Showing 10 of 21 results
Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean ($M$), variance ($\sigma^2$), skewness ($S$), and kurtosis ($\kappa$) for net-kaon multiplicity distributions as well as the ratio $\sigma^2/M$ and the products $S\sigma$ and $\kappa\sigma^2$ are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.
We report measurements of the nuclear modification factor, $R_{ \mathrm{CP}}$, for charged hadrons as well as identified $\pi^{+(-)}$, $K^{+(-)}$, and $p(\overline{p})$ for Au+Au collision energies of $\sqrt{s_{_{ \mathrm{NN}}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV. We observe a clear high-$p_{\mathrm{T}}$ net suppression in central collisions at 62.4 GeV for charged hadrons which evolves smoothly to a large net enhancement at lower energies. This trend is driven by the evolution of the pion spectra, but is also very similar for the kaon spectra. While the magnitude of the proton $R_{ \mathrm{CP}}$ at high $p_{\mathrm{T}}$ does depend on collision energy, neither the proton nor the anti-proton $R_{ \mathrm{CP}}$ at high $p_{\mathrm{T}}$ exhibit net suppression at any energy. A study of how the binary collision scaled high-$p_{\mathrm{T}}$ yield evolves with centrality reveals a non-monotonic shape that is consistent with the idea that jet-quenching is increasing faster than the combined phenomena that lead to enhancement.
We present measurements of bulk properties of the matter produced in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, and 39 GeV using identified hadrons ($\pi^\pm$, $K^\pm$, $p$ and $\bar{p}$) from the STAR experiment in the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). Midrapidity ($|y|<$0.1) results for multiplicity densities $dN/dy$, average transverse momenta $\langle p_T \rangle$ and particle ratios are presented. The chemical and kinetic freeze-out dynamics at these energies are discussed and presented as a function of collision centrality and energy. These results constitute the systematic measurements of bulk properties of matter formed in heavy-ion collisions over a broad range of energy (or baryon chemical potential) at RHIC.
The average number of participating nucleons (⟨Npart⟩) for various collision centralities in Au+Au collisions at √sNN = 7.7–39 GeV.
Midrapidity (|y| < 0.1) transverse momentum spectra for (b) π- in Au+Au collisions at √sNN = 7.7 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (a) π+ in Au+Au collisions at √sNN = 7.7 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (d) K− in Au+Au collisions at √sNN = 7.7 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (c) K+ in Au+Au collisions at √sNN = 7.7 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (f) p¯ in Au+Au collisions at √sNN = 7.7 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (e) p in Au+Au collisions at √sNN = 7.7 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (b) π− in Au+Au collisions at √sNN = 11.5 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (a) π+ in Au+Au collisions at √sNN = 11.5 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (d) K− in Au+Au collisions at √sNN = 11.5 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (c) K+ in Au+Au collisions at √sNN = 11.5 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (f) p¯ in Au+Au collisions at √sNN = 11.5 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (e) p in Au+Au collisions at √sNN = 11.5 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (b) π− in Au+Au collisions at √sNN = 19.6 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (a) π+ in Au+Au collisions at √sNN = 19.6 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (d) K− in Au+Au collisions at √sNN = 19.6 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (c) K+ in Au+Au collisions at √sNN = 19.6 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (f) p¯ in Au+Au collisions at √sNN = 19.6 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (e) p in Au+Au collisions at √sNN = 19.6 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (b) π− in Au+Au collisions at √sNN = 27 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (a) π+ in Au+Au collisions at √sNN = 27 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (d) K− in Au+Au collisions at √sNN = 27 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (c) K+ in Au+Au collisions at √sNN = 27 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (f) p¯ in Au+Au collisions at √sNN = 27 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (e) p in Au+Au collisions at √sNN = 27 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (b) π− in Au+Au collisions at √sNN = 39 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (a) π+ in Au+Au collisions at √sNN = 39 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (d) k- in Au+Au collisions at √sNN = 39 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (c) k+ in Au+Au collisions at √sNN = 39 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (f) pbar in Au+Au collisions at √sNN = 39 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Midrapidity (|y| < 0.1) transverse momentum spectra for (e) p in Au+Au collisions at √sNN = 39 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.
