Raju Venugopalan

Computing quark and gluon distribution functions for very large nuclei

We argue that the distribution functions for quarks and gluons are computable at small {ital x} for sufficiently large nuclei, perhaps larger than can be physically realized. For such nuclei, we argue that weak coupling methods may be used. We show that the computation of the distribution functions can be recast as a many-body problem with a modified propagator, a coupling constant which depends on the multiplicity of particles per unit rapidity per unit area, and for non-Abelian gauge theories, some extra media-dependent vertices. We explicitly compute the distribuiton function for gluons to lowest order, and argue how they may be computed in higher order.

Gluon distribution functions for very large nuclei at small transverse momentum

We show that the gluon distribution function for very large nuclei may be computed for small transverse momentum as correlation functions of an ultraviolet finite two-dimensional Euclidean field theory. This computation is valid to all orders in the density of partons per unit area, but to lowest order in [alpha][sub [ital s]]. The gluon distribution function is proportional to 1/[ital x], and the effect of the finite density of partons is to modify the dependence on the transverse momentum for small transverse momenta.

Green's function in the color field of a large nucleus.

We compute the Green’s functions for scalars, fermions and vectors in the color field associated with the infinite momentum frame wavefunction of a large nucleus. Expectation values of this wavefunction can be computed by integrating over random orientations of the valence quark charge density. This relates the Green’s functions to correlation functions of a two dimensional, ultraviolet finite, field theory. We show how one can compute the sea quark distribution functions, and explictly compute them in the kinematic range of transverse momenta, α 2 � 2 << k 2 t << � 2 , where � 2 is the average color charge squared per unit area. When m 2 << � 2 ∼ A 1/3 , the sea quark contribution to the infinite momentum frame wave function saturates at a value that is the same as that for massless sea quarks.

Nucleation of quark-gluon plasma from hadronic matter

The energy densities achieved during central collisions of large nuclei at Brookhavens AGS may be high enough to allow the formation of quark-gluon plasma. Calculations based on relativistic nucleation theory suggest that rare events, perhaps one in every 10[sup 2] or 10[sup 3], undergo the phase transition. Experimental ramifications may include an enhancement in the ratio of pions to baryons, a reduction in the ratio of deuterons to protons, and a larger source size as seen by hadron interferometry.

Dynamical growth rate of a diffuse interface in first-order phase transitions.

We compute the dynamical prefactor in the nucleation rate of bubbles or droplets in first-order phase transitions for the case where both viscous damping and thermal dissipation are significant. This result, which generalizes previous work on nucleation, may be applied to study the growth of bubbles or droplets in condensed matter systems as well as in heavy ion collisions and in the expansion of the early universe.

Parametric estimate of the relative photon yields from the glasma and the quark-gluon plasma in heavy-ion collisions

Recent classical-statistical numerical simulations have established the bottom-up thermalization scenario of Baier et al. as the correct weak coupling effective theory for thermalization in ultrarelativistic heavy-ion collisions. We perform a parametric study of photon production in the various stages of this bottom-up framework to ascertain the relative contribution of the off-equilibrium Glasma relative to that of a thermalized Quark-Gluon Plasma. Taking into account the constraints imposed by the measured charged hadron multiplicities at RHIC and the LHC, we find that Glasma contributions are important especially for large values of the saturation scale at both energies. These non-equilibrium effects should therefore be taken into account in studies where weak coupling methods are employed to compute photon yields.

Screening mass from chiral perturbation theory, virial expansion, and the lattice.

We calculate the electric screening mass in hot hadronic matter using two different approaches, chiral perturbation theory and the relativistic virial expansion with empirical phase shifts, and compare the results to each other and to a gas of free pions and [rho] mesons. We also compute the electric screening mass for noninteracting, charged bosons with mass [ital m] on a lattice to study likely finite size effects in lattice gauge theory simulations of continuum QCD. For a lattice of given size, the continuum can be properly represented only for a window in the ratio [ital T]/[ital m].

Probing short-range nucleon-nucleon interactions with an Electron-Ion Collider

We derive the cross-section for exclusive vector meson production in high energy deeply inelastic scattering off a deuteron target that disintegrates into a proton and a neutron carrying large relative momentum in the final state. This cross-section can be expressed in terms of a novel gluon Transition Generalized Parton Distribution (T-GPD); the hard scale in the final state makes the T-GPD sensitive to the short distance nucleon-nucleon interaction. We perform a toy model computation of this process in a perturbative framework and discuss the time scales that allow the separation of initial and final state dynamics in the T-GPD. We outline the more general computation based on the factorization suggested by the toy computation: in particular, we discuss the relative role of point-like and geometric Fock configurations that control the parton dynamics of short range nucleon-nucleon scattering. With the aid of exclusive

Effective kinetic description of the early-time dynamics in heavy-ion collisions

J/Psi

Parton distributions of large nuclei at small x

production data at HERA, as well as elastic nucleon-nucleon cross-sections, we estimate rates for exclusive deuteron photo-disintegration at a future Electron-Ion Collider (EIC). Our results, obtained using conservative estimates of EIC integrated luminosities, suggest that center-of-mass energies