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

To study the nature of the quark-hadron phase transition, it is important to investigate the space-time structure of the hadron-emitting source in heavy-ion collisions. Measurements of HBT correlations have proven to be a powerful tool to gain information about the source. In these proceedings, we report the current status of the analysis of source parameters obtained from L\'evy fits to the measured one-dimensional two-pion correlation functions in Au+Au collisions at $\sqrt...

The influence of Bose-Einstein statistics on multi-particle production characterized for various systems and energies by the STAR collaboration provides interesting information about the space-time dynamics of relativistic heavy-ion collisions at RHIC. We present the centrality and transverse mass dependence measurements of the two-pion interferometry in Au+Au collisions at $\sqrt{s_{\rm{NN}}}$ = 62.4 GeV and Cu+Cu collisions at $\sqrt{s_{\rm{NN}}}$ = 62.4 GeV and 200 GeV. We...

Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory from the STAR experiment have been analyzed using three-pion correlations to study whether pions are emitted independently at freezeout. We have made a high-statistics measurement of the three-pion correlation function and calculated the normalized three-particle correlator to obtain a quantitative measurement of the degree of chaoticity in the freeze-out environment.

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 $\sqrt{s_{NN}}=200$ GeV Au-Au and $\sqrt{s_{NN}}=2.76$ TeV Pb-Pb most central collisions. In the granular source model the larger initial system breakup time may lead to the larger HBT radii $R_{\rm out}$, $R_{\rm ...

We present the preliminary results on direct photon interferometry measurements in Au+Au collisions at $\sqrt{s_{\rm{NN}}}$ = 62.4 and 200 GeV using the STAR (Solenoidal Tracker at RHIC) detector. Photons are reconstructed via $e^+/e^-$ conversions in STAR Time Projection Chamber(TPC) and energy deposited by photons in STAR Barrel Electromagnetic Calorimeter(BEMC). The two-photon correlations are measured using (1) both photons measured using BEMC; (2) one photon from convers...

In this paper, we continue our phenomenological studies of heavy-ion collisions using 3+1d anisotropic hydrodynamics (aHydro). In previous works, we compared quasiparticle aHydro (aHydroQP) with ALICE 2.76 TeV Pb-Pb and RHIC 200 GeV Au-Au collision results. At both energies, the agreement was quite good between aHydroQP and the experimental data for many observables. In this work, we present comparisons of the Hanbury Brown--Twiss (HBT) radii and their ratios determined using...

Two-pion correlation functions, measured as a function of azimuthal emission angle with respect to the reaction plane, provide novel information on the anisotropic shape and orientation of the pion-emitting zone formed in heavy ion collisions. We present the first experimental determination of this information, for semi-central Au+Au collisions at 2-6 AGeV. The source extension perpendicular to the reaction plane is greater than the extension in the plane, and tilt of the pio...

We present the results of a systematic study of the shape of the pion distribution in coordinate space at freeze-out in Au+Au collisions at RHIC using two-pion Hanbury Brown-Twiss (HBT) interferometry. Oscillations of the extracted HBT radii vs. emission angle indicate sources elongated perpendicular to the reaction plane. The results indicate that the pressure and expansion time of the collision system are not sufficient to completely quench its initial shape.

High-statistics $\pi^-\pi^-$ and $\pi^+\pi^+$ femtoscopy data are presented for Au+Au collisions at $\sqrt{s_\mathrm{NN}}=2.4$ GeV, measured with HADES at SIS18/GSI. The experimental correlation functions allow the determination of the space-time extent of the corresponding emission sources via a comparison to models. The emission source, parametrized as three-dimensional Gaussian distribution, is studied in dependence on pair transverse momentum, azimuthal emission angle wit...

The results of mid-rapidity ($0 < y < 0.8$) neutral pion spectra over an extended transverse momentum range ($1 < p_T < 12$ GeV/$c$) in $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions, measured by the STAR experiment, are presented. The neutral pions are reconstructed from photons measured either by the STAR Barrel Electro-Magnetic Calorimeter (BEMC) or by the Time Projection Chamber (TPC) via tracking of conversion electron-positron pairs. Our measurements are compared to previou...