311 research outputs found

### 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

### 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

### Double Pomeron Opportunities at SQRT(s) = 1.8 Tev

I describe possible ways to discover hard double pomeron exchange (HDPE) with
the existing detectors at the Fermilab Tevatron, by using the small-angle
``luminosity'' counters as a veto. Estimates of the cross sections and
backgrounds are made. In addition to the intrinsic importance of HDPE, its
observation would be useful for calibrating the detectors, and for estimating
the ``survival probability'' of rapidity gaps.Comment: 8 pages, LaTeX, 1 PostScript figure availble from the author
([email protected]), MSUHEP-93-0

### 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

### Proton-nucleus cross section at high energies

Cross sections for proton inelastic collision with different nuclei are
described within the Glauber and multiple scattering approximations. A
significant difference between approximate `Glauber' formula and exact
calculations with a geometrical scaling assumption for very high-energy cross
section is shown. Experimental values of proton-proton cross sections obtained
using extensive air shower data are based on the relationship of proton-proton
and respective proton-air absorption cross sections. According to obtained
results values reported by the Akeno and Fly's Eye experimental groups are
about 10% overestimated. The proper energy dependence of absorption cross
section for collisions with air nuclei is of a great importance for studies of
high energy cosmic rays using the Monte Carlo technique.Comment: 9pp (9 eps figures

### Measurement of exclusive production of scalar $\chi_{c0}$ meson in proton-(anti)proton collisions via $\chi_{c0} \to \pi^{+}\pi^{-}$ 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

### 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

### Unified Model for Small-t and High-t Scattering at High Energies: Predictions at RHIC and LHC

The urgency of predictions in large-t region at LHC stimulated us to present
a unified model of small and high t scattering at high energies. Our model is
based upon a safe theoretical ground: analyticity, unitarity, Regge behavior,
gluon exchange and saturation of bounds established in axiomatic quantum field
theory. We make precise predictions for the behavior of the differential cross
sections at high t, the evolution of the dip-shoulder structure localized in
the region of -t between 0.5 and 0.8 GeV**2 and the radical violation of the
exponential behavior of the first diffraction cone at small t.Comment: 6 pages, 2 table, 7 figures. Misprints are correcte

### Systematic Regge theory analysis of omega photoproduction

Systematic analysis of available data for $\omega$-meson photoproduction is
given in frame of Regge theory. At photon energies above 20 GeV the
$\gamma{+}p{\to}\omega{+}p$ reaction is entirely dominated by Pomeron exchange.
However, it was found that Pomeron exchange model can not reproduce the
$\gamma{+}p{\to}\rho{+}p$ and $\gamma{+}p{\to}\omega{+}p$ data at high energies
simultaneously with the same set of parameters. The comparison between $\rho$
and $\omega$ data indicates a large room for meson exchange contribution to
$\omega$-meson photoproduction at low energies. It was found that at low
energies the dominant contribution comes from $\pi$ and $f_2$-meson exchanges.
There is smooth transition between the meson exchange model at low energies and
Regge theory at high energies.Comment: 7 pages, 8 figures, revtex

### Questions and Remarks About Clans in Multiparticle Dynamics

The fact that several important effects in multiparticle dynamics, on which
QCD has not yet satisfactory predictions, have been interpreted in terms of the
validity of negative binomial (Pascal) regularity and related clan properties
at the level of simpler substructures, raises intriguing questions on clan
properties in all classes of collisions, the main one being whether clans are
observable objects or merely a mathematical concept. We approach this problem
by studying clan masses and rapidity distributions in each substructure for
e+e- annihilation and hh collisions, and find that such properties can indeed
characterise the different components. These results support the idea that
clans could be observable, a challenging problem for future experiments.Comment: 11 pages; 3 figures; latex 2e and amsmat

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