In this erratum we report changes on the $D^0$ $p_T$ spectra and nuclear modification factor ($R_{AA}$) in Au+Au collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV by fixing the errors in the efficiency and selection criteria that affected the Au+Au results. The p+p reference spectrum has changed as well and is updated with new fragmentation parameters.
$D^0$ $p_{\rm T}$ differential invariant yield in p+p collisions (open circles), which has been updated with the latest global analysis of charm fragmentation ratios from Ref and also taking into account the $p_{\rm T}$ dependence of the fragmentation ratio between $D^0$ and $D^{*{\pm}}$ from PYTHIA 6.4. The systematic uncertainties are shown as square brackets.
Centrality dependence of the $D^0$ $p_{\rm T}$ differential invariant yield in Au+Au collisions (solid symbols). The curves are number-of-binary-collision-scaled Levy functions from fitting to the p+p result (open circles), which has been updated with the latest global analysis of charm fragmentation ratios from Ref and also taking into account the $p_{\rm T}$ dependence of the fragmentation ratio between $D^0$ and $D^{*{\pm}}$ from PYTHIA 6.4. The arrow denotes the upper limit with 90% confidence level of the last data point for 10$-$40% collisions. The systematic uncertainties are shown as square brackets.
Panels (ab), $D^0$ $R_{\rm AA}$ for peripheral 40$-$80% and semi a central 10$-$40% collisions; Panel (c), $D^0$ $R_{\rm AA}$ for 0$-$10% most central events (blue circles) compared with model calculations from the TAMU (solid curve), SUBATECH (dashed curve), Torino (dot-dashed curve), Duke (long-dashed and long-dot-dashed curves), and LANL groups (filled band). The open symbol indicates the result with the extrapolated p+p reference. The vertical lines and brackets around the data points denote the statistical and systematic uncertainties respectively. The vertical bars around unity denote the overall normalization uncertainties in the Au+Au and p+p data, respectively. The $R_{\rm AA}$ probability distribution for the 0$-$0.7 GeV/$c$ data point is largely skewed. The uncertainty we report is the 68.3% probability range with respect to the measured central value assuming Gaussian distribution.
We present results on strange and multi-strange particle production in Au+Au collisions at $\sqrt{s_{NN}}=62.4$ GeV as measured with the STAR detector at RHIC. Mid-rapidity transverse momentum spectra and integrated yields of $K^{0}_{S}$, $\Lambda$, $\Xi$, $\Omega$ and their anti-particles are presented for different centrality classes. The particle yields and ratios follow a smooth energy dependence. Chemical freeze-out parameters, temperature, baryon chemical potential and strangeness saturation factor obtained from the particle yields are presented. Intermediate transverse momentum ($p_T$) phenomena are discussed based on the ratio of the measured baryon-to-meson spectra and nuclear modification factor. The centrality dependence of various measurements presented show a similar behavior as seen in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV.
Correction factors (acceptance × efficiency) for the most central events ( 0−5% for KS0, Λ and Ξ; 0−20% for Ω) at mid-rapidity (|y| < 1) as a function of pT for the different particle species as obtained via embedding. The branching ratio of the measured decay channel is not factored into this plot.
Correction factors (acceptance × efficiency) for the most central events ( 0−5% for KS0, Λ and Ξ; 0−20% for Ω) at mid-rapidity (|y| < 1) as a function of pT for the different particle species as obtained via embedding. The branching ratio of the measured decay channel is not factored into this plot.
Efficiency corrected pT spectra for the different centrality bins and for the various particles. Note that 7 centrality bins have been used for the KS0 and the Λ while only 6 and 3 have been used for the Ξ and Ω, respectively. Errors are statistical only. The Λ spectra are corrected for the feed-down of the Ξ decay.
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.
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.
No description provided.
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.
We present first measurements of the evolution of the differential transverse momentum correlation function, {\it C}, with collision centrality in Au+Au interactions at $\sqrt{s_{NN}} = 200$ GeV. {\it C} exhibits a strong dependence on collision centrality that is qualitatively similar to that of number correlations previously reported. We use the observed longitudinal broadening of the near-side peak of {\it C} with increasing centrality to estimate the ratio of the shear viscosity to entropy density, $\eta/s$, of the matter formed in central Au+Au interactions. We obtain an upper limit estimate of $\eta/s$ that suggests that the produced medium has a small viscosity per unit entropy.
