HEP Phenomenology·hep-ph

Wed·Sep 30, 2020Wednesday·September 30, 2020

31 papers—23 primary·8 cross-listed·reconstructed*

01*
Modified MIT Bag Models -- part II: QCD phase diagram and hot quark stars
Luiz L. Lopes🇧🇷 · Carline Biesdorf🇧🇷 · K. D. Marquez🇧🇷 · Debora P. Menezes🇧🇷
In the present work we use the modified versions of the MIT bag model, on which both a vector field and a self-interacting term are introduced, to obtain hot quark matter and to investigate the QCD phase diagram. We first analyze two-flavored quark matter constrained to both the freeze-out and the liquid-gas phase transition at the hadronic phase. Later, three-flavored quark matter subject to $β$ equilibrium and charge neutrality is used to compute quark star macroscopic properties, which are confronted with recent observational massive and canonical star radius results. Finally, a comparison with QCD phase diagrams obtained from the Nambu-Jona-Lasinio model is performed.
hep-phastro-ph.HEnucl-thPhys.Scripta(2021)·45 citations
02*
Studying explicit $U (1)_{A}$ symmetry breaking in hot and magnetised two flavour non-local NJL model constrained using lattice results
Mahammad Sabir Ali🇮🇳 · Chowdhury Aminul Islam🇨🇳 · Rishi Sharma🇮🇳
We study the two flavour non-local Nambu\textemdash Jona-Lasinio (NJL) model in the presence of a magnetic field and explore the chiral crossover in presence of a non-local form of the 't Hooft determinant term. Its coupling is governed by a dimensionless parameter $c$ . This term is responsible for the explicit breaking of $U (1)_{A}$ symmetry. We have attempted a systematic analysis of the model parameters by fitting to self-consistent lattice QCD calculations. Three parameters of the model are fixed by $e B = 0$ results from published lattice QCD on the chiral condensate, the pion decay constant ( $F_{π}$ ), and the pion mass ( $m_{π}$ ). The difference of the $u$ and $d$ quark condensates in the presence of a magnetic field ( $e B$ ) is quite sensitive to $c$ and we fix $c$ using published lattice QCD results for this observable. We see no evidence that $c$ depends on $e B$ . The crossover temperature decreases with increasing $e B$ only for condensate values at the lower end of the allowed values (as already seen in~\cite{Pagura:2016pwr}) and $F_{π}$ at the upper end of the allowed values. We further check our model predictions by calculating the topological susceptibility with the fitted $c$ values and comparing it with lattice results. Since the topological susceptibility is related to the extent of the $U (1)_{A}$ symmetry breaking, we find that it is sensitive to the value of $c$ .
hep-phnucl-thPRD(2021)·16 citations
03*
On gauge invariance of transverse momentum dependent distributions at small-x
Renaud Boussarie🇺🇸 · Yacine Mehtar-Tani🇺🇸
Transverse momentum dependent (TMD) distributions at small x exhibit a rich infinite twist structure that encompasses the leading twist (partonic) distributions as well as the physics of gluon saturation. Progress to further the connection between the standard TMD framework at moderate x and small x has been recently made. In this context, we show that light cone Wilson line operators at small-x can be formulated in terms of transverse gauge links. This new formulation of small x operators allows a direct matching with the standard leading twist gluon TMD distributions and provides an efficient and general prescription for computing TMD distributions at small x beyond leading twist.
hep-phnucl-thPoS(2021)·0 citations
04*
Resolving the Bethe-Salpeter kernel
Si-Xue Qin🇨🇳 · Craig D. Roberts🇨🇳
A novel method for constructing a Bethe-Salpeter kernel for the meson bound-state problem is described. It produces a closed-form kernel that is symmetry-consistent (discrete and continuous) with the gap equation defined by any admissible gluon-quark vertex. Applicable even when the diagrammatic content of that vertex is unknown, the scheme can foster new synergies between continuum and lattice approaches to strong interactions. The framework is illustrated by demonstrating that the presence of a dressed-quark anomalous magnetic moment in the gluon-quark vertex, an emergent feature of strong interactions, can remedy many defects of widely used meson bound-state kernels, including the level ordering of pseudoscalar and vector meson radial excitations.
hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2021)·50 citations
05*
Revisiting transverse momentum broadening in dense QCD media
Joao Barata🇪🇸 · Yacine Mehtar-Tani🇺🇸 · Alba Soto-Ontoso🇺🇸 · Konrad Tywoniuk🇳🇴
We reconsider the problem of transverse momentum broadening of a highly-energetic parton suffering multiple scatterings in dense colored media, such as the thermal Quark-Gluon plasma or large nuclei. In the framework of Molière's theory of multiple scattering we re-derive a simple analytic formula, to be used in jet quenching phenomenology, that accounts for both the multiple soft and hard Rutherford scattering regimes. Further, we discuss the sensitivity of momentum broadening to modeling of the non-perturbative infrared sector by presenting a detailed analytic and numerical comparison between the two widely used models in phenomenology: the Hard Thermal Loop and the Gyulassy-Wang potentials. We show that for the relevant values of the parameters the non-universal, model dependent contributions are negligible, at LHC, RHIC and EIC energies thus consolidating the predictive power of jet quenching theory.
hep-phPRD(2021)·59 citations
06*
Magnetic corrections to the boson self-coupling and boson-fermion coupling in the linear sigma model with quarks
Alejandro Ayala🇲🇽 · José Luis Hernández🇲🇽 · L. A. Hernández🇲🇽 · Ricardo L. S. Farias🇧🇷 · R. Zamora🇨🇱
We compute the magnetic field-induced modifications to the boson self-coupling and the boson-fermion coupling, in the static limit, using an effective model of QCD, the linear sigma model with quarks. The former is computed for arbitrary field strengths as well as using the strong field approximation. The latter is obtained in the strong field limit. The arbitrary field result for the boson self-coupling depends on the ultraviolet renormalization scale and this dependence cannot be removed by a simple vacuum subtraction. Using the strong field result as a guide, we find the appropriate choice for this scale and discuss the physical implications. The boson-fermion coupling depends on the Schwinger's phase and we show how this phase can be treated consistently in such a way that the magnetic field induced vertex modification is both gauge invariant and can be written with an explicit factor corresponding to energy-momentum conservation for the external particles. Both couplings show a modest decrease with the field strength.
hep-phhep-thnucl-thPRD(2020)·26 citations
07*
Lattice-motivated QCD coupling and hadronic contribution to muon $g - 2$
Gorazd Cvetic🇨🇱 · Reinhart Kogerler🇩🇪
We present an updated version of a QCD coupling which fulfills various physically motivated conditions: at high momenta it practically coincides with the perturbative QCD (pQCD) coupling; at intermediate momenta it reproduces correctly the physics of the semihadronic tau decay; and at very low momenta it is suppressed as suggested by large-volume lattice calculations. An earlier presented analysis is updated here in the sense that the Adler function, in the regime $∣ Q^{2} ∣ ≲ 1 GeV^{2}$ , is evaluated by a renormalon-motivated resummation method. This Adler function is then used here in the evaluation of the quantities related with the semihadronic (strangeless) $τ$ -decay spectral functions, including Borel-Laplace sum rules in the (V+A)-channel. The analysis is then extended to the evaluation of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment, $a_{μ}^{had (1)}$ , where we include in the Adler function the V-channel higher-twist OPE terms which are regulated in the infrared (IR) by mass parameters which are expected to be $≲ 1$ GeV. The correct value of $a_{μ}^{had (1)}$ can be reproduced with the mentioned IR-regulating mass parameters if the value of the condensate $⟨ O_{4} ⟩_{V + A}$ is positive (and thus the gluon condensate value is positive). This restriction and the requirement of the acceptable quality of the fits to the various mentioned sum rules then lead us to the restriction $0.1171 < α_{s} (M_{Z}^{2}; M S) < 0.1180$ .
hep-phJ.Phys.G(2021)·16 citations
08*
Kinematical distributions of coherent neutrino trident production in gauged $L_{μ} - L_{τ}$ model
Takashi Shimomura🇯🇵 · Yuichi Uesaka🇯🇵
We analyze the distributions of energy, opening angle and invariant mass in muonic neutrino trident production processes, $ν_{μ} \to ν_{μ} μ μ$ , in a minimal gauged $U (1)_{L_{μ} - L_{τ}}$ model, in which the discrepancy of anomalous magnetic moment of muon can be solved. It is known that the total cross sections of the neutrino trident production are degenerate in new physics parameters, the new gauge coupling and gauge boson mass, and therefore other observables are needed to determine these parameters. From numerical analyses, we find that the muon energy and invariant mass distributions show the differences among the new physics parameter sets with which the total cross sections have the same value, while the anti-muon energy and opening angle distributions are not sensitive to the parameters.
