalization of the scalar sector where the
mass of the Higgs particle does not represent a measure of observable
interactions at the Higgs mass scale. In this approach the Higgs particle could
be very heavy, even heavier than 1 TeV, and remain nevertheless a relatively
narrow resonance. | hep-ph |
Two-particle Correlations in multi-Regge Kinematics: Multi-jet production at the LHC is an important process to study. In
particular, events with final state kinematic configurations where we have two
jets widely separated in rapidity with similar pT and lots of mini-jets or jets
populating the space in between are relevant for the high energy limit of QCD.
Keeping the jet multiplicity fixed, the study of these events is a good ground
to test different models of multi-particle production in hadron-hadron
collisions. We report on a comparison between the predictions of the old
multiperipheral Chew-Pignotti model and those of BFKL for the single jet
rapidity distributions and for jet-jet rapidity correlations. | hep-ph |
BFKL Pomeron and the survival factor: We consider the absorptive corrections and the rapidity gap survival factor
which are necessary to provide the unitarization of the BFKL Pomeron. In
particular we discuss the role of the enhanced screening diagrams. | hep-ph |
Lecture notes on the Skyrme model: This lecture provides a pedagogical instruction to the basic concepts of the
Skyrme model and its some applications. As the preliminary for understanding
the Skyrme model, we first briefly explain the large $N_c$ expansion, chiral
symmetry and its breaking. Next we give a brief review of nonlinear sigma model
including the power counting scheme of the chiral perturbation theory, starting
from the linear sigma model. We then give an exhaust explanation of the Skyrme
model and its applications. After the presentation of the Skyrme model for
baryons in free space, we introduce how to study the baryonic matter and medium
modified hadron properties by using the Skyrme model. Finally we discuss a way
to incorporate the lowest-lying vector mesons into the Skyrme model based on
the hidden local symmetry. Some possible further developments are also covered. | hep-ph |
Top Quark Physics: In this contribution I review the physics of top quarks at a future Linear
Collider. Main emphasis is put on the process e+ e- to ttbar close to
threshold. Different physical observables, their sensitivity to the basic
parameters and their theoretical prediction are discussed. Recent higher order
calculations are shown to have a considerable impact on a precise determination
of the top quark mass. It is pointed out how the use of mass definitions
different from the pole mass scheme become important in this respect. Continuum
top quark production above threshold is discussed briefly. | hep-ph |
A Higgslike Dilaton: We examine the possibility that the recently discovered 125 GeV higgs like
resonance actually corresponds to a dilaton: the Goldstone boson of scale
invariance spontaneously broken at a scale f. Comparing to LHC data we find
that a dilaton can reproduce the observed couplings of the new resonance as
long as f ~ v, the weak scale. This corresponds to the dynamical assumption
that only operators charged under the electroweak gauge group obtain VEVs. The
more difficult task is to keep the mass of the dilaton light compared to the
dynamical scale, Lambda ~ 4 pi f, of the theory. In generic, non-supersymmetric
theories one would expect the dilaton mass to be similar to Lambda. The mass of
the dilaton can only be lowered at the price of some percent level (or worse)
tuning and/or additional dynamical assumptions: one needs to suppress the
contribution of the condensate to the vacuum energy (which would lead to a
large dilaton quartic coupling), and to allow only almost marginal deformations
of the CFT. | hep-ph |
New-Physics Search in gamma gamma --> t tbar: We performed an analysis on possible anomalous top-quark couplings generated
by SU(2) x U(1) gauge-invariant dimension-6 effective operators, applying the
optimal-observable procedure to the final lepton/b-quark momentum distribution
in gamma gamma --> t tbar --> l X/b X. We studied how many such anomalous
coupling constants could be determined altogether through these distributions. | hep-ph |
Revealing the source of the radial flow patterns in proton--proton
collisions using hard probes: In this work, we propose a tool to reveal the origin of the collective-like
phenomena observed in proton--proton collisions. We exploit the fundamental
difference between the underlying mechanisms, color reconnection (CR) and
hydrodynamics, which produce radial flow patterns in \textsc{Pythia}~8 and
\textsc{Epos}~3, respectively. Specifically, we proceed by examining the
strength of the coupling between the soft and hard components which, by
construction, is larger in \textsc{Pythia}~8 than in \textsc{Epos}~3. We study
the transverse momentum ($p_{\rm T}$) distributions of charged pions, kaons and
(anti)protons in inelastic pp collisions at $\sqrt{s}=$ 7\,TeV produced at
mid-rapidity. Specific selections are made on an event-by-event basis as a
function of the charged particle multiplicity and the transverse momentum of
the leading jet ($p_{\rm T}^{\rm jet}$) reconstructed using the
\textsc{FastJet} algorithm at mid-pseudorapidity ($|\eta|<1$). From our
studies, quantitative and qualitative differences between \textsc{Pythia}~8 and
\textsc{Epos}~3 are found in the $p_{\rm T}$ spectra when (for a given
multiplicity class) the leading jet $p_{\rm T}$ is increased. In addition, we
show that for low-multiplicity events the presence of jets can produce radial
flow-like behavior. Motivated by our findings, we propose to perform a similar
analysis using experimental data from RHIC and LHC. | hep-ph |
Real time simulations of high energy nuclear collisions: We discuss real time simulations of high energy nuclear collisions in a
classical effective theory of QCD at small x. At high transverse momenta, our
results match the lowest order predictions of pQCD based mini-jet calculations.
We discuss novel non-perturbative behaviour of the small x modes seen at small
transverse momenta. | hep-ph |
Implementation of target mass corrections and higher-twist effects in
the xFitter framework: Knowledge of parton distribution functions (PDFs) at large momentum fraction
$ x $ is not only important to study the flavor and spin dynamics of quarks in
the nucleon, but also to search for signals of new physics at collider
experiments. It is well known now that the nonperturbative QCD effects
generally play a more significant role at such kinematic regions. In this work,
we present an open-source QCD analysis of PDFs considering target mass
corrections (TMCs) and higher-twist (HT) effects which are necessary when the
analysis includes also data points from deep inelastic scattering (DIS) with
larger values of $ x $ and smaller values of photon virtuality $ Q^2 $. To this
aim, we use the xFitter package, as a comprehensive and powerful tool for
studying PDFs. We report and discuss our recent activities on the
implementation of TMCs and HT effects in the xFitter framework in a
user-friendly way, so that the user can switch on or off them, and also choose
between different options. We check the validity of the modifications by
performing sample analyses of PDFs considering TMCs and HT effects and using a
wide range of DIS data. | hep-ph |
Mass of the Stabilized Radion in the Limit of Finite Quartic Coupling: We present an exact treatment of the modulus stabilization condition with the
general boundary conditions of the bulk scalar field in the Randall-Sundrum
model. We find analytical expressions for the value of the modulus and the mass
of the radion. | hep-ph |
Hard colour singlet exchange at the Tevatron from the BFKL equation: We study rapidity gaps between jets in ppbar collisions at the Tevatron by a
novel solution of the nonforward BFKL equation including nonleading effects
through the consistency constraint and running coupling. Results differ from
earlier calculations based on the asymptotic Mueller-Tang formula, but agree
with D0 data when including full event simulation using PYTHIA to model the gap
survival probability. | hep-ph |
Non-linear corrections to the longitudinal structure function $F_{L}$
from the parametrization of $F_{2}$: Laplace transform approach: The non-linear corrections (NLC) to the longitudinal structure function in a
limited approach is derived at low values of the Bjorken variable $x$ by using
the Laplace transforms technique. The non-linear behavior of the longitudinal
structure function is determined with respect to the Gribov-Levin-Ryskin
Mueller-Qiu (GLR-MQ) and Altarelli-Martinelli (AM) equations. These results
show that the non-linear longitudinal structure function can be determined
directly in terms of the parametrization of $F_{2}(x,Q^{2})$ and the derivative
of the proton structure function with respect to $\ln{Q^{2}}$. These
corrections improve the behavior of the longitudinal structure function at low
values of $Q^{2}$ in comparison with other parametrization methods. | hep-ph |
D_{sJ}^+(2317)\to D_s^+π^0 decay width: We use the QCD sum rules to analize the hadronic decay $D_{sJ}^{+}(2317)\to
D_s^+\pi^0$, in the hypotesis that the $D_{sJ}^{+}(2317)$ can be identified as
a four-quark state. We use a diquak-antidiquark current and work to the order
of $m_s$ in full QCD, without relying on $1/m_c$ expansion. We find that the
partial decay width of the hadronic isospin violating mode is proportional to
the isovector quark condensate, $\langle0|\bar{d}d-\bar{u}u|0\rangle$. The
estimated partial decay width is of the order of 6 keV. | hep-ph |
Non-Unitary $3 \times 3$ Mixing in Majorana Neutrinos and Vector-like
Quark Models: Non-unitary $3 \times 3$ mixing matrices are present in many extensions of
the Standard Model. One of the most simple extensions is the addition of $n_R$
right-handed neutrinos without imposing Lepton Number Conservation
($n_R$$\nu$SM). In the region of the parameter space where the usual seesaw
approximation is valid, deviations from $3 \times 3$ unitarity of the leptonic
mixing matrix are negligible, while one has three light neutrinos and two or
three heavy neutrinos with masses close to the GUT scale. This gap between the
mass scales occurs while having order 1 Yukawa couplings, providing a natural
explanation for the smallness of light neutrino masses - hence the name seesaw.