The correlation function C, C is plotted in units of (GeV/c)$^2$ and the relative azimuthal angle ∆φ in radians for 70-80% centrality in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Relative statistical errors range from 0.8% in peripheral collisions to 0.9% in the most central collisions at the peak of the distribution.
The correlation function C, C is plotted in units of (GeV/c)$^2$ and the relative azimuthal angle ∆φ in radians for 70-80% centrality in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Relative statistical errors range from 0.8% in peripheral collisions to 0.9% in the most central collisions at the peak of the distribution.
The correlation function C, C is plotted in units of (GeV/c)$^2$ and the relative azimuthal angle ∆φ in radians for 30-40% centrality in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Relative statistical errors range from 0.8% in peripheral collisions to 0.9% in the most central collisions at the peak of the distribution.
We report STAR results on the azimuthal anisotropy parameter v2 for strange particles K0S, L and Lbar at midrapidity in Au+Au collisions at sNN = 130 GeV at RHIC. The value of v2 as a function of transverse momentum of the produced particles pt and collision centrality is presented for both particles up to pt 3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2 measurement is compared with hydrodynamic model calculations. The physics implications of the pt integrated v2 magnitude as a function of particle mass are also discussed.
$v_2$ of $K_s^0$ as a function of $p_T$ for 0-11% centrality in Au+Au collisions at 130 GeV. Systematic errors of $\pm$0.005 for particle identification and background subtraction and $^{+0}_{-0.005}$ for nonflow effects.
$v_2$ of $K_s^0$ as a function of $p_T$ for 11-45% centrality in Au+Au collisions at 130 GeV. Systematic errors of $\pm$0.005 for particle identification and background subtraction and $^{+0}_{-0.005}$ for nonflow effects.
$v_2$ of $\Lambda+\bar{\Lambda}$ as a function of $p_T$ for 0-11% centrality in Au+Au collisions at 130 GeV. Systematic errors of $\pm$0.005 for particle identification and background subtraction and $^{+0}_{-0.005}$ for nonflow effects.
We report the first observations of the first harmonic (directed flow, v_1), and the fourth harmonic (v_4), in the azimuthal distribution of particles with respect to the reaction plane in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). Both measurements were done taking advantage of the large elliptic flow (v_2) generated at RHIC. From the correlation of v_2 with v_1 it is determined that v_2 is positive, or {\it in-plane}. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.
$v_1$ of charged particles as a function of pseudorapidity for 10-70% centrality. Non-flow systematic uncertainties are approximately 20%.
$v_2$ with respect to the second harmonic event plane as a function of $p_T$ for the minimum bias Au+Au collisions. Background from secondary particles is expected to be less than 15%. Non-flow systematic uncertainties are approximately 20%. Fluctuations in initial geometry can lead to an effect of about a factor of 1.2 to 1.5.
$v_4$ with respect to the second harmonic event plane as a function of $p_T$ for the minimum bias Au+Au collisions. Background from secondary particles is expected to be less than 15%. Non-flow systematic uncertainties are approximately 20%. Fluctuations in initial geometry can lead to an effect of about a factor of 1.2 to 1.5.
We report on K*0 production at mid-rapidity in Au+Au and Cu+Cu collisions at \sqrt{s_{NN}} = 62.4 and 200 GeV collected by the Solenoid Tracker at RHIC (STAR) detector. The K*0 is reconstructed via the hadronic decays K*0 \to K+ pi- and \bar{K*0} \to K-pi+. Transverse momentum, pT, spectra are measured over a range of pT extending from 0.2 GeV/c to 5 GeV/c. The center of mass energy and system size dependence of the rapidity density, dN/dy, and the average transverse momentum, <pT>, are presented. The measured N(K*0)/N(K) and N(\phi)/N(K*0) ratios favor the dominance of re-scattering of decay daughters of K*0 over the hadronic regeneration for the K*0 production. In the intermediate pT region (2.0 < pT < 4.0 GeV/c), the elliptic flow parameter, v2, and the nuclear modification factor, RCP, agree with the expectations from the quark coalescence model of particle production.
The K$\pi$ pair invariant mass distribution integrated over the $K^{*0}$ $p_T$ for minimum bias Au+Au collisions at $\sqrt{s_{NN}}$ =200 GeV after mixed-event background subtraction.
The K$\pi$ pair invariant mass distribution integrated over the $K^{*0}$ $p_T$ for minimum bias Au+Au collisions at $\sqrt{s_{NN}}$ =62.4 GeV after mixed-event background subtraction.
The K$\pi$ pair invariant mass distribution integrated over the $K^{*0}$ $p_T$ for minimum bias Cu+Cu collisions at $\sqrt{s_{NN}}$ =200 GeV after mixed-event background subtraction.
Rapidity-odd directed flow($v_1$) measurements for charged pions, protons and antiprotons near mid-rapidity ($y=0$) are reported in $\sqrt{s_{NN}} =$ 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV Au + Au collisions as recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). At intermediate impact parameters, the proton and net-proton slope parameter $dv_1/dy|_{y=0}$ shows a minimum between 11.5 and 19.6 GeV. In addition, the net-proton $dv_1/dy|_{y=0}$ changes sign twice between 7.7 and 39 GeV. The proton and net-proton results qualitatively resemble predictions of a hydrodynamic model with a first-order phase transition from hadronic matter to deconfined matter, and differ from hadronic transport calculations.
Directed flow for protons versus rapidity for central (0-10$\%$), intermediate-centrality (10-40$\%$) and peripheral (40-80$\%$) Au+Au collisions at $\sqrt{s_{NN}}$ = 39, 27, 19.6, 11.5 and 7.7 GeV. Errors are statistical only.
Directed flow for $\pi^{-}$ versus rapidity for central (0-10$\%$), intermediate-centrality (10-40$\%$) and peripheral (40-80$\%$) Au+Au collisions at $\sqrt{s_{NN}}$ = 39, 27, 19.6, 11.5 and 7.7 GeV. Errors are statistical only.
Directed flow for protons and anti-protons versus rapidity for intermediate-centrality (10-40$\%$) Au+Au collisions at $\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5 and 7.7 GeV. Errors are statistical only.
The transversity distribution, which describes transversely polarized quarks in transversely polarized nucleons, is a fundamental component of the spin structure of the nucleon, and is only loosely constrained by global fits to existing semi-inclusive deep inelastic scattering (SIDIS) data. In transversely polarized $p^\uparrow+p$ collisions it can be accessed using transverse polarization dependent fragmentation functions which give rise to azimuthal correlations between the polarization of the struck parton and the final state scalar mesons. This letter reports on spin dependent di-hadron correlations measured by the STAR experiment. The new dataset corresponds to 25 pb$^{-1}$ integrated luminosity of $p^\uparrow+p$ collisions at $\sqrt{s}=500$ GeV, an increase of more than a factor of ten compared to our previous measurement at $\sqrt{s}=200$ GeV. Non-zero asymmetries sensitive to transversity are observed at a $Q^2$ of several hundred GeV and are found to be consistent with the former measurement and a model calculation. %we observe consistent with the former measurement are observed.} We expect that these data will enable an extraction of transversity with comparable precision to current SIDIS datasets but at much higher momentum transfers where subleading effects are suppressed.
Squared 4-momentum transfer $Q^2$ vs x coverage of STAR .
$A_{UT}$ as a function of $\eta$ for $<p_{T}>$ = 13 GeV/c and $<M_{inv}>$ = 1 GeV/($c^2$) (Upper panel of the fig. 3). Kinematic variables $<x>$, $<z>$ as a function of $\eta$ for $<p_{T}>$ = 13 GeV/c and $<M_{inv}>$ = 1 GeV/($c^2$) (Lower panel of the fig. 3). In addition to statistical uncertainties, systematic uncertainties originating from PID and trigger bias systematic uncertainties are also mentioned for $A_{UT}$.
$A_{UT}$ as a function of $<M_{inv}>$ for pT bin $<p_{T}>$ = 4 GeV/c for $\eta > 0$ and $\eta < 0$. In addition to statistical uncertainties, systematic uncertainties originating from PID and trigger bias systematic uncertainties are also mentioned.
Forum