arXiv subjects

Ya-Qin Gao

Publications and source records attributed to Ya-Qin Gao.

5 recordsLinked to original sources

arXiv2022

Thermal freeze-out parameters and pseudo-entropy from charged hadron spectra in high energy collisions

We collected the transverse momentum (mass) spectra of charged hadrons ($π^{-}$, $π^{+}$, $K^{-}$, $K^{+}$, $\overline{p}$, and $p$) produced in collisions over a center-of-mass energy range from 2.70 to 200 GeV (per nucleon pair). The modified Tsallis--Pareto-type function (the TP-like function) with average transverse flow velocity is used to describe the contribution of participant or constituent quarks to transverse momentum of considered hadron. The experimental spectra of $π^{\mp}$ and $K^{\mp}$ (or $\overline{p}$ and $p$) are fitted by the convolution of two (or three) TP-like functions due to the fact that two (or three) constituent quarks are regarded as two (or three) energy resources in the formation of considered hadron. From the reasonable fits to the spectra, the thermal freeze-out parameters are extracted, and the pseudo-entropy is newly defined and extracted. Some parameters quickly change in the energy range of less than 7.7 GeV, and slowly change in the energy range of greater than 7.7 GeV, indicating the variation of collision mechanism at around 7.7 GeV.

hep-ph↗

arXiv2022

An energy independent scaling of transverse momentum spectra of direct (prompt) photons from two-body processes in high-energy proton-proton collisions

Transverse momentum spectra of direct (prompt) photons from two-body processes in high-energy proton-proton (p+p) collisions are analyzed in this paper. We collected the experimental invariant cross-sections at mid-rapidity in p+p collisions measured by the UA6, CCOR, R806, R110, PHENIX, NA24, CMS, ALICE, and ATLAS Collaborations over a center-of-mass energy range from 24.3 GeV to 13 TeV. In fitting the data, we used different kinds of functions which include the revised Tsallis--Pareto-type function (the TP-like function) at the particle level, the convolution of two TP-like functions at the quark level, and the root-sum-of-squares of two revised Tsallis-like functions in which the quark chemical potentials $μ_i=μ_B/3$ or $μ_i=0$, where $μ_B$ is the baryon chemical potential. We have extracted the values of three main free parameters: the effective temperature $T$, power index $n_0$ (or entropy index $q$), and correction index $a_0$. After analyzing the changing trends of the parameters, we found that $T$, $q$, and $a_0$ increase and $n_0$ decreases with the increase of collision energy. Based on the analyses of transverse momentum spectra, an energy independent scaling, i.e. the $x_T$ scaling, is obtained.

hep-ph↗

arXiv2019

Light particle and quark chemical potentials from negatively to positively charged particle yield ratios corrected by removing strong and weak decays

The yield ratios of negatively to positively charged pions ($π^-/π^+$), negatively to positively charged kaons ($K^-/K^+$), and anti-protons to protons ($\bar p/p$) produced in mid-rapidity interval in central gold-gold (Au-Au) collisions, central lead-lead (Pb-Pb) collisions, and inelastic (INEL) or non-single-diffractive (NSD) proton-proton ($pp$) collisions, as well as in forward rapidity region in INEL $pp$ collisions are analyzed in the present work. Over an energy range from a few GeV to above 10 TeV, the chemical potentials of light flavor particles (pion, kaon, and proton) and quarks (up, down, and strange quarks) are extracted from the mentioned yield ratios in which the contributions of strong decay from high-mass resonance and weak decay from heavy flavor hadrons are removed. Most energy dependent chemical potentials show the maximum at about 4 GeV, while the energy dependent yield ratios do not show such an extremum.

hep-ph↗

arXiv2019

Energy dependent chemical potentials of light particles and quarks from yield ratios of antiparticles to particles in high energy collisions

We collect the yields of charged pions ($π^-$ and $π^+$), charged kaons ($K^-$ and $K^+$), anti-protons ($\bar p$), and protons ($p$) produced in mid-rapidity interval (in most cases) in central gold-gold (Au-Au), central lead-lead (Pb-Pb), and inelastic or non-single-diffractive proton-proton ($pp$) collisions at different collision energies. The chemical potentials of light particles and quarks are extracted from the yield ratios, $π^-/π^+$, $K^-/K^+$, and $\bar p/p$, of antiparticles to particles over an energy range from a few GeV to above 10 TeV. At a few GeV ($\sim4$ GeV), the chemical potentials show, and the yield ratios do not show, different trends comparing with those at other energies, though the limiting values of the chemical potentials and the yield ratios at very high energy are 0 and 1 respectively.

hep-ph↗

arXiv2018

Chemical potentials of light flavor quarks from yield ratios of negative to positive particles in Au+Au collisions at RHIC

The transverse momentum spectra of $π^{-}$, $π^{+}$, $K^{-}$, $K^{+}$, $\bar{p}$, and $p$ produced in Au+Au collisions at center-of-mass energy $\sqrt{s_{NN}}=7.7$, 11.5, 19.6, 27, 39, 62.4, 130, and $200$ GeV are analyzed in the framework of a multisource thermal model. The experimental data measured at midrapidity by the STAR Collaboration are fitted by the (two-component) standard distribution. The effective temperature of emission source increases obviously with the increase of the particle mass and the collision energy. At different collision energies, the chemical potentials of up, down, and strange quarks are obtained from the antiparticle to particle yield ratios in given transverse momentum ranges available in experiments. With the increase of logarithmic collision energy, the chemical potentials of light flavor quarks decrease exponentially.

nucl-th↗