HEP Phenomenology·hep-ph
20 papers—12 primary·8 cross-listed·reconstructed*
We present analytical results at four-loop level for the -function of the coupling of a generic gauge group and any number of different quark representations. From this we can directly derive the gluino contribution to the strong coupling -function of supersymmetric extensions of the Standard Model.
V. Kubarovsky🇺🇸 · M.B. Voloshin🇺🇸
LHCb recently announced the discovery of two exotic structures in the decay channel, which have been referred to as charmonium-pentaquark states. Resolving between the models and clarifying the nature of the discovered hidden-charm pentaquark peaks, and possibly searching for similar peaks with other quantum numbers, requires further experimental studies. The states were observed in the decay mode . Thus, it is natural to expect that these pentaquarks can be produced in the photoproduction process where these states will appear as s-channel resonances at photon energy around 10 GeV. The energy and luminosity of the CLAS12 photon beam permit the detailed studies of the production and decay properties of the pentaquark resonances. By this reason the pentaquark search at Jefferson Laboratory looks extremely attractive.
Csaba Balázs🇦🇺 · Tong Li🇦🇺
We infer dark matter properties from gamma ray residuals extracted using eight different interstellar emission scenarios proposed by the Fermi-LAT Collaboration to explain the Galactic Center gamma ray excess. Adopting the most plausible simplified ansatz, we assume that the dark matter particle is a Majorana fermion interacting with standard fermions via a scalar mediator. Using this theoretical hypothesis and the Fermi residuals we calculate Bayesian evidences, including Fermi-LAT exclusion limits from 15 dwarf spheroidal galaxies as well. Our Bayes factors single out four of the Fermi scenarios as compatible with the simplified dark matter model. In the most preferred scenario the dark matter (mediator) mass is in the 100-500 (1-200) GeV range and its annihilation is dominated by top quark final state. Less preferred but still plausible is annihilation into b\bar{b} and tau^+tau^- final states with an order of magnitude lower dark matter mass. Our conclusion is that the properties of dark matter extracted from gamma ray data are highly sensitive to the modeling of the interstellar emission.
Hjalte Frellesvig🇬🇷 · Damiano Tommasini🇬🇷 · Christopher Wever🇩🇪
This is a contribution to the proceedings of the 2016 "Loops and legs" conference, based on the talk by HF. The talk was based on the paper "On the reduction of Generalized Polylogarithms to and and on the reduction thereof" by the three authors, published in March 2016 in JHEP.
Hai-Nan Lin🇨🇳 · Xin Li🇨🇳 · Zhe Chang🇨🇳
It has been observed that photons in the prompt emission of some gamma-ray bursts (GRBs) are highly polarized. The high polarization is used by some authors to give a strict constraint on the Lorentz invariance violation (LIV). If the Lorentz invariance is broken, the polarization vector of a photon may rotate during its propagation. The rotation angle of polarization vector depends on both the photon energy and the distance of source. It is believed that if high polarization is observed, then the relative rotation angle (denoted by ) of polarization vector of the highest energy photon with respect to that of the lowest energy photon should be no more than . Otherwise, the net polarization will be severely suppressed, thus couldn't be as high as what was actually observed. In this paper, we will give a detailed calculation on the evolution of GRB polarization arising from LIV effect duration the propagation. It is shown that the polarization degree rapidly decrease as increases, and reaches a local minimum at , then increases until , after that decreases again until , etc. The polarization degree as a function of oscillates with a quasi-period , while the oscillating amplitude gradually decreases to zero. Moreover, we find that a considerable amount (more than of the initial polarization) of polarization degree can be conserved when . The polarization observation in a higher and wider energy band, a softer photon spectrum, and a higher redshift GRB is favorable in order to tightly constrain LIV effect.
R. N. Faustov🇷🇺 · V. O. Galkin🇷🇺
Semileptonic decays are investigated in the framework of the relativistic quark model based on the quasipotential approach and the quark-diquark picture of baryons. The decay form factors are expressed through the overlap integrals of the initial and final baryon wave functions. All calculations are done without employing nonrelativistic and heavy quark expansions. The momentum transfer dependence of the decay form factors is explicitly determined in the whole accessible kinematical range without any extrapolations or model assumptions. Both the heavy-to-heavy and heavy-to-light decay branching fractions are calculated. The results agree within error bars with the experimental value of the branching fraction of the decay. From the recent LHCb data on the ratio of the branching fractions of the heavy-to-light and heavy-to-heavy semileptonic decays the ratio of the Cabbibo-Kobayashi-Maskawa matrix elements is obtained. It is consistent with the corresponding ratio determined from the inclusive meson decays.
