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Nuclear Theory·nucl-th

Wednesday·March 4, 2020

8 papers—3 primary·5 cross-listed

All8Primary3Cross-lists5
  1. 04

    Searching for dark photons in hyperon decays

    Jhih-Ying Su🇹🇼 · Jusak Tandean🇹🇼

    That massless dark photons could exist and have flavor-changing magnetic-dipole interactions with down-type light quarks is an attractive possibility which may be realized in various new-physics scenarios. It is potentially testable not only in kaon processes but also via two-body hyperon decays involving missing energy carried away by the massless dark photon. We explore the latter within a simplified model approach and take into account constraints from the kaon sector. We find that the branching fractions of some of these hyperon modes are allowed to be as high as a few times . Such numbers are likely to be within the sensitivity reaches of ongoing experiments like BESIII and future ones at super charm-tau factories.

    ↳ hep-phhep-exnucl-thPRD(2020)·25 citations
  2. 05

    Perturbative Thermal QCD: Formalism and Applications

    Jacopo Ghiglieri🇫🇷 · Aleksi Kurkela🇨🇭 · Michael Strickland🇺🇸 · Aleksi Vuorinen🇫🇮

    In this review article, we discuss the current status and future prospects of perturbation theory as a means of studying the equilibrium thermodynamic and near-equilibrium transport properties of deconfined QCD matter. We begin with a brief introduction to the general topic, after which we review in some detail the foundations and modern techniques of the real- and imaginary-time formalisms of thermal field theory, covering e.g. the different bases used in the real-time formalism and the resummations required to deal with soft and collinear contributions. After this, we discuss the current status of applications of these techniques, including topics such as electromagnetic rates, transport coefficients, jet quenching, heavy quarks and quarkonia, and the Equations of State of hot quark-gluon plasma as well as cold and dense quark matter. Finally, we conclude with our view of the future directions of the field, i.e. how we anticipate perturbative calculations to contribute to our collective understanding of strongly interacting matter in the coming years.

    ↳ hep-phhep-thnucl-thPhys.Rept.(2020)·193 citations
  3. 06

    Chemical freeze-out parameters of net-kaons in heavy-ion collisions

    Paolo Alba🇩🇪 · Rene Bellwied🇺🇸 · Valentina Mantovani-Sarti🇩🇪 · Jacquelyn Noronha-Hostler🇺🇸 · Paolo Parotto🇺🇸 · Israel Portillo-Vazquez🇺🇸 · Claudia Ratti🇺🇸 · Jamie M. Stafford🇺🇸

    We study chemical freeze-out parameters for heavy-ion collisions by performing two different thermal analyses. We analyze results from thermal fits for particle yields, as well as, net-charge fluctuations in order to characterize the chemical freeze-out. The Hadron Resonance Gas (HRG) model is employed for both methods. By separating the light hadrons from the strange hadrons in thermal fits, we study the proposed flavor hierarchy. For the net-charge fluctuations, we calculate the mean-over-variance ratio of the net-kaon fluctuations in the HRG model at the five highest energies of the RHIC Beam Energy Scan (BES) for different particle data lists. We compare these results with recent experimental data from the STAR collaboration in order to extract sets of chemical freeze-out parameters for each list. We focused on particle lists which differ largely in the number of resonant states. By doing so, our analysis determines the effect of the amount of resonances included in the HRG model on the freeze-out conditions. Our findings have potential impact on various other models in the field of relativistic heavy-ion collisions.

    ↳ hep-phnucl-thNPA(2021)·2 citations
  4. 07

    Nuclear system size scan for freeze-out properties in relativistic heavy-ion collisions by using a multiphase transport model

    Dong-Fang Wang🇨🇳 · Song Zhang🇨🇳 · Yu-Gang Ma🇨🇳

    A system size scan program was recently proposed for the STAR experiments at the Relativistic Heavy Ion Collider(RHIC). In this study, we employ a multiphase transport (AMPT) model for considering the bulk properties at the freeze-out stage for , , , , , , and collisions at RHIC energies of 200, 20, and 7.7 GeV. The results for collisions are comparable with those of previous experimental STAR data. The transverse momentum spectra of charged particles (, , , and ) at the kinetic freeze-out stage, based on a blast-wave model, are also discussed. In addition, we use a statistical thermal model to extract the parameters at the chemical freeze-out stage, which agree with those from other thermal model calculations. It was found that there is a competitive relationship between the kinetic freeze-out parameter and the radial expansion velocity , which also agrees with the STAR or ALICE results. We found that the chemical freeze-out strangeness potential remains constant in all collision systems and that the fireball radius is dominated by , which can be well fitted by a function of with . In addition, we calculated the nuclear modification factors for different collision systems with respect to the system, and found that they present a gradual suppression within a higher range from small to large systems.

    ↳ hep-phnucl-exnucl-thPRC(2020)·9 citations
  5. 08

    Wigner function formalism and the evolution of thermodynamic quantities in an expanding magnetized plasma

    S. M. A. Tabatabaee🇮🇷 · N. Sadooghi🇮🇷

    By combining the Wigner function formalism of relativistic quantum kinetic theory with fundamental equations of relativistic magnetohydrodynamics (MHD), we present a novel approach to determine the proper time evolution of the temperature and other thermodynamic quantities in a uniformly expanding hot, magnetized, and weakly interacting plasma. The aim is to study the contribution of quantum corrections to this evolution. We first determine the corresponding Wigner function in terms of the solution of the Dirac equation in the presence of a constant magnetic field. Using this function, we then compute the energy-momentum tensor of the above-mentioned plasma, which eventually yields its energy density and pressure. Plugging these quantities in the energy equation of relativistic MHD, we arrive, after choosing an appropriate coordinate system, at a differential equation for the temperature as a function of the proper time. The numerical solution of this equation leads finally to the proper time evolution of the temperature. The latter is then used to determine the evolution of a large number of thermodynamic quantities in this expanding and magnetized plasma. We compare our results with other existing results from relativistic MHD. We also comment on the effect of point to point decaying magnetic fields on the thermodynamic properties of this plasma.

    ↳ hep-phhep-thnucl-thPRD(2020)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE