Gluon saturation effects on J/Psi production in heavy ion collisions

We consider a novel mechanism for J/Psi production in nuclear collisions arising due to the high density of gluons. We calculate the resulting J/Psi production cross section as a function of rapidity and centrality. We evaluate the nuclear modification factor and show that the rapidity distribution of the produced J/Psi's is significantly more narrow in AA collisions due to the gluon saturation effects. Our results indicate that gluon saturation in the colliding nuclei is a significant source of J/Psi suppression that can be disentangled from the quark-gluon plasma effects.Comment: 5 pages, 3 figures; v2: typos corrected; presentation improve

Diffractive dissociation and saturation scale from non-linear evolution in high energy DIS

This paper presents the first numerical solution to the non-linear evolution equation for diffractive dissociation processes in deep inelastic scattering. It is shown that the solution depends on one scaling variable $\tau = Q^2/Q^{D 2}_s(x,x_0)$, where $Q^D_s(x,x_0)$ is the saturation scale for the diffraction processes. The dependence of the saturation scale $Q^D_s(x,x_0)$ on both $x$ and $x_0$ is investigated, ($Y_0 = \ln(1/x_0)$ is a minimal rapidity gap for the diffraction process). The $x$ - dependence of $Q^D_s$ turns out to be the same as of the saturation scale in the total inclusive DIS cross section. In our calculations $Q^D_s(x,x_0)$ reveals only mild dependence on $x_0$. The scaling is shown to hold for $x \ll x_0$ but is violated at $x \sim x_0$.Comment: 13 pages, 9 figure

D-instantons and multiparticle production in N=4 SYM

N=4 Super-symmetric Yang-Mills theory (N=4 SYM) in the strong coupling regime has been successfully applied (through the AdS/CFT correspondence) to the description of strongly coupled plasma which is a multiparticle state. Yet, the high-energy scattering in the strong coupling limit of N=4 SYM is purely elastic, so this multiparticle final state can never be produced: this is because in this limit the theory is dual to weak supergravity, and the dominant interaction is the elastic graviton exchange. Here we propose a resolution of this dilemma by considering the contribution of D-instantons in $AdS_5$ bulk space to the scattering amplitude. We argue that D-instantons coupled to dilatons and axions are responsible for multiparticle production in strongly coupled N=4 SYM, and the corresponding cross section increases with energy. We evaluate the intercept and the slope of the corresponding Pomeron trajectory in terms of the typical size of the D-instanton, and argue that the resulting physical picture may resemble the real world.Comment: 22 pp and 11 figures in the eps forma

A Quantitative Investigation of the Pomeron

A comparative investigation of various Pomeron models is carried out through the study of their predicted values of $\sigma_{tot}$, B, and $\frac{\sigma_{el}}{\sigma_{tot}}$ in high energy pp and p$\bar{p}$ scattering. Our results strongly support a picture of the Pomeron in which we have both moderate blackening and expansion of the p($\bar{p}$) - p amplitude in impact parameter space as a function of energy in the ISR-SSC domain. In particular, we obtain an excellent reproduction of the data with a hybrid eikonal model which combines the hard Lipatov-like QCD Pomeron with the old fashioned soft Pomeron and Regge terms. Our analysis shows that the additive quark model, at least in the naive form, is not compatible with the data.Comment: pages 15, Late