983 research outputs found

### Large multiplicity fluctuations and saturation effects in onium collisions

This paper studies two related questions in high energy onium-onium
scattering: the probability of producing an unusually large number of particles
in a collision, where it is found that the cross section for producing a
central multiplicity proportional to $k$ should decrease exponentially in
$\sqrt{k}$. Secondly, the nature of gluon (dipole) evolution when dipole
densities become so high that saturation effects due to dipole-dipole
interactions become important: measures of saturation are developed to help
understand when saturation becomes important, and further information is
obtained by exploiting changes of frame, which interchange unitarity and
saturation corrections.Comment: 30 pages LaTeX2e, 11 figures included using epsfig. Compressed
postscript of whole paper also available at
http://www.hep.phy.cam.ac.uk/theory/papers

### Parton Saturation-An Overview

The idea of partons and the utility of using light-cone gauge in QCD are
introduced. Saturation of quark and gluon distributions are discussed using
simple models and in a more general context. The Golec-Biernat W\usthoff model
and some simple phenomenology are described. A simple, but realistic, equation
for unitary, the Kovchegov equation, is discussed, and an elementary derivation
of the JIMWLK equation is given.Comment: Cargese Lectures, 34 pages, 19 figure

### Single and Double BFKL Pomeron Exchange and a Dipole Picture of High Energy Hard Processes

Onium-onium scattering at high energy is used to illustrate a dipole picture
of high energy hard scattering in the large $N_c$ limit. Single and double BFKL
pomeron exchanges are calculated in the leading logarithmic approximation. An
expression is given for the triple pomeron coupling when one of the pomeron's
momentum is zero while the other two have momentum transfer, t. This expression
is explicit and could be evaluated numerically. It has a $(-t)^{-{1\over 2}}$
singularity at t=0.Comment: CU-TP-625, minor TeX problems of previous version have been fixe

### Large Scale Rapidity Correlations in Heavy Ion Collisions

We discuss particle production mechanisms for heavy ion collisions. We
present an argument demonstrating how the fluctuations of the number of
produced particles in a series of classical emissions can account for KNO
scaling. We predict rapidity correlations in the particle production in the
event by event analysis of heavy ion collisions on the rapidity scales of the
order of one over the strong coupling constant.Comment: REVTeX, 13 pages, 3 figure

### BFKL Dynamics in Jet Evolution

We calculate $e^+e^- \to Q\bar{Q}(k) + anything in a certain momentum, k,
region for heavy quark-antiquark (Q\bar{Q})production. In our chosen region we
find that the number of heavy quark pairs produced is determined by BFKL
dynamics and the energy dependence of the number of pairs is given by$\alpha
p-1$ the hard pomeron intercept.Comment: 14 pages, Latex, 4 figure

### A Simple Derivation of the JIMWLK Equation

A simple derivation of the Jalilian-Marian, Iancu, McLerran, Weigert,
Leonidov and Kovner (JIMWLK) equation for the evolution of small-x QCD
wavefunctions is given. The derivation makes use of the equivalence between the
evolution of a (in general complicated) small-x wavefunction with that of the
evolution of the (simple) dipole probing the wavefunction in a high energy
scattering.Comment: 11 pages, 3 figures, corrected typo in abstract titl

### High energy hadron-nucleus scattering

Theoretical expectations for hadron-nucleus scattering at high energy if the basic hadron-hadron interaction is due to Regge poles and cuts arising in multiperipheral or soft field theory models are described. Experiments at Fermilab may provide a critical test of such models. (auth

### Parton Saturation at Small x and in Large Nuclei

Quark and gluon distributions in the light-cone wavefunction of a high energy
hadron or nucleus are calculated in the saturation regime. One loop
calculations are performed explicitly using the equivalence between the parton
distribution in the light-cone wavefunction and the production distribution of
that parton in a current-nucleon (nucleus) scattering. We argue that, except
for some overall numerical factors, the Weizsacker- Williams wavefunction
correctly gives the physics of the gluon distribution in a light-cone
wavefunction.Comment: 24 pages, 4 figure

### Toward Equilibration in the Early Stages After a High Energy Heavy Ion Collision

The early stages in the evolution of the gluons produced in the central
region of a head-on high-energy heavy ion collision is studied. An equation is
given for the rate of change of transverse momentum into longitudinal momentum
where the longitudinal direction is along the collision axis. We are able to
follow the system up to the time where equilibration seems to be setting in,
but we are unable to actually follow the system as it reaches equilibrium.Comment: 18 pages, Late

### The triple pomeron interaction in the perturbative QCD

The triple pomeron interaction is studied in the perturbative approach of
BFKL-Bartels. At finite momentum transfers $\sqrt{-t}$ the contribution
factorizes in the standard manner with a triple-pomeron vertex proportional to
$1/\sqrt{-t}$. At $t=0$ the contribution is finite, although it grows faster
with energy than for finite $t$ and does not factorize.Comment: 17 pages, 4 figures, LATE

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