Pomerons and Lattices: a Progress Report

We report on some attempts to use lattice QCD to investigate topics in strong interactions phenomenology which are usually interpreted in terms of soft Pomeron exchange.Comment: Talk presented at LAT96, 3 pages, Latex, one style file and 2 PostScript pictures include

The perturbative odderon in elastic p p and p pbar scattering

Different models for the odderon-proton coupling are considered and their effects on the differential cross section in the dip region in elastic p p and p pbar scattering are investigated. An allowed range for the size of a possible diquark cluster in the proton can be obtained from a geometrical model.Comment: Talk presented at the conference QCD 02 in Montpellier, France. 4 pages, 3 figure

Pomeron physics: an update

Key issues in pomeron physics include whether the hard and soft pomerons are distinct objects, and whether the hard pomeron is already present in amplitudes at $Q^2=0$. It is urgent to learn how to combine perturbative and nonperturbative concepts, and to construct a sound theory of perturbative evolution at small $x$. Other questions are whether screening corrections are small, and gap survival probabilities large. Finally, do diffractive processes present a good way to discover the Higgs?Comment: 12 pages, 23 figures embedded with epsf Summary talk at Diffraction2000, Calabria, September 200

The Interest of Large-t Elastic Scattering

Existing data for large-$t$ $pp$ elastic-scattering differential cross-sections are energy-independent and behave as $t^{-8}$. This has been explained in terms of triple-gluon exchange, or alternatively through triple-singlet exchange. A discussion is given of the problems raised by each of these explanations, and of the possibility that at RHIC or LHC energies the exchange of three BFKL pomerons might result in a rapid rise with energy.Comment: 6 pages, plain tex, 3 figures embedded with eps

Experimental study of Pomeron

A Pomeron phenomenon remains a mystery. A short review of the experimental situation in diffractive physics and an account of some spectacular manifestations of the Pomeron are given.Comment: 17 pages, 7 Figs, LATEX. Talk given at the conference "From the smallest to largest distances", ITEP, Moscow, 24-26 May 2001. Changes: Fig.2 replace

Measurement of exclusive production of scalar χc0\chi_{c0} meson in proton-(anti)proton collisions via χc0→π+π−\chi_{c0} \to \pi^{+}\pi^{-} decay

We consider a measurement of exclusive production of scalar $\chi_{c}(0^{++})$ meson in the proton-proton collisions at LHC and RHIC and in the proton-antiproton collisions at the Tevatron via $\chi_{c0} \to \pi^{+}\pi^{-}$ decay. The corresponding amplitude for exclusive double-diffractive $\chi_{c0}$ meson production was obtained within the $k_{t}$-factorization approach including virtualities of active gluons and the corresponding cross section is calculated with unintegrated gluon distribution functions (UGDFs) known from the literature. The four-body $p p \to p p \pi^+ \pi^-$ reaction constitutes an irreducible background to the exclusive $\chi_{c0}$ meson production. We calculate several differential distributions for $pp(\bar{p}) \to pp(\bar{p})\chi_{c0}$ process including absorptive corrections. The influence of kinematical cuts on the signal-to-background ratio is investigated. Corresponding experimental consequences are discussed.Comment: 16 pages, 10 figures, 2 table

Properties of Factorial Cumulant to Factorial Moment Ratio

It is shown that the ratio of factorial cumulant moments to factorial moments for a multiplicity distribution truncated in the tail reveals oscillations in sign similar to those observed in experimental data. It is suggested that this effect be taken into account in the analysis of data in order to obtain correct physical information on the multiplicity distributions.Comment: (LaTeX + epsfig, 8 pages including 3 PostScript figures, all encoded via uufiles), DFTT 46/9

The Landshoff-Nachtmann Pomeron on the Lattice

We investigate the Landshoff-Nachtmann two-gluon-exchange model of the Pomeron using gluon propagators computed in the Landau gauge within quenched lattice QCD calculations. We first determine an effective gluon-quark coupling by constraining the Pomeron-quark coupling to its phenomenological value \beta_0 = 2\, \gev^{-1}. We then provide predictions for a variety of diffractive processes. As the propagators have been evaluated entirely from QCD first principles (although in the quenched approximation), our results provide a consistency check of the Landshoff-Nachtmann model. We address the issue of the possible gauge-dependence of our results, which will be the object of a future study.Comment: uuencoded, compressed tar file, 13 pages latex, 4 Postscript figures, requires epsf.st

Nonextensive Statistics and Multiplicity Distribution in Hadronic Collisions

The multiplicity distribution of particles in relativistic gases is studied in terms of Tsallis' nonextensive statistics. For an entropic index q>1 the multiplicity distribution is wider than the Poisson distribution with the same average number of particles, being similar to the negative binomial distribution commonly used in phenomenological analysis of hadron production in high-energy collisions

Wounded quarks and diquarks in heavy ion collisions

A model in which the soft collisions of the nucleon are described in terms of interactions of its two constituents (a quark and a diquark) is proposed. When adjusted to describe precisely the elastic proton-proton scattering data and supplemented with the idea of wounded constituents, the model accounts rather well for the centrality dependence of particle production in the central rapidity region at RHIC energies.Comment: 8 pages, 4 figures, added references; corrected typo in Eq. (15