Radial and elliptic flow in non-central heavy ion collisions can constrain the effective Equation ofState(EoS) of the excited nuclear matter. To this end, a model combining relativistic hydrodynamics and a hadronic transport code (RQMD [1]) is developed. For an EoS with a first order phase transition, the model reproduces both the radial and elliptic flow data at the SPS. With the EoS fixed from SPS data, we quantify predictions at RHIC where the Quark Gluon Plasma(QGP) pressure is expected to drive additional radial and elliptic flow. Currently, the strong elliptic flow observed in the first RHIC measurements does not conclusively signal this nascent QGP pressure. Additional measurements are suggested to pin down the EoS.1. By colliding heavy nuclei at the SPS and RHIC accelerating facilities, physicists hope to excite hadronic matter into a new phase consisting of deconfined quarks and gluons -the Quark Gluon Plasma(QGP) [2]. After the collision, the produced particles move collectively or f low and this flow may quantify the effective Equation of State(EoS) of the matter. In central PbPb collisions at the SPS, a strong radial flow is observed [3]. The matter develops a collective transverse velocity approaching (1/2)c. In non-central collisions, a radial and an elliptic flow are observed [4][5][6]. Since in non-central collisions the initial nucleus-nucleus overlap region has an elliptic shape, the initial pressure gradient is larger along the impact parameter and the matter moves preferentially in this direction [7].The phase transition to the QGP influences both the radial and elliptic flows. QCD lattice simulations show an approximately 1st order phase transition [8]. Over a wide range of energy densities e = .5 − 1.4 GeV /f m 3 , the temperature and pressure are nearly constant. Over this range then, the ratio of pressure to energy density p/e, decreases and reaches a minimum at a particular energy density known as the softest point, e sp ≈ 1.4 GeV /f m 3 [9]. When the initial energy density is close to e sp , the small pressure (relative to e) cannot effectively accelerate the matter. However, when the initial energy density is well above e sp , p/e approaches 1/3, and the larger pressure drives collective motion [9,10]. At a time of ∼ 1 f m/c, the energy densities at the SPS( √ s N N = 17 GeV ) and RHIC ( √ s N N = 130 GeV ) are very approximately 4 and 7 GeV /f m 3 respectively [11,12]. Based on these experimental estimates, the hard QGP phase is expected to live significantly longer at RHIC than at the SPS. The final flows of the produced particles should reflect this difference. In this paper we pose the question: Can both the radial and elliptic flow at the SPS and RHIC be described by a single effective EoS?Since the various hadron species have different elastic cross sections, they freezeout (or decouple) from the hot fireball at different times [13]. Because flow builds up over time, it is essential to model this differential freezeout. It was ignored in previous hydrodynamic simulations of non-c...

We investigate the thermalization of charm quarks in high energy heavy ion collisions. To this end, we calculate the diffusion coefficient in the perturbative Quark Gluon Plasma and relate it to collisional energy loss and momentum broadening. We then use these transport properties to formulate a Langevin model for the evolution of the heavy quark spectrum in the hot medium. The model is strictly valid in the non-relativistic limit and for all velocities γv < α

We express the heavy quark diffusion coefficient as the temporal variation of a Wilson line along the Schwinger-Keldysh contour. This generalizes the classical formula for diffusion as a force-force correlator to a non-Abelian theory. We use this formula to compute the diffusion coefficient in strongly coupled N 4 Yang-Mills theory by studying the fluctuations of a string in AdS 5 S 5 . The string solution spans the full Kruskal plane and gives access to contour correlations. The diffusion coefficient is D 2= p T and is therefore parametrically smaller than momentum diffusion, =e p 1=4T. The quark mass must be much greater than T p in order to treat the quark as a heavy quasiparticle. The result is discussed in the context of the Relativistic Heavy Ion Collider (RHIC) experiments.

We develop a dipole model for HERA DIS data which incorporates the impact parameter distribution of the proton. The model describes the inclusive total γ * p cross-sections as well as the diffractive J/ψ differential cross-sections. We compare the model with previous approaches and show that the t-distributions are sensitive to saturation phenomena. We estimate the boundary of the saturation region and show that it dominates the data in the low-Q 2 region where the total γ * p cross-section exhibits the same universal rise as hadronic cross-sections. The model is then extended to nuclei and shows good agreement with the nuclear shadowing data at small-x. Finally, we estimate the saturation scale in nuclei.