hep-phhep-exPRD(2021)·11 citations
09*
Search for new light particles at ILC main beam dump
Yasuhito Sakaki🇯🇵 · Daiki Ueda🇯🇵
We perform a feasibility study of a beam dump experiment at the International Linear Collider (ILC). To investigate the sensitivity to new light particles at the experiment, we consider models for axion-like particles (ALPs) and a light scalar particle coupled to charged leptons. For both models, we show that the detection sensitivity is almost an order of magnitude higher than other beam dump experiments in the small coupling region. For ALPs, it is shown that the ILC beam dump experiment is highly complementary to bounds from astrophysics. In addition, for the model of the scalar particle, the region favored by the muon $g - 2$ experiment can be explored.
hep-phhep-exPRD(2021)·42 citations
10*
Analytic representation of all planar two-loop five-point Master Integrals with one off-shell leg
Dhimiter D. Canko🇬🇷 · Costas G. Papadopoulos🇬🇷 · Nikolaos Syrrakos🇬🇷
We present analytic expressions in terms of polylogarithmic functions for all three families of planar two-loop five-point Master Integrals with one off-shell leg. The calculation is based on the Simplified Differential Equations approach. The results are relevant to the study of many $2 \to 3$ scattering processes of interest at the LHC, especially for the leading-color $W + 2$ jets production.
hep-phhep-thJHEP(2021)·87 citations
11*
Diffractive deeply inelastic scattering in future electron-ion colliders
D. Bendova🇨🇿 · J. Cepila🇨🇿 · J. G. Contreras🇨🇿 · V. P. Goncalves🇧🇷 · M. Matas🇨🇿
The impact of nonlinear effects in the diffractive observables that will be measured in future electron-ion collisions is investigated. We present, for the first time, the predictions for the diffractive structure function and reduced cross sections derived using the solution to the Balitsky--Kovchegov equation with the collinearly-improved kernel and including the impact-parameter dependence. We demonstrate that the contribution of the diffractive events is enhanced in nuclear collisions and that the study of the ratio between the nuclear and proton predictions will be useful to discriminate among different models of the dipole-target scattering amplitude and, consequently, will allow us to constrain the description of QCD dynamics in parton densities.
hep-phnucl-thEPJC(2021)·22 citations
12*
Cone-size dependent jet spectrum in heavy-ion collisions
Yacine Mehtar-Tani🇺🇸 · Daniel Pablos🇳🇴 · Konrad Tywoniuk🇳🇴
Jets in the vacuum correspond to multi-parton configurations that form via a branching process sensitive to the soft and collinear divergences of QCD. In heavy-ion collisions, energy loss processes that are stimulated via interactions with the medium, affect jet observables in a profound way. Jet fragmentation factorizes into a three-stage process, involving vacuum-like emissions above the medium scale, induced emissions enhanced by the medium length and, finally, long-distance vacuum-like fragmentation. This formalism leads to a novel, non-linear resummation of jet energy loss. In this talk we present new results on the combined effects of small- $R$ resummation and energy loss to compute the $R$ -dependent jet spectrum in heavy-ion collisions.
hep-phnucl-thPoS(2021)·2 citations
13*
Holographic quark matter with colour superconductivity and a stiff equation of state for compact stars
Kazem Bitaghsir Fadafan🇮🇷 · Jesus Cruz Rojas🇬🇧 · Nick Evans🇬🇧
We present a holographic model of QCD with a first order chiral restoration phase transition with chemical potential, mu. The first order behaviour follows from allowing a discontinuity in the dual description as the quarks are integrated out below their constituent mass. The model predicts a deconfined yet massive quark phase at intermediate densities (350 MeV< mu <500 MeV), above the nuclear density phase, which has a very stiff equation of state and a speed of sound close to one. We also include a holographic description of a colour superconducting condensate in the chirally restored vacuum and study the resulting equation of state. They provides a well behaved first order transition from the deconfined massive quark phase at very high density (mu>500 MeV). We solve the Tolman-Oppenheimer-Volkoff equations with the resulting equations of state and find stable hybrid stars with quark cores. We compute the tidal deformability for these hybrid stars and show they are consistent with LIGO/Virgo data on a neutron star collision. Our holographic model shows that quark matter could be present at the core of such compact stars.
