M. M. de Moura

The results from the STAR Collaboration on directed flow (${v}_{1}$), elliptic flow (${v}_{2}$), and the fourth harmonic (${v}_{4}$) in the anisotropic azimuthal distribution of particles from Au+Au collisions at $\sqrt{{s}_{\mathit{NN}}}=200\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ are summarized and compared with results from other experiments and theoretical models. Results for identified particles are presented and fit with a blast-wave model. Different anisotropic flow analysis methods are compared and nonflow effects are extracted from the data. For ${v}_{2}$, scaling with the number of constituent quarks and parton coalescence are discussed. For ${v}_{4}$, scaling with ${v}_{2}^{2}$ and quark coalescence are discussed.

The STAR collaboration at the BNL Relativistic Heavy-Ion Collider (RHIC) reports measurements of the inclusive yield of nonphotonic electrons, which arise dominantly from semileptonic decays of heavy flavor mesons, over a broad range of transverse momenta ($1.2<{p}_{T}<10\text{ }\text{ }\mathrm{GeV}/c$) in $p+p$, $d+\mathrm{Au}$, and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{\mathrm{NN}}}=200\text{ }\text{ }\mathrm{GeV}$. The nonphotonic electron yield exhibits an unexpectedly large suppression in central $\mathrm{Au}+\mathrm{Au}$ collisions at high ${p}_{T}$, suggesting substantial heavy-quark energy loss at RHIC. The centrality and ${p}_{T}$ dependences of the suppression provide constraints on theoretical models of suppression.

We present strange particle spectra and yields measured at midrapidity in $\sqrt{s}=200$ GeV proton-proton ($p+p$) collisions at the BNL Relativistic Heavy Ion Collider (RHIC). We find that the previously observed universal transverse mass (${m}_{T}\ensuremath{\equiv}\sqrt{{{p}_{T}}^{2}+{m}^{2}}$) scaling of hadron production in $p+p$ collisions seems to break down at higher ${m}_{T}$ and that there is a difference in the shape of the ${m}_{T}$ spectrum between baryons and mesons. We observe midrapidity antibaryon to baryon ratios near unity for \ensuremath{\Lambda} and \ensuremath{\Xi} baryons and no dependence of the ratio on transverse momentum, indicating that our data do not yet reach the quark-jet dominated region. We show the dependence of the mean transverse momentum $\ensuremath{\langle}{p}_{T}\ensuremath{\rangle}$ on measured charged particle multiplicity and on particle mass and infer that these trends are consistent with gluon-jet dominated particle production. The data are compared with previous measurements made at the CERN Super Proton Synchrotron and Intersecting Storage Rings and in Fermilab experiments and with leading-order and next-to-leading-order string fragmentation model predictions. We infer from these comparisons that the spectral shapes and particle yields from $p+p$ collisions at RHIC energies have large contributions from gluon jets rather than from quark jets.

Transverse momentum spectra of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, $p$, and $\overline{p}$ up to $12\text{ }\text{ }\mathrm{GeV}/c$ at midrapidity in centrality selected $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$ are presented. In central $\mathrm{Au}+\mathrm{Au}$ collisions, both ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and $p(\overline{p})$ show significant suppression with respect to binary scaling at ${p}_{T}\ensuremath{\gtrsim}4\text{ }\text{ }\mathrm{GeV}/c$. Protons and antiprotons are less suppressed than ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, in the range $1.5\ensuremath{\lesssim}{p}_{T}\ensuremath{\lesssim}6\text{ }\text{ }\mathrm{GeV}/c$. The ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ and $\overline{p}/p$ ratios show at most a weak ${p}_{T}$ dependence and no significant centrality dependence. The $p/\ensuremath{\pi}$ ratios in central $\mathrm{Au}+\mathrm{Au}$ collisions approach the values in $p+p$ and $d+\mathrm{Au}$ collisions at ${p}_{T}\ensuremath{\gtrsim}5\text{ }\text{ }\mathrm{GeV}/c$. The results at high ${p}_{T}$ indicate that the partonic sources of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, $p$, and $\overline{p}$ have similar energy loss when traversing the nuclear medium.