Junjie Cao🇨🇳 · Yangle He🇨🇳 · Liangliang Shang🇨🇳 · Wei Su🇨🇳 · Peiwen Wu🇰🇷 · Yang Zhang🇨🇳
Given the fact that the relatively light Higgsino mass favored in natural supersymmetry usually results in a sizable scattering cross section between the neutralino dark matter and the nucleon, we study the impact of the recently updated direct detection bounds from LUX experiment, including both Spin Independent (SI) and Spin Dependent (SD) measurements, on the parameter space of natural Next-to-Minimal Supersymmetric Standard Model (nNMSSM). Different from the common impression that the SI bound is stronger than the SD one, we find that the SD bound is complementary to the SI bound and in some cases much more powerful than the latter in limiting the nNMSSM scenarios. After considering the LUX results, nNMSSM is severely limited, e.g. for the peculiar scenarios of the NMSSM where the next-to-lightest CP-even Higgs corresponds to the Higgs boson discovered at the LHC, the samples obtained in our random scan are excluded by more than . By contrast, the monojet search at the LHC Run-I can not exclude any sample of nNMSSM. We also investigate the current status of nNMSSM and conclude that, although the parameter points with low fine tuning are still attainable, they are distributed in some isolated parameter islands which are difficult to get. Future dark matter direct search experiments such as XENON-1T will provide a better test of nNMSSM.
If dark matter is an axion-like-particle a significant fraction of the present day relic abundance could be concentrated in compact gravitationally bound miniclusters. We study the minicluster masses compatible with the dark matter relic density constraint. If they form from fluctuations produced by PQ symmetry breaking, minicluster masses up to hundreds of solar masses are possible, although over most of the parameter space they are much lighter. The size of these objects is typically within a few orders of magnitude of an astronomical unit. We also show that miniclusters can form if an axion gets mass from a hidden sector with a first order phase transition that takes a relatively long time to complete. Therefore they can appear in models where PQ symmetry is broken before inflation, compatible with large axion decay constants and string theory UV completions.
Zhi-Gang Wang🇨🇳 · Jun-Xia Zhang🇨🇳
In this article, we study the ground states and the first radial excited states of the tensor-tensor type scalar hidden-charm tetraquark states with the QCD sum rules. We separate the ground state contributions from the first radial excited state contributions unambiguously, and obtain the QCD sum rules for the ground states and the first radial excited states, respectively. Then we search for the Borel parameters and continuum threshold parameters according to four criteria and obtain the masses of the tensor-tensor type scalar hidden-charm tetraquark states, which can be confronted to the experimental data in the future.
In this contribution we study the prospects of measuring double Higgs production at a potential 100 TeV future circular collider. We apply an analysis procedure that utilises reconstructed Higgs pairs from multiple final state event topologies in order to maintain high selection efficiencies. Signal purity is then further improved by means of a artificial neural network classifier. The results of this analysis for the high luminosity LHC show significant potential, however when applied to a 100 TeV hadron collider we find that such a measurement is likely to suffer from a very poor signal to background ratio. Such a measurement at the FCC is therefore likely to be significantly more challenging than at the high luminosity phase of the LHC.
Artur M Ankowski🇺🇸 · Camillo Mariani🇺🇸
Future neutrino-oscillation experiments are expected to bring definite answers to the questions of neutrino-mass hierarchy and violation of charge-parity symmetry in the lepton sector. To realize this ambitious program it is necessary to ensure a significant reduction of uncertainties, particularly those related to neutrino-energy reconstruction. In this paper, we discuss different sources of systematic uncertainties, paying special attention to those arising from nuclear effects and detector response. By analyzing nuclear effects we show the importance of developing accurate theoretical models, capable to provide quantitative description of neutrino cross sections, together with the relevance of their implementation in Monte Carlo generators and extensive testing against lepton-scattering data. We also point out the fundamental role of efforts aiming to determine detector responses in test-beam exposures.
Katsuya Hashino🇯🇵 · Mitsuru Kakizaki🇯🇵 · Shinya Kanemura🇯🇵 · Pyungwon Ko🇰🇷 · Toshinori Matsui🇰🇷
We calculate the spectrum of gravitational waves originated from strongly first order electroweak phase transition in the extended Higgs model with a real singlet field. In order to calculate the bubble nucleation rate, we perform a two-field analysis to evaluate bounce solutions connecting the true and the false vacua using the one-loop effective potential at finite temperatures. Imposing the Sakharov condition of the departure from thermal equilibrium for baryogenesis, we survey allowed regions of parameters of the model. We then investigate the gravitational waves produced at electroweak bubble collisions in the early Universe, such as the sound wave, the bubble wall collision and the plasma turbulence. We find that the strength at the peak frequency can be large enough to be detected at future space-based gravitational interferometers such as eLISA, DECIGO and BBO. Predicted deviations in the various Higgs boson couplings are also evaluated at the zero temperature, and are shown to be large enough too. Therefore, in this model strongly first order electroweak phase transition can be tested by the combination of the precision study of various Higgs boson couplings at LHC, the measurement of the triple Higgs boson coupling at future lepton colliders and the shape of the spectrum of gravitational wave detectable at future gravitational interferometers.