hep-phastro-ph.HEhep-thPRD(2021)·43 citations
14*
Diquark and nucleons under strong magnetic fields in the NJL model
M. Coppola🇦🇷 · D. Gomez Dumm🇦🇷 · N. N. Scoccola🇦🇷
We study the description of nucleons and diquarks in the presence of a uniform strong magnetic field within the framework of the two-flavor Nambu-Jona--Lasinio (NJL) model. Diquarks are constructed through the resummation of quark loop chains using the random phase approximation, while nucleons are treated as bound quark-diquark states described by a relativistic Fadeev equation, using the static approximation for quark exchange interactions. For charged particles, analytical calculations are performed using the Ritus eigenfunction method, which properly takes into account the breakdown of translation invariance that arises from the presence of Schwinger phases. Within this scheme, for definite model parametrizations we obtain numerical predictions for diquark and nucleon masses, which are compared with Chiral Perturbation Theory and Lattice QCD results. In addition, numerical estimations for nucleon magnetic moments are obtained.
hep-phhep-latPRD(2020)·10 citations
15*
No-scale hybrid inflation with R-symmetry breaking
Ahmad Moursy🇪🇬
In this paper we provide a no-scale supergravity scenario of hybrid inflation with R-symmetry being broken maximally. We investigate the inflation dynamics in details in both cases of pure F-term hybrid inflation and when adding constant Fayet-Iliopoulos D-terms. The effective inflation potential is asymptotically flat in a region of the parameter space in both cases. We explore all regions in the parameter space when discussing the constraints from the observables. We point out a connection between inflation, R-symmetry breaking and GUT scales. The moduli backreaction and SUSY breaking effects are investigated in a specific stabilization mechanism. We emphasis that a successful reheating is not affected by R-symmetry breaking, but it has interesting consequences. We study the reheating in flipped GUT model. We argue in favor of $Z_{2}$ symmetry associated with flipped GUT models to avoid phenomenologically dangerous operators and allow for decay channels for the inflaton to right-handed neutrinos (sneutrinos).
hep-phhep-thJHEP(2021)·9 citations
16*
Momentum transfer squared dependence of exclusive quarkonia photoproduction in UPCs
Cheryl Henkels🇧🇷 · Emmanuel G. de Oliveira🇧🇷 · Roman Pasechnik🇸🇪 · Haimon Trebien🇧🇷
In this paper, we study fully differential quarkonia photoproduction observables in ultraperipheral collisions (UPCs) as functions of momentum transfer squared. We employ the dipole picture of the QCD part of the scattering with proton and nucleus targets, with the projectile being a quasi-real photon flux emitted by an incoming hadron. We analyse such observables for ground $J / ψ$ , $Υ (1 S)$ and excited $ψ^{'}$ , $Υ (2 S)$ states whose light-front wave functions are obtained in the framework of interquark potential model incorporating the Melosh spin transformation. Two different low- $x$ saturation models, one obtained by solving the Balitsky--Kovchegov equation with the collinearly improved kernel and the other with a Gaussian impact-parameter dependent profile, are used to estimate the underlined theoretical uncertainties of our calculations. The results for the proton target and with charmonium in the final state are in agreement with the available HERA data, while in the case of nucleus target we make predictions for $γ A$ and $AA$ differential cross sections at different $W$ and at $s = 5.02$ TeV, respectively.
hep-phPRD(2021)·10 citations
17*
Dark Matter Interferometry
Joshua W. Foster🇺🇸 · Yonatan Kahn🇺🇸 · Rachel Nguyen🇺🇸 · Nicholas L. Rodd🇺🇸 · Benjamin R. Safdi🇺🇸
The next generation of ultralight dark matter (DM) direct detection experiments, which could confirm sub-eV bosons as the dominant source of DM, will feature multiple detectors operating at various terrestrial locations. As a result of the wave-like nature of ultralight DM, spatially separated detectors will each measure a unique DM phase. When the separation between experiments is comparable to the DM coherence length, the spatially-varying phase contains information beyond that which is accessible at a single detector. We introduce a formalism to extract this information, which performs interferometry directly on the DM wave. In particular, we develop a likelihood-based framework that combines data from multiple experiments to constrain directional information about the DM phase space distribution. We show that the signal in multiple detectors is subject to a daily modulation effect unique to wave-like DM. Leveraging daily modulation, we illustrate that within days of an initial discovery multiple detectors acting in unison could localize directional parameters of the DM velocity distribution such as the direction of the solar velocity to sub-degree accuracy, or the direction of a putative cold DM stream to the sub-arcminute level. We outline how to optimize the locations of multiple detectors with either resonant cavity (such as ADMX or HAYSTAC) or quasistatic (such as ABRACADABRA or DM-Radio) readouts to have maximal sensitivity to the full 3-dimensional DM velocity distribution.
