HEP Phenomenology·hep-ph

Thu·Oct 1, 2015Thursday·October 1, 2015

22 papers—11 primary·11 cross-listed·reconstructed*

01*
The flavor-blind principle: A symmetrical approach to the Gatto-Sartori-Tonin relation
U. J. Saldaña-Salazar🇲🇽
We perform a systematic study of the generic Gatto-Sartori-Tonin relation, $tan^{2} θ_{ij} = m_{i} / m_{j}$ . This study of fermion mixing phenomena leads us to the necessary conditions that are needed in order to obtain it without any approximation. We begin by considering two Dirac fermion families. By means of the hierarchy in the masses, it is found that a sufficient and necessary condition is to have a normal matrix with $m_{11} = 0$ . This matrix can be decomposed into two different linearly independent contributions. The origin for such two independent contributions can be naturally explained by what we shall call the flavor-blind principle. This principle states that Yukawa couplings shall be either flavor-blind or decomposed into several sets obeying distinct permutation symmetries. In general, it is shown that the symmetry properties of the introduced set of Yukawa matrices follow for $n$ fermion families the unique sequential breaking $S_{n L} \otimes S_{n R} \to S_{(n - 1) L} \otimes S_{(n - 1) R} \to \dots \to S_{2 L} \otimes S_{2 R} \to S_{2 A}$ . The particular case of three fermion families explains why the four mass ratios parametrization that we recently proposed can be used even in the case of no hierarchical masses.
hep-phPRD(2016)·12 citations
02*
Lorentz and CPT Violation in Top-Quark Production and Decay
Micheal S. Berger🇺🇸 · Alan Kostelecky🇺🇸 · Zhi Liu🇺🇸
The prospects are explored for testing Lorentz and CPT symmetry in the top-quark sector. We present the relevant Lagrange density, discuss physical observables, and describe the signals to be sought in experiments. For top-antitop pair production via quark or gluon fusion with subsequent semileptonic or hadronic decays, we obtain the matrix element in the presence of Lorentz violation using the narrow-width approximation. The issue of testing CPT symmetry in the top-quark sector is also addressed. We demonstrate that single-top production and decay is well suited to a search for CPT violation, and we present the matrix elements for single-top production in each of the four tree-level channels. Our results are applicable to searches for Lorentz violation and studies of CPT symmetry in collider experiments, including notably high-statistics top-antitop and single-top production at the Large Hadron Collider.
hep-phPRD(2016)·54 citations
03*
Physics of neutrino flavor transformation through matter-neutrino resonances
Meng-Ru Wu🇩🇪 · Huaiyu Duan🇺🇸 · Yong-Zhong Qian🇺🇸
In astrophysical environments such as core-collapse supernovae and neutron star-neutron star or neutron star-black hole mergers where dense neutrino media are present, matter-neutrino resonances (MNRs) can occur when the neutrino propagation potentials due to neutrino-electron and neutrino-neutrino forward scattering nearly cancel each other. We show that neutrino flavor transformation through MNRs can be explained by multiple adiabatic solutions similar to the Mikheyev-Smirnov-Wolfenstein mechanism. We find that for the normal neutrino mass hierarchy, neutrino flavor evolution through MNRs can be sensitive to the shape of neutrino spectra and the adiabaticity of the system, but such sensitivity is absent for the inverted hierarchy.
hep-phastro-ph.HEnucl-thPLB(2016)·61 citations
04*
On the Treatment of Resonances in Next-to-Leading Order Calculations Matched to a Parton Shower
Tomáš Ježo🇮🇹 · Paolo Nason🇮🇹
In this work we present a new subtraction method for next-to-leading order calculations that is particularly convenient even when narrow resonances are present. The method is particularly suitable for the implementation of next-to-leading order calculations matched to parton shower generators. It allows at the same time for the inclusion of all finite width effects, including interferences, and for a consistent treatment of resonances in the shower approach, preserving the mass of resonances near their peak. We implement our method, in a fully general and automatic way, within the POWHEG BOX framework, and illustrate it using as a test case the process of $pp \to μ^{+} ν_{μ} j_{b} j$ , that is dominated by $t$ -channel single top production.
