Extensive Air Showers and Accelerator Data - The NEEDS Workshop

Very high energy cosmic rays are typically studied by measuring extensive air showers formed by secondary particles produced in collisions with air nuclei. The indirect character of the measurement makes the physics interpretation of cosmic ray data strongly dependent on simulations of multiparticle production in showers. In April 2002 about 50 physicists met in Karlsruhe to discuss various aspects of hadronic multiparticle production with the aim of intensifying the interaction between high energy physics and cosmic ray groups. Current and upcoming possibilities at accelerators for measuring features of hadronic interactions of relevance to air showers were the focus of the workshop. This article is a review of the discussions and conclusions.Comment: 10 pages, 11 figures, talk given at 12th ISVHECRI, Geneva, July 15-20, 200

Study of Multiparticle Spikes in Central 4.5A GeV/c C-Cu Collisions

An analysis of local fluctuations, or spikes, is performed for charged particles produced in central C-Cu collisions at 4.5 GeV/$c$/nucleon. The distributions of spike-centers and the maximum density distributions are investigated for different narrow pseudorapidity windows to search for multiparticle dynamical correlations. Two peaks over statistical background are observed in the spike-center distributions with the structure similar to that expected from the coherent gluon radiation model and recently found in hadronic interactions. The dynamical contribution to maximum density fluctuations are obtained to be hidden by statistical correlations, though behavior of the distributions shows qualitative agreement with that from the one-dimensional intermittency model. The observed features of the two different approaches, coherent vs. stochastic, to the formation of the local dynamical fluctuations are discussed.Comment: 12 pages, LaTeX, 2 eps fig

Fragmentation of Nuclei at Intermediate and High Energies in Modified Cascade Model

The process of nuclear multifragmentation has been implemented, together with evaporation and fission channels of the disintegration of excited remnants in nucleus-nucleus collisions using percolation theory and the intranuclear cascade model. Colliding nuclei are treated as face--centered--cubic lattices with nucleons occupying the nodes of the lattice. The site--bond percolation model is used. The code can be applied for calculation of the fragmentation of nuclei in spallation and multifragmentation reactions.Comment: 19 pages, 10 figure

Charged particle multiplicities in pp interactions at √s = 0.9, 2.36, and 7 TeV

Measurements of primary charged hadron multiplicity distributions are presented for non-single-diractive events in proton-proton collisions at centre-of-mass energies of √s = 0.9, 2.36, and 7 TeV, in five pseudorapidity ranges from |η| < 0.5 to |η| < 2.4. The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and the 7 TeV run in 2010. The multiplicity distribution at √s = 0.9 TeV is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with √s is underestimated by most event generators. The average transverse momentum as a function of the multiplicity is also presented. The measurement of higher-order moments of the multiplicity distribution confirms the violation of Koba-Nielsen-Olesen scaling that has been observed at lower energies

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