Other regions of the parameter space, with lighter heavy neutrinos - with an eV
or keV mass, for instance - and bigger deviations from unitarity of the
leptonic mixing matrix, are still allowed by experiment. In fact, whenever
heavy neutrino masses are many orders of magnitude below the GUT scale there
are interesting phenomenological implications at low energies. To analyse such
regions with precision, one needs an exact parameterisation, since
approximations that were valid in the usual seesaw case now fail. This thesis
will consist of a study and classification of regions of the 3$\nu$SM parameter
space in the light of a newly-developed exact parameterisation. Furthermore, it
will also include a study of models with vector-like quarks, another simple
extension of the SM, that contains a $3 \times 3$ non-unitary quark mixing
matrix. Studying the most interesting regions of the parameter space of
vector-like quarks models also benefits from the use of the aforementioned
exact parameterisation. These regions are phenomenologically rich and may
explain certain open questions like the CKM unitarity problem/Cabibbo angle
anomaly. A chapter discussing the experimental implications of these models is
also included. | hep-ph |
Indirect Searches for $Z'$-like Resonances at the LHC: We explore the possibility of indirectly observing the effects of $Z'$-like
particles with electroweak strength couplings in the Drell-Yan channel at the
LHC with masses above the resonance direct search reach. We find that, mostly
due to statistical limitations, this is very unlikely in almost all classes of
models independently of the spin of the resonance. Not unexpectedly, the one
possible exception to this general result is the case of degenerate
Kaluza-Klein (KK) excitations of the photon and $Z$ that occur in some
extra-dimensional models. In this special case, the strong destructive
interference with the Standard Model (SM) exchanges below the resonance mass
leads to a well-known significant suppression of the cross section and thus
increased sensitivity to this particular new physics scenario. | hep-ph |
Higgs inflation and Higgs portal dark matter with right-handed neutrinos: We investigate the Higgs inflation and the Higgs portal dark matter with the
right-handed neutrino. The dark matter and the right-handed neutrino in the
Higgs inflation play important roles in explaining the recent experimental
results of the Higgs and top masses, and the cosmic microwave background by
BICEP2 at the same time. This inflation model predicts $805~{\rm GeV} \lesssim
m_{\rm DM} \lesssim1220~{\rm GeV}$ for the DM mass, $1.05 \times10^{14}~{\rm
GeV} \lesssim M_R \lesssim 2.04 \times10^{14}~{\rm GeV}$ for the right-handed
neutrino mass, and $8.42 \lesssim \xi \lesssim 12.4$ for the non-minimal
coupling within $m_H=125.6 \pm 0.35~{\rm GeV}$ for the Higgs and $M_t=173.34
\pm 0.76~{\rm GeV}$ for the top masses. | hep-ph |
Reducing the Quadratic Divergence in the Higgs Mass Squared Without Top
Partners: We examine a model with multiple scalar fields to see whether it is possible
to reduce the fine- tuning of the SM Higgs mass without introducing low scale
top partners. Our approach may be regarded as a generalization of the condition
proposed by Veltman, who attempted to predict the Higgs mass using the
criterion that the various low energy contributions to the quadratic divergence
of the Higgs mass cancel. Although the Veltman condition predicts the wrong
Higgs mass in the Standard Model, it can still be adapted to extended Higgs
sectors. Furthermore, theories with additional Higgs bosons can lead to
suppressed Yukawa couplings of the top quark to the 125 GeV Higgs, making the
associated one-loop divergence smaller. Here, we review possible extensions of
the Standard Model where the Veltman condition could be realized, and study in
detail one minimal model with two extra scalar fields. For this model and for a
cutoff of 5 TeV, we show that the overall fine-tuning can be considerably
lowered without introducing low-scale Landau poles, albeit the Higgs sector
will be strongly coupled at the cutoff. Models where the top Yukawa coupling is
reduced, in particular, will be within the reach of the upcoming LHC searches. | hep-ph |
Errata for "The Higgs Hunter's Guide": Errata are given for "The Higgs Hunter's Guide". These errata should be
applied to the second printing of the book, dated 1991. The second printing has
already corrected numerous errors and misprints contained in the originally
published 1990 edition. | hep-ph |
Soft scalar masses in supergravity with horizontal U(1)_X gauge symmetry: In supergravity with modular invariance and horizontal $U(1)_X$ gauge
symmetry there is a relation between modular weights and $U(1)_X$ charges. The
soft scalar masses are then strongly correlated with Yukawa matrices. The
implications for FCNC are discussed. | hep-ph |
Top quark pair production at small transverse momentum in hadronic
collisions: We investigate the transverse momentum resummation for top quark pair
production at hadron colliders using the soft-collinear effective theory and
the heavy-quark effective theory. We derive the factorization formula for
$t\bar{t}$ production at small pair transverse momentum, and show in detail the
procedure for calculating the key ingredient of the factorization formula: the
next-to-leading order soft functions. We compare our numerical results with
experimental data and find that they are consistent within theoretical and
experimental uncertainties. To verify the correctness of our resummation
formula, we expand it to the next-to-leading order and the
next-to-next-to-leading order, and compare those expressions with the exact
fixed-order results numerically. Finally, using the results of transverse
momentum resummation, we discuss the transverse-momentum-dependent
forward-backward asymmetry at the Tevatron. | hep-ph |
Models of Flavor with Discrete Symmetries: In an attempt to understand the observed patterns of lepton and quark masses,
models invoking a flavor symmetry $G_f$, under which the Standard Model
generations are charged, have been proposed. One particularly successful
symmetry, U(2), has been extensively discussed in the literature. The Yukawa
matrices in models based on this symmetry reproduce the observed mass ratios in
the lepton and quark sectors. The features of the symmetry that determine the
texture of the Yukawa matrices can be found in other symmetries as well. We
present a model based on a minimal, non-Abelian discrete symmetry that
reproduces the Yukawa matrices associated with U(2) theories of flavor. In
addition to reproducing the mass and mixing angle relations obtained in such
theories, the different representation structure of our new horizontal symmetry
allows for solutions to the solar and atmospheric neutrino problems. | hep-ph |
Squark production with R-symmetry beyond NLO at the LHC: The Minimal R-symmetric Supersymmetric Standard Model (MRSSM) provides a
realisation of supersymmetry in which the parameter space is less constrained
by the current LHC data than in the simplest supersymmetric scenarios. In the
present paper, we obtain the most precise theoretical predictions in the MRSSM
for squark production at the LHC, enabling accurate interpretations of LHC data
in terms of the MRSSM. We perform threshold resummation of soft gluon
corrections to the total cross sections for the production of
squark-(anti)squark pairs at the LHC in the MRSSM framework. The resummation is
carried out using the direct QCD method and reaches the
next-to-next-to-leading-logarithmic (NNLL) accuracy, which requires calculating
the one-loop matching coefficients in the relevant production channels. The
resummed cross sections are then matched to the available NLO results and
evaluated for $\sqrt{S}=13.6$ TeV. Compared with the Minimal Supersymmetric
Standard Model (MSSM), the cross sections in the MRSSM can be significantly
reduced, implying less stringent limits on squark and gluino masses. Our
results carry significant implications for exploring the viability of
supersymmetry at the LHC. The results of our calculation are publicly available
as a numerical package. | hep-ph |
Large Top Mass and Non-Linear Representation of Flavour Symmetry: We consider an effective theory (ET) approach to flavour-violating processes
beyond the Standard Model (SM), where the breaking of flavour symmetry is
described by spurion fields whose low-energy vacuum expectation values are
identified with the SM Yukawa couplings. Insisting on canonical mass dimensions
for the spurion fields, the large top-quark Yukawa coupling also implies a
large expectation value for the associated spurion, which breaks part of the
flavour symmetry already at the UV scale Lambda of the ET. Below that scale,
flavour symmetry in the ET is represented in a non-linear way by introducing
Goldstone modes for the partly broken flavour symmetry and spurion fields
