Nuclear Theory·nucl-th

Tuesday·November 5, 2019

20 papers—12 primary·8 cross-listed

13
The range of elementary interactions: a criticism of the standard classroom approach
B. Hernández-Bermejo
The finite scope of the some elementary interactions is usually presented to Physics students as a natural consequence of the time-energy uncertainty relation. It is demonstrated that this heuristic derivation is not a priori valid. Accordingly, it is argued the doubtful usefulness of this "proof" in the classroom, for it may lead to misconceptions.
↳ physics.pop-phnucl-thphysics.ed-phEur.J.Phys.(1997)·0 citations
14
Soft contribution to the damping rate of a hard photon in a weakly magnetized hot medium
Ritesh Ghosh🇮🇳 · Bithika Karmakar🇮🇳 · Munshi G Mustafa🇮🇳
We consider weakly magnetized hot QED plasma comprising electrons and positrons. There are three distinct dispersive (longitudinal and two transverse) modes of a photon in a thermo-magnetic medium. At lowest order in coupling constant, photon is damped in this medium via Compton scattering and pair creation process. We evaluate the damping rate of hard photon by calculating the imaginary part of the each transverse dispersive modes in a thermo-magnetic QED medium. We note that one of the fermions in the loop of one-loop photon self-energy is considered as soft and the other one is hard. Considering the resummed fermion propagator in a weakly magnetized medium for the soft fermion and the Schwinger propagator for hard fermion, we calculate the soft contribution to the damping rate of hard photon. In weak field approximation the thermal and thermo-magnetic contributions to damping rate get separated out for each transverse dispersive mode. The total damping rate for each dispersive mode in presence of magnetic field is found to be reduced than that of the thermal one. This formalism can easily be extended to QCD plasma.
↳ hep-phhep-latnucl-thPRD(2020)·17 citations
15
Nonperturbative renormalization of staple-shaped Wilson line operators in lattice QCD
Phiala Shanahan🇺🇸 · Michael L. Wagman🇺🇸 · Yong Zhao🇺🇸
Quark bilinear operators with staple-shaped Wilson lines are used to study transverse-momentum-dependent parton distribution functions (TMDPDFs) from lattice quantum chromodynamics (QCD). Here, the renormalization factors for the isovector operators, including all mixings between operators with different Dirac structures, are computed nonperturbatively in the regularization-independent momentum subtraction scheme for the first time. This study is undertaken in quenched QCD with three different lattice spacings. With Wilson flow applied to the gauge fields in the calculations, the operator mixing pattern due to chiral symmetry breaking with the lattice regularization is found to be significantly different from that predicted by one-loop lattice perturbation theory calculations. These results constitute a critical step towards the systematic extraction of TMDPDFs from lattice QCD.
↳ hep-lathep-phnucl-thPRD(2020)·80 citations
16
Chiral magnetic response to arbitrary axial imbalance
Miklos Horvath🇨🇳 · Defu Hou🇨🇳 · Jinfeng Liao🇺🇸 · Hai-cang Ren🇺🇸
The response of chiral fermions to time and space dependent axial imbalance & constant magnetic field is analyzed. The axialvector-vector-vector (AVV) three-point function is studied using a real-time approach at finite temperature in the weak external field approximation. The chiral magnetic conductivity is given analytically for noninteracting fermions. It is pointed out that local charge conservation plays an important role when the axial imbalance is inhomogeneous. Proper regularization is needed which makes the constant axial imbalance limit delicate: for static but spatially oscillating chiral charge the current of the chiral magnetic effect (CME) vanishes. In the homogeneous (but possible time-dependent) limit of the axial imbalance the CME current is determined solely by the chiral anomaly. As a phenomenological consequence, the observability of the charge asymmetry caused by the CME turns out to be a matter of interplay between various scales of the system. Possible plasma instabilities resulting from the gradient corrections to the CME current are also pointed out.
↳ hep-phcond-mat.str-elhep-thnucl-thPRD(2020)·18 citations
17
Spectrum of fully-heavy tetraquarks from a diquark+antidiquark perspective
M. A. Bedolla🇲🇽 · J. Ferretti🇺🇸 · C. D. Roberts🇨🇳 · E. Santopinto🇮🇹