Centrality dependence of dN/dy normalized by ⟨Npart⟩/2 for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 7.7 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties. For clarity, ⟨Npart⟩ uncertainties are not added in quadrature.
Centrality dependence of dN/dy normalized by ⟨Npart⟩/2 for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 11.5 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties. For clarity, ⟨Npart⟩ uncertainties are not added in quadrature.
Centrality dependence of dN/dy normalized by ⟨Npart⟩/2 for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 19.6 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties. For clarity, ⟨Npart⟩ uncertainties are not added in quadrature.
Centrality dependence of dN/dy normalized by ⟨Npart⟩/2 for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 27 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties. For clarity, ⟨Npart⟩ uncertainties are not added in quadrature.
Centrality dependence of dN/dy normalized by ⟨Npart⟩/2 for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 39 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties. For clarity, ⟨Npart⟩ uncertainties are not added in quadrature.
Centrality dependences of <pT> for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 7.7 GeV. Errors shown are quadrature sum of statistical and systematic uncertainties where the latter dominates.
Centrality dependences of <pT> for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 11.5 GeV. Errors shown are quadrature sum of statistical and systematic uncertainties where the latter dominates.
Centrality dependences of <pT> for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 19.6 GeV. Errors shown are quadrature sum of statistical and systematic uncertainties where the latter dominates.
Centrality dependences of <pT> for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 27 GeV. Errors shown are quadrature sum of statistical and systematic uncertainties where the latter dominates.
Centrality dependences of <pT> for π+, π−, K+, K−, p, and p ̄ at midrapidity (|y|<0.1) in Au+Au collisions at √sNN = 39 GeV. Errors shown are quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of π−/π+, K−/K+, and p ̄/p ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 7.7 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of π−/π+, K−/K+, and p ̄/p ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 11.5 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of π−/π+, K−/K+, and p ̄/p ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 19.6 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of π−/π+, K−/K+, and p ̄/p ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 27 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of π−/π+, K−/K+, and p ̄/p ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 39 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of K−/π−, p ̄/π−, K+/π+, and p/π+ ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 7.7 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of K−/π−, p ̄/π−, K+/π+, and p/π+ ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 11.5 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of K−/π−, p ̄/π−, K+/π+, and p/π+ ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 19.6 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of K−/π−, p ̄/π−, K+/π+, and p/π+ ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 27 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
Variation of K−/π−, p ̄/π−, K+/π+, and p/π+ ratios as a function of ⟨Npart⟩ at midrapidity (|y| < 0.1) in Au+Au collisions at 39 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
The midrapidity (|y| < 0.1) dN/dy normalized by ⟨Npart⟩/2 as a function of √sNN for π±, K±, and p and p ̄ in 0–5% Au+Au collisions at BES energies. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
⟨mT⟩ − m of π±, K±, and p and p ̄ as a function of √sNN . Midrapidity (|y| < 0.1) results are shown for 0–5% central Au+Au collisions at BES energies. The errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
π−/π+, K−/K+, and p ̄/p ratios at midrapidity (|y| < 0.1) in central 0–5% Au+Au collisions at √sNN = 7.7, 11.5, 19.6, 27, and 39 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
K/π ratio at midrapidity (|y| < 0.1) for central 0–5% Au+Au collisions at √sNN = 7.7, 11.5, 19.6, 27, and 39 GeV. Errors shown are the quadrature sum of statistical and systematic uncertainties where the latter dominates.
The GCE model particle yields fits shown along with standard deviations for Au+Au 7.7 and Au+Au 39 GeV in 0–5% central collisions. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature.
The GCE model particle ratios fits shown along with standard deviations for Au+Au 7.7 and Au+Au 39 GeV in 0–5% central collisions. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature.
The SCE model particle yields fits shown along with standard deviations for Au+Au 7.7 and Au+Au 39 GeV in 0–5% central collisions. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature.
The SCE model particle ratios fits shown along with standard deviations for Au+Au 7.7 and Au+Au 39 GeV in 0–5% central collisions. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature.
Chemical freeze-out parameter γS plotted vs ⟨Npart⟩ in GCE for particle yields fit. Uncertainties represent systematic errors.
Chemical freeze-out parameter μB plotted vs ⟨Npart⟩ in GCE for particle yields fit. Uncertainties represent systematic errors.
Chemical freeze-out parameter μS plotted vs ⟨Npart⟩ in GCE for particle yields fit. Uncertainties represent systematic errors.
Chemical freeze-out parameter Tch plotted vs ⟨Npart⟩ in GCE for particle yields fit. Uncertainties represent systematic errors.
Chemical freeze-out parameter R plotted vs ⟨Npart⟩ in GCE for particle yields fit. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter γS between results from particle yield fits to particle ratio fits in GCE plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter μB between results from particle yield fits to particle ratio fits in GCE plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter μS between results from particle yield fits to particle ratio fits in GCE plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter Tch between results from particle yield fits to particle ratio fits in GCE plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Chemical freeze-out parameter γS plotted vs ⟨Npart⟩ in SCE for particle yields fit. Uncertainties represent systematic errors.
Chemical freeze-out parameter μB plotted vs ⟨Npart⟩ in SCE for particle yields fit. Uncertainties represent systematic errors.
Chemical freeze-out parameter Tch plotted vs ⟨Npart⟩ in SCE for particle yields fit. Uncertainties represent systematic errors.
Chemical freeze-out parameter R plotted vs ⟨Npart⟩ in SCE for particle yields fit. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter γS between yield and ratio fits in SCE plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter μB between yield and ratio fits in SCE plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter Tch between yield and ratio fits in SCE plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter γS between GCE and SCE results using particle ratios in fits plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter μB between GCE and SCE results using particle ratios in fits plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter Tch between GCE and SCE results using particle ratios in fits plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter γS between GCE and SCE results using particle yields in fits plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter μB between GCE and SCE results using particle yields in fits plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter Tch between GCE and SCE results using particle yields in fits plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Ratio of chemical freeze-out parameter R between GCE and SCE results using particle yields in fits plotted vs ⟨Npart⟩. Uncertainties represent systematic errors.
Extracted chemical freeze-out temperature vs baryon chemical potential for (a) GCE and (b) SCE cases using particle yields as input for fitting. Curves represent two model predictions [81,82]. The gray bands represent the theoretical prediction ranges of the Cleymans et al. model [81]. Uncertainties represent systematic errors.
Extracted chemical freeze-out temperature vs baryon chemical potential for (a) GCE and (b) SCE cases using particle yields as input for fitting. Curves represent two model predictions [81,82]. The gray bands represent the theoretical prediction ranges of the Cleymans et al. model [81]. Uncertainties represent systematic errors.
Extracted chemical freeze-out temperature vs baryon chemical potential for (a) GCE and (b) SCE cases using particle yields as input for fitting. Curves represent two model predictions [81,82]. The gray bands represent the theoretical prediction ranges of the Cleymans et al. model [81]. Uncertainties represent systematic errors.
"Choice on constraints: Extracted chemical freeze-out temperatures shown in panels (a), (c), and (e) and baryon chemical potentials shown in panels (b), (d), and (f) for GCE using particle yields as input for fitting, respectively, for Au+Au collisions at √sNN = 7.7, 19.6, and 39 GeV. Results are compared for three initial conditions: μQ = 0, μQ constrained to B/2Q value, and μQ constrained to B/2Q along with μS constrained to 0. Uncertainties represent systematic errors."
"Choice on constraints: Extracted chemical freeze-out temperatures shown in panels (a), (c), and (e) and baryon chemical potentials shown in panels (b), (d), and (f) for GCE using particle yields as input for fitting, respectively, for Au+Au collisions at √sNN = 7.7, 19.6, and 39 GeV. Results are compared for three initial conditions: μQ = 0, μQ constrained to B/2Q value, and μQ constrained to B/2Q along with μS constrained to 0. Uncertainties represent systematic errors."
"Choice on constraints: Extracted chemical freeze-out temperatures shown in panels (a), (c), and (e) and baryon chemical potentials shown in panels (b), (d), and (f) for GCE using particle yields as input for fitting, respectively, for Au+Au collisions at √sNN = 7.7, 19.6, and 39 GeV. Results are compared for three initial conditions: μQ = 0, μQ constrained to B/2Q value, and μQ constrained to B/2Q along with μS constrained to 0. Uncertainties represent systematic errors."