transforming under the residual symmetry. As a result, the dominance of certain
flavour structures in rare quark decays can be understood in terms of the
1/Lambda expansion in the ET. We also discuss the generalization to
2-Higgs-doublet models with large tan(beta). | hep-ph |
Refined renormalization group improvement for thermally resummed
effective potential: We newly develop a renormalization group (RG) improvement for thermally
resummed effective potentials. In this method, $\beta$-functions are
consistently defined in resummed perturbation theories, so that order-by-order
RG invariance is not spoiled after thermal resummation. With this improvement,
scale dependences of phase transition quantities such as a critical
temperature, which are known to be notoriously large at the one-loop order, are
greatly reduced compared to calculations with the conventional
$\overline{\text{MS}}$ scheme. By taking advantage of the RG invariance, we
also devise a resummation method that can incorporate potentially harmful large
logarithmic terms and temperature-dependent power corrections in a generic
form. We point out that a resummed one-loop effective potential refined by the
method can give results that agree with those obtained by resummed two-loop
effective potentials within errors. | hep-ph |
Dashen's theorem and electromagnetic masses of the mesons: Employing $U(3)_L\times U(3)_R$ chiral field theory, we find that Dashen's
theorem, which holds for pseudoscalar mesons, can be generalized to the sector
of axial-vector mesons, however, fails for vector mesons. | hep-ph |
Mixing dynamics of dimension-five interactions
(scalar/pseudoscalar-photon) in magnetized medium: In many extentions of standard model, dimension-5 scalar di-photon
($g_{\gamma\gamma\phi}\phi$ $F^{\mu\nu}F_{\mu\nu}$ ) or pseudoscalar di-photon
($g_{\gamma\gamma a}a\tilde{F}^{\mu\nu} F_{\mu\nu} $, ) interaction
materializes due to scale symmetry breaking or $U_A(1)$ symmetry breaking. In a
magnetized vacuum (i.e., in an external background field $\bar{F}_{\mu\nu} $)
the transverse degrees of freedom of the photons-- for such systems-- can be
described in terms of the form factors constructed out of the background field
strength tensor ($\bar{F}_{\mu\nu} $) and the same for dynamical photon
($f^{\mu\nu}$); they happen to be $\bar{F}_{\mu\nu}f^{\mu\nu}$ and
${\tilde{\bar{F}}_{\mu\nu}f^{\mu\nu}}$. These form factors transform
differently under CP transformation. While $\bar{F}_{\mu\nu}f^{\mu\nu}$
(describing polarization orthogonal to B ($|\gamma_{||} >$)) is CP even,
the other one, ${\tilde{\bar{F}}_{\mu\nu}f^{\mu\nu}}$( describing
polarization along B ($|\gamma_\bot >$), is CP odd. In the interaction
Lagrangian, if the scalar is interchanged with the pseudoscalar, the role of
the two form factors just gets interchanged. Thus for nearly degenerate
strengths of the coupling constants ( $g_{\gamma\gamma\phi}$ and
$g_{\gamma\gamma _a}$ ) and masses ($m_\phi$ and $m_a$ ) of the respective
candidates, proper identification of one from the other may become very
difficult in laboratory or astrophysics based experiments. The basic motivation
of this investigation is to reduce this uncertainty through incorporation of
parity violating ({\it originating through magnetized medium effects }) part of
the photon self-energy in the effective Lagrangian. This step, in turn affects
the (Pseudo) Scalar Photon mixing dynamics drastically and brings out a
significant change in the spectrum of the electromagnetic beam undergoing such
interaction. | hep-ph |
Multiparton webs beyond three loops: Correlators of Wilson-line operators are fundamental ingredients for the
study of the infrared properties of non-abelian gauge theories. In perturbation
theory, they are known to exponentiate, and their logarithm can be organised in
terms of collections of Feynman diagrams called webs. We study the
classification of webs to high perturbative orders, proposing a set of tools to
generate them recursively: in particular, we introduce the concept of Cweb, or
correlator web, which is a set of skeleton diagrams built with connected gluon
correlators, instead of individual Feynman diagrams. As an application, we
enumerate all Cwebs entering the soft anomalous dimension matrix for
multi-parton scattering amplitudes at four loops, and we compute the mixing
matrices for all Cwebs connecting four or five Wilson lines at that loop order,
verifying that they obey sum rules that were derived or conjectured in the
literature. Our results provide the colour building blocks for the calculation
of the soft anomalous dimension matrix at four-loop order. | hep-ph |
Wilson Expansion of QCD Propagators at Three Loops: Operators of
Dimension Two and Three: In this paper we construct the Wilson short distance operator product
expansion for the gluon, quark and ghost propagators in QCD, including
operators of dimension two and three, namely, A^2, m^2, m A^2, \ovl{\psi} \psi
and m^3. We compute analytically the coefficient functions of these operators
at three loops for all three propagators in the general covariant gauge. Our
results, taken in the Landau gauge, should help to improve the accuracy of
extracting the vacuum expectation values of these operators from lattice
simulation of the QCD propagators. | hep-ph |
Mapping the phase diagram of strongly interacting matter: We employ a conformal mapping to explore the thermodynamics of strongly
interacting matter at finite values of the baryon chemical potential $\mu$.
This method allows us to identify the singularity corresponding to the critical
point of a second-order phase transition at finite $\mu$, given information
only at $\mu=0$. The scheme is potentially useful for computing thermodynamic
properties of strongly interacting hot and dense matter in lattice gauge
theory. The technique is illustrated by an application to a chiral effective
model. | hep-ph |
The Neutral Higgs Effects on Rare Decays $B \to X_s l^+ l^-$ in T2HDM: We calculate the new physics contributions to the branching ratios of the
rare decays $B \to X_s l^+ l^-$ $(l=e, \mu)$ induced by neutral Higgs bosons
loop diagrams in the top quark two-Higgs-doublet model (T2HDM). From the
numerical calculations, we find that (a) the neutral Higgs boson's correction
to $B \to X_s l^+ l^-$ decays interferes constructively with its standard model
counterpart, but small in magnitude; (b) the neutral Higgs contributions to the
branching ratio of $B \to X_s l^+ l^-$ decay can be neglected safely if their
masses are larger than 100 GeV and $\tan\beta \leq 40$. | hep-ph |
$ρ$ meson generalized parton distributions in the Nambu--Jona-Lasinio
model: In this paper, both the unpolarized and the polarized $\rho$ meson
generalized parton distributions are investigated in the framework of the
Nambu--Jona-Lasinio model using proper time regularization scheme. The symmetry
properties of $\rho$ meson generalized parton distributions are checked. The
three independent distribution functions in deep inelastic scattering,
$F_1(x)$, $b_1(x)$ and $g_1(x)$, and the Sachs-like charge, magnetic, and
quadruple form factors $G_C(t)$, $G_M(t)$ and $G_Q(t)$, which are the first
Mellin moments of unpolarized generalized parton distributions are obtained. In
addition, the $u$ quark axial vector form factors $\tilde{F}_1^u(t)$ and
$\tilde{F}_2^u(t)$ related to the axial currents from the polarized generalized
parton distributions are studied. The impact parameter dependent parton
distribution functions, which are the two-dimensional Fourier transform of
generalized parton distributions are studied, too. The obtained $\rho$ meson
generalized parton distributions satisfy the required properties well. | hep-ph |
The first-order factorizable contributions to the three-loop massive
operator matrix elements $A_{Qg}^{(3)}$ and $ΔA_{Qg}^{(3)}$: The unpolarized and polarized massive operator matrix elements $A_{Qg}^{(3)}$
and $\Delta A_{Qg}^{(3)}$ contain first-order factorizable and non-first-order
factorizable contributions in the determining difference or differential
equations of their master integrals. We compute their first-order factorizable
contributions in the single heavy mass case for all contributing Feynman
diagrams. Moreover, we present the complete color-$\zeta$ factors for the cases
in which also non-first-order factorizable contributions emerge in the master
integrals, but cancel in the final result as found by using the method of
arbitrary high Mellin moments. Individual contributions depend also on
generalized harmonic sums and on nested finite binomial and inverse binomial
sums in Mellin $N$-space, and correspondingly, on Kummer-Poincar\'e and
square-root valued alphabets in Bjorken-$x$ space. We present a complete
discussion of the possibilities of solving the present problem in $N$-space
analytically and we also discuss the limitations in the present case to
analytically continue the given $N$-space expressions to $N \in \mathbb{C}$ by
strict methods. The representation through generating functions allows a well
