Multiplicities, fluctuations and correlations

The recent results on hadron multiplicities in heavy and light quark fragmentation, multiplicity local fluctuations and multiparticle correlations submitted to the Conference are reviewed.Comment: 5 pages, 4 eps figs. Talk given at the 31st International Conference on High Energy Physics (ICHEP02), Amsterdam, The Netherlands, 24-31 July 2002. To appear in the Proceeding

The effect of many sources on the genuine multiparticle correlations

We report on a study aimed to explore the dependence of the genuine multiparticle correlations on the number of sources when the influence of other possible factors during multihadron production are avoided. The analysis utilised the normalised cumulants calculated in three-dimensional phase space of the reaction ee -> Z -> hadrons using a large Monte Carlo sample. The multi-sources events were simulated by overlaying a few independent single ee annihilation events. It was found that as the number of sources increases, the cumulants do not change significantly their structure, but those of an order higher than two decrease fast in their magnitude. This reduction and its amount can be understood in terms of combinatorial considerations of source mixing which dilutes the correlations. The diminishing of the genuine correlations is consistent with recent cumulant measurements in hadron and nucleus induced reactions and should also be relevant to other dynamical correlations like the Bose-Einstein one, in ee -> WW -> hadrons and in nucleus-nucleus reactions

Coherent particle production in collisions of relativistic nuclei

Here we give the results of our study of features of dense groups, or spikes, of particles produced in Mg-Mg and C-Cu collisions at, respectively, 4.3 and 4.5 GeV/c/nucleon aimed to search for a coherent, Cerenkov-like, mechanism of hadroproduction. We investigate the distributions of spike centers and, for Mg-Mg interactions, the energy spectra of negatively charged particles in spikes. The spike-center distributions are obtained to exhibit the structure expected from coherent gluon-jet emission dynamics. This structure is similar in both cases considered, namely for all charged and negatively charged particles, and is also similar to that observed recently for all-charged-particle spikes in hadronic interactions. The energy distribution within spikes is found to have a significant peak over the inclusive background, while the inclusive spectrum shows exponential decrease with two characteristic values of average kinetic energy. The value of the peak energy and its width are in a good agreement with those expected for pions produced in a nuclear medium in the framework of the Cerenkov quantum approach. The peak energy obtained is consistent with the value of the cross-section maximum observed in coincidence nucleon-nucleus interaction experiments.Comment: 8 pages, 5 figures. Invited talk presented by E.S. at the 9th International Workshop on Multiparticle Production: New Frontiers in Soft Physics and Correlations on the Threshold of the Third Millenium, Turin, Italy, June 12 - 17, 200

Description of local multiplicity fluctuations and genuine multiparticle correlations

Various parametrizations of the multiplicity distribution are studied using the recently published large statistics OPAL results on multidimensional local fluctuations and genuine correlations in e+e- -> Z -> hadrons. The measured normalized factorial and cumulant moments are compared to the predictions of the negative binomial distribution, the modified and generalized versions of it, the log-normal distribution and the model of the generalized birth process with immigration. This is the first study which uses the multiplicity distribution parametrizations to describe high-order genuine correlations. Although the parametrizations fit well the measured fluctuations and correlations for low orders, they do show certain deviations at high orders. We have shown that it is necessary to incorporate the multiparticle character of the correlations along with the property of self-similarity to attain a good description of the measurements.Comment: 15 pages, 2 ps figure

The many sources effect on the genuine multihadron correlations

Here we report on a study aimed to explore the dependence of the genuine multiparticle correlations on the number of sources while the influence of other possible factors affecting the multihadron production is avoided. The analysis utilised the normalised cumulants, calculated in three-dimensional phase space, of the reaction e+e- -> Z -> hadrons using a large Monte Carlo event sample. The multi-sources reactions were simulated by overlaying a few independent single e+e- annihilation events. It was found that as the number of sources S increases, the cumulants do not change significantly their structure, but those of an order q>2 (i.e. more than 2 pions) decrease fast in their magnitude. This reduction can be understood in termsof combinatorial considerations of source mixing which dilutes the correlations by a factor of about 1/S^{q-1} which can also serve as a method to estimated the number of sources. This expected suppression is well reproduced by recent cumulant measurements in hadron and nucleus induced reactions both in one (rapidity) and two (rapidity vs. azimuthal angle) dimensions. The diminishing genuine correlations effect should also appear in other dynamical correlations like the Bose-Einstein in e+e- -> W+W- -> hadrons and in nucleus-nucleus reactions.Comment: 12 pages, 4 figs. Invited talk presented by G. Alexander at the 9th International Workshop on Multiparticle Production: New Frontiers in Soft Physics and Correlations on the Threshold of the Third Millenium, Turin, Italy, June 12 - 17, 200

Multihadron production features in different reactions

We consider multihadron production processes in different types of collisions in the framework of the picture based on dissipating energy of participants and their types. In particular, the similarities of such bulk observables like the charged particle mean multiplicity and the pseudorapidity density at midrapidity measured in nucleus-nucleus, (anti)proton-proton and electron-positron interactions are analysed. Within the description proposed a good agreement with the measurements in a wide range of nuclear collision energies from AGS to RHIC is obtained. The predictions up to the LHC energies are made and compared to experimental extrapolations.We consider multihadron production processes in different types of collisions in the framework of the picture based on dissipating energy of participants and their types. In particular, the similarities of such bulk observables like the charged particle mean multiplicity and the pseudorapidity density at midrapidity measured in nucleus-nucleus, (anti)proton-proton and electron-positron interactions are analysed. Within the description proposed a good agreement with the measurements in a wide range of nuclear collision energies from AGS to RHIC is obtained. The predictions up to the LHC energies are made and compared to experimental extrapolations.We consider multihadron production processes in different types of collisions in the framework of the picture based on dissipating energy of participants and their types. In particular, the similarities of such bulk observables like the charged particle mean multiplicity and the pseudorapidity density at midrapidity measured in nucleus‐nucleus, (anti)proton‐proton and electron‐positron interactions are analysed. Within the description proposed a good agreement with the measurements in a wide range of nuclear collision energies from AGS to RHIC is obtained. The predictions up to the LHC energies are made and compared to experimental extrapolations