"Choice on constraints: Extracted chemical freeze-out temperatures shown in panels (a), (c), and (e) and baryon chemical potentials shown in panels (b), (d), and (f) for GCE using particle yields as input for fitting, respectively, for Au+Au collisions at √sNN = 7.7, 19.6, and 39 GeV. Results are compared for three initial conditions: μQ = 0, μQ constrained to B/2Q value, and μQ constrained to B/2Q along with μS constrained to 0. Uncertainties represent systematic errors."
"Choice on constraints: Extracted chemical freeze-out temperatures shown in panels (a), (c), and (e) and baryon chemical potentials shown in panels (b), (d), and (f) for GCE using particle yields as input for fitting, respectively, for Au+Au collisions at √sNN = 7.7, 19.6, and 39 GeV. Results are compared for three initial conditions: μQ = 0, μQ constrained to B/2Q value, and μQ constrained to B/2Q along with μS constrained to 0. Uncertainties represent systematic errors."
"Choice on constraints: Extracted chemical freeze-out temperatures shown in panels (a), (c), and (e) and baryon chemical potentials shown in panels (b), (d), and (f) for GCE using particle yields as input for fitting, respectively, for Au+Au collisions at √sNN = 7.7, 19.6, and 39 GeV. Results are compared for three initial conditions: μQ = 0, μQ constrained to B/2Q value, and μQ constrained to B/2Q along with μS constrained to 0. Uncertainties represent systematic errors."
"Choice on including more particles: Extracted chemical freeze-out parameters (a) Tch, (b) μB, and (c) γS along with (d) χ2/ndf for GCE using particle yields as input for fitting. Results are compared for Au+Au collisions at √sNN = 39 GeV for four different sets of particle yields used in fitting. Uncertainties represent systematic errors."
"Choice on including more particles: Extracted chemical freeze-out parameters (a) Tch, (b) μB, and (c) γS along with (d) χ2/ndf for GCE using particle yields as input for fitting. Results are compared for Au+Au collisions at √sNN = 39 GeV for four different sets of particle yields used in fitting. Uncertainties represent systematic errors."
"Choice on including more particles: Extracted chemical freeze-out parameters (a) Tch, (b) μB, and (c) γS along with (d) χ2/ndf for GCE using particle yields as input for fitting. Results are compared for Au+Au collisions at √sNN = 39 GeV for four different sets of particle yields used in fitting. Uncertainties represent systematic errors."
"Choice on including more particles: Extracted chemical freeze-out parameters (a) Tch, (b) μB, and (c) γS along with (d) χ2/ndf for GCE using particle yields as input for fitting. Results are compared for Au+Au collisions at √sNN = 39 GeV for four different sets of particle yields used in fitting. Uncertainties represent systematic errors."
"Blast wave model fits of π±, K±, p and p p¯ T spectra in 0–5% central Au+Au collisions at √sNN = (a) 7.7, (b) 11.5, (c) 19.6, (d) 27, and (e) 39 GeV. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature. Here, the uncertainties are smaller than the symbol size."
"Blast wave model fits of π±, K±, p and p p¯ T spectra in 0–5% central Au+Au collisions at √sNN = (a) 7.7, (b) 11.5, (c) 19.6, (d) 27, and (e) 39 GeV. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature. Here, the uncertainties are smaller than the symbol size."
"Blast wave model fits of π±, K±, p and p p¯ T spectra in 0–5% central Au+Au collisions at √sNN = (a) 7.7, (b) 11.5, (c) 19.6, (d) 27, and (e) 39 GeV. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature. Here, the uncertainties are smaller than the symbol size."
"Blast wave model fits of π±, K±, p and p p¯ T spectra in 0–5% central Au+Au collisions at √sNN = (a) 7.7, (b) 11.5, (c) 19.6, (d) 27, and (e) 39 GeV. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature. Here, the uncertainties are smaller than the symbol size."