synchronized representation of the first-order factorizable results over a
17-letter alphabet. We finally obtain representations in terms of iterated
integrals over the corresponding alphabet in $x$-space, also containing up to
weight {\sf w = 5} special constants, which can be rationalized to
Kummer-Poincar\'e iterated integrals at special arguments. The analytic
$x$-space representation requires separate analyses for the intervals $x \in
[0,1/4], [1/4,1/2], [1/2,1]$ and $x > 1$. We also derive the small and large
$x$ limits of the first-order factorizable contributions. | hep-ph |
The single parton fragmentation functions of heavy quarkonium in soft
gluon factorization: We study the single parton fragmentation functions (FFs) at the input
factorization scale $\mu_0\gtrsim 2m_Q$, with heavy quark mass $m_Q$, in the
soft gluon factorization (SGF) approach. We express the FFs in terms of
perturbatively calculable short distance hard parts for producing a heavy
quark-antiquark pair in all possible states, convoluted with corresponding soft
gluon distribution for the hadronization of the pair to a heavy quarkonium. We
compute the perturbative short distance hard parts for producing a heavy quark
pair in all possible $S$-wave and $P$-wave states up to $O(\alpha_s^2)$. With
our results, the SGF can be further used to study the heavy quarkonium
production at the hadron colliders and heavy quarkonium production within a
jet. | hep-ph |
Progress in Lattice QCD Relevant for Flavor Physics: Recent Lattice QCD results relevant for Kaon, Charm and B Physics are
summarized. There is general agreement among calculations using a wide range of
different lattice actions. This bolsters confidence in the lattice results and
in their quoted errors. One notes considerable progress since CKM2008 in
reducing lattice errors with some quantities now being calculated at the
subpercent to a few percent level accuracy. Much work remains, however, and
further improvements can be expected in the coming years. | hep-ph |
How suppressed are the radiative interference effects in heavy unstable
particle production?: We present a \lq\lq theorem" which quantifies, for inclusive processes, the
level of suppression of the radiative interference effects between the
production and decay stages of heavy {\it unstable} particles. The theorem,
which is based on very general physical arguments, is applicable to all orders
in the coupling. | hep-ph |
Light-meson properties from the Bethe-Salpeter equation: We discuss how to extract observables from an inhomogeneous vertex
Bethe-Salpeter equation without resorting to the corresponding homogeneous
equation. As an example we present a prediction for the $e^+e^-$ decay width of
the $\rho(1450)$ or $\rho'$ meson. We also attempt to identify the momentum
range contributing to a vector meson's decay constant. | hep-ph |
Linear Collider Signal of a Wino LSP in Anomaly Mediated Scenarios: Selectron (smuon) pair-production in a next generation Linear Collider,
yielding a fast electron (muon) trigger, a visible heavily ionizing track
and/or a resolved soft pion impact parameter and overall $\mET$, is shown to
provide a smoking gun signature for Anomaly Mediated Supersymmetry Breaking
models with a neutral Wino as the Lightest Supersymmetric Particle, nearly
mass-degenerate with the lighter chargino. | hep-ph |
Parity violating magnetization at neutrino pair emission using trivalent
lanthanoid ions: A new detection method using magnetization generated at triggered radiative
emission of neutrino pairs (RENP), $ |e \rangle \rightarrow | g \rangle +
\gamma + \sum_{ij}\nu_i \bar{\nu}_j $ (atomic de-transition from state $|e
\rangle $ to state $|g \rangle$ emitting sum of neutrino pairs
$\sum_{ij}\nu_i\bar{\nu}_j$ accompanied by a photon $\gamma$), is investigated
in order to determine unknown neutrino properties; absolute neutrino masses of
$\nu_i$ and Majorana/Dirac distinction. Magnetization associated with RENP
events has parity violating component intrinsic to weak interaction enforced by
crystal field effect in solids, and greatly helps background rejection of
quantum electrodynamic (QED) origin even when these backgrounds are amplified.
In proposed experiments we prepare a coherently excited body of trivalent
lanthanoid ions, Er$^{3+}$ (a best candidate ion so far found), doped in a
transparent dielectric crystal. The magnetic moment $\mu \langle
\vec{S}\cdot\vec{k} \rangle/k $ arising from generated electron spin $\vec{S}$
parallel to trigger photon direction $\vec{k}/k$ is parity odd, and is absent
in QED processes. The generated magnetic field of order nano gauss is stored in
crystals long after pair emission event till spin relaxation time. An improved
calculation method of coherent rate and angular distribution of magnetization
is developed in order to incorporate finite size effect of crystal target
beyond the infinite size limit in previous calculations. | hep-ph |
How Penguins Started to Fly: A mechanism explaining a strong enhancement of nonleptonic weak decays was
suggested in 1975, later to be dubbed the penguin. This mechanism extends
Wilson's ideas about the operator product expansion at short distances and
reveals an intricate interplay of subtle features of the theory such as heavy
quark masses in Glashow-Iliopoulos-Maini cancellation, light quarks shaping the
chiral properties of QCD, etc. The penguins have subsequently evolved to play a
role in a variety of fields in present-day particle phenomenology. I will
describe the history of this idea and review its subsequent development. The
recent measurement of direct CP violation in K decays gives a new confirmation
of the penguin mechanism. | hep-ph |
Renormalization Group Effects on the Mass Relation Predicted by the
Standard Model with Generalized Covariant Derivatives: Renormalization group analysis is made on the relation $m_{\rm H} \simeq
\sqrt{2}m_t$ for masses of the top quark and the Higgs boson, which is
predicted by the standard model based on generalized covariant derivatives with
gauge and Higgs fields. This relation is a low energy manifestation of a tree
level constraint which holds among the quartic Higgs self-coupling constant and
the Yukawa coupling constants at a certain high energy scale $\mu_0$. With the
renormalization group equation at one-loop level, the evolution of the
constraint is calculated from $\mu_0$ down to the low energy region around the
observed top quark mass. The result of analysis shows that the Higgs boson mass
is in $m_t \lesssim m_{\rm H} \lesssim \sqrt{2}m_t$ for a wide range of the
energy scale $\mu_0 \gtrsim m_t$ and it approaches to 177 GeV ($\approx m_t$)
for large values of $\mu_0$. | hep-ph |
Analysis of the $X(6600)$, $X(6900)$, $X(7300)$ and related tetraquark
states with the QCD sum rules: In this work, we re-investigate the mass spectrum of the ground state, first,
second and third radial excited states of the diquark-antidiquark type
fully-charm tetraquark states with the QCD sum rules plus Regge trajectories.
We take account of the CMS and ATLAS experimental data and preform a
self-consistent analysis, then try to make possible assignments of the
$X(6600)$, $X(6900)$ and $X(7300)$ in the picture of tetraquark states with the
$J^{PC}=0^{++}$ or $1^{+-}$. | hep-ph |
Neutrino oscillations in the early Universe: We discuss the oscillations effects on neutrinos in the early Universe and
update the cosmological constraints on the oscillation parameters. It is shown
that sterile LOW solution to the solar neutrino problem is almost completely
excluded from cosmological nucleosynthesis considerations. Two possibilities
for the relaxation of this constraint are discussed: high primordial helium-4
yield and a relic lepton asymmetry present at nucleosynthesis epoch. The
numerical analysis proved that Y_p=0.25 only relaxes the constraint on LOW
solution, while L > 10^{-5} is capable to remove it. | hep-ph |
Quirky Explanations for the Diphoton Excess: We propose two simple quirk models to explain the recently reported 750 GeV
diphoton excesses at ATLAS and CMS. It is already well-known that a real
singlet scalar $\phi$ with Yukawa couplings $\phi \bar X X$ to vector-like
fermions $X$ with mass $m_X > m_\phi/2$ can easily explain the observed signal,
provided $X$ carries both SM color and electric charge. We instead consider
first the possibility that the pair production of a fermion, charged under both
SM gauge groups and a confining $SU(3)_v$ gauge group, is responsible. If pair
produced it forms a quirky bound state, which promptly annihilates into gluons,
photons, v-gluons and possibly SM fermions. This is an extremely minimal model
to explain the excess, but is already in some tension with existing displaced
searches, as well as dilepton and dijet resonance bounds. We therefore propose
a hybrid Quirk-Scalar model, in which the fermion of the simple $\phi \bar X X$
toy model is charged under the additional $SU(3)_v$ confining gauge group.