hep-phJHEP(2015)·220 citations
05*
Electroweak chiral Lagrangian with a light Higgs
J.J. Sanz-Cillero🇪🇸
In this talk we discuss the structure of electroweak low-energy effective theories where the Higgs is non-linearly realized, typically in scenarios where the Higgs is a pseudo Nambu-Goldstone boson of some beyond Standard Model symmetry. The organization of the perturbative counting and the relevance of the various next-to-leading order contributions is studied. We discuss some new results on the structure of the one-loop ultraviolet divergences and the contribution from tree-level heavy resonance exchanges to the low-energy effective theory, which are applied to a couple of explicit examples in order to show how, in the non-linear effective theory -the electroweak chiral Lagrangian with a light Higgs (ECLh)-, one-loop corrections can be as important as the contribution from higher dimension operators.
hep-ph3 citations
06*
Phenomenology of a pseudoscalar glueball and charmed mesons
Walaa I. Eshraim🇩🇪
We study the vacuum properties of the pseudoscalar glueball and charmed mesons by using the so-called extended Linear Sigma Model (eLSM). This model includes scalar and pseudoscalar mesons, as well as vector and axial-vector mesons. We calculate the mesonic and baryonic decays of the pseudoscalar glueball, where we fixed its mass to $2.6$ GeV, as predicted by lattice-QCD simulations, and take a closer look at the scalar-isoscalar decay channel. As a second step, we enlarge the so-called extended linear Sigma model (eLSM) by including the charm quark to a global $U (4)_{r} \times U (4)_{l}$ chiral symmetry. Most of the parameters of the model have been determined in a previous work by fitting hadron properties involving three quark flavours. Only three new parameters, all related to the current charm quark mass, appear when introducing charmed mesons. We compute charmed mesons masses, weak decay constants, and strong decay widths of (open and hidden) charmed mesons. Moreover, we calculate the decay width of a pseudoscalar ground state charmonium $η_{c}$ into a pseudoscalar glueball and the decay widths of a scalar charmonium $χ_{c 0}$ into the scalar glueball.
hep-ph6 citations
07*
Study of two- and three-meson decay modes of tau-lepton with Monte Carlo generator TAUOLA
Olga Shekhovtsova🇵🇱
The study of the $τ$ -lepton decays into hadrons has contributed to a better understanding of non-perturbative QCD and light-quark meson spectroscopy, as well as to the search of new physics beyond the Standard Model. The two- and three-meson decay modes, considering only those permitted by the Standard Model, are the predominant decays and together with the one-pion mode compose more than $85%$ of the hadronic $τ$ -lepton decay width. In this note we review the theoretical results for these modes implemented in the Monte Carlo event generator TAUOLA and present at the same time a comparison with the Belle Collaboration data for the two-pion decay mode and the BaBar preliminary data for the three-pion decay mode as well for the decay mode into two-kaon and one-pion.
hep-phhep-latPoS(2016)·0 citations
08*
Study of the $f_{2} (1270)$ and $a_{2} (1320)$ resonances in $γ^{*} (Q^{2}) γ$ collisions
N.N. Achasov🇷🇺 · A.V. Kiselev🇷🇺 · G.N. Shestakov🇷🇺
We discuss studies of the $Q^{2}$ dependence of the $f_{2} (1270)$ and $a_{2} (1320)$ production cross sections in $γ^{*} (Q^{2}) γ$ collisions at current and coming into operation colliders with a high luminosity. Changing the dominant helicity amplitude occurs in the reactions $γ^{*} (Q^{2}) γ \to f_{2} (1270)$ and $γ^{*} (Q^{2}) γ \to a_{2} (1320)$ with increasing $Q^{2}$ . This is caused by the coming of the QCD asymptotics. It is shown that the transition to the asymptotic behavior of QCD in the amplitudes $γ^{*} (Q^{2}) γ \to f_{2} (1270), a_{2} (1320)$ is provided by the compensation of the contributions of ground vector states $ρ$ and $ω$ in $Q^{2}$ -channel with the contributions of their radial excitations.
hep-phhep-exnucl-thJETP Lett.(2015)·7 citations
09*
GravitinoPack and decays of supersymmetric metastable particles
Helmut Eberl🇦🇹 · Vassilis C. Spanos🇬🇷
We present the package GravitinoPack that calculates the two- and three-body decays of unstable supersymmetric particles involving the gravitino in the final or initial state. In a previous paper, we already showed results for the gravitino decays into two and three particles. In this paper, we incorporate the processes where an unstable neutralino, stau or stop decays into a gravitino and Standard Model particles. This is the case in gravitino dark matter supersymmetric models, where the gravitino is the lightest SUSY particle. We give instructions for the installation and the use of the package. In the numerical analysis, we discuss various MSSM scenarios. We show that the calculation of all the decay channels and the three-body decay branching ratios is essential for the accurate application of cosmological bounds on these models.