"Blast wave model fits of π±, K±, p and p p¯ T spectra in 0–5% central Au+Au collisions at √sNN = (a) 7.7, (b) 11.5, (c) 19.6, (d) 27, and (e) 39 GeV. Uncertainties on experimental data represent statistical and systematic uncertainties added in quadrature. Here, the uncertainties are smaller than the symbol size."
"Variation of Tkin with <β> for different energies and centralities. The centrality increases from left to right for a given energy. The data points other than BES energies are taken from Refs. [43,66]. Uncertainties represent systematic uncertainties."
"Variation of Tkin with <β> for different energies and centralities. The centrality increases from left to right for a given energy. The data points other than BES energies are taken from Refs. [43,66]. Uncertainties represent systematic uncertainties."
"Variation of Tkin with <β> for different energies and centralities. The centrality increases from left to right for a given energy. The data points other than BES energies are taken from Refs. [43,66]. Uncertainties represent systematic uncertainties."
"Variation of Tkin with <β> for different energies and centralities. The centrality increases from left to right for a given energy. The data points other than BES energies are taken from Refs. [43,66]. Uncertainties represent systematic uncertainties."
"Variation of Tkin with <β> for different energies and centralities. The centrality increases from left to right for a given energy. The data points other than BES energies are taken from Refs. [43,66]. Uncertainties represent systematic uncertainties."
" (a) Energy dependence of kinetic and chemical freezeout temperatures for central heavy-ion collisions. The curves represent various theoretical predictions [81,82]. (b) Energy dependence of average transverse radial flow velocity for central heavy-ion collisions. The data points other than BES energies are taken from Refs. [43,53–64,66] and references therein. The BES data points are for 0–5% central collisions, AGS energies are mostly for 0–5%, SPS energies are for mostly 0–7%, and top RHIC and LHC energies are for 0–5% central collisions. Uncertainties represent systematic uncertainties."
The extreme temperatures and energy densities generated by ultra-relativistic collisions between heavy nuclei produce a state of matter with surprising fluid properties. Non-central collisions have angular momentum on the order of 1000$\hbar$, and the resulting fluid may have a strong vortical structure that must be understood to properly describe the fluid. It is also of particular interest because the restoration of fundamental symmetries of quantum chromodynamics is expected to produce novel physical effects in the presence of strong vorticity. However, no experimental indications of fluid vorticity in heavy ion collisions have so far been found. Here we present the first measurement of an alignment between the angular momentum of a non-central collision and the spin of emitted particles, revealing that the fluid produced in heavy ion collisions is by far the most vortical system ever observed. We find that $\Lambda$ and $\overline{\Lambda}$ hyperons show a positive polarization of the order of a few percent, consistent with some hydrodynamic predictions. A previous measurement that reported a null result at higher collision energies is seen to be consistent with the trend of our new observations, though with larger statistical uncertainties. These data provide the first experimental access to the vortical structure of the "perfect fluid" created in a heavy ion collision. They should prove valuable in the development of hydrodynamic models that quantitatively connect observations to the theory of the Strong Force. Our results extend the recent discovery of hydrodynamic spin alignment to the subatomic realm.
Lambda and AntiLambda polarization as a function of collision energy. A 0.8% error on the alpha value used in the paper is corrected in this table. Systematic error bars include those associated with particle identification (negligible), uncertainty in the value of the hyperon decay parameter (2%) and reaction plane resolution (2%) and detector efficiency corrections (4%). The dominant systematic error comes from statistical fluctuations of the estimated combinatoric background under the (anti-)$\Lambda$ mass peak.
Lambda and AntiLambda polarization as a function of collision energy calculated using the new $\alpha_\Lambda=0.732$ updated on PDG2020. Systematic error bars include those associated with particle identification (negligible), uncertainty in the value of the hyperon decay parameter (2%) and reaction plane resolution (2%) and detector efficiency corrections (4%). The dominant systematic error comes from statistical fluctuations of the estimated combinatoric background under the (anti-)$\Lambda$ mass peak.