Constraints on the new heavy fermion $X$ are then significantly relaxed. The
main additional signals of this model are possible dilepton, dijet and diphoton
resonances at $\sim$ 2 TeV or more from quirk annihilation, and the production
of v-glueballs through quirk annihilation and $\phi$ decay. The glueballs can
give rise to spectacular signatures, including displaced vertices and events
with leptons, photons and $Z$-bosons. If the Quirk-Scalar model is responsible
for the 750 GeV excess it should be discovered in one of these channels with 20
or $300 \mathrm{fb}^{-1}$ of LHC run 2 data. | hep-ph |
Charged Lepton Spectrum Approximation in a Three Body Nucleon Decay: Only phase space is typically used to obtain final state particle spectra in
rare decay searches, which is a crude approximation in the case of three body
processes. We will demonstrate how both dynamics and phase space can be
approximately accounted for, in processes such as nucleon decays $p \rightarrow
e^+ \bar{\nu} \nu$ or $p \rightarrow \mu^+ \bar{\nu} \nu$ originating from
Grand Unification models, using general effective Fermi theory formalism of
electroweak muon decay $\mu \rightarrow e^+ \bar{\nu} \nu$. This approach
allows for a more precise and only weakly model dependent approximation of
final particle spectra for these and similar decays, which may improve rare
process searches in current and near-future experiments. | hep-ph |
Threshold effects on prediction for proton decay in non-supersymmetric
$E_6$ GUT with intermediate trinification symmetry: We consider a non-supersymmetric $E_6$ Grand Unified Theory (GUT) with
intermediate trinification symmetry $SU(3)_C \times SU(3)_L \times SU(3)_R
\times D$ (D denoted as D-parity for discrete left-right symmetry) and study
the effect of one-loop threshold corrections arising due to every class of
superheavy particles (scalars, fermions and vectors). It is observed that, the
intermediate mass scale $M_I$ and $\sin^2\theta_W$ remain unaffected by GUT
threshold contributions. The threshold modified unification mass scale $M_U$ is
in excellent agreement with the present experimental proton decay constraint.
The novel feature of the model is that GUT threshold uncertainty of $M_U$ is
found to be controlled by superheavy scalars only, leading to a very predictive
scenario for proton decay, which can be verifiable within the foreseeable
experiments. | hep-ph |
Definition and Evolution of Transverse Momentum Distributions: We consider the definition of unpolarized transverse-momentum-dependent
parton distribution functions while staying on-the-light-cone. By imposing a
requirement of identical treatment of two collinear sectors, our approach,
compatible with a generic factorization theorem with the soft function
included, is valid for all non-ultra-violet regulators (as it should), an issue
which causes much confusion in the whole field. We explain how large logarithms
can be resummed in a way which can be considered as an alternative to the use
of Collins-Soper evolution equation. The evolution properties are also
discussed and the gauge-invariance, in both classes of gauges, regular and
singular, is emphasized. | hep-ph |
High Energy Photon-Photon and Electron-Photon Collisions: The advent of a next linear $e^\pm e^-$ collider and back-scatterd laser
beams will allow the study of a vast array of high energy processes of the
Standard Model through the fusion of real and virtual photons and other gauge
bosons. As examples, I discuss virtual photon scattering $\gamma^* \gamma^* \to
X$ in the region dominated by BFKL hard Pomeron exchange and report the
predicted cross sections at present and future $e^\pm e^-$ colliders. I also
discuss exclusive $\gamma \gamma$ reactions in QCD as a measure of hadron
distribution amplitudes and a new method for measuring the anomalous magnetic
and quadrupole moments of the $W$ and $Z$ gauge bosons to high precision in
polarized electron-photon collisions. | hep-ph |
Restoration of Parity and the Right-Handed Analog of the CKM Matrix: In a recent Letter we determined analytically the right-handed quark mixing
matrix in the minimal Left-Right symmetric theory with generalized Parity. We
derived its explicit form as a series expansion in a small parameter that
measures the departure from hermiticity of quark mass matrices. Here we analyze
carefully the convergence of the series by including higher order terms and by
comparing with numerical results. We apply our findings to some
phenomenological applications such as the production and decays of the
right-handed gauge boson $W_R$, the neutrinoless double beta decay, the decays
of the heavy scalar doublet, the strong CP parameter and the theoretical limits
on the new mass scale from the $K$ and $B$-meson physics. In particular, we
demonstrate that the relevant coupling for the production of the $W_R$ gauge
boson at hadronic colliders and for the neutrinoless double beta decay equals
its left-handed counterpart, within a percent. We also demonstrate that the
stability of the theoretical lower limit on the $W_R$ mass from the $K$-meson
physics is due to a partial cancellation of the external phases of the
right-handed mixing matrix. | hep-ph |
Azimuthal angles in diffractive ep collisions: We investigate azimuthal correlations in deep inelastic diffractive
scattering, e + p -> e + \tilde{p} + X. The dependence of the ep cross section
on the angle between the lepton plane and some direction in the hadronic final
state can be written in a simple form; its measurement can be used to constrain
the cross section for longitudinally polarised photons. Using the model of
nonperturbative two-gluon exchange of Landshoff and Nachtmann we calculate the
distribution of the azimuthal jet angle in diffractive dijet production and
find that useful bounds on the longitudinal cross section for such events might
be obtained from its measurement. We then discuss the predictions of this model
for the dependence of the ep cross section on the azimuthal angle of the proton
remnant \tilde{p}, which contains information about the helicity content of the
pomeron. | hep-ph |
SuperIso program and flavor data constraints: We present here an overview of the SuperIso program which is a public code
dedicated to the calculation of flavor physics observables in supersymmetry.
The main purpose of the SuperIso program is to provide, by confronting the
theoretical predictions to the experimental data for flavor observables,
indirect constraints on the parameters of supersymmetry. These constraints can
then provide limits on physical masses of yet undiscovered new particles, such
as charged Higgs bosons. | hep-ph |
Light diffraction by a strong standing electromagnetic wave: The nonlinear quantum interaction of a linearly polarized x-ray probe beam
with a focused intense standing laser wave is studied theoretically. Because of
the tight focusing of the standing laser pulse, diffraction effects arise for
the probe beam as opposed to the corresponding plane wave scenario. A
quantitative estimate for realistic experimental conditions of the ellipticity
and the rotation of the main polarization plane acquired by the x-ray probe
after the interaction shows that the implementation of such vacuum effects is
feasible with future X-ray Free Electron Laser light. | hep-ph |
Spin-dependent Pomeron and Odderon in elastic proton-proton scattering: We introduce a new model of near-forward elastic proton-(anti)proton
scattering at high energy based on the modern formulation of Pomeron and
Odderon in terms of Wilson lines and generalized TMDs (GTMDs). We compute the
helicity-dependent elastic amplitudes $\phi_{1,2,3,4,5}$ in this model and
study their energy dependence from the nonlinear small-$x$ evolution equations.
While both Pomeron and Odderon contribute to helicity-flip processes in
general, in the forward limit $t=0$ only the double helicity-flip amplitude
$\phi_2$, dominated by the spin-dependent Odderon, survives. This may affect
the extraction of the $\rho$ parameter as well as the total cross section in
the LHC energy domain and beyond. | hep-ph |
A two particle hidden sector and the oscillations with photons: We present a detailed study of the oscillations and optical properties for
vacuum, in a model for the dark sector that contains axion-like particles and
hidden photons. In this model, both can couple to photons. We provide bounds
for the couplings versus the mass, using current results from ALPS-I and PVLAS.
We also discuss the challenges for the detection of models with more than one
hidden particle in light shining trough wall-like experiments. | hep-ph |
Topics in Electroweak Physics: We briefly discuss five topics in Precision Electroweak Physics: i) the
recently proposed Effective Scheme of Renormalization, ii) evidence for
electroweak bosonic corrections derived from the radiative correction
Delta_r_eff, iii) an approach to estimate the scale of new physics in a
hypothetical Higgs-less scenario, iv) simple and accurate formulae for s^2_eff,
M_W, Gamma_l, and their physical applications, v) a recent proposal concerning
the field renormalization constant for unstable particles. | hep-ph |
On Distinguishing Radions From Higgs Bosons: Radion couplings are almost identical to Higgs boson couplings, making it
very difficult to distinguish the two states when the radion mass and vacuum
expectation value are similar to those of the Higgs boson. The only real
difference lies in the fact that the coupling of radions to off-shell fermions
is proportional to the momentum rather than the mass of the fermion. This extra
contribution gets cancelled in all tree-level processes and shows up only in
loop-induced processes like Phi -> gamma gamma and Phi -> gg. We perform a
careful calculation of the branching ratios and establish that they can prove
crucial in clearly distinguishing a radion from a Higgs boson. This claim is
made concrete by evaluating the exclusive cross-sections in a radiative process
involving elementary scalars. | hep-ph |
Pairing Phase Transitions of Matter under Rotation: The phases and properties of matter under global rotation have attracted much
interest recently. In this paper we investigate the pairing phenomena in a
system of fermions under the presence of rotation. We find that there is a
generic suppression effect on pairing states with zero angular momentum. We
demonstrate this effect with the chiral condensation and the color
superconductivity in hot dense QCD matter as explicit examples. In the case of
chiral condensation, a new phase diagram in the temperature-rotation parameter
space is found, with a nontrivial critical point. | hep-ph |
Translation of Time-Reversal Violation in the Neutral K-Meson System
into a Table-Top Mechanical System: Weak interactions break time-reversal (T) symmetry in the two-state system of
neutral K mesons. We present and discuss a two-state mechanical system, a
Foucault-type pendulum on a rotating table, for a full representation of K0
K0bar transitions by the pendulum motions including T violation. The pendulum
moves with two different oscillation frequencies and two different magnetic
dampings. Its equation of motion is identical with the differential equation
for the real part of the CPT-symmetric K-meson wave function. The pendulum is
able to represent microscopic CP and T violation with CPT symmetry owing to the
macroscopic Coriolis force which breaks the symmetry under reversal-of-motion.
