All-loop calculations of total, elastic and single diffractive cross sections in RFT via the stochastic approach

We apply the stochastic approach to the calculation of the Reggeon Field Theory (RFT) elastic amplitude and its single diffractive cut. The results for the total, elastic and single difractive cross sections with account of all Pomeron loops are obtained.Comment: 4 pages, 3 figures; prepared for the proceedings of the workshop 'Diffraction-2012', Puerto del Carmen, Lanzarote, September 10 - 15, 201

Regge description of spin-spin asymmetry in photon diffractive dissociation

We explore the possibility whether the gluon helicity distribution $\Delta G(x)$ can be extracted from a comparison of experimental data on the longitudinal spin-spin asymmetry $A_{LL}$ in $\gamma p$ diffractive deep inelastic scattering with calculations performed within the framework of perturbative QCD (pQCD). The data could be obtained at the future HERA collider in scattering of polarized electrons/positrons off polarized protons. In this paper we look for such kinematical regions where contributions to $A_{LL}$ from soft processes (reggeon exchanges) are suppressed to guarantee an applicability of pQCD. It is shown that for the square of the center-of-mass energy $s_{\gamma p} \geq 10^3 GeV^2$, the hadronic diffractive mass $M_X \leq 10 GeV/c^2$, the momentum transferred to the proton $\Delta_T\leq 0.5 GeV/c$, and $Q^2\geq4 (GeV/c)^2$ the longitudinal spin-spin asymmetry due to reggeon exchanges is less than 10^{-4}. This value is presumably lower than the asymmetry which can be measured with modern experimental technique. This means that the pQCD prediction can be reliably compared with data in this kinematical region.Comment: 44 pages, LaTeX, 12 figure

Leading neutron spectra

It is shown that the observation of the spectra of leading neutrons from proton beams can be a good probe of absorptive and migration effects. We quantify how these effects modify the Reggeized pion-exchange description of the measurements of leading neutrons at HERA. We are able to obtain a satisfactory description of all the features of these data. We also briefly discuss the corresponding data for leading baryons produced in hadron-hadron collisions.Comment: 17 pages, 8 figures; sentence and reference added, reference corrected, to be published in EPJ

Exclusive charm production in pbar p collisions at s^1/2 <15 GeV

We discuss the open charm production in peripheral reactions $\bar pp\to \bar Y_cY_c$ and $\bar pp\to M_c\bar M_c$, where $Y_c$ and $M_c$ stand for $\Lambda_c^+,\Sigma_c^+$ and $D,D^*$, respectively, at $\sqrt{s}\lesssim 15$ GeV, which corresponds to the energy range of FAIR. Our consideration is based on the topological decomposition of the planar quark and diquark diagrams which allows to estimate consistently meson and baryon exchange trajectories and energy scale parameters as well. The spin dependence is determined by the effective interaction of lowest exchanged resonance. Unknown parameters are fixed by an independent analysis of open strangeness production in $\bar pp\to \bar YY$ and $\bar pp\to \bar KK$ reactions and of SU(4) symmetry. We present the corresponding cross sections and longitudinal double-spin asymmetries for exclusive binary reactions with open charm mesons and baryons in the final state. The polarization observables have a non-trivial $t$ and $s$ dependence which is sensitive to details of the open charm production mechanism.Comment: 26 pages, 18 figure

Probabilistic model of Reggeon Field Theory

The stochastic model of classical system of particles (partons), which dynamics includes random walk in plane as well as processes of death, splitting, annihilation and fusion of partons, is considered. A set of equations for multiparticle distribution functions for this system can be described in terms of diagrams of the Reggeon Field Theory (RFT) with supercritical pomeron, where rapidity plays a role of the time variable. The multiparticle inclusive distributions of partons correspond to multi-pomeron states in this analogy. In order to calculate the amplitude of hadron interaction at given energy we define an operator of linkage of any pair of partons from two parton sets (the projectile and the target). The form of the hadron-interaction (parton-linkage) operator is determined from the requirement for the result to be in correspondence to the RFT formulas. It is shown that the requirement of Lorentz invariance of the amplitude is fulfilled in this interpretation only at definite relation between the probabilities of parton splitting, annihilation and fusion. Interpretation of various methods of s-channel unitarization is discussed in terms of the model.Comment: 30 pages, 4 figures, uses axodraw.sty. To appear in ``Multiple Facets of Quantization and Supersymmetry / Michael Marinov Memorial Volume'', World Scientifi

Screening and Anti-Screening Effects in J/psi Production on Nuclei

The nuclear effects in J/psi hadro- and electroproduction on nuclei are considered in framework of reggeon approach. It is shown that screening regime which holds for electroproduction at x_F > 0.7 and for hadroproduction at x_F > -(0.3-0.4) is changed with anti-screening regime for smaller x_F values.Comment: 6 pages, 6 figures. Small changes in wordin

Oxidation of carbon monoxide over Ag (111) by preadsorbed active oxygen studied by XPS and UPS

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Anomalous suppression of π0\pi^0 production at large transverse momentum in Au + Au and d + Au collisions at sNN=\sqrt{{\bf s}_{\bf NN}} = 200 GeV

We propose a model of suppression of large $p_T$-pions in heavy ion collisions based on the interaction of the large $p_T$ pion with the dense medium created in the collision. The model is practically the same as the one previously introduced to describe $J/\psi$ suppression. Both the $p_T$ and the centrality dependence of the data are reproduced. In deuteron-gold collisions, the effect of the final state interaction with the dense medium turns out to be negligibly small. Here the main features of the data are also reproduced both at mid and at forward rapidities.Comment: 20 pages, latex, 3 postscript figures. Last version, to be published in EJP

Resonance Production on Nuclei at High Energies: Nuclear-Medium Effects and Space-Time Picture

The influence of nuclear matter on the properties of coherently produced resonances is discussed. It is shown that, in general, the mass distribution of resonance decay products has a two-component structure corresponding to decay outside and inside the nucleus. The first (narrow) component of the amplitude has a Breit-Wigner form determined by the vacuum values of mass and width of the resonance. The second (broad) component corresponds to interactions of the resonance with the nuclear medium. It can be also described by a Breit-Wigner shape with parameters depending e.g. on the nuclear density and on the cross section of the resonance-nucleon interaction. The resonance production is examined both at intermediate energies, where interactions with the nucleus can be considered as a series of successive local rescatterings, and at high energies, $E>E_{crit}$, where a change of interaction picture occurs. This change of mechanisms of the interactions with the nucleus is typical for the description within the Regge theory approach and is connected with the nonlocal nature of the reggeon interaction.Comment: 22 pages LaTeX, 1 Postscript file containing 7 figures; addition in beginning of Ch. 2; Nucl. Phys. A, to be publishe

Coherent J/psi production - a novel feature at LHC?

Energy dependence of heavy quarkonia production in hadron-nucleus collisions is studied in the framework of the Glauber-Gribov theory. We emphasize a change in the space-time picture of heavy-quark state production on nuclei with energy. Longitudinally ordered scattering of a heavy-quark system takes place at low energies, while with increasing energy it transforms to a coherent scattering of projectile partons on the nuclear target. The characteristic energy scale for this transition depends on masses and rapidities of produced particles. For J/psi, produced in the central rapidity region, the transition happens at RHIC energies. The parameter-free calculation of J/psi in dAu collisions is in good agreement with recent RHIC data. We use distributions of gluons in nuclei to predict suppression of heavy quarkonia at LHC.Comment: 13 pages, 4 figures; experimental data and reference included, conclusions unchanged; to appear in Phys. Lett.