Hard Photons from a Non-Equilibrated Quark-Gluon Plasma with Finite Baryon Density at a Two-Loop Level

We study hard photon production from a two-loop level （bremsstrahlung and annihilation with scattering） in a chemically equilibrating quark-gluon plasma at finite baryon density based on Jüttner distribution of partons of the system. We find that the photon yield from the two-loop level increases obviously with the increasing initial quark chemical potential.

Near-threshold K^*(892)^+ meson production in the interaction of π−mesons with nuclei

We study the inclusive production of strange vector K^∗(892)^+ mesons in π−A reactions at near-threshold laboratory incident pion momenta of 1.4-2.0 GeV/c via a nuclear spectral function approach.The approach accounts for incoherent primary π−meson-proton π−p→K^∗(892)^+Σ^− production processes as well as the influence of the scalar K^∗(892)^+-nucleus potential(or the K^∗(892)^+ in-medium mass shift)on these processes.We calculate the absolute differential and total cross sections for the production of K∗(892)+mesons from carbon and tungsten nuclei at laboratory angles of 0∘-45∘and at the aforementioned momenta in five scenarios for the aforenoted shift.We show that the K^∗(892)^+ momentum distributions and their excitation functions(absolute and relative)possess a high sensitivity to changes in the in-medium K^∗(892)^+ mass shift in the low-momentum region of 0.1-0.6 GeV/c.Therefore,the measurement of such observables in a dedicated experiment at the GSI pion beam facility in the near-threshold momentum domain will allow us to get valuable information on the K^∗(892)^+ in-medium properties.

Constituent quark number scaling from strange hadron spectra in pp collisions at ■=13 TeV

We show that the p_T spectra ofΩ^-andφat midrapidity in the inelastic events in pp collisions at■=13 TeV exhibit a constituent quark number scaling property,which is a clear signal of quark combination mechanism at hadronization.We use a quark combination model with equal velocity combination approximation to systematically study the production of identified hadrons in pp collisions at■=13 TeV.The midrapidity spectra for protons,∧,Ξ^-,Ω^-,φand K~*in the inelastic events are simultaneously fitted by the model.The multiplicity dependence of the yields of these hadrons are also well understood.The strong p_T dependence of the p/φratio is well explained by the model,which further suggests that the production of two hadrons with similar masses is determined by their quark content at hadronization.The p_T spectra of strange hadrons at midrapidity in different multiplicity classes in pp collisions at■=13 TeV are predicted for further tests of the model.The midrapidity p_T spectra of soft(p_T<2 GeV/c)strange quarks and up/down quarks at hadronization in pp collisions at■=13 TeV are extracted.