Video clips of the pendulum motions are shown as supplementary material. | hep-ph |
Intrinsic transverse momentum and transverse spin asymmetries: We investigate leading twist transverse momentum dependent origins of
transverse spin asymmetries in hadron-hadron collisions. The chiral-odd T-odd
distribution function with intrinsic transverse momentum dependence, which
would signal an intrinsic handedness of quarks inside a hadron, could account
for single spin asymmetries and at the same time for the large cos(2 phi)
asymmetry in the unpolarized Drell-Yan cross section, which still lacks
understanding. We show explicitly how it would relate unpolarized and polarized
observables measurable with proton-proton collisions at RHIC. It would offer a
new possibility to access the transversity distribution function. | hep-ph |
Autoencoders for Semivisible Jet Detection: The production of dark matter particles from confining dark sectors may lead
to many novel experimental signatures. Depending on the details of the theory,
dark quark production in proton-proton collisions could result in semivisible
jets of particles: collimated sprays of dark hadrons of which only some are
detectable by particle collider experiments. The experimental signature is
characterised by the presence of reconstructed missing momentum collinear with
the visible components of the jets. This complex topology is sensitive to
detector inefficiencies and mis-reconstruction that generate artificial missing
momentum. With this work, we propose a signal-agnostic strategy to reject
ordinary jets and identify semivisible jets via anomaly detection techniques. A
deep neural autoencoder network with jet substructure variables as input proves
highly useful for analyzing anomalous jets. The study focuses on the
semivisible jet signature; however, the technique can apply to any new physics
model that predicts signatures with anomalous jets from non-SM particles. | hep-ph |
Final state strong interaction constraints on weak D0 -> K0S pi+ pi-
decay amplitudes: Weak decay tree and annihilation - t-channel W - exchange amplitudes for the
D0 -> K0S pi+ pi- process are calculated using quasi two-body QCD factorization
approach and unitarity constraints. Final state strong kaon-pion and pion-pion
interactions in S, P and D waves are described through corresponding form
factors including many resonances. Preliminary results compare well with the
effective mass distributions of the Belle and BABAR Collaboration analyses. | hep-ph |
Should we still believe in constrained supersymmetry?: We calculate Bayes factors to quantify how the feasibility of the constrained
minimal supersymmetric standard model (CMSSM) has changed in the light of a
series of observations. This is done in the Bayesian spirit where probability
reflects a degree of belief in a proposition and Bayes' theorem tells us how to
update it after acquiring new information. Our experimental baseline is the
approximate knowledge that was available before LEP, and our comparison model
is the Standard Model with a simple dark matter candidate. To quantify the
amount by which experiments have altered our relative belief in the CMSSM since
the baseline data we compute the Bayes factors that arise from learning in
sequence the LEP Higgs constraints, the XENON100 dark matter constraints, the
2011 LHC supersymmetry search results, and the early 2012 LHC Higgs search
results. We find that LEP and the LHC strongly shatter our trust in the CMSSM
(with $M_0$ and $M_{1/2}$ below 2 TeV), reducing its posterior odds by a factor
of approximately two orders of magnitude. This reduction is largely due to
substantial Occam factors induced by the LEP and LHC Higgs searches. | hep-ph |
Finite Theories and the SUSY Flavor Problem: We study a finite SU(5) grand unified model based on the non-Abelian discrete
symmetry A_4. This model leads to the democratic structure of the mass matrices
for the quarks and leptons. In the soft supersymmetry breaking sector, the
scalar trilinear couplings are aligned and the soft scalar masses are
degenerate, thus solving the SUSY flavor problem. | hep-ph |
Dark matter annihilation into leptons through gravity portals: Dark matter (DM) constitutes 85% of the matter in the Universe. However, its
specific particle property is still unclear. The fundamentals of DM particles
subject to gravitational interaction, and that the lepton excess in cosmic rays
may originate from DM particles, inspired us to investigate DM particle
properties beyond the standard model. We assume that a leptophilic SU(2)
doublet exists in nature as the mediator connecting DM with visible leptons.
Since general relativity is not renormalizable at the quantum level, it should
be regarded as an effective field theory's leading order term. One species of
the next-to-leading-order term should be operators linear to the Ricci scalar
and containing scalar fields, such as the Higgs field, scalar DM, or the newly
introduced SU(2) scalar doublet. These operators can cause DM annihilation
through gravity portals. We analyzed constraints from the cosmic antiproton
flux, DM relic abundance, cosmic positron flux, cosmic microwave background,
and direct detection experiments. The result shows that there is a vast
parameter space that is compatible with current experiments. DM with a mass of
electroweak scale is only allowed to annihilate into leptons. We further show
that the purely gravitational DM better explains the DArk Matter Particle
Explorer cosmic lepton excess. Our work provides a promising mechanism for DM
particles to connect with standard model particles. | hep-ph |
Explaining jet quenching with perturbative QCD alone: We present a new formulation of jet quenching in perturbative QCD beyond the
eikonal approximation. Multiple scattering in the medium is modelled through
infra-red-continued (2 -> 2) scattering matrix elements in QCD and the parton
shower describing further emissions. The interplay between these processes is
arranged in terms of a formation time constraint such that coherent emissions
can be treated consistently. Emerging partons are hadronised by the Lund string
model, tuned to describe LEP data in conjunction with the parton shower. Based
on this picture we obtain a good description of the nuclear modification factor
R_AA at RHIC and LHC. | hep-ph |
Neutrino mass generation from the perspective of presymmetry: The Standard Model (SM) with one right-handed neutrino per generation is
revisited with presymmetry being the global $U(1)_{B-L}$ symmetry of an
electroweak theory of leptons and quarks with initially postulated symmetric
fractional charges. The cancellation of gauge anomalies and the
non-perturbative normalization of lepton charges proceed through the mixing of
local and topological charges, the global $B-L$ measuring the induced charge
associated with a unit of topological charge, and the mathematical replacement
of the original fractional charges with the experimentally observed ones. The
$U(1)_{B-L}$ symmetry of the SM with Dirac neutrinos is seen as a residual
presymmetry. High-scale and low-scale seesaw mechanisms proposed to explain the
mass of neutrinos are examined from the perspective of presymmetry, be they of
Majorana or pseudo-Dirac type. We find that the tiny mass splitting in
pseudo-Dirac neutrinos and the mass of heavy neutrinos ride on the opposite
ends of the seesaw. We show that pseudo-Dirac neutrinos contain extra sterile
neutrinos with imprints of presymmetry and for heavy ones we get constraints
favoring the low-scale linear seesaw over the inverse variant. | hep-ph |
Measuring $|V_{ub}|$ at future B-Factories: We calculate the so--called Fermi motion parameter $p_{_F}$ of ACCMM model
using the variational method in a potential model approach. We also propose
hadronic invariant mass distribution as an alternative experimental observable
to measure $V_{ub}$ at future asymmetric $B$ factories. | hep-ph |
Application of a Revised Moliere Theory to the Description of the
Landau-Pomeranchuk Effect: Using the Coulomb corrections to some important parameters of a revised
Moliere multiple scattering theory, we have obtained analytically and
numerically the Coulomb corrections to the quantities of the Migdal theory of
the Landau-Pomeranchuk (LPM) effect for sufficiently thick targets. We showed
that the Coulomb correction to the spectral bremsstrahlung rate of this theory
allows completely eliminating the discrepancy between the theory and experiment
at leastfor high Z experimental targets. | hep-ph |
Meson Production and Spectroscopy at HERA: Selected recent results from the H1 and ZEUS experiments are reviewed,
illustrating some of the many facets of ``meson physics'' at the HERA ep
collider. The results cover exclusive elastic and proton-dissociative
diffractive vector meson production and comparisons with recent theoretical
calculations show that perturbative QCD models are successful in describing
these processes when at least one of the involved scales have large values.