hep-phastro-ph.COhep-exPRD(2021)·64 citations
18*
Jet momentum broadening in the pre-equilibrium Glasma
Andreas Ipp🇦🇹 · David I. Müller🇦🇹 · Daniel Schuh🇦🇹
Jets are important probes of heavy ion collisions as they can provide information on the interaction of a highly energetic parton with the medium it traverses. In the hydrodynamic stage of dense, strongly interacting matter, these interactions can be explained in terms of scattering processes, soft gluon emission and collinear parton splittings. However, jets originate even before the hydrodynamic stage. Here we report on the first numerical simulation of transverse momentum broadening of jets stemming from the interaction of partons with boost-invariantly expanding Glasma flux tubes. The Glasma stage is a pre-hydrodynamic stage based on the Color Glass Condensate framework. Our calculation shows strong time-dependence and an intrinsic anisotropy of momentum broadening in the directions transverse to the jet propagation direction.
hep-phhep-latnucl-thPLB(2020)·78 citations
19*
Precise predictions for $WH$ +jet production at the LHC
R. Gauld🇳🇱 · A. Gehrmann-De Ridder🇨🇭 · E. W. N. Glover🇬🇧 · A. Huss🇨🇭 · I. Majer🇨🇭
We present precise predictions for the production of a Higgs boson in association with a hadronic jet and a $W$ boson at hadron colliders. The behaviour of QCD corrections are studied for fiducial cross sections and distributions of the charged gauge boson and jet-related observables. The inclusive process (at least one resolved jet) and the exclusive process (exactly one resolved jet) are contrasted and discussed. The inclusion of QCD corrections up to $O (α_{s}^{3})$ leads to a clear stabilisation of the predictions and contributes substantially to a reduction of remaining theoretical uncertainties.
hep-phhep-exPLB(2021)·19 citations
20*
Radiative three-body D-meson decays in and beyond the standard model
Nico Adolph🇩🇪 · Joachim Brod🇺🇸 · Gudrun Hiller🇩🇪
We study radiative charm decays $D \to P_{1} P_{2} γ$ , $P_{1, 2} = π, K$ in QCD factorization at leading order and within heavy hadron chiral perturbation theory. Branching ratios including resonance contributions are around $\sim 1 0^{- 3}$ for the Cabibbo-favored modes into $K π γ$ and $\sim 1 0^{- 5}$ for the singly Cabibbo-suppressed modes into $π^{+} π^{-} γ, K^{+} K^{-} γ$ , and thus in reach of the flavor factories BES III and Belle II. Dalitz plots and forward-backward asymmetries reveal significant differences between the two QCD frameworks; such observables are therefore ideally suited for a data-driven identification of relevant decay mechanisms in the standard-model dominated $D \to K π γ$ decays. This increases the potential to probe new physics with the $D \to π^{+} π^{-} γ$ and $D \to K^{+} K^{-} γ$ decays, which are sensitive to enhanced dipole operators. CP asymmetries are useful to test the SM and look for new physics in neutral $∣Δ C ∣ = 1$ transitions. Cuts in the Dalitz plot enhance the sensitivity to new physics due to the presence of both $s$ - and $t, u$ -channel intermediate resonances.
hep-phEPJC(2021)·15 citations
21*
Large Density Perturbations from Reheating to Standard Model particles due to the Dynamics of the Higgs Boson during Inflation
Aliki Litsa🇸🇪 · Katherine Freese🇺🇸 · Evangelos I. Sfakianakis🇳🇱 · Patrick Stengel🇸🇪 · Luca Visinelli🇳🇱
Cosmic Microwave Background (CMB) observations are used to constrain reheating to Standard Model (SM) particles after a period of inflation. As a light spectator field, the SM Higgs boson acquires large field values from its quantum fluctuations during inflation, gives masses to SM particles that vary from one Hubble patch to another, and thereby produces large density fluctuations. We consider both perturbative and resonant decay of the inflaton to SM particles. For the case of perturbative decay from coherent oscillations of the inflaton after high scale inflation, we find strong constraints on the reheat temperature for the inflaton decay into heavy SM particles. For the case of resonant particle production (preheating) to (Higgsed) SM gauge bosons, we find temperature fluctuations larger than observed in the CMB for a range of gauge coupling that includes those found in the SM and conclude that such preheating cannot be the main source of reheating the Universe after inflation.
hep-phastro-ph.COPRD(2021)·16 citations
22*
Neutrino Oscillation Constraints on U(1)' Models: from Non-Standard Interactions to Long-Range Forces
Pilar Coloma🇪🇸 · M.C. Gonzalez-Garcia🇺🇸 · Michele Maltoni🇪🇸
We quantify the effect of gauge bosons from a weakly coupled lepton flavor dependent $U (1)^{'}$ interaction on the matter background in the evolution of solar, atmospheric, reactor and long-baseline accelerator neutrinos in the global analysis of oscillation data. The analysis is performed for interaction lengths ranging from the Sun-Earth distance to effective contact neutrino interactions. We survey $\sim 10000$ set of models characterized by the six relevant fermion $U (1)^{'}$ charges and find that in all cases, constraints on the coupling and mass of the $Z^{'}$ can be derived. We also find that about 5% of the $U (1)^{'}$ model charges lead to a viable LMA-D solution but this is only possible in the contact interaction limit. We explicitly quantify the constraints for a variety of models including $U (1)_{B - 3 L_{e}}$ , $U (1)_{B - 3 L_{μ}}$ , $U (1)_{B - 3 L_{τ}}$ , $U (1)_{B - \frac{3}{2} (L_{μ} + L_{τ})}$ , $U (1)_{L_{e} - L_{μ}}$ , $U (1)_{L_{e} - L_{τ}}$ , $U (1)_{L_{e} - \frac{1}{2} (L_{μ} + L_{τ})}$ . We compare the constraints imposed by our oscillation analysis with the strongest bounds from fifth force searches, violation of equivalence principle as well as bounds from scattering experiments and white dwarf cooling. Our results show that generically, the oscillation analysis improves over the existing bounds from gravity tests for $Z^{'}$ lighter than $\sim 1 0^{- 11}$ eV. In the contact interaction limit, we find that for most models listed above there are values of $g^{'}$ and $M_{Z^{'}}$ for which the oscillation analysis provides constraints beyond those imposed by laboratory experiments. Finally we illustrate the range of $Z^{'}$ and couplings leading to a viable LMA-D solution for two sets of models.
hep-phastro-ph.HEhep-exJHEP(2021)·92 citations
23*
Confinement and the Global $S U (3)$ Color Symmetry
Ying Chen🇨🇳
The global $S U (3)$ color symmetry and its physical consequences are discussed. The Nöther current is actually governed by the conserved matter current of color charges if the color field generated by this charge is properly polarized. The color field strength of a charge can have a uniform part due to the nontrivial QCD vacuum field and the nonzero gluon condensate, which implies that the self-energy of a system with a net color charge is infinite and thereby cannot exist as a free state. This is precisely what the color confinement means. Accordingly, the Cornell type potential with the feature of the Casimir scaling is derived for a color singlet system composed of a static color charge and an anti-charge. The uniform color field also implies that a hadron has a minimal size and a minimal energy. Furthermore, the global $S U (3)$ color symmetry requires that the minimal irreducible color singlet systems can only be $q q ˉ$ , $q q q$ , $g g$ , $g g g$ , $q q ˉ g$ , $q q q g$ and $q ˉ q ˉ q ˉ g$ , etc., as such a multi-quark systems can only exist as a molecular configurations if there are no other binding mechanisms.
hep-phhep-exhep-lathep-thCPC(2021)·2 citations
24*
Heavy quark momentum diffusion from the lattice using gradient flow
Luis Altenkort🇩🇪 · Alexander M. Eller🇩🇪 · Olaf Kaczmarek🇩🇪 · Lukas Mazur🇩🇪 · Guy D. Moore🇩🇪 · Hai-Tao Shu🇩🇪
We apply the gradient flow on a color-electric two-point function that encodes the heavy quark momentum diffusion coefficient. The simulations are done on fine isotropic lattices in the quenched approximation at $1.5 T_{c}$ . The continuum extrapolation is performed at fixed flow time followed by a second extrapolation to zero flow time. Perturbative calculations of this correlation function under Wilson flow are used to enhance the extrapolations of the non-perturbative lattice correlator. The final estimate for the continuum correlator at zero flow time largely agrees with one obtained from a previous study using the multi-level algorithm. We perform a spectral reconstruction based on perturbative model fits to estimate the heavy quark momentum diffusion coefficient. The approach we present here yields high-precision data for the correlator and is also applicable for actions with dynamical fermions.