We present measurements of three-particle correlations for various harmonics in Au+Au collisions at energies ranging from $\sqrt{s_{{\rm NN}}}=7.7$ to 200 GeV using the STAR detector. The quantity $\langle\cos(m\phi_1+n\phi_2-(m+n)\phi_3)\rangle$ is evaluated as a function of $\sqrt{s_{{\rm NN}}}$, collision centrality, transverse momentum, $p_T$, pseudo-rapidity difference, $\Delta\eta$, and harmonics ($m$ and $n$). These data provide detailed information on global event properties like the three-dimensional structure of the initial overlap region, the expansion dynamics of the matter produced in the collisions, and the transport properties of the medium. A strong dependence on $\Delta\eta$ is observed for most harmonic combinations consistent with breaking of longitudinal boost invariance. Data reveal changes with energy in the two-particle correlation functions relative to the second-harmonic event-plane and provide ways to constrain models of heavy-ion collisions over a wide range of collision energies.
We present measurements of 2$^{nd}$ order azimuthal anisotropy ($v_{2}$) at mid-rapidity $(|y|<1.0)$ for light nuclei d, t, $^{3}$He (for $\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV) and anti-nuclei $\bar{\rm d}$ ($\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, and 19.6 GeV) and $^{3}\bar{\rm He}$ ($\sqrt{s_{NN}}$ = 200 GeV) in the STAR (Solenoidal Tracker at RHIC) experiment. The $v_{2}$ for these light nuclei produced in heavy-ion collisions is compared with those for p and $\bar{\rm p}$. We observe mass ordering in nuclei $v_{2}(p_{T})$ at low transverse momenta ($p_{T}<2.0$ GeV/$c$). We also find a centrality dependence of $v_{2}$ for d and $\bar{\rm d}$. The magnitude of $v_{2}$ for t and $^{3}$He agree within statistical errors. Light-nuclei $v_{2}$ are compared with predictions from a blast wave model. Atomic mass number ($A$) scaling of light-nuclei $v_{2}(p_{T})$ seems to hold for $p_{T}/A < 1.5$ GeV/$c$. Results on light-nuclei $v_{2}$ from a transport-plus-coalescence model are consistent with the experimental measurements.
We present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in Au+Au collisions for energies ranging from $\sqrt{s_{NN}}=7.7$ GeV to 200 GeV. The third harmonic $v_3^2\{2\}=\langle \cos3(\phi_1-\phi_2)\rangle$, where $\phi_1-\phi_2$ is the angular difference in azimuth, is studied as a function of the pseudorapidity difference between particle pairs $\Delta\eta = \eta_1-\eta_2$. Non-zero {\vthree} is directly related to the previously observed large-$\Delta\eta$ narrow-$\Delta\phi$ ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity Quark Gluon Plasma (QGP) phase. For sufficiently central collisions, $v_3^2\{2\}$ persist down to an energy of 7.7 GeV suggesting that QGP may be created even in these low energy collisions. In peripheral collisions at these low energies however, $v_3^2\{2\}$ is consistent with zero. When scaled by pseudorapidity density of charged particle multiplicity per participating nucleon pair, $v_3^2\{2\}$ for central collisions shows a minimum near {\snn}$=20$ GeV.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Npart values are for the corresponding centrality at 200 GeV.
Npart values are for the corresponding centrality at 200 GeV.
Npart values are for the corresponding centrality at 200 GeV.
Npart values are for the corresponding centrality at 200 GeV.
Npart values are for the corresponding centrality at 200 GeV.
Npart values are for the corresponding centrality at 200 GeV.
Npart values are for the corresponding centrality at 200 GeV.
Npart values are for the corresponding centrality at 200 GeV.
No description provided.
Elliptic flow (v_2) values for identified particles at midrapidity in Au + Au collisions measured by the STAR experiment in the Beam Energy Scan at the Relativistic Heavy Ion Collider at sqrt{s_{NN}}= 7.7--62.4 GeV are presented for three centrality classes. The centrality dependence and the data at sqrt{s_{NN}}= 14.5 GeV are new. Except at the lowest beam energies we observe a similar relative v_2 baryon-meson splitting for all centrality classes which is in agreement within 15% with the number-of-constituent quark scaling. The larger v_2 for most particles relative to antiparticles, already observed for minimum bias collisions, shows a clear centrality dependence, with the largest difference for the most central collisions. Also, the results are compared with A Multiphase Transport Model and fit with a Blast Wave model.