hep-phComput.Phys.Commun.(2016)·11 citations
10*
Top Quark Pair Production in Association with a Jet with NLO QCD Off-Shell Effects at the Large Hadron Collider
G. Bevilacqua🇮🇹 · H. B. Hartanto🇩🇪 · M. Kraus🇩🇪 · M. Worek🇩🇪
We present a complete description of top quark pair production in association with a jet in the dilepton channel. Our calculation is accurate to next-to-leading order in QCD (NLO) and includes all non-resonant diagrams, interferences and off-shell effects of the top quark. Moreover, non-resonant and off-shell effects due to the finite W gauge boson width are taken into account. This calculation constitutes the first fully realistic NLO computation for top quark pair production with a final state jet in hadronic collisions. Numerical results for differential distributions as well as total cross sections are presented for the Large Hadron Collider (LHC) at 8 TeV. With our inclusive cuts, NLO predictions reduce the unphysical scale dependence by more than a factor of 3 and lower the total rate by about 13% compared to leading order QCD (LO) predictions. In addition, the size of the top quark off-shell effects is estimated to be below 2%.
hep-phhep-exPRL(2016)·87 citations
11*
Searching for Dark Matter Constituents with Many Solar Masses
Paul H. Frampton🇬🇧
Searches for dark matter (DM) constituents are presently mainly focused on axions and WIMPs despite the fact that far higher mass constituents are viable. We discuss and dispute whether axions exist and those arguments for WIMPs which arise from electroweak supersymmetry. We focus on the highest possible masses and argue that, since if they constitute all DM they cannot be baryonic, they must uniquely be primordial black holes. Observational constraints require them to be of intermediate masses mostly between a hundred and a hundred thousand solar masses. Known search strategies include wide binaries, CMB distortion and, most promisingly, extended microlensing experiments.
hep-phastro-ph.GAgr-qcMod.Phys.Lett.A(2016)·41 citations
12*
Hydrodynamic Waves in an Anomalous Charged Fluid
Navid Abbasi🇮🇷 · Ali Davody🇮🇷 · Kasra Hejazi🇮🇷 · Zahra Rezaei🇮🇷
We study the collective excitations in a relativistic fluid with an anomalous $U (1)$ current. In $3 + 1$ dimensions at zero chemical potential, in addition to ordinary sound modes we find two propagating modes in presence of an external magnetic field. The first one which is a transverse degenerate mode, propagates with a velocity proportional to the coefficient of gravitational anomaly; this is in fact the Chiral Alfvén wave recently found in \cite{Yamamoto:2015ria}. Another one is a wave of density perturbation, namely a chiral magnetic wave (CMW). The velocity dependence of CMW on the chiral anomaly coefficient is well known. We compute the dependence of CMW's velocity on the coefficient of gravitational anomaly as well. We also show that the dissipation splits the degeneracy of CAW. At finite chiral charge density we show that in general there may exist five chiral hydrodynamic waves. Of these five waves, one is the CMW while the other four are mixed Modified Sound-Alfvén waves. It turns out that in propagation transverse to the magnetic field no anomaly effect appear while in parallel to the magnetic field we find sound waves become dispersive due to anomaly.
↳ hep-thhep-phnucl-thPLB(2016)·18 citations
13*
Charm Degrees of Freedom in Quark Gluon Plasma
Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Sayantan Sharma🇺🇸
Lattice QCD studies on fluctuations and correlations of charm quantum number have established that deconfinement of charm degrees of freedom sets in around the chiral crossover temperature, $T_{c}$ , i.e. charm degrees of freedom carrying fractional baryonic charge start to appear. By reexamining those same lattice QCD data we show that, in addition to the contributions from quark-like excitations, the partial pressure of charm degrees of freedom may still contain significant contributions from open-charm meson and baryon-like excitations associated with integral baryonic charges for temperatures up to $1.2 T_{c}$ . Charm quark-quasiparticles become the dominant degrees of freedom for temperatures $T > 1.2 T_{c}$ .
