Hadron multiplicities

We review results on hadron multiplicities in high-energy particle collisions. Both theory and experiment are discussed. The general procedures used to describe particle multiplicity in quantum chromodynamics (QCD) are summarized. The QCD equations for the generating functions of the multiplicity distributions are presented both for fixed and running coupling strengths. The mean multiplicities of gluon and quark jets, their ratio, higher moments, and the slopes of multiplicities as a function of energy scale, are among the main global features of multiplicity for which QCD results exist. Recent data from high energy e⁺e⁻ experiments, including results for separated quark and gluon jets, allow rather direct tests of these results. The theoretical predictions are generally quite successful when confronted with data. Jet and subjet multiplicities are described. Multiplicity in limited regions of phase space is discussed in the context of intermittency and fractality. The problem of singularities in the generating functions is formulated. Some special features of average multiplicities in heavy quark jets are described.     

Consequences of hadron-nucleus multiplicity parametrization

Some interesting consequences are analyzed of a new parametrization for the hadron-nucleus multiplicity distributions and they are compared with the experimental data. Further, it is illustrated how the scaling property for the average multiplicity will be modified and it is found that the experimental data support this behaviour.     

Colour confinement in hadron-nucleus collisions

We study the evolution of colour confinement in hadron-nucleus collisions and determine the resultingx _F dependence for the suppression of quarkonium production on nuclear targets. The Landau-Pomeranchuk effect applied to colour bremsstrahlung is shown to play a considerable role in the from of the suppression.     

Long-range correlations in hadron-nucleus interactions

An analysis of correlations in rapidity of charged particles produced in proton and antiproton interactions on hydrogen, argon and xenon at 200 GeV is presented. Positive long-range correlations are observed in interactions on heavy targets. The dependence of rapidity correlations between the forward and backward hemisphere on the number of projectile collisions is discussed.     

Multiplicities in highp t hadron-nucleus interactions

We present results obtained in π^? A (A=C, Cu, Pb) — collisions at 38 GeV/c. A single particle trigger selects events with one charged particle in the central region and large transverse momentum. The effect of this trigger on the multiplicities of all charged particles and of protons is shown.     

Particle production in high-energy hadron-nucleus interactions

The pseudorapidity (η) distributions of fast particles (β>0.7) emitted in inelastic hadron interactions with carbon, copper and lead were measured for incoming energies from 50 to 150GeV at the CERN Super Proton Synchrotron. Their dependence on target mass (A) and projectile (h) obeys <v>-scaling as expected. Their energy dependence is in contrast with most model predictions.     

Transient fission and multiplicities

The de-excitation chain of the compound nucleus is treated, including the transient character of the fission process. The equations can handle all type of emission and take into account all the nuclei of the decay chain. The results show that the particles behave differently under the transient regime.     

Inclusive hadron-nucleus scattering at high energy

The multiple scattering series of Glauber and Matthiae for hadron-nucleus scattering is summed to a simple analytical expression. It reproduces quantitatively the main features of the experimental cross section for the reaction ${}^4\text{He}\text{+}{}^{\mathrm{A}}\text{Z →}{}^4\text{He + X}$ at 1 GeV/nucleon.     

Multifractal thermodynamics of hadron-hadron and hadron-nucleus interactions

It is shown that the constant-specific-heat approximation is applicable to multifractal thermodynamics of hadron-hadron and hadron-nucleus interactions at high energies. Moreover, the constant specific heats calculated from experimental data on hadron-hadron and hadron-nucleus interactions have approximately the same value for both these types of multifractal multiproduction. Thus this parameter may turn out to be an universal characteristic of the hadron-hadron and hadron-nucleus interactions. Some relationship of this phenomenon to multifractal thermodynamics at the onset of chaos is briefly discussed. Received: 16 December 1997 / Revised version: 2 April 1998     

Rescattering effects in hadron-nucleus and heavy-ion collisions

We review the extension of the factorization formalism of perturbative QCD to coherent soft rescattering associated with hard scattering in high energy nuclear collisions. We emphasize the ability to quantify high order corrections and the predictive power of the factorization approach in terms of universal non-perturbative matrix elements. Although coherent rescattering effects are power suppressed by the hard scales of the scattering, they are enhanced by the nuclear size and could play an important role in understanding the novel nuclear dependence observed in high energy nuclear collisions.Arrival of the final proofs: 22 July 2005PACS: 12.38.Bx, 12.39.St, 24.85. + p     

The nuclear response in high-energy hadron-nucleus interactions

In an experiment at the CERN Super Proton Synchrotron (SPS) studying hadron-nucleus interactions, slow particles which are mainly knockout protons were measured with an electronic detector. Their dependence on the target mass, incoming energy, and projectile is shown. We discuss the use of the number of protons as a measure for the number of interactions of the projectile and conclude that the emitted protons measure the impact parameter of the reaction.     

Dispersion of the multiplicity distribution in hadron-nucleus collisions

It is argued that the measurements of the dispersion of the multiplicity distribution in hadron-nucleus collisions favour the processes of particle production in a sequence of collisions of the incident hadron with target nucleons. On the other hand, generation of particles on groups of nucleons treated as single units leads to large discrepancies.     

Next-to-leading order corrections to multiplicities

It is desirable to develop a systematic and practical method in perturbative QCD to analyze the semi-hard processes in the fragmentation of jets. In this paper, an integral equation with angular ordering is introduced to analyze the multiplicities of hadrons in high-energy jet productions. In order to demonstrate how the method works, the method is applied in the next-to-leading order to the energy dependence of the multiplicity and to the ratio of multiplicities in a gluon jet and in a quark jet. The results agree with the calculations done by Mueller by a different method.     

Length of the formation zone from inclusive hadron-nucleus collisions

It is proposed to study the length of the formation zone by measuring theA-dependence and the energy-dependence of inclusive processes in projectile fragmentation region. The sensitivity of the method is studied, as well as its dependence on the underlying reaction mechanism.     

General properties of polymer systems

We prove the existence of the thermodynamic limit for the pressure and show that the limit is a convex, continuous function of the chemical potential.The existence and analyticity properties of the thermodynamic limit for the correlation functions is then derived; we discuss in particular the Mayer Series and the virial expansion.In the special case of Monomer-Dimer systems it is established that no phase transition is possible; moreover it is shown that the Mayer Series for the density is a series of Stieltjes, which yields upper and lower bounds in terms of Padé approximants.Finally it is shown that the results obtained for polymer systems can be used to study classical lattice systems.Work presented in partial fullfilment of the Ph. D. Thesis.