Fluctuations and correlations in statistical models of hadron production

An extension of the standard concept of the statistical ensembles is suggested. Namely, the statistical ensembles with extensive quantities fluctuating according to an externally given distribution are introduced. Applications in the statistical models of multiple hadron production in high energy physics are discussed.     

A statistical analysis of hadron spectrum: Quantum chaos in hadrons

The nearest-neighbor mass-spacing distribution of the meson and baryon spectrum (up to 2.5 GeV) is described by the Wigner surmise corresponding to the statistics of the Gaussian orthogonal ensemble of random matrix theory. This can be viewed as a manifestation of quantum chaos in hadrons. Received: 30 September 2002 / Accepted: 21 November 2002 / Published online: 4 February 2003 RID="a" ID="a"Present address: Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA; e-mail: vlad@phy.ohiou.edu Communicated by G. Orlandini     

Exotic hadron bound state production at hadron colliders

The non-relativistic wave function framework is applied to study the production and decay of exotic hadrons, which can be effectively described as bound states of other hadrons. Employing the factorized formulation,with the help of event generators, we investigate the production of exotic hadrons in multiproduction processes at high energy hadron colliders. This study provides crucial information for the measurements of the relevant exotic hadrons.     

Multi-jet production in hadron collisions

The advent of high-energy hadron colliders necessitates efficient and accurate computation of multi-jet production processes, both as QCD processes in their own right and as backgrounds for other physics. The algorithm that performs these tasks and a brief numerical study of multi-jet processes are presented. Received: 21 February 2002 / Published online: 22 May 2002     

Recombination model for hadron production

We calculate baryon distributions in the fragmentation region ofpp collision using Das and Hwa picture of quark recombination. A new estimation of the sea quark distributions in proton is obtained by fitting the pseudoscalar meson data at fixedP _T taking account of parton transverse momenta.     

Forward gluon production in hadron–hadron scattering with pomeron loops

We discuss new physical phenomena expected in particle production in hadron–hadron collisions at high energy, as a consequence of pomeron loop effects in the evolution equations for the color glass condensate. We focus on gluon production in asymmetric, ‘dilute–dense’, collisions: a dilute projectile scatters off a dense hadronic target, whose gluon distribution is highly evolved. This situation is representative for particle production in proton–proton collisions at forward rapidities (say, at LHC) and admits a dipole factorization similar to that of deep inelastic scattering (DIS). We show that at sufficiently large forward rapidities, where the pomeron loop effects become important in the evolution of the target wavefunction, gluon production is dominated by ‘black spots’ (saturated gluon configurations) up to very large values of the transverse momentum, well above the average saturation momentum in the target. In this regime, the produced gluon spectrum exhibits diffusive scaling, so like DIS at sufficiently high energy.     

Diffractive production and hadron structure

Analysis of diffractive production on nuclei implied cross sections of the diffractively produced system on nucleons which are smaller than the corresponding projectile nucleon cross sections. We provide a natural explanation for this feature in the Good-Walker coherent production formalism. A specific realization of the Good-Walker formalism stated in terms of quarks and connecting electric flux tubes and some ensuing consequences are also discussed briefly.     

The origin of thermal hadron production

Multihadron production in high energy collisions, from e⁺e^- annihilation to heavy ion interactions, shows remarkable thermal behaviour, specified by a universal “Hagedorn” temperature. We argue that this hadronic radiation is formed by tunneling through the event horizon of colour confinement, i.e., that it is the QCD counterpart of Hawking-Unruh radiation from black holes. It is shown to be emitted at a universal temperature T_H ≃ (σ/2 π)^1/2, where σ denotes the string tension. Since the event horizon does not allow information transfer, the radiation is thermal “at birth”.     

A one-dimensional model of associated production in high-energy hadron collisions

We estimate production processes in the one-dimensional approximation of the dual unitary approach to hadron collisions. Strange particle production is in satisfactory agreement with estimates from data; charmed particle production is found to be observably large.     

A study of the double hadron neutrino production on nuclei

The nuclear medium influence on the dihadron neutrino charged current production is investigated using the data obtained with SKAT bubble chamber. An indication is obtained that the nuclear attenuation of the dihadron production is more expressed for kinematically closest hadron pairs. The experimental data are compared with predictions of the string model.     

High-energy hadron production and inclusive reactions

Recent data on multiparticle production at high energies are reviewed. The major topics include exclusive analyses, multiplicity distributions, single-particle inclusive spectra, and correlations. An effort is made to explore the physical significance of these results.     

Thermal hadron production in Si-Au collisions

The most abundantly produced hadron species in Si - Au collisions at the BNL-AGS (nucleons, pions, kaons, antikaons and hyperons) are shown to be in accord with emission from a thermal resonance gas source. Within the uncertainties of the present data, two freeze-out points are possible. The best agreement is obtained for a temperature T ? 110 MeV and a baryochemical potential μ_B ? 540 MeV, corresponding to about 1/3 standard nuclear density. Another possible point lies at about twice nuclear density, with T ? 160 MeV and μ_B ? 620 MeV. Our analysis takes the isopin asymmetry of the initial state fully into account.     

Backward hadron production in neutrino-nucleus interactions

The production of backward pions in lepton-nucleus collisions is analyzed. We show that a large yield of high momentum backward pions can be explained by the Regge asymptotic of the distribution of nucleons carrying a large momentum fraction in the nuclear target. The calculated spectra of pions emitted in the ν+ Ne →μ+π⁻+ X and ν+²H →μ+π⁻+ X reactions are in satisfactory agreement with the available experimental data. Received: 22 July 1999 / Revised version: 22 November 1999     

Charged Higgs production at hadron colliders

We study the production and decay of charged Higgs bosons,H ^±, at TEVATRON and SSC energies as a function of the top massm _t and theH ^± massm _H . We give the cross sections for events arising from bothH ^±→τν andtb decays, together with those of the competing background processes. In particular, form _t >m _H we studyH ^± W ^? andW ⁺ W ^? production and thet→bτν decay.