↳ hep-lathep-phPRD(2021)·97 citations
25*
Warm bounce in loop quantum cosmology and the prediction for the duration of inflation
L. N Barboza🇧🇷 · L. L. Graef🇧🇷 · Rudnei O. Ramos🇧🇷
We study and estimate probabilistic predictions for the duration of the preinflationary and slow-roll phases after the bounce in loop quantum cosmology, determining how the presence of radiation in the prebounce phase affects these results. We present our analysis for different classes of inflationary potentials that include the monomial power-law chaotic type of potentials, namely, for the quadratic, quartic and sextic potentials and also for a Higgs-like symmetry breaking potential, considering different values for the vacuum expectation value in the latter case. We obtain the probability density function for the number of inflationary e-folds and for other relevant quantities for each model and produce probabilistic results drawn from these distributions. This study allows us to discuss under which conditions each model could eventually lead to observable signatures on the spectrum of the cosmic microwave background, or, else, be also excluded for not predicting a suffcient amount of accelerated expansion. The effect of radiation on the predictions for each model is explicitly quantified. The obtained results indicate that the number of inflationary e-folds in loop quantum cosmology is not a priori an arbitrary number, but can in principle be a predictable quantity, even though the results are dependent on the model and on the amount of radiation in the Universe prior to the start of the inflationary regime.
↳ gr-qcastro-ph.COhep-phhep-thPRD(2020)·18 citations
26*
Explorations beyond dilaton chiral perturbation theory in the eight-flavor SU(3) gauge theory
Maarten Golterman🇺🇸 · Yigal Shamir🇮🇱
We continue our study of spectroscopy data for the SU(3) gauge theory with eight fundamental fermions, motivated by the effective field theory framework of dilaton chiral perturbation theory (dChPT). At leading order dChPT predicts a constant mass anomalous dimension $γ_{m}$ , consistent with the assumed proximity of an infrared fixed point. For the relatively large fermion masses simulated by the LatKMI collaboration, the influence of the infrared fixed point diminishes, and our fits suggest that $γ_{m}$ starts running. Since a complete higher-order analysis is not feasible with presently available data, we adopt a more phenomenological approach. We propose a partial extension to higher orders, which incorporates the running of $γ_{m}$ into the tree-level lagrangian. We find that this extension successfully describes the full fermion-mass range of the LatKMI data, including the pion taste splittings which arise from using staggered fermions in the lattice simulations. We also investigate a more general class of dilaton potentials proposed in the literature, using both the LSD and LatKMI data sets, concluding that these data favor the form predicted by dChPT.
↳ hep-lathep-phhep-thPRD(2020)·38 citations
27*
On the gravitational wave sources from the NANOGrav 12.5-yr data
Ligong Bian🇨🇳 · Rong-Gen Cai🇨🇳 · Jing Liu🇨🇳 · Xing-Yu Yang🇨🇳 · Ruiyu Zhou🇨🇳
The NANOGrav Collaboration recently reported a strong evidence for a stochastic common-spectrum process in the pulsar-timing data. We evaluate the evidence of interpreting this process as mergers of super massive black hole binaries and/or various stochastic gravitational wave background sources in the early Universe, including first-order phase transitions, cosmic strings, domain walls, and large amplitude curvature perturbations. We discuss the implications of the constraints on these possible sources. It is found that the cosmic string is the most favored source against other gravitational wave sources based on the Bayes factor analysis.
↳ astro-ph.COgr-qchep-phhep-thPRD(2021)·99 citations
28*
Implications of Gravitational-wave Production from Dark Photon Resonance to Pulsar-timing Observations and Effective Number of Relativistic Species
Ryo Namba🇨🇳 · Motoo Suzuki🇨🇳
The coherent oscillation of axionic fields naturally drives copious production of dark photon particles in the early universe, due to resonance and tachyonic enhancement. During the process, energy is abruptly transferred from the former to the latter, sourcing gravitational wave generation. The resulting gravitational waves are eventually to be observed as stochastic background today. We report analytical results of this production and connect them to the recent pulsar-timing results by the NANOGrav collaboration. We show an available parameter space, around the mass $m_{ϕ} \sim 1 0^{- 13} eV$ and the decay constant $f_{ϕ} \sim 1 0^{16} GeV$ with a dimensionless coupling of $O (1)$ , for our mechanism to account for the signal. A mechanism to avoid the axion over-dominating the universe is a necessary ingredient of this model, and we discuss a possibility to recover a symmetry and render the axion massless after the production. We also comment on potential implications of the required effective number of relativistic species to the determination of the present Hubble constant.
