Directed and Elliptic Flow in Pb+Pb collisions at 40 and 158 AGeV

Directed and elliptic flow are reported for charged pions and protons as a function of transverse momentum, rapidity, and centrality in 40 and 158 AGeV Pb + Pb collisions. The standard method of correlating particles with an event plane is used. The directed flow of protons is small and shows little variation near to midrapidity, but rises fast towards projectile rapidity in the 40 AGeV data. For most peripheral collisions the flat region becomes negative resulting in $v_1$ changing sign three times. Elliptic flow doesn't seem to change very much from 40 AGeV to 158 AGeV. The difference is smaller than anticipated from the overall energy dependence from AGS to RHIC.Comment: Presented at 16th International Conference on Ultrarelativistic Nucleus-Nucelus Collisions, Quark Matter 2002 (QM 2002), Nantes, France, 18-24 Jul 2002, 4 pages, 3 figure

Anisotropic flow

Recent experimental results on directed and elliptic flow, theoretical developments, and new techniques for anisotropic flow analysis are reviewed.Comment: 10 pages, review talk at Quark Matter 2002 conference, Nantes, France, July 2002 Corrected typographical errors in the reference section. No other change

Radial and elliptic flow at RHIC: further predictions

Using a hydrodynamic model, we predict the transverse momentum dependence of the spectra and the elliptic flow for different hadrons in Au+Au collisions at sqrt(s) = 130 A GeV. The dependence of the differential and p_t-integrated elliptic flow on the hadron mass, equation of state and freeze-out temperature is studied both numerically and analytically.Comment: 6 pages incl. 7 figures; added v2 for phi mesons in Table 1, plus some related explanatory text. This version to appear in Physics Letters

Symmetry constraints for the emission angle dependence of Hanbury Brown--Twiss radii

We discuss symmetry constraints on the azimuthal oscillations of two-particle correlation (Hanbury Brown--Twiss interferometry) radii for non-central collisions between equal spherical nuclei. We also propose a new method for correcting in a model-independent way the emission angle dependent correlation function for finite event plane resolution and angular binning effects.Comment: 8 pages revtex4, 2 tables, no figures. Short Section VI added and correction algorithm in Section VII made more explicit. Submitted to Physical Review

Anisotropic flows from initial state of a fast nucleus

We analyze azimuthal anisotropy in heavy ion collisions related to the reaction plane in terms of standard reggeon approach and find that it is nonzero even when the final state interaction is switched off. This effect can be interpreted in terms of partonic structure of colliding nuclei. We use Feynman diagram analysis to describe details of this mechanism. Main qualitative features of the appropriate azimuthal correlations are discussed.Comment: 16 pages, 11 figures. This paper is an extended version of a talk given at Session of Nuclear Physics Division of Russian Academy of Sciences in November 200

Thermal Recombination: Beyond the Valence Quark Approximation

Quark counting rules derived from recombination models agree well with data on hadron production at intermediate transverse momenta in relativistic heavy-ion collisions. They convey a simple picture of hadrons consisting only of valence quarks. We discuss the inclusion of higher Fock states that add sea quarks and gluons to the hadron structure. We show that, when recombination occurs from a thermal medium, hadron spectra remain unaffected by the inclusion of higher Fock states. However, the quark number scaling for elliptic flow is somewhat affected. We discuss the implications for our understanding of data from the Relativistic Heavy Ion Collider.Comment: 5 pages, 5 figure

Anisotropic Flow from RHIC to the LHC

Anisotropic flow is recognized as one of the main observables providing information on the early stage of a heavy-ion collision. At RHIC the large observed anisotropic flow and its successful description by ideal hydrodynamics is considered evidence for an early onset of thermalization and almost ideal fluid properties of the produced strongly coupled Quark Gluon Plasma. This write-up discusses some key RHIC anisotropic flow measurements and for anisotropic flow at the LHC some predictions.Comment: 4 pages, 6 figures, hotquarks 200

Θ\Theta vacua states in heavy ion collisions in presence of dissipation and noise

We have studied possible formation of $\Theta$ vacua states in heavy ion collisions. Random phases of the chiral fields were evolved in a finite temperature potential, incorporating the breaking of $U_A(1)$ symmetry. Initial random phases very quickly settle into oscillation around the values dictated by the potential. The simulation study indicate that an initial $\Theta$=0 state do not evolve into a $\Theta$ $\neq$ 0 state. However, an initial $\Theta$ $\neq$ 0 state, if formed in heavy ion collision, can survive, as a coherent superposition of a number of modes.Comment: 6 pages, 6 figure

Differential Transverse Flow in Central C-Ne and C-Cu Collisions at 3.7 GeV/nucleon

Differential transverse flow of protons and pions in central C-Ne and C-Cu collisions at a beam energy of 3.7 GeV/nucleon was measured as a function of transverse momentum at the SKM-200-GIBS setup of JINR. In agreement with predictions of a transversely moving thermal model, the strength of proton differential transverse flow is found to first increase gradually and then saturate with the increasing transverse momentum in both systems. While pions are preferentially emitted in the same direction of the proton transverse flow in the reaction of C-Ne, they exhibit an anti-flow to the opposote direction of the proton transverse flow in the reaction of C-Cu due to stronger shadowing effects of the heavier target in thr whole range of transverse momentum.Comment: 15 pages, 5 figure

Thermal fluctuations in the interacting pion gas

We derive the two-particle fluctuation correlator in a thermal gas of pi-mesons to the lowest order in an interaction due to a resonance exchange. A diagrammatic technique is used. We discuss how this result can be applied to event-by-event fluctuations in heavy-ion collisions, in particular, to search for the critical point of QCD. As a practical example, we determine the shape of the rapidity correlator.Comment: 12 pages, 4 figures, RevTe