Pion Interferometry of $\sqrt{s_{NN}} = 130$ GeV Au+Au Collisions at RHIC

Measurements of femtoscopic correlations in high-energy heavy-ion collisions aim to unravel the space-time structure of the particle-emitting source (the quark-gluon plasma). Recent results indicate that the pion pair source exhibits a power-law behavior and can be described well by a L\'evy distribution. In this study, L\'evy fits were performed to the measured one-dimensional two-pion correlation functions in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. The three extracted ...

We investigate identical pion HBT intensity interferometry for central Au+Au collisions at 1.23A GeV. High-statistics $\pi^-\pi^-$ and $\pi^+\pi^+$ data are measured with HADES at SIS18/GSI. The radius parameters, derived from the correlation function depending on relative momenta in the longitudinal-comoving system and parametrized as three-dimensional Gaussian distribution, are studied as function of transverse momentum. A substantial charge-sign difference of the source ra...

We present results of analyses of two-pion interferometry in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV measured in the STAR detector as part of the RHIC Beam Energy Scan program. The extracted correlation lengths (HBT radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass ($m_{T}$) of the particles. The azimuthal analysis allows extraction of the eccentricity of the...

Pion-kaon correlation functions are constructed from central Au+Au data taken at $\sqrt{s_{NN}} = 130$ GeV. The results suggest that pions and kaons are not emitted at the same average space-time point. Space-momentum correlations, i.e. transverse flow, lead to a space-time emission asymmetry of pions and kaons that is consistent with the data. This result provides new independent evidence that the system created at RHIC undergoes a collective transverse expansion.

The STAR Collaboration has measured two-pion correlation functions versus emission angle with respect to the event plane in non-central Au+Au collisions at \sqrt{s_{NN}}=130, 200 GeV. In the context of a parameterized freezeout scenario, the data suggest an out-of-plane freezeout geometry, and a rapid system evolution to freezeout.

Results from a one day $\sqrt{s_{NN}} = 19.6$ GeV Au+Au test run at RHIC using the STAR detector are presented. The quality of these results from only 175,000 triggered events demonstrates some of STAR's physics capabilities for the upcoming beam energy scan at RHIC. From these 19.6 GeV Au+Au collisions, we have analyzed the transverse mass spectra of $\pi^{\pm}$, $K^{\pm}$, $p$, and $\bar{p}$ at midrapidity and $m_T - m_0$ $< 1.0$ GeV/$c^2$. We have also measured the two-pio...

We investigate the two-pion interferometry in ultrarelativistic heavy ion collisions in the granular source model of quark-gluon plasma droplets. The pion transverse momentum spectra and HBT radii of the granular sources agree well with the experimental data of the most central Au-Au collisions at $\sqrt{s_{NN}}=200$ GeV at RHIC and Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV at LHC. In the granular source model the larger initial system breakup time for the LHC collisions a...

We consistently analyze two-pion correlation functions and three-pion correlation functions of 130$A$ GeV Au+Au collisions measured at RHIC, applying three models of partially coherent pion sources. The effect of long-lived resonances on the chaoticity in the two-pion correlation function is estimated on the basis of a statistical model. We find that the chaoticity extracted from the three-pion correlation function is consistent with that extracted from the two-pion correlati...

A summary of current interferometry data in relativistic heavy ions is presented. At sqrt{s}=17GeV a sudden increase in the pion source volume is observed for central PbPb collisions. This seems to imply that the pion phase density has reached a limit. The source size of different particles decreases with mass when the transverse velocity is held constant but increases with mass when the transverse mass is held constant. The antiproton source radius is larger than the pro...

Two-pion correlations in sqrt(s_NN)=130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k_T by the PHENIX experiment at RHIC. The k_T dependent transverse radii are similar to results from heavy ion collisions at sqrt(s_NN) = 4.1, 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R_out/R_side) is consistent with unity and independe...