↳ hep-lathep-phnucl-thPRD(2016)·58 citations
14*
Radiatively Induced Breaking of Conformal Symmetry in a Superpotential
A. B. Arbuzov🇷🇺 · D. J. Cirilo-Lombardo🇦🇷
Radiatively induced symmetry breaking is considered for a toy model with one scalar and one fermion field unified in a superfield. It is shown that the classical quartic self-interaction of the superfield possesses a quantum infrared singularity. Application of the Coleman-Weinberg mechanism for effective potential leads to the appearance of condensates and masses for both scalar and fermion components. That induces a spontaneous breaking of the initial classical symmetries: the supersymmetry and the conformal one. The energy scales for the scalar and fermion condensates appear to be of the same order, while the renormalization scale is many orders of magnitude higher. A possibility to relate the considered toy model to conformal symmetry breaking in the Standard Model is discussed.
↳ hep-thhep-phmath-phmath.MPPLB(2016)·1 citation
15*
Running Masses in the Nucleon and its Resonances
Craig D. Roberts🇺🇸
An overarching scientific challenge for the coming decade is to discover the meaning of confinement, its relationship to dynamical chiral symmetry breaking (DCSB) - the origin of visible mass - and the connection between them. In progressing toward meeting this challenge, significant progress has been made using continuum methods in QCD. For example, a novel understanding of gluon and quark confinement and its consequences has begun to emerge from quantum field theory; a clear picture is being drawn of how hadron masses emerge dynamically in a universe with light quarks; and ground-state hadron wave functions with a direct connection to QCD are becoming available, which reveal that quark-quark correlations are crucial in hadron structure. There is growing experimental support for this body of predictions in both elastic and nucleon-to-resonance-transition form factors.
↳ nucl-thhep-lathep-phnucl-exJPS Conf.Proc.(2016)·5 citations
16*
Eternal inflation in a dissipative and radiation environment: Heated demise of eternity
Gustavo S. Vicente🇧🇷 · Leandro A. da Silva🇧🇷 · Rudnei O. Ramos🇧🇷
Eternal inflation is studied in the context of warm inflation. We focus on different tools to analyze the effects of dissipation and the presence of a thermal radiation bath on the fluctuation-dominated regime, for which the self-reproduction of Hubble regions can take place. The tools we explore are the threshold inflaton field and threshold number of e-folds necessary to establish a self-reproduction regime and the counting of Hubble regions, using generalized conditions for the occurrence of a fluctuation-dominated regime. We obtain the functional dependence of these quantities on the dissipation and temperature. A Sturm-Liouville analysis of the Fokker-Planck equation for the probability of having eternal inflation and an analysis for the probability of having eternal points are performed. We have considered the representative cases of inflation models with monomial potentials of the form of chaotic and hilltop ones. Our results show that warm inflation tends to initially favor the onset of a self-reproduction regime for smaller values of the dissipation. As the dissipation increases, it becomes harder than in cold inflation (i.e., in the absence of dissipation) to achieve a self-reproduction regime for both types of models analyzed. The results are interpreted and explicit analytical expressions are given whenever that is possible.
↳ astro-ph.COgr-qchep-phhep-thPRD(2016)·9 citations
17*
On Distributions of Emission Sources and Speed of Sound in Proton-proton (Proton-antiproton) Collisions
Li-Na Gao🇨🇳 · Fu-Hu Liu🇨🇳
The revised (three-source) Landau hydrodynamic model is used in this paper to study the (pseudo)rapidity distributions of charged particles produced in proton-proton and proton-antiproton collisions at high energies. The central source is assumed to contribute with a Gaussian function which covers the rapidity distribution region as wide as possible. The target and projectile sources are assumed to emit isotropically particles in their respective rest frames. The model calculations obtained with a Monte Carlo method are fitted to the experimental data over an energy range from 0.2 to 13 TeV. The values of the squared speed-of-sound parameter in different collisions are then extracted from the width of the rapidity distributions.
↳ nucl-thhep-exhep-phnucl-exAdv.High Energy Phys.(2015)·8 citations
18*
Nuclear Reactions at Intermediate Energies
Radhey Shyam🇮🇳
In the domain of Nuclear reactions at intermediate energies, the QCD coupling constant $α_{s}$ is large enough ( $\sim$ 0.3 - 0.5) to render the perturbative calculational techniques inapplicable. In this regime the quarks are confined into colorless hadrons and it is expected that effective field theories of hadron interactions via exchange of hadrons, provide useful tools to describe such reactions. In this contribution we discuss applications of one such theory, the effective Lagrangian model, in describing the hadronic reactions at intermediate energies whose measurements are the focus of a vast international experimental program.
