In high-energy nuclear collisions, light nuclei can be regarded as a cluster of baryons and their yields are sensitive to the baryon density fluctuations. Thus, the production of light nuclei can be used to study the QCD phase transition, at which the baryon density fluctuation will be enhanced. The yield ratio of light nuclei, defined as $N(t)$$\times$$N(p)$/$N^2(d)$, is predicted to be sensitive observable to search for the 1st-order phase transition and/or QCD critical point in heavy-ion collisions. In this paper, we present the energy and centrality dependence of (anti)deuteron and triton production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4, and 200 GeV measured by the STAR experiment at RHIC. We show beam-energy dependence for the coalescence parameter, $B_2(d)$ and $B_3(t)$, particle ratios, $d/p$, $t/p$, and $t/d$, and the yield ratio of $N(t)$$\times$$N(p)$/$N^2(d)$. More importantly, non-monotonic energy dependence is observed for the yield ratio, $N(t)$$\times$$N(p)$/$N^2(d)$, in 0-10\% central Au+Au collisions with a peak around 20-30 GeV. Their physics implications on QCD critical point search and change of the equation of state will be discussed.
Invariant differential yields of deuterons and anti-deuterons in pp collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV and the yields of tritons, $^{3}$He nuclei and their anti-nuclei at $\sqrt{s}$ = 7 TeV have been measured with the ALICE detector at the CERN Large Hadron Collider. The measurements cover a wide transverse momentum ($p_{\text{T}}$) range in the rapidity interval $|y|<0.5$, extending both the energy and the $p_{\text{T}}$ reach of previous measurements up to 3 GeV/$c$ for $A=2$ and 6 GeV/$c$ for $A=3$. The coalescence parameters of (anti-)deuterons and $^{3}\overline{\text{He}}$ nu…
In this proceeding, we present on our first measurements of identified particle ($π$, $K$, $p$, $K_{s}^{0}$, $Λ$, $ϕ$, $Ξ^{-}$) production and anisotropic flow ($v_{1}$, $v_{2}$) in Au+Au collisions at ${\sqrt{s_{\rm NN}} = \rm{3\,GeV}}$. Various models including thermal and transport model calculations are compared to data, these results imply that the matter produced in the 3 GeV Au+Au collisions is considerably different from that at higher energies.
The study of the production of nuclei and antinuclei in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper, the production of protons, deuterons and $^3$He and their charge conjugates at midrapidity is studied as a function of the charged-particle multiplicity in inelastic pp collisions at $\sqrt{s}=5.02$ TeV using the ALICE detector. Within the uncertainties, the yields of nuclei in pp collisions at $\sqrt{s}=5.02$ TeV are compatible with those in pp collisions at different energies an…
In these proceedings, we present the second order ($v_{2}$) and the third order ($v_{3}$) azimuthal anisotropy measurements of strange and multi-strange hadrons such as $K^{0}_{S}$, $Λ$, $\barΛ$, $ϕ$, $Ξ^{-}$, $\barΞ^{+}$, $Ω^{-}$, $\barΩ^{+}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV at STAR. The centrality dependence of $v_{2}$ and $v_{3}$ as well as the number of constituent quark scaling (NCQ scaling) for all the particles mentioned above are discussed. The ratio of $v_{2}$ of $ϕ$ mesons to that of $\bar{p}$ is presented at $\sqrt{s_{NN}}$ = 54.4 GeV which gives a hint of ma…
In these proceedings, we present the higher-order cumulants of proton multiplicity distributions of the fixed-target (FXT) run in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 3.0 GeV. The cumulant ratios are presented as a function of centrality and collision energy. The proton cumulant ratio C4/C2 is consistent with fluctuations driven by baryon number conservation and indicates an energy regime dominated by hadronic interactions. These data imply that the QCD critical point could exist at energies higher than 3 GeV if created in heavy-ion collisions.