Using a relativized diquark model Hamiltonian, we calculate the masses of $J^{P C} = 0^{++}$ ground-state tetraquarks in the following systems: $b s b ˉ s ˉ$ , $bb n ˉ n ˉ$ ( $n = u, d$ ), $bb s ˉ s ˉ$ , $cc c ˉ c ˉ$ , $bb b ˉ b ˉ$ , $b c b ˉ c ˉ$ and $bb c ˉ c ˉ$ . We also compute extensive spectra for the fully-heavy quark flavour combinations. Finally, as a test of the diquark model approach, we compute the masses of fully-heavy baryons in the diquark model. Our results may be compared soon to the forthcoming experimental data for fully-heavy three-quark systems.
↳ hep-phhep-exhep-latnucl-ex+1EPJC(2020)·190 citations
18
The dipole picture and the non-relativistic expansion
Miguel Ángel Escobedo🇫🇮 · Tuomas Lappi🇫🇮
We study exclusive quarkonium production in the dipole picture at next-to-leading order (NLO) accuracy, using the non-relativistic expansion for the quarkonium wavefunction. This process offers one of the best ways to obtain information about gluon distributions at small $x$ , in ultraperipheral heavy ion collisions and in deep inelastic scattering. The quarkonium light cone wave functions needed in the dipole picture have typically been available only at tree level, either in phenomenological models or in the nonrelativistic limit. In this paper, we discuss the compatibility of the dipole approach and the non-relativistic expansion and compute NLO relativistic corrections to the quarkonium light-cone wave function in light-cone gauge. Using these corrections we recover results for the NLO decay width of quarkonium to $e^{+} e^{-}$ and we check that the non-relativistic expansion is consistent with ERBL evolution and with B-JIMWLK evolution of the target. The results presented here will allow computing the exclusive quarkonium production rate at NLO once the one loop photon wave function with massive quarks, currently under investigation, is known.
↳ hep-phnucl-thPRD(2020)·23 citations
19
Jet quenching test of the QCD matter created at RHIC and the LHC needs opacity-resummed medium induced radiation
Xabier Feal🇪🇸 · Carlos A. Salgado🇪🇸 · Ricardo A. Vazquez🇪🇸
After almost two decades of investigation, jet quenching has become a fundamental tool to study the properties of the QCD matter produced in high-energy nuclear collisions. Despite the large progress in both experimental and theoretical tools, several unknowns remain to be solved. In particular the systematics of the QCD matter parameters extracted at different energies and centralities is still puzzling. On the other hand, a lot of attention has been put in the last few years to a correct resummation of the multiple scatterings that the particles of the jet suffer when traversing the QCD matter. Present formalisms have substantially improved the multiple-soft or single hard scattering approximations, common in the last twenty years. We show here that medium parameters extracted with full resummed medium-induced gluon radiation spectra significantly differ from these two extreme approximations, providing a natural systematics for different collision energies and centralities, with no inconsistencies. For the case of the full resummation this ensures that the density of scattering centers as a function of the temperature qualitatively agree with the equation of state computed in lattice QCD.
↳ hep-phnucl-thPLB(2021)·49 citations
20
Time-evolution of magnetic field in hot nuclear matter with fluctuating topological charge
Kirill Tuchin🇺🇸
The time-evolution of the magnetic field in hot homogeneous nuclear matter has two qualitatively different stages separated by the sphaleron transition time $τ_{c}$ . At early times the axial chemical potential and the corresponding chiral conductivity $σ_{χ}$ are slow functions of time. The soft chiral modes $k < σ_{χ}$ of the magnetic field grow exponentially with time, which is known as the chiral instability. At later times $σ_{χ}$ fluctuates due to the sphaleron transitions and can be regarded as a random process. It is argued that the average magnetic field is exponentially damped at later times. The time-evolution of the average magnetic energy is more complicated and depends on the electrical conductivity of the chiral matter but does not depend on chirality. It exhibits instability only if the matter is a poor electrical conductor, such as the quark-gluon plasma near the critical temperature. The precise conditions for the instability and the growth rate of the unstable modes are derived.
↳ hep-phnucl-thPRC(2020)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE