C. Anson

Energy dependence of the freeze-out eccentricity from the azimuthal dependence of HBT at STAR

Non-central heavy-ion collisions create an out-of-plane-extended participant zone that expands toward a more round state as the system evolves. The recent RHIC beam energy scan at of 7.7, 11.5 and 39 GeV provides an opportunity to explore the energy dependence of the freeze-out eccentricity. The new low-energy data from STAR complement high statistics data sets at of 62.4 and 200 GeV. Hanbury Brown–Twiss (HBT) interferometry allows us to determine the size of pion-emitting source regions. The dependence of the HBT radius parameters on the azimuthal angle relative to the reaction plane has been extracted. These dependences can be related to the freeze-out eccentricity. The new results from STAR are consistent with a monotonically decreasing freeze-out eccentricity and constrain any minimum, suggested by previously available data, to lie in the range between 11.5 and 39 GeV. Of several models, UrQMD appears to best predict the STAR and AGS data.

Elliptic flow of identified hadrons in Au+Au collisions at √sNN=7.7–62.4 GeV

Measurements of the elliptic flow, upsilon(2), of identified hadrons (pi(+/-), K-+/-, K-s(0), p, (p) over bar, phi, Lambda, (Lambda) over bar, Xi(-), (Xi) over bar (+), Omega(-), (Omega) over bar (+)) in Au + Au collisions at root s(NN) = 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV are presented. The measurements were done at midrapidity using the time-projection chamber and the time-of-flight detectors of the Solenoidal Tracker at RHIC experiment during the beam-energy scan program at Relativistic Heavy Ion Collider. A significant difference in the upsilon(2) values for particles and the corresponding antiparticles was observed at all transverse momenta for the first time. The difference increases with decreasing center-of-mass energy, root s(NN) (or increasing baryon chemical potential, mu(B)), and is larger for the baryons as compared to the mesons. This implies that particles and antiparticles are no longer consistent with the universal number-of-constituent quark (NCQ) scaling of upsilon(2) that was observed at root s(NN) = 200 GeV. However, for the selected group of particles (p(+), K+, K-s(0), p, Lambda, Xi(-), Omega(-)) NCQ scaling at (m(T) - m(0))/n(q) > 0.4 GeV/c(2) is not violated within +/- 10%. The upsilon(2) values for f mesons at 7.7 and 11.5 GeV are approximately two standard deviations from the trend defined by the other hadrons at the highest measured p(T) values.

Transverse Momentum Distribution and Nuclear Modification Factor of Charged Particles in p plus Pb Collisions at root(NN)-N-s=5.02 TeV

The transverse momentum (p(T)) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p+Pb collisions at sqrt[s(NN)]=5.02 TeV with the ALICE detector at the LHC. The p(T) spectra measured near central rapidity in the range 0.5<p(T) <20 GeV/c exhibit a weak pseudorapidity dependence. The nuclear modification factor R(pPb) is consistent with unity for p(T) above 2 GeV/c. This measurement indicates that the strong suppression of hadron production at high p(T) observed in Pb+Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.

Production of Σ (1385)±and Ξ (1530)0in p–Pb collisions at √sNN=5.02 TeV

The transverse momentum distributions of the strange and double-strange hyperon resonances ([Formula: see text], [Formula: see text]) produced in p-Pb collisions at [Formula: see text] TeV were measured in the rapidity range [Formula: see text] for event classes corresponding to different charged-particle multiplicity densities, [Formula: see text]d[Formula: see text]/d[Formula: see text]. The mean transverse momentum values are presented as a function of [Formula: see text]d[Formula: see text]/d[Formula: see text], as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of [Formula: see text]d[Formula: see text]/d[Formula: see text]. The equivalent ratios to pions exhibit an increase with [Formula: see text]d[Formula: see text]/d[Formula: see text], depending on their strangeness content.The transverse momentum distributions of the strange and double-strange hyperon resonances (

Jet-Hadron Correlations in sqrt{s_{NN}} = 200 GeV Au+Au and p+p Collisions

\Sigma (1385)^{\pm }

Fluctuations of charge separation perpendicular to the event plane and local parity violation in sqrt(sNN)=200 GeV Au+Au collisions at RHIC

Σ(1385)±,

First measurement of Ξc0production in pp collisions at s=7 TeV

\Xi (1530)^{0}