Average Particle Multiplicity Research Articles

An investigation of Renyi entropy in high-energy nucleus–nucleus collisions

A study of Renyi entropy of shower particles has been carried out using 16O, 28Si, and 32S projectiles in interaction with AgBr and CNO target present in nuclear emulsion at an incident momentum of 4.5 AGeV/c. The analysis reveals interesting experimental observations for both groups of targets. A comparison of the experimental results with the results obtained from analyzing the event sample generated by the UrQMD code is also presented. Renyi entropy values increase with the increase of projectile mass. This increase is weaker in case of CNO target. The calculated values of second-order Renyi entropy H2 are shown to vary linearly with the logarithm of average particle multiplicity ln⟨n⟩ for both targets. The dependence of Renyi entropy on the logarithm of average particle multiplicity ln⟨n⟩ indicates the presence of long-range correlation in high-energy nucleus–nucleus interactions. The variation is found to be stronger in the case of experimental events in comparison to the UrQMD simulated events indicating stronger long-range correlation for the experimental data.

Jet energy density in hadron-hadron collisions at high energies

The average particle multiplicity density dN/deta is the dynamical quantity which reflects some regularities of particle production in low-pT range. The quantity is an important ingredient of z-scaling. Experimental results on charged particle density are available for pp, pA and AA collisions while experimental properties of the jet density are still an open question. The goal of this work is to find the variable which will reflect the main features of the jet production in low transverse energy range and play the role of the scale factor for the scaling function psi(z) and variable z in data z-presentation. The appropriate candidate is the variable we called "scaled jet energy density". Scaled jet energy density is the probability to have a jet with defined ET in defined xT and pseudorapidity regions. The PYTHIA6.2 Monte Carlo generator is used for calculation of scaled jet energy density in proton-proton collisions over a high energy range (sqrt s = 200-14000 GeV) and at eta = 0. The properties of the new variable are discussed and sensitivity to "physical scenarios" applied in the standard Monte Carlo generator is noted. The results of scaled jet energy density at LHC energies are presented and compared with predictions based on z-scaling.

Kinetic equation with exact charge conservation.

A kinetic master equation for multiplicity distributions is formulated for charged particles which are created or destroyed only in pairs due to the conservation of their Abelian charge. It allows one to study time evolution of the multiplicity distributions in a relativistic many-body system with arbitrary average particle multiplicities. It is shown to reproduce the equilibrium results for both canonical (rare particles) and grand canonical (abundant particles) systems. For canonical systems, the equilibrium multiplicity is much lower and the relaxation time is much shorter than the naive extrapolation from grand canonical results. Implications for chemical equilibration in heavy-ion collisions are also discussed.

Nucleon and deuteron induced spallation reactions

The intranuclear cascade (INC)+evaporation model is used to display the gross features of proton, neutron and deuteron induced spallation reactions between 200 MeV and 2 GeV incident energy per nucleon. Particular attention is focused on average particle multiplicities and their dependencies upon target mass number and incident energy. Simple formulae are derived to allow an easy use of these results. They are expected to provide a rapid survey of the gross features of spallation reactions. The decomposition of particle multiplicities and of cross-sections into cascade and evaporation components is performed and discussed. The impact parameter dependence is investigated. The excitation energy left in the target at the end of the cascade step is also studied, as well as the gross properties of the subsequent evolution of the target remnant. It is shown that neutron differential cross-sections can be split into components with reasonably identified physical origin, which exhibit simple power laws as functions of the target mass number.

The charged particle multiplicity distributions in e+e−annihilation processes in the LEP experiments

A review is presented of the results obtained in an investigation of the charged particle multiplicity distributions in e+e− annihilation processes in experiments on the LEP accelerator at CERN. Universality in the energy dependence for the average charged particle multiplicity in e+e− and p±p collisions, the KNO scaling for the e+e− data, the structure in the multiplicity distribution and its relation to the number of jets in an event, the average particle multiplicities in quark and gluon jets, the pattern of clans, and other questions are discussed.

Implications of Bose-Einstein statistics within an uncorrelated-jet model

The framework of an uncorrelated-jet model (UJM) is used to investigate the implications of Bose-Einstein statistics in multiplicity moments and inclusive spectra. An asymptotic expansion for the grand microcanonical density of states is derived. The choice of the transverse-momentum cutoff function near ${p}_{T}=0$ is found to be of utmost importance for obtaining significant Bose-Einstein-type correlations between particles. A strong enhancement of average particle multiplicity and correlation moments with energy is found in some cases, in contrast to the conventional UJM with Boltzmann statistics. Several rapidity distributions showing the violation of Feynman scaling (plateau behavior) are presented.