Furthermore a search for odderon induced exclusive photoproduction of
pseudoscalar and tensor mesons is described; upper limits for the cross
sections are below recent theoretical predictions. Finally the status of open
charm meson spectroscopy in inclusive final states is reported. | hep-ph |
Radiative decays \$D^*_{(s)}\to D_{(s)}γ$ in covariant confined
quark model: Radiative decays $D^*_{(s)}\to D_{(s)}\gamma$ are revisited in light of new
experimental data from the \textit{BABAR} and BESIII collaborations. The
radiative couplings $g_{D^*D\gamma}$ encoding nonperturbative QCD effects are
calculated in the framework of the covariant confined quark model developed by
us. We compare our results with other theoretical studies and experimental
data. The couplings (in $\textrm{GeV}^{-1}$) $|g_{D^{*+}D^+\gamma}| = 0.45(9)$
and $|g_{D^{*0}D^0\gamma}| = 1.72(34)$ calculated in our model agree with the
corresponding experimental data $|g_{D^{*+}D^+\gamma}|=0.47(7)$ and
$|g_{D^{*0}D^0\gamma}|=1.77(16)$. The most interesting case is the decay
$D^*_s\to D_s\gamma$, for which a recent prediction based on light-cone sum
rules at next-to-leading order $|g_{D^*_s D_s\gamma}|=0.60(19)$ deviates from
the first (and only to date) lattice QCD result $|g_{D^*_s D_s\gamma}|=0.11(2)$
at nearly $3\sigma$. Our calculation yields $|g_{D^*_s D_s\gamma}|=0.29(6)$,
which falls somehow between the two mentioned results, although it is larger
than those predicted in other studies using quark models or QCD sum rules. | hep-ph |
Power Counting For and Symmetries of the Effective Field Theory For NN
Interactions: The appropriate power counting for the effective field theory of NN
interactions is reviewed. It is more subtle than in most effective field
theories since in the limit that the S-wave NN scattering lengths go to
infinity it is governed by a nontrivial fixed point. The leading two body terms
in the effective field theory for nucleon self interactions are scale invariant
and invariant under Wigner SU(4) spin-isospin symmetry in this limit. Higher
body terms with no derivatives (i.e., three and four body terms) are
automatically invariant under Wigner symmetry. | hep-ph |
Quarkonium production in hadronic collisions: We summarize the theoretical description of charmonium and bottonium
production in hadronic collisions and compare it to the available data from
hadron-nucleon interactions. With the parameters of the theory established by
these data, we obtain predictions for quarkonium production at RHIC and LHC
energies. | hep-ph |
Inclusive Quark Production in $e^{+}e^{-}$-Annihilation - A Path
Integral Approach: The single-particle inclusive differential cross-section for a reaction
$a+b\to c+X$ is written as imaginary part of a correlation function in a
forward scattering amplitude for $a+b\to a+b$ in a modified effective theory.
In this modified theory the interaction Hamiltonian $\tilde H_I$ equals $H_I$
of the original theory up to a certain time. Then there is a sign change and
$\tilde H_I$ becomes nonlocal. This is worked out in detail for scalar field
models and for QED plus the abelian gluon model. A suitable path integral for
direct calculations of inclusive cross sections is presented. | hep-ph |
Mixed QCD-electroweak corrections to Higgs boson production in gluon
fusion: We compute the 3-loop O(\alpha \alpha_s) correction to the Higgs boson
production cross section arising from light quarks using an effective theory
approach. Our calculation probes the factorization of QCD and electroweak
perturbative corrections to this process. We combine our results with the best
current estimates for contributions from top and bottom quarks to derive an
updated theoretical prediction for the Higgs boson production cross section in
gluon fusion. With the use of the MSTW 2008 parton distribution functions that
include the newest experimental data, our study results in cross sections
approximately 4-6% lower for intermediate Higgs boson masses than those used in
recent Tevatron analyses that imposed a 95% confidence level exclusion limit of
a Standard Model Higgs boson with M_H=170 GeV. | 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 |
Exotic and nonexotic magnetic transitions in the context of the SELEX
and GRAAL experiments: We calculate magnetic transition moments in the chiral quark-soliton model,
with explicit SU(3)-symmetry breaking taken into account. The dynamical model
parameters are fixed by experimental data for the magnetic moments of the
baryon octet and from the recent measurements of $\Theta^{+}$ mass. Known
magnetic transition moments $\mu_{\Lambda\Sigma}$, $\mu_{N\Delta}$ are
reproduced and predictions for other octet-decuplet and octet-antidecuplet
transitions are given. In particular $\mu_{\Sigma\Sigma^{\ast}}$ recently
constrained by SELEX is shown to be below $0.82 \mu_N$. The recent GRAAL data
on $\eta$ photoproduction off the nucleon are explained in terms of a new
narrow antidecuplet neutron-like resonance. | hep-ph |
Magnetic Moment of Leptons: We show that the magnetic moment of leptons is significantly modified in
thermal background as compared to the corresponding vacuum value. We compare
the magnetic moment of all different leptons near nucleosynthesis. It is shown
that the significance of thermal corrections depends on the temperature of the
universe and the respective lepton mass. In the early universe, particle mass
was growing quadratically with temperature which affects the corresponding
value of magnetic moment. Intrinsic magnetic moment is inversely proportional
to mass whereas thermal corrections to the neutrino dipole moment is
proportional to neutrino mass for the Dirac type neutrino in the minimal
standard model. Therefore the effect of temperature is not the same for charged
leptons and neutrinos. | hep-ph |
Mirror model for sterile neutrinos: Sterile neutrinos are studied as subdominant contribution to solar neutrino
physics. The mirror-matter neutrinos are considered as sterile neutrinos. We
use the symmetric mirror model with gravitational communication between mirror
and visible sectors. This communication term provides mixing between visible
and mirror neutrinos with the basic scale mu=v^2/M_Pl=5*10^-6 eV, where v=174
GeV is the vacuum expectation value of the standard electroweak group and M_Pl
is the Planckian mass. It is demonstrated that each mass eigenstate of active
neutrinos splits into two states separated by small Delta m^2. Unsuppressed
oscillations between active and sterile neutrinos nu_a --> nu_s occur only in
transitions between each of these close pairs (``windows''). These oscillations
are characterized by very small Delta m^2 and can suppress the flux and distort
spectrum of pp-neutrinos in detectable way. The other observable effect is
anomalous seasonal variation of neutrino flux, which appears in LMA solution.
The considered subdominant neutrino oscillations nu_a <--> nu_s can reveal
itself as big effects in observations of supernova neutrinos and high energy
(HE) neutrinos. In the case of HE neutrinos they can provide a very large
diffuse flux of active neutrinos unconstrained by the e-m cascade upper limit. | hep-ph |
Isolated prompt photon pair production at hadron colliders with
kt-factorization: In the framework of the kt-factorization approach, the isolated prompt photon
pair production in pp and p \bar p collisions at high energies is studied. The
consideration is based on the quark-antiquark annihilation, quark-gluon
scattering and gluon-gluon fusion subprocesses, where the non-zero transverse
momenta of incoming partons are taken into account. The unintegrated quark and
gluon densities in a proton are determined using the Kimber-Martin-Ryskin
prescription. The numerical analysis covers the total and differential
production cross sections and extends to specific angular correlations between
the produced prompt photons. Theoretical uncertainties of our evaluations are
studied and comparison with the NLO pQCD calculations is performed. The
numerical predictions are compared with the recent experimental data taken by
the D0, CDF, CMS and ATLAS collaborations at the Tevatron and LHC energies. | hep-ph |
Spontaneous Peccei-Quinn symmetry breaking renders sterile neutrino,
axion and $χ$boson to be candidates for dark matter particles: We study the Peccei-Quinn (PQ) symmetry of the sterile right-handed neutrino
sector and the gauge symmetries of the Standard Model. Due to four-fermion
interactions, spontaneous breaking of these symmetries at the electroweak scale
generates top-quark Dirac mass and sterile-neutrino Majorana mass. The top
quark channel yields massive Higgs, $W^\pm$ and $Z^0$ bosons. The sterile
neutrino channel yields the heaviest sterile neutrino Majorana mass, sterile
Nambu-Goldstone axion (or majoron) and massive scalar $\chi$boson. Four-fermion
operators effectively induce their tiny couplings to SM particles. We show that
a sterile QCD axion is the PQ solution to the strong CP problem. The lightest
and heaviest sterile neutrinos ($m_N^e\sim 10^2$ keV and $m_N^\tau\sim 10^2$
GeV), a sterile QCD axion ($m_a< 10^{-8}$ eV, $g_{a\gamma}< 10^{-13} {\rm
GeV}^{-1}$) and a Higgs-like $\chi$boson ($m_\chi\sim 10^2$ GeV) can be dark
matter particle candidates, for the constraints of their tiny couplings and
long lifetimes inferred from the $W$-boson decay width, Xenon1T and precision
fine-structure-constant experiments. The axion and $\chi$boson couplings to SM
particles are below the values reached by current laboratory experiments and
astrophysical observations for directly or indirectly detecting dark matter
particles. | hep-ph |
Relativistic corrections to the semi-inclusive decay of $\bmψ$ and
$\bmΥ$: In the framework of the nonrelativistic quantum chromodynamics factorization
formalism, we study the processes of $\psi(nS)$ and $\Upsilon(nS)$ decay into a
lepton pair or a charm pair associated with two jets up to the next-to-leading
order in velocity expansion. We present the analytic expressions for the
differential decay rate to the invariant mass of the lepton pair or charm pair.
