Parity-odd domains, corresponding to non-trivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the system's orbital momentum axis. We investigate a three particle azimuthal correlator which is a P even observable, but directly sensitive to the charge separation effect. We report measurements of charged hadrons near center-of-mass rapidity with this observable in Au+Au and Cu+Cu collisions at √ sNN =200 GeV using the STAR detector. A signal consistent with several expectations from the theory is detected. We discuss possible contributions from other effects that are not related to parity violation.

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We present the first measurements of identified hadron production, azimuthal anisotropy, and pion interferometry from Au + Au collisions below the nominal injection energy at the BNL Relativistic Heavy-Ion Collider (RHIC) facility. The data were collected using the large acceptance solenoidal tracker at RHIC (STAR) detector at √ s NN = 9.2 GeV from a test run of the collider in the year 2008. Midrapidity results on multiplicity density dN/dy in rapidity y, average transverse momentum p T , particle ratios, elliptic flow, and Hanbury-Brown-Twiss (HBT) radii are consistent with the corresponding results at similar √ s NN from fixed-target experiments. Directed flow measurements are presented for both midrapidity and forward-rapidity regions. Furthermore the collision centrality dependence of identified particle dN/dy, p T , and particle ratios are discussed. These results also demonstrate that the capabilities of the STAR detector, although optimized for √ s NN = 200 GeV, are suitable for the proposed QCD critical-point search and exploration of the QCD phase diagram at RHIC.

An investigation on the presence of the forwardbackward correlations in the pions multiplicity, emitted in 16 O − Ag/Br interactions at energy E lab = 60 A GeV are carried out. The study of the forward-backward correlation between various observables which is separated by two different pseudorapidity intervals can be treated as an important probe to defining the primordial conditions for the formation of the Quark Gluon Plasma (QGP). We have observed the dependency of correlation fluctuations and correlation strength on pseudorapidity (η) and the increasing width of the pseudorapidity bin size Δη. The roughness of the multiplicities and the particle number deviations are also investigated. The nuclear photographic emulsion technique has been employed to collect the experimental data. We have performed the FRITIOF and Ultra-relativistic Quantum Molecular Dynamics (UrQMD) simulations to compare the experimental results with the simulated results. The analysis strongly indicates the presence of forward-backward correlations in the experimental distributions of pions beyond statistical noise. We have also analyzed the ring-and jet-like structure to confirm the presence of the forward-backward correlations in the multiplicities of 16 O − Ag/Br interactions at 60 A GeV. We have also taken the variations of correlation fluctuations and correlation strength in η and Δη space, respectively for the ring-like and jet-like structure. The average behavior of correlation parameters of ring-like events strongly differs from jet-like events due to expected Cherenkov Gluon radiation.

Visibility graphs (VGs), horizontal visibility graphs (HVGs) and the sandbox algorithm (SB) are applied for multifractal characterization of complex network systems that are converted from time series measurements, are used to characterize the fluctuations in pseudorapidity densities of singly charged particles produced in [Formula: see text]O–AgBr interactions at 60[Formula: see text]A[Formula: see text]GeV. The work presents the analysis of ring-like and jet-like events in terms of multifractality characterization of [Formula: see text]O–AgBr interactions at 60[Formula: see text]A[Formula: see text]GeV. We systematically compared the experimental events of both ring- and jet-like events with Monte Carlo (MC) simulated events. The investigation reveals that the multifractal spectrum for the jet-like events and ring-like events is different and can be distinguished. The ring-like events have its parameters slightly higher than that of jet-like events. Further analysis shows that the strength of the nonstatistical fluctuations is larger for ring-like events than those of jet-like events. The SB method presented here appears to be more useful than the conventional methods used for multifractal characterization.