Minijets and the behavior of inelasticity at high energies

Abstract

We present an extension of the interacting gluon model, used previously to calculate inelasticities and leading particle spectra in hadronic and nuclear collisions, which incorporate also the production of minijets. As a result we get inelasticity slowly increasing towards some limited value. PACS number(s1: 13.85.Hd, 12.38.Mh, 13.87.CeThe concept of inelasticity plays an important role in cosmic ray and accelerator physics. Whereas in the former it is crucial for the understanding and interpretation of the development of cosmic ray cascades, in the latter it is an indispensable ingredient of any statistical model of multiparticle production processes. Inelasticity is usually defined as the fraction K of the available energy 6 , in a given interaction, effectively employed for multiparticle production. The energy dependence of inelasticity is a problem of great interest both for the interpretation of cosmic ray data and also for quark-gluon plasma (QGP) physics since inelasticity decreasing with energy would make the formation of Q G P more difficult. Experimentally the situation is not clear and many authors have proposed different behavior of the average inelasticity ( K ) as a function of d s [I].One of the models which in a natural way leads to ( K ) decreasing with energy is the interacting gluon model (IGM) 121. It included originally only soft gluonic interactions and used the phenomenological soft gluongluon cross section as an input. However, it was claimed recently that semi-hard QCD interactions (which produce the so-called minijets) represent an important fraction (-25%) of the total cross section already at the CERN collider energies and are expected to be even more important at higher energies [3]. In this paper we discuss therefore the effect of the inclusion of such semihard component to the original IGM.In the framework of the IGM, in a first approximation, valence quarks do not interact at all but instead form leading particles. The interaction is supposed to come entirely from the gluonic contents of the colliding hadrons via the formation of gluonic fireballs (clusters). The originally predicted decrease of ( K ) with energy can be traced to the assumption that the phenomenological behavior of gluon-gluon cross section ugg(9) is limited to 1 /3 < ugg < const behavior, to the 1 /x form of the gluonic structure functions for small x (see below for details) and to the assumed constancy with energy of the percentage p of the energy-momentum of the projectile allocated t o gluons. Here we shall relax the first condition by allowing the QCD semi-hard interaction mechanism which leads to u, increasing with energy. The probability of depositing fractions x and y of the energy momenta of the incoming hadrons in the central region of reaction, by means of the gluon-gluon interactions, is given by the formula [2] where which is defined by the mass m a of the lightest possible produced state.The function w ( x , y ) (called "spectral function") con-(2) tains all the dynamical input of the model and is pro...

Leading particle effect, inelasticity, and the connection between average multiplicities ine+e−andppBatista1, Covolan2 1999Phys. Rev. D111100View full textAdd to dashboardCite

“…We have presented in this paper a description of the inclusive reaction pp → pX in the whole phase space within the Regge-Mueller formalism, modified by the renormalization of the diffractive cross section. The average multiplicity and the average inelasticity were obtained from the leading proton spectrum and both of them resulted to be increasing functions of energy, in agreement with [4,5] and particularly with [7]. The energy dependence of these quantities is such that allows one to accommodate very well the charged particle multiplicities n ch e + e − and n ch pp by an universal function once an appropriate relation is used.…”

“…The question is that it requires a previous knowledge about the energy dependence of the inelasticity and about the behavior of the average leading particle multiplicity which constitute themselves problematic subjects. In particular, the energy dependence of the average inelasticity is a very much disputed question since there are opposite claims that this quantity increases [4,5,6,7] or that it decreases [8,9,10] with increasing energy at quite different rates. In spite of the of models predicting extreme behaviors, i.e.…”

The Interacting Gluon Model: a review

“…Its original application to the description of inelasticity [12] and multiparticle production processes in hydrodynamical treatments [13] was followed by more refined applications to leading charm production [14] and to single diffraction dissociation, both in hadronic reactions [15] and in reactions originated by photons [16]. These works allowed for providing the systematic description of the leading particle spectra [17] and clearly demonstrated that they are very sensitive to the amount of gluonic component in the diffracted hadron as observed in [18] and [19].…”

Nonlinear waves in a quark gluon plasma

“…A very recent and improved analysis by the STAR collaboration has given further support to this picture [15]. A more solid evidence of this phenomenon may come from the study of jets at the Large Hadron Colider (LHC), where the energy released by the nuclear projectiles in the central rapidity region will be larger [16] and so the formed fireball will be larger and live longer, allowing for a more complete study of waves.…”