↳ nucl-thhep-phnucl-exEPJ Web Conf.(2016)·0 citations
19*
Ionization of atoms by slow heavy particles, including dark matter
B. M. Roberts🇦🇺 · V. V. Flambaum🇦🇺 · G. F. Gribakin🇬🇧
Atoms and molecules can become ionized during the scattering of a slow, heavy particle off a bound electron. Such an interaction involving leptophilic weakly interacting massive particles (WIMPs) is a promising possible explanation for the anomalous 9 sigma annual modulation in the DAMA dark matter direct detection experiment [R. Bernabei et al., Eur. Phys. J. C 73, 2648 (2013)]. We demonstrate the applicability of the Born approximation for such an interaction by showing its equivalence to the semiclassical adiabatic treatment of atomic ionization by slow-moving WIMPs. Conventional wisdom has it that the ionization probability for such a process should be exponentially small. We show, however, that due to nonanalytic, cusp-like behaviour of Coulomb functions close to the nucleus this suppression is removed, leading to an effective atomic structure enhancement. Crucially, we also show that electron relativistic effects actually give the dominant contribution to such a process, enhancing the differential cross section by up to 1000 times.
↳ physics.atom-phastro-ph.COastro-ph.GAhep-phPRL(2016)·32 citations
20*
Connections between cosmic-ray physics, gamma-ray data analysis and Dark Matter detection
Daniele Gaggero🇮🇹
Cosmic-ray (CR) physics has been a prolific field of research for over a century. The open problems related to CR acceleration, transport and modulation are deeply connected with the indirect searches for particle dark matter (DM). In particular, the high-quality gamma-ray data released by Fermi-LAT are under the spotlight in the scientific community because of a recent claim about a inner Galaxy anomaly: The necessity to disentangle the astrophysical emission due to CR interactions from a possible DM signal is therefore compelling and requires a deep knowledge of several non-trivial aspects regarding CR physics. I review all these connections in this contribution. In the first part, I present a detailed overview on recent results regarding modeling of cosmic-ray (CR) production and propagation: I focus on the necessity to go beyond the standard and simplified picture of uniform and homogeneous diffusion, showing that gamma-ray data point towards different transport regimes in different regions of the Galaxy; I sketch the impact of large-scale structure on CR observables, and -- concerning the interaction with the Heliosphere -- I mention the necessity to consider a charge-dependent modulation scenario. In the second part, all these aspects are linked to the DM problem. I analyze the claim of a inner Galaxy excess and discuss the impact of the non-trivial aspects presented in the first part on our understanding of this anomaly.
↳ astro-ph.HEhep-phPoS(2016)·6 citations
21*
Disentangling random thermal motion of particles and collective expansion of source from transverse momentum spectra in high energy collisions
Hua-Rong Wei🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸
In the framework of a multisource thermal model, we describe experimental results of the transverse momentum spectra of final-state light flavour particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead ( $p$ -Pb), and proton-proton ( $p$ - $p$ ) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, by using the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein), Tsallis, and two- or three-component standard distributions which can be in fact regarded as different types of "thermometers" or "thermometric scales" and "speedometers". A central parameter in the three distributions is the effective temperature which contains information on the kinetic freeze-out temperature of the emitting source and reflects the effects of random thermal motion of particles as well as collective expansion of the source. To disentangle both effects, we extract the kinetic freeze-out temperature from the intercept of the effective temperature ( $T$ ) curve as a function of particle's rest mass ( $m_{0}$ ) when plotting $T$ versus $m_{0}$ , and the mean transverse flow velocity from the slope of the mean transverse momentum ( $⟨ p_{T} ⟩$ ) curve as a function of mean moving mass ( $m$ ) when plotting $⟨ p_{T} ⟩$ versus $m$ .
↳ nucl-exhep-exhep-phnucl-thJ.Phys.G(2016)·42 citations
22*
Compton Scattering and Nucleon Polarisabilities in Chiral EFT: Update and Future
Harald W. Griesshammer (George Washington U.)🇺🇸 · Judith A. McGovern (U. of Manchester)🇬🇧 · Daniel R. Phillips (Ohio U.)🇺🇸
We review theoretical progress and prospects for determining the nucleon's static dipole polarisabilities from Compton scattering on few-nucleon targets, including new values; see Refs. [1-5] for details and a more thorough bibliography.
↳ nucl-thhep-lathep-phnucl-exAIP Conf.Proc.(2016)·3 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.