The ϕ meson production in small collision systems observed by PHENIX

The measurements of light hadron production in small collision systems (such as p+Al, p+Au, d+Au, 3He+Au) may allow to explore the quarkgluon plasma formation and to determine the main hadronization mechanism in the considered collisions. Such research has become particularly crucial with the observation of the light hadrons collective behavior in p/d/3He+Au collisions at √SNN = 200 GeV and in p+Al collisions at the same energy at forward and backward rapidities. Among the large variety of light hadrons, ϕ meson is of particular interest since its production is sensitive to the presence of the quark-gluon plasma. The paper presents the comparison of the obtained experimental results on ϕ meson production to different light hadron production in p+Al and 3He+Au at √SNN = 200 GeV at midrapidity. The comparisons of ϕ meson production in p+Al, p+Au, d+Au, and 3He+Au collisions at √SNN = 200 GeV at midrapidity to theoretical models predictions (PYTHIA model and default and string melting versions of the AMPT model) are also provided. The results suggest that the QGP can be formed in p/d/3He+Au collisions, but the volume and lifetime of the produced medium might be insufficient for observation of strangeness enhancement effect. Conceivably, the main hadronization mechanism of ϕ meson production in p+Al collisions is fragmentation, while in p/d/3He+Au collisions this process occurs via coalescence.

Strangeness Enhancement at LHC Energies Using the Thermal Model and EPOSLHC Event Generator

The strangeness enhancement signature of QGP formation at LHC energies is carefully tackled in the present study. Based on HRG, the particle ratios of mainly strange and multistrange particles are studied at energies from lower s ~ 0.001 up to 13 TeV. The strangeness enhancement clearly appeared at more high energies, and the ratios are confronted to the available experimental data. The particle ratios are also studied using the Cosmic Ray Monte Carlo (CRMC) interface model with its two different event generators, namely, EPOS 1.99 and EPOSlhc, which show a good agreement with the model calculations at the whole range of the energy. We utilize them to produce some particles ratios. EPOS 1.99 is used to estimate particle ratios at lower energies from AGS up to the Relativistic Heavy Ion Collider (RHIC) while EPOSlhc is used at LHC energies. The production of kaons and lambda particles is studied in terms of the mean multiplicity in p-p collisions at energies ranging from 4 to 26 GeV. We find that both HRG model and the used event generators, EPOS 1.99 and EPOSlhc, can describe the particle ratios very well. Additionally, the freeze-out parameters are estimated for different collision systems, such as p-p and Pb-Pb, at LHC energies using both models.

Measurements of $${\Xi }{^-} $$ and $$\overline{\Xi }{^+} $$ production in proton–proton interactions at $$\sqrt{s_{NN}}$$ = 17.3 $$\hbox {Ge}\hbox {V}$$ in the NA61/SHINE experiment

The production of $$\Xi (1321)^{-}$$ Ξ ( 1321 ) - and $$\overline{\Xi }(1321)^{+}$$ Ξ ¯ ( 1321 ) + hyperons in inelastic p+p interactions is studied in a fixed target experiment at a beam momentum of 158 $$\hbox {Ge}\hbox {V}\!/\!c$$ Ge / c . Double differential distributions in rapidity $${y}$$ y and transverse momentum $$p_{T}$$ p T are obtained from a sample of 33M inelastic events. They allow to extrapolate the spectra to full phase space and to determine the mean multiplicity of both $${\Xi }{^-} $$ Ξ - and $$\overline{\Xi }{^+} $$ Ξ ¯ + . The rapidity and transverse momentum spectra are compared to transport model predictions. The $${\Xi }{^-} $$ Ξ - mean multiplicity in inelastic p+p interactions at 158 $$\hbox {Ge}\hbox {V}\!/\!c$$ Ge / c is used to quantify the strangeness enhancement in A+A collisions at the same centre-of-mass energy per nucleon pair.