We report systematic measurements of bulk properties of the system created in Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The transverse momentum spectra of $π^{\pm}$, $K^{\pm}$, and $p$($\bar{p}$) are studied at mid-rapidity $(\lvert y \rvert < 0.1)$ for different centrality classes. We also present mid-rapidity measurement of particle yields $(dN/dy)$ and particle ratios in Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV. The kinetic freeze-out parameters ($T_{kin}$ and $\langle β\rangle$) are extracted from parti…
In this proceedings, we have presented the invariant yield measurements of strange and multi strange hadrons such as $K^{0}_{S}$, $Λ$, $\barΛ$, $ϕ$, $Ξ^{-}$, $\barΞ^{+}$, $Ω^{-}$, $\barΩ^{+}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV at midrapidity ($|y|<0.5$). The second and third-order azimuthal anisotropic flow of the above mentioned particles at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV are also discussed. Some of the important observables such as nuclear modification factor ($R_{CP}$), baryon to meson ratio ($Ω/ϕ$), transverse momentum dependence of $v_{2}$ and $v_{3}$ are measured. The n…
Light nuclei and hyper-nuclei are produced in abundance in heavy-ion collisions. The production mechanism of these species in heavy-ion collisions still remains to be understood. In these proceedings, we report the transverse momentum and centrality dependence of elliptic flow ($v_2$) of $d$, $t$, and $^3\text{He}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 14.6, 19.6, 27, and 54.4 GeV. Mass number scaling of $v_2(p_T)$ of light nuclei is shown. We also report the first observation of hyper-nuclei $^{3}_Λ$H and $^{4}_Λ$H directed flow ($v_1$) in $\sqrt{s_{NN}}$ = 3 GeV mid-central (5-40\%) Au+Au…
Production of $e^{+}e^{-}$ from U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV and Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6, 27, 39, 62.4, and 200 GeV as measured by STAR
We present recent results from Al(beam)+Au(target) collisions at $\sqrt{s_{NN}}=4.9$ GeV and Au+Au collisions at $\sqrt{s_{NN}}=4.5$\kern 0.16667em GeV from the STAR fixed-target (FXT) program. We report transverse mass spectra of protons, $K^0_S$ and $Λ$, rapidity density distributions of $π^\pm$, $K^0_S$ and $Λ$, directed flow of protons, $π^\pm$, $K^0_S$ and $Λ$, and elliptic flow of protons and $π^{\pm}$. These are the first measurements of pion directed and elliptic flow in this energy range at RHIC. Pion and proton elliptic flow show mass ordering. Measurements are compared with the publ…
We investigate the squeezed back-to-back correlations (BBC) of $K^+$$K^-$, caused by the mass modification of the particle in the dense medium formed in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV and Au+Au collisions at $\sqrt{s_{NN}}=62.4$ GeV. Considering some kaons may be not affected by the medium, we further study the BBC functions of $K^+$$K^-$ when parts of all kaons have a mass-shift. Our results indicate that the BBC functions of $K^+$$K^-$ can be observed when only about 10$\%$ of all kaons have a mass-shift in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV and the peripheral collisions …
Measurements of Non-photonic Electron Production and Azimuthal Anisotropy in $\sqrt {s_{NN}} = 39$, 62.4 and 200 GeV \auau\ Collisions from STAR at RHIC
The measurement of J/{psi} azimuthal anisotropy is presented as a function of transverse momentum for different centralities in Au+Au collisions at {sqrt{s_{NN}}} = 200 GeV. The measured J/{psi} elliptic flow is consistent with zero within errors for transverse momentum between 2 and 10 GeV/c. Our measurement suggests that J/{psi} with relatively large transverse momentum are not dominantly produced by coalescence from thermalized charm quarks, when comparing to model calculations.
Different regions on the QCD phase diagram can be investigated by varying the collision energy and the centrality in heavy-ion collisions. In our latest measurements at the PHENIX experiment at RHIC, we utilize Lévy-type sources to describe the measured HBT correlation functions. In this paper we report the current status of the analysis of the centrality and beam energy dependence of the Lévy source parameters in Au+Au collisions from $\sqrt{s_{NN}}$ = 15 GeV to $\sqrt{s_{NN}}$ = 200 GeV.
Light nuclei production is expected to be sensitive to baryon density fluctuations and can be used to probe the signatures of QCD critical point and/or a first-order phase transition in heavy-ion collisions. In this proceedings, we present the spectra and yields of protons ($p$) and light nuclei ($d$, $t$, $^{3}\mathrm{He}$, $^{4}\mathrm{He}$) in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV by the STAR experiment. Finally, it is found that the kinetic freeze-out dynamics (temperature $T_{kin}$ $vs.$ average radial flow velocity $\langleβ_{T}\rangle$) at 3 GeV extracted with the blast-w…