↳ astro-ph.COgr-qchep-phhep-thPRD(2020)·48 citations
29*
Radial profile of heavy quarks in jets in high-energy nuclear collisions
Sa Wang🇨🇳 · Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
In high energy nuclear collisions, heavy flavor tagged jets are useful hard probes to study the properties of the quark-gluon plasma (QGP). In this talk, we present the first theoretical prediction of the $D^{0}$ meson radial distributions in jets relative to the jet axis both in p+p and Pb+Pb collisions at $5.02$ TeV, it shows a nice agreement with the available experimental data. The in-medium jet evolution in the study is described by a Monte Carlo transport model which has been incorporated with the initial events as input provided by the next-to-leading order (NLO) plus parton shower (PS) event generator SHERPA. In such evolution process, both elastic and inelastic parton energy loss in the hot and dense medium are taken into account. Within this same simulation framework, we predict different modification patterns of the radial profile of charm and bottom quarks in jets in Pb+Pb collisions: jet quenching effect will lead the charm quarks diffuse to lager radius while lead the bottom quarks distributed closer to jet axis.
↳ nucl-thhep-phPoS(2021)·3 citations
30*
Deconfinement critical point of lattice QCD with $N_{f} = 2$ Wilson fermions
Francesca Cuteri🇩🇪 · Owe Philipsen🇩🇪 · Alena Schön🇩🇪 · Alessandro Sciarra🇩🇪
The $SU (3)$ pure gauge theory exhibits a first-order thermal deconfinement transition due to spontaneous breaking of its global $Z_{3}$ center symmetry. When heavy dynamical quarks are added, this symmetry is broken explicitly and the transition weakens with decreasing quark mass until it disappears at a critical point. We compute the critical hopping parameter and the associated pion mass for lattice QCD with $N_{f} = 2$ degenerate standard Wilson fermions on $N_{τ} \in {6, 8, 10}$ lattices, corresponding to lattice spacings $a = 0.12 fm$ , $a = 0.09 fm$ , $a = 0.07 fm$ , respectively. Significant cut-off effects are observed, with the first-order region growing as the lattice gets finer. While current lattices are still too coarse for a continuum extrapolation, we estimate $m_{π}^{c} \approx 4 GeV$ with a remaining systematic error of $\sim 20%$ . Our results allow to assess the accuracy of the LO and NLO hopping expanded fermion determinant used in the literature for various purposes. We also provide a detailed investigation of the statistics required for this type of calculation, which is useful for similar investigations of the chiral transition.
↳ hep-lathep-phnucl-thPRD(2021)·51 citations
31*
Scattering Amplitudes for Monopoles: Pairwise Little Group and Pairwise Helicity
Csaba Csaki🇺🇸 · Sungwoo Hong🇺🇸 · Yuri Shirman🇺🇸 · Ofri Telem🇺🇸 · John Terning🇺🇸 · Michael Waterbury🇺🇸
On-shell methods are particularly suited for exploring the scattering of electrically and magnetically charged objects, for which there is no local and Lorentz invariant Lagrangian description. In this paper we show how to construct a Lorentz-invariant S-matrix for the scattering of electrically and magnetically charged particles, without ever having to refer to a Dirac string. A key ingredient is a revision of our fundamental understanding of multi-particle representations of the Poincaré group. Surprisingly, the asymptotic states for electric-magnetic scattering transform with an additional little group phase, associated with pairs of electrically and magnetically charged particles. The corresponding "pairwise helicity" is identified with the quantized "cross product" of charges, $e_{1} g_{2} - e_{2} g_{1}$ , for every charge-monopole pair, and represents the extra angular momentum stored in the asymptotic electromagnetic field. We define a new kind of pairwise spinor-helicity variable, which serves as an additional building block for electric-magnetic scattering amplitudes. We then construct the most general 3-point S-matrix elements, as well as the full partial wave decomposition for the $2 \to 2$ fermion-monopole S-matrix. In particular, we derive the famous helicity flip in the lowest partial wave as a simple consequence of a generalized spin-helicity selection rule, as well as the full angular dependence for the higher partial waves. Our construction provides a significant new achievement for the on-shell program, succeeding where the Lagrangian description has so far failed.
↳ hep-thhep-phJHEP(2021)·54 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.