Tigran Kalaydzhyan🇺🇸 · Elena Murchikova🇺🇸
In certain circumstances, chiral (parity-violating) medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark-gluon plasma, liquid helium 3He-A, neutron stars and the Early Universe. We study first-order hydrodynamics of a chiral fluid on a vortex background and in an external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density (chiral vortical and chiral magnetic waves) and transverse velocity (chiral Alfven wave). We demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the wave is absent and the excitation reduces to the charge diffusion mode. We also comment on the frame-dependent contributions to the obtained propagation velocities.
Christof Gattringer🇦🇹 · Carlotta Marchis🇦🇹
We propose a new approach to strong coupling series and dual representations for non-abelian lattice gauge theories using the SU(2) case as an example. The Wilson gauge action is written as a sum over "abelian color cycles" (ACC) which correspond to loops in color space around plaquettes. The ACCs are complex numbers which can be commuted freely such that the strong coupling series and the dual representation can be obtained as in the abelian case. Using a suitable representation of the SU(2) gauge variables we integrate out all original gauge links and identify the constraints for the dual variables in the SU(2) case. We show that the construction can be generalized to the case of SU(2) gauge fields with staggered fermions. The result is a strong coupling series where all gauge integrals are known in closed form and we discuss its applicability for possible dual simulations. The abelian color cycle concept can be generalized to other non-abelian gauge groups such as SU(3).
Shahin Mamedov🇦🇿 · Berin Belma Sirvanli🇹🇷 · Ibrahim Atayev🇦🇿 · Narmin Huseynova🇦🇿
The axial-vector form factor of the nucleons is considered in the framework of hard-wall model of holographic QCD. A new interaction term between the bulk gauge and matter fields was included into the interaction Lagrangian. We obtain the axial-vector form factor of nucleons in the boundary QCD from the bulk action using AdS/CFT correspondence. The momentum square dependence of the axial-vector form factor is analysed numerically.
Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇩🇪 · Kyriakos Hadjiyiannakou🇺🇸 · Karl Jansen🇩🇪 · Fernanda Steffens🇩🇪 · Christian Wiese🇩🇪
We present results for the dependence of the unpolarized, helicity, and transversity isovector quark distributions in the proton using lattice QCD, employing the method of quasi-distributions proposed by Ji in 2013. Compared to a previous calculation by us, the errors are reduced by a factor of about 2.5. Moreover, we present our first results for the polarized sector of the proton, which indicate an asymmetry in the proton sea in favor of the antiquarks for the case of helicity distributions, and an asymmetry in favor of the antiquarks for the case of transversity distributions.
Antje Peters🇩🇪 · Pedro Bicudo🇵🇹 · Luka Leskovec🇺🇸 · Stefan Meinel🇺🇸 · Marc Wagner🇩🇪
We investigate heavy-light four-quark systems with bottom quarks of finite mass which are treated in the framework of NRQCD. We focus on , where we recently found evidence for the existence of a tetraquark state using static bottom quarks. Furthermore, we report on an investigation of the four-quark system with quantum numbers again using static bottom quarks.
Ongoing progress in understanding and evaluating charge symmetry breaking in hypernuclei is discussed in connection to recent measurements of the binding energy at MAMI [A1 Collaboration: PRL 114 (2015) 232501] and of the excitation energy at J-PARC [E13 Collaboration: PRL 115 (2015) 222501].
Constantia Alexandrou🇨🇾 · Martha Constantinou🇨🇾 · Kyriakos Hadjiyiannakou🇺🇸 · Christos Kallidonis🇨🇾 · Giannis Koutsou🇨🇾 · Karl Jansen🇩🇪 · Haralambos Panagopoulos🇨🇾 · Fernanda Steffens🇩🇪 · Alejandro Vaquero🇮🇹 · Christian Wiese🇩🇪
The exact decomposition of the proton spin has been a much debated topic, on the experimental as well as the theoretical side. In this talk we would like to report on recent non-perturbative results and ongoing efforts to explore the proton spin from lattice QCD. We present results for the relevant generalized form factors from gauge field ensembles that feature a physical value of the pion mass. These generalized form factors can be used to determine the total spin and angular momentum carried by the quarks. In addition we present first results for our ongoing effort to compute the angular momentum of the gluons in the proton.
Eleonora Di Valentino🇫🇷 · Francois R. Bouchet🇫🇷
Tram et al. 2016 recently pointed out that power-law inflation in presence of a dark radiation component may relieve the 3.3 sigma tension which exists within standard LCDM between the determination of the local value of the Hubble constant by Riess et al. (2016) and the value derived from CMB anisotropy data by the Planck collaboration. In this comment, we simply point out that this interesting proposal does not help in solving the tension between the Planck data and, e.g., the weak lensing measurements. Moreover, when the latest constraints on the reionization optical depth obtained from Planck HFI data are included in the analysis, the tension reappears and this scenario looses appeal.
* 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.