The difference in $v_{2}$ between particles (X) and their corresponding antiparticles $\bar{X}$ (see legend) as a function of $\sqrt{s_{NN}}$ for 10%-40% central Au + Au collisions. The systematic errors are shown by the hooked error bars. The dashed lines in the plot are fits with a power-law function.
No description provided.
The difference in $v_{2}$ between protons and antiprotons as a function of $\sqrt{s_{NN}}$ for 0%-10%, 10%-40% and 40%-80% central Au + Au collisions. The systematic errors are shown by the hooked error bars. The dashed lines in the plot are fits with a power-law function.
No description provided.
The relative difference. The systematic errors are shown by the hooked error bars. The dashed lines in the plot are fits with a power-law function.
No description provided.
The $v_{2}$ difference between protons and antiprotons (and between $\pi^{+}$ and $pi^{-}$) for 10%-40% centrality Au+Au collisions at 7.7, 11.5, 14.5, and 19.6 GeV. The $v_{2}{BBC} results were slightly shifted horizontally.
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Balance functions have been measured in terms of relative pseudorapidity ($\Delta \eta$) for charged particle pairs at the Relativistic Heavy-Ion Collider (RHIC) from Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7 GeV to 200 GeV using the STAR detector. These results are compared with balance functions measured at the Large Hadron Collider (LHC) from Pb+Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV by the ALICE Collaboration. The width of the balance function decreases as the collisions become more central and as the beam energy is increased. In contrast, the widths of the balance functions calculated using shuffled events show little dependence on centrality or beam energy and are larger than the observed widths. Balance function widths calculated using events generated by UrQMD are wider than the measured widths in central collisions and show little centrality dependence. The measured widths of the balance functions in central collisions are consistent with the delayed hadronization of a deconfined quark gluon plasma (QGP). The narrowing of the balance function in central collisions at $\sqrt{s_{\rm NN}}$ = 7.7 GeV implies that a QGP is still being created at this relatively low energy.
We present measurements of $\Omega$ and $\phi$ production at mid-rapidity from Au+Au collisions at nucleon-nucleon center-of-mass energies $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27 and 39 GeV by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). Motivated by the coalescence formation mechanism for these strange hadrons, we study the ratios of $N(\Omega^{-}+\Omega^{+})/(2N(\phi))$. These ratios as a function of transverse momentum ($p_T$) fall on a consistent trend at high collision energies, but start to show deviations in peripheral collisions at $\sqrt{s_{NN}}$ = 19.6, 27 and 39 GeV, and in central collisions at 11.5 GeV in the intermediate $p_T$ region of 2.4-3.6 GeV/c. We further evaluate empirically the strange quark $p_T$ distributions at hadronization by studying the $\Omega/\phi$ ratios scaled by the number of constituent quarks. The NCQ-scaled $\Omega/\phi$ ratios show a suppression of strange quark production in central collisions at 11.5 GeV compared to $\sqrt{s_{NN}} >= 19.6$ GeV. The shapes of the presumably thermal strange quark distributions in 0-60% most central collisions at 7.7 GeV show significant deviations from those in 0-10% most central collisions at higher energies. These features suggest that there is likely a change of the underlying strange quark dynamics in the transition from quark-matter to hadronic matter at collision energies below 19.6 GeV.
Phi Meson Spectra.
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ks(pTs) = N(Omega+Anti-Omega)_(pT=3pTs)/2N(phi)_(pT=2pTs) N is the invariant yield.
ks(pTs) = N(Omega+Anti-Omega)_(pT=3pTs)/2N(phi)_(pT=2pTs) N is the invariant yield.
ks(pTs) = N(Omega+Anti-Omega)_(pT=3pTs)/2N(phi)_(pT=2pTs) N is the invariant yield.
ks(pTs) = N(Omega+Anti-Omega)_(pT=3pTs)/2N(phi)_(pT=2pTs) N is the invariant yield.
ks(pTs) = N(Omega+Anti-Omega)_(pT=3pTs)/2N(phi)_(pT=2pTs) N is the invariant yield.
ks(pTs) = N(Omega+Anti-Omega)_(pT=3pTs)/2N(phi)_(pT=2pTs) N is the invariant yield.
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