Probing Short Range Nucleon Correlations in High Energy Hard Quasielastic pd Reactions

We show that the strong dependence of the amplitude for $NN$ hard scattering on the collision energy can be used to magnify the effects of short range nucleon correlations in quasielastic $pd$ scattering. Under specific kinematical conditions the effect of initial and final state interactions can be accounted for by rescaling the cross section calculated within the plane wave impulse approximation. The feasibility to investigate the role of relativistic effects in the deuteron wave function is demonstrated by comparing the predictions of different formalisms. Binding effects due to short range correlations in deuteron are discussed as well.Comment: 18 pages (LaTex) + 10 postscript figs (available on request

Leading twist coherent diffraction on nuclei in deep inelastic scattering at small x and nuclear shadowing

We extend the theory of leading twist nuclear shadowing to calculate leading twist nuclear diffractive parton distribution functions (nDPDFs). We observe that the quark and gluon nPDFs have different patterns of the $A$-dependence. It is found that the probability of diffraction in the quark channel increases with $A$, reaching about 30% at $x \sim 10^{-4}$ for $A \sim 200$, and weakly decreases with $Q^2$. In the gluon channel, the probability of diffraction is large for all nuclei ($\sim 40$% for heavy nuclei at $x \sim 10^{-4}$ and $Q_0^2 \sim 4$ GeV$^2$), it weakly depends on $A$ and it decreases rather fast with increasing $Q^2$ -- the probability decreases by approximately a factor of two as $Q^2$ changes from 4 GeV$^2$ to 100 GeV$^2$. We also find that nuclear shadowing breaks down Regge factorization of nDPDFs, which is satisfied experimentally in the nucleon case. All these novel effects in nDPDFs are large enough to be straightforwardly measured in ultraperipheral collisions at the LHC.Comment: 14 pages, 7 figures. Extended discussion. Final version published in PL

Elastic and large t rapidity gap vector meson production in ultraperipheral proton-ion collisions

We evaluate the cross sections for the production of vector mesons in exclusive ultraperipheral proton-ion collisions at LHC. We find that the rates are high enough to study the energy and momentum transfer dependence of vector mesons - rho,phi, J/psi, Upsilon photoproduction in gamma p scattering in a wide energy range extending the measurements which were performed at HERA, providing new information about interplay of soft and hard physics in diffraction. Also, we calculate the contributions to the vector meson yield due to production of vector mesons off nuclear target by photons emitted by proton. We find, that least in the case of Upsilon production it is feasible to observe simultaneously both these processes. Such measurements would increase the precision with which the A-dependence of exclusive onium production can be determined. This would also enable one to estimate the amount of nuclear gluon shadowing of generalized gluon distributions at much smaller x than that is possible in AA collisions and to measure the cross sections for photoproduction processes in a significantly wider energy range than that achieved in experiments with fixed nuclear targets. We also present the cross section for vector meson production in pA collisions at RHIC. In addition, we consider production of vector mesons off protons with large rapidity gaps and large t. These processes probe small x dynamics of the elastic interaction of small dipoles at high energies and large but finite t, that is in the kinematics where DGLAP evolution is strongly suppressed. We estimate that this process could be studied at LHC up to W ~1 TeV with detectors which will be available at LHC.Comment: 21 pages, 9 figures, a reference to experimental data is adde

Fading out of J/psi color transparency in high energy heavy ion peripheral collisions

We provide predictions for the J/psi coherent production in the peripheral heavy ion collisions at LHC and at RHIC using the leading twist model of nuclear shadowing based on the QCD factorization theorem for diffraction and the HERA hard diffraction data. We demonstrate that for the LHC kinematics this model leads to a bump-shape distribution in rapidity which is suppressed overall as compared to the expectations of the color transparency regime by a factor 6. This is significantly larger suppression than that expected within the impact parameter eikonal model. Thus we show that the interaction of spatially small wave package for which the total cross section of interaction with nucleons is small is still strongly shadowed by nuclear medium in high energy processes.Comment: 13 pages, 7 figure

Diffraction at HERA, Color Opacity and Nuclear Shadowing

The QCD factorization theorem for diffractive processes in DIS is used to derive formulae for the leading twist contribution to the nuclear shadowing of parton distributions in the low thickness limit. Based on the current analyzes of diffraction at HERA we find that the average strength of the interactions which govern diffraction in the gluon sector at $x \le 10^{-3}, Q_0=2 GeV$ is ~50 mb. This is 3 times larger than in the quark sector and suggests that applicability of DGLAP approximation requires significantly larger $Q_0$ in the gluon sector. We use this information to estimate quark and gluon shadowing for heavy nuclei and to calculate its$Q^2$ depen- dence. For A~200 the amount of the gluon shadowing: $G_A/AG_N\sim 0.25-0.4$ at $x<10^{-3},Q=2GeV$ is sensitive to the probability of the small size configurations within wave function of the gluon "partonometer" at the $Q_0$ scale. At this scale for $A\sim 200$ the nonperturbative contribution to the gluon density is reduced by a factor of 4-5 at $x \le 10^{-3}$ unmasking PQCD physics in the gluon distribution of heavy nuclei. Such shadowing would strongly modify the first stage of the heavy ion collisions at LHC, and would lead to large color opacity effects in $eA$ collisions at x<0.001. The leading twist contribution to the cross section of the coherent $J/\psi$ production off $A\ge 12$ nuclei at $\sqrt s \ge 70$ GeV is strongly reduced as compared to the naive color transparency expectations. The Gribov black body limit for $F_{2A}(x,Q^2)$ is extended to the case of the gluon distributions in nuclei and shown to be relevant for the HERA kinematics of $eA$ collisions. Properties of the final states are also briefly discussed.Comment: 42 pages, 10 figures, final version to appear in Europ. Jour.of Phys., discussion of a number of issues is substantially extended, two figures and several references are adde

Searching for Color Coherent Effects at Intermediate Q2Q^2 via Double Scattering Processes

We propose that measuring the $Q^2$ dependence of the number of final-state interactions of the recoil protons in quasi-elastic electron scattering from light nuclei is a new method to investigate Color Coherent effects at {\bf intermediate} values of $Q^2$ ({$\sim$ few $(GeV/c)^2$}). This is instead of measuring events without final-state interactions. Our calculations indicate that such measurements could reveal significant color transparency effects for the highest of the energies initially available at CEBAF. Measurements that detect more than one hadron in the final state, which require the use of large acceptance ($4\pi$) detectors, are required.Comment: 19 pages in RevTex, 5 postscript figures available from [email protected]