Nuclear Theory·nucl-th

Wednesday·March 4, 2020

8 papers—3 primary·5 cross-listed

01
Momentum-dependent flow fluctuations as a hydrodynamic response to initial geometry
Maurício Hippert · David Dobrigkeit Chinellato · Matthew Luzum · Jorge Noronha · Tiago Nunes da Silva · Jun Takahashi
We propose a redefinition of the principal component analysis (PCA) of anisotropic flow that makes it more directly connected to fluctuations of the initial geometry of the system. Then, using state-of-the-art hydrodynamic simulations, we make an explicit connection between flow fluctuations and a cumulant expansion of the initial transverse geometry. In particular, we show that the second principal component of elliptic flow is generated by higher-order cumulants, and therefore probes smaller length scales of the initial state. With this information, it will be possible to put new constraints on properties of the early-time dynamics of a heavy-ion collision, including small-scale structure, as well as properties of the quark-gluon plasma.
nucl-thnucl-exNPA(2021)·3 citations
02
Variation after $K$ -projection in antisymmetrized molecular dynamics for low-energy dipole excitations in $^{10}$ Be and $^{16}$ O
Yuki Shikata · Yoshiko Kanada-En'yo
For study of dipole excitations, a new method of variation after $K$ -projection in the framework of antisymmetrized molecular dynamics (AMD) with the deformation $β$ constraint was proposed. The method was applied to $^{10}$ Be and $^{16}$ O to describe low-energy dipole excitations and found to be a useful and economical approach for dipole excitations. In the application to $^{10}$ Be, two dipole states in low-energy region were described. For $^{16}$ O, the $1_{1}^{-}$ and $1_{2}^{-}$ states with remarkable dipole strengths were obtained. The $1_{1}^{-}$ state is characterized by significant toroidal dipole (TD) and compressional dipole strengths, whereas the $1_{2}^{-}$ has significant TD strength and shows a developed $α +^{16}$ O cluster structure. Dipole properties in $^{16}$ O were discussed by analysis of current densities of the dipole transitions.
nucl-thPTEP(2020)·9 citations
03
Does the spin tensor play any role in non-gravitational physics?
F. Becattini (University of Florence)🇮🇹
In view of the recent polarization measurements in ultra-relativistic heavy ion collisions, we discuss the possibility of a physical meaning of the spin angular momentum in quantum field theory and relativistic hydrodynamics.
nucl-thgr-qchep-thNPA(2021)·13 citations
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 $1 0^{- 4}$ . 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
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
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
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 $^{10} B +^{10} B$ , $^{12} C +^{12} C$ , $^{16} O +^{16} O$ , $^{20} Ne +^{20} Ne$ , $^{40} Ca +^{40} Ca$ , $^{96} Zr +^{96} Zr$ , and $^{197} Au +^{197} Au$ collisions at RHIC energies $s_{N N}$ of 200, 20, and 7.7 GeV. The results for $^{197} Au +^{197} Au$ collisions are comparable with those of previous experimental STAR data. The transverse momentum $p_{T}$ spectra of charged particles ( $π^{\pm}$ , $K^{\pm}$ , $p$ , and $p ˉ$ ) 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 $T_{k in}$ and the radial expansion velocity $β_{T}$ , which also agrees with the STAR or ALICE results. We found that the chemical freeze-out strangeness potential $μ_{s}$ remains constant in all collision systems and that the fireball radius $R$ is dominated by $⟨ N_{Part} ⟩$ , which can be well fitted by a function of $a ⟨ N_{Part} ⟩^{b}$ with $b \approx 1/3$ . In addition, we calculated the nuclear modification factors for different collision systems with respect to the $^{10} B +^{10} B$ system, and found that they present a gradual suppression within a higher $p_{T}$ range from small to large systems.
↳ hep-phnucl-exnucl-thPRC(2020)·9 citations
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