Multiparticle production in nuclear collisions using effective-energy approach

The dependencies of charged particle pseudorapidity density and transverse energy pseudorapidity density at midrapidity on the collision energy and on the number of nucleon participants, or centrality, measured in nucleus-nucleus collisions are studied in the energy range spanning a few GeV to a few TeV per nucleon. The study is based on the earlier proposed model, combining the constituent quark picture together with Landau relativistic hydrodynamics and shown to interrelate the measurements from different types of collisions. Within this picture, the dependence on the number of participants in heavy-ion collisions are found to be well described in terms of the effective energy defined as a centrality-dependent fraction of the collision energy. The effectiveenergy approach is shown to reveal a similarity in the energy dependence for the most central and centrality data in the entire available energy range. Predictions are made for the forthcoming higher-energy measurements in heavy-ion collisions at the LHC

Multiparticle production in nuclear collisions using effective-energy approach

The dependencies of charged particle pseudorapidity density and transverse energy pseudorapidity density at midrapidity on the collision energy and on the number of nucleon participants, or centrality, measured in nucleus-nucleus collisions are studied in the energy range spanning a few GeV to a few TeV per nucleon. The study is based on the earlier proposed model, combining the constituent quark picture together with Landau relativistic hydrodynamics and shown to interrelate the measurements from different types of collisions. Within this picture, the dependence on the number of participants in heavy-ion collisions are found to be well described in terms of the effective energy defined as a centrality-dependent fraction of the collision energy. The effectiveenergy approach is shown to reveal a similarity in the energy dependence for the most central and centrality data in the entire available energy range. Predictions are made for the forthcoming higher-energy measurements in heavy-ion collisions at the LHC

Multihadron production dynamics exploring energy balance in hadronic to nuclear collisions

The multihadron production in nucleus-nucleus collisions and its interrelation with that in (anti)proton-proton interactions are studied by exploring the charged particle mean multiplicity collision-energy and centrality dependencies in the measurements to date. The study is performed in the framework of the recently proposed effective-energy approach which, under the proper scaling of the collision energy, combines the constituent quark picture with Landau relativistic hydrodynamics counting for the centrality-defined effective energy of participants and relating different types of collisions. Within this approach, the multiplicity energy dependence and the pseudorapidity spectra from the most central nuclear collisions are well reproduced. The study of the multiplicity centrality dependence reveals a new scaling between the measured pseudorapidity spectra and the calculations. By means of this scaling, called the energy balanced limiting fragmentation scaling, one reproduces the pseudorapidity spectra for all centralities. The scaling elucidates some differences in the multiplicity and midrapidity density centrality dependence obtained at RHIC and LHC. These findings reveal an inherent similarity in the multiplicity energy dependence from the most central collisions and centrality data. A new regime in heavy-ion collisions to occur at about a TeV energy is indicated, similar to that observed in the earlier studies of the midrapidity densities. Predictions are made for the mean multiplicities to be measured in proton-proton and heavy-ion collisions at the LHC.The relation of multihadron production in nucleus-nucleus and (anti)proton-proton collisions is studied by exploring the collision-energy and centrality dependencies of the charged particle mean multiplicity in the measurements to date. The study is performed in the framework of the recently proposed effective-energy approach which, under the proper scaling of the collision energy, combines the constituent quark picture with Landau relativistic hydrodynamics counting for the centrality-defined effective energy of participants. Within this approach, the multiplicity energy dependence and the pseudorapidity spectra from the most central nuclear collisions are well reproduced. The study of the multiplicity centrality dependence reveals a new scaling between the measured pseudorapidity spectra and the calculations. By means of this scaling, referred to as energy-balanced limiting fragmentation scaling, one reproduces the pseudorapidity spectra for all centralities. The scaling elucidates some differences in the multiplicity and midrapidity density centrality dependence obtained at RHIC and LHC. These findings reveal an inherent similarity in the multiplicity energy dependence from the most central collisions and centrality data. Predictions are made for the mean multiplicities to be measured in proton-proton and heavy-ion collisions at the LHC.The multihadron production in nucleus-nucleus collisions and its interrelation with that in (anti)proton-proton interactions are studied by exploring the charged particle mean multiplicity collision-energy and centrality dependencies in the measurements to date. The study is performed in the framework of the recently proposed effective-energy approach which, under the proper scaling of the collision energy, combines the constituent quark picture with Landau relativistic hydrodynamics counting for the centrality-defined effective energy of participants and relating different types of collisions. Within this approach, the multiplicity energy dependence and the pseudorapidity spectra from the most central nuclear collisions are well reproduced. The study of the multiplicity centrality dependence reveals a new scaling between the measured pseudorapidity spectra and the calculations. By means of this scaling, called the energy balanced limiting fragmentation scaling, one reproduces the pseudorapidity spectra for all centralities. The scaling elucidates some differences in the multiplicity and midrapidity density centrality dependence obtained at RHIC and LHC. These findings reveal an inherent similarity in the multiplicity energy dependence from the most central collisions and centrality data. A new regime in heavy-ion collisions to occur at about a TeV energy is indicated, similar to that observed in the earlier studies of the midrapidity densities. Predictions are made for the mean multiplicities to be measured in proton-proton and heavy-ion collisions at the LHC

The role of responsibility for treatment choice in early breast cancer

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