We find that the ratio of the next-to-leading order short-distance coefficient
to the leading order one is in the range from -5.5 to -12.4. The relativistic
corrections are so large that they modify the leading order prediction
significantly. Utilizing the analytic expressions, we also investigate the
relativistic corrections in different kinematic regions and their dependence on
the masses of the initial-state quarkonium and the final-state fermion. In
addition, we study the momentum distribution of $D^{*+}$ in the process
$\Upsilon(1S)\to c\bar{c}gg\to D^{*+}X$. | hep-ph |
Detecting Boosted Dark Photons with Gaseous Detectors: We search for indirect signals of $\mathscr{O}$(keV) dark matter annihilating
or decaying into $\mathscr{O}$(eV) dark photons. These dark photons will be
highly boosted and have decay lengths larger than the Milky Way, and can be
absorbed by neutrino or dark matter experiments at a rate dependent on the
photon-dark photon kinetic mixing parameter and the optical properties of the
experiment. We show that current experiments can not probe new parameter space,
but future large-scale gaseous detectors with low backgrounds (i.e. CYGNUS,
NEXT, PANDAX-III) may be sensitive to this signal when the annihilation cross
section is especially large. | hep-ph |
Contributions of order ${\cal O}(m_{\rm quark}^2)$ to $K_{\ell 3}$ form
factors and unitarity of the CKM matrix: The form factors for the $K_{\ell 3}$ semileptonic decay are computed to
order $O(p^4)$ in generalized chiral perturbation theory. The main difference
with the standard $O(p^4)$ expressions consists in contributions quadratic in
quark masses, which are described by a single divergence-free low-energy
constant, $A_3$. A new simultaneous analysis is presented for the CKM matrix
element $V_{us}$, the ratio $F_K/F_{\pi}$, $K_{\ell 3}$ decay rates and the
scalar form factor slope $\lambda_0$. This framework easily accommodates the
precise value for $V_{ud}$ deduced from superallowed nuclear $\beta$-decays. | hep-ph |
Structure of Pion Photoproduction Amplitudes: We derive and apply the finite energy sum rules to pion photoproduction. We
evaluate the low energy part of the sum rules using several state-of-the-art
models. We show how the differences in the low energy side of the sum rules
might originate from different quantum number assignments of baryon resonances.
We interpret the observed features in the low energy side of the sum rules with
the expectation from Regge theory. Finally, we present a model, in terms of a
Regge-pole expansion, that matches the sum rules and the high-energy
observables. | hep-ph |
Specific Dark Matter signatures from hidden U(1): Several constructions motivate the existence of a dark $U(1)_D$ gauge boson
which interacts with the Standard Model only through its kinetic mixing or loop
induced processes. We describe two typical examples with specific signatures in
particular we show that a region with relatively light WIMPS, $M_{Z_D}\lsim 40$
GeV and a kinetic mixing $10^{-4} \lsim \delta \lsim 10^{-3} $ is not yet
excluded by the last experimental data and seems to give promising signals in a
near future. We also show that conditions from anomaly cancelation generate
tri-vector couplings $Z_D Z \gamma$ leading to a specific gamma ray line
observable by FERMI telescope. | hep-ph |
Implication of Super-Kamiokande Data on R-parity Violation: R-parity violating bilinear (soft) terms in the supersymmetric standard model
would be the leading source for nonzero neutrino masses and mixing. We point
out that the mixing between neutralinos (charginos) and neutrinos (charged
leptons) driven by the bilinear terms take factorized forms, which may enable
us to probe the neutrino mixing parameters in a collider. It is then shown that
the Super-Kamiokande data on atmospheric neutrinos require all the baryon
number violating couplings to be substantially suppressed: $\lambda''_{\rm any}
<10^{-9}$. | hep-ph |
Interplay of Hard and Soft Processes at JLab Energies: Even at moderate energy machines, there is a regime where hard pion
electroproduction proceeds by a perturbatively calculable process. The process,
we claim, is not the leading twist fragmentation one but rather a higher twist
process that produces kinematically isolated pions. Semiexclusive data may
teach us more about parton distribution functions of the target and the pion
distribution amplitude. In addition, there is a connection to generalized
parton distribution calculations of exclusive processes in that the
perturbative kernel is the same. | hep-ph |
New Pattern of Chiral Symmetry Restoration: In this talk I summarize our recent works on the chiral symmetry restoration
in the large flavor QCD using the hidden local symmetry (HLS) as an effective
field theory of QCD. Bare parameters in the HLS are determined by matching the
HLS with QCD at the matching scale through the Wilsoninan matching conditions.
This Wilsonian matching leads to the vector manifestation of the Wigner
realization of the chiral symmetry in which the symmetry is restored by the
massless degenerate pion (and its flavor partners) and rho meson (and its
flavor partners) as the chiral partner. | hep-ph |
Direct stau production at the LHC: We investigate the direct production of supersymmetric scalar taus at the
LHC. We present the general calculation of the dominant cross section
contributions for hadronic stau pair production within the MSSM, taking into
account left-right mixing of the stau eigenstates. We find that b-quark
annihilation and gluon fusion can enhance the cross sections by more than one
order of magnitude with respect to the Drell-Yan predictions. For long-lived
staus, we consider CMSSM parameter regions with such enhanced cross sections
and possible consequences from recent searches. We find that regions of
exceptionally small stau yields, favoured by cosmology, are in tension with a
recent CMS limit on m_stau. | hep-ph |
Correlation of Theoretical Uncertainties in PDF Fits and Theoretical
Uncertainties in Predictions: We show how to account for correlations between theoretical uncertainties
incorporated in parton distribution function (PDF) fits, and the theoretical
uncertainties in the predictions made using these PDFs. We demonstrate by
explicit calculations, both analytical and numerical, that these correlations
can lead to corrections to the central values of the predictions, and
reductions in both the PDF uncertainties and the theoretical uncertainties in
the prediction. We illustrate our results with predictions for top production
rapidity distributions and the Higgs total cross-section at the LHC, using the
NLO NNPDF3.1 PDF set which incorporates missing higher order uncertainties. We
conclude that the inclusion of correlations can increase both the accuracy and
precision of predictions involving PDFs, particularly for processes with data
already included in the PDF fit. | hep-ph |
Cosmology and New Physics: A comparison of the standard models in particle physics and in cosmology
demonstrates that they are not compatible, though both are well established.
Basics of modern cosmology are briefly reviewed. It is argued that the
measurements of the main cosmological parameters are achieved through many
independent physical phenomena and this minimizes possible interpretation
errors. It is shown that astronomy demands new physics beyond the frameworks of
the (minimal) standard model in particle physics. More revolutionary
modifications of the basic principles of the theory are also discussed. | hep-ph |
Lepton Flavor Violating Process in Bi-maximal texture of Neutrino
Mixings: We investigate the lepton flavor violation in the framework of the MSSM with
right-handed neutrinos taking the large mixing angle MSW solution in the
quasi-degenerate and the inverse-hierarchical neutrino masses. We predict the
branching ratio of $\mu \to e+\gamma$ and $\tau \to \mu+\gamma$ processes
assuming the degenerate right-handed Majorana neutrino masses. We find that the
branching ratio in the quasi-degenerate neutrino mass spectrum is 100 times
smaller than the ones in the inverse-hierarchical and the hierarchical neutrino
spectra. We emphasize that the magnitude of $U_{e3}$ is one of important
ingredients to predict BR($\mu \to e +\gamma $). The effect of the deviation
from the complete-degenerate right-handed Majorana neutrino masses are also
estimated. Furtheremore, we examine the $S_{3\sL}\times S_{3\sR}$ model, which
gives the quasi-degenerate neutrino masses, and the Shafi-Tavartkiladze model,
which gives the inverse-hierarchical neutrino masses. Both predicted branching
ratios of $\mu\to e+\gamma$ are smaller than the experimantal bound. | hep-ph |
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