ar X iv : h ep - p h / 04 01 22 3 v 1 2 8 Ja n 20 04 Description of pp - interactions with very high multiplicity at 70 GeV / c

The collective behavior of secondary particles in pp interactions at 70 GeV/c is studied. A Two Stage Gluon Model is offered to describe processes with very high multiplicity. An active role of gluons is shown in multiparticle dynamics. The analysis of multiplicity distributions has revealed a possibility of a thermodynamic interpretation of these interactions. A mechanism of the soft photon production as a signature of the quark-gluon system is proposed. PACS: 12.38Qk; 12.40Ee; 13.85Rm. These investigations have been carried out in the framework of the project ”Thermalization”(JINR). This project is aimed at studying the collective behaviour of secondary particles in proton interactions at 70 GeV/c [1]. According to the present understanding of hadronic structure, based on quantum chromodynamics (QCD) [2], protons consist of quarks and gluons. We have developed a Two Stage Gluon model [3] to describe high energy multiparticle production (MP) in proton interactions. At the first stage of the model QCD and thermodynamical approaches are used. At the second stage (hadronization) a phenomenological description is applied. After the inelastic collision of two protons a part of the energy of these moving particles is converted into the thermal one. Constituents of the proton, quarks and gluons, have enough energy to be described by pQCD, because the strong coupling reaches a small value. Quarks and gluons become liberated. Our model investigations have shown that the quark division of primary protons accompanied by hadron production in pp interactions at 70 GeV is absent. MP is realized by gluons. This study has confirmed the idea of P.Carruthers about a passive role of quarks [4]. We have used one of the most generally accepted methods to study multiparticle dynamics: the multiplicity distribution (MD) analysis. Two schemes of interactions are offered. They are distinguished only by the quark-gluon (QG) stage. If we want to study the gluon division inside the QG system (QGS), the scheme branch model is used. If we are not interested in what is going inside QGS the second scheme thermodynamic model should be applied. In the both schemes some of gluons (not all of them) leave QGS and convert to real hadrons. Using the thermodynamic interpretation we can say that active gluons are evaporated from hot QGS. After the evaporation they pass the stage of hadronization. Processes of pp interactions at 70 GeV/c were investigated experimentally [5]. MD of charged particles were limited to 20 secondaries. Among them there are n charged mesons ( π or π−) and two leading protons: p + p → nπ + 2N . In Thermalization project it is planned to observe events with high multiplicities. The production of soft photons could give the information about the early stage of QG interactions [1, 6]. The choice of the MP scheme is based on comparison with experimental data [5]. Physicists from JINR (Dubna) used generator PYTHIA and obtained MD of charged hadrons [5]. It was shown that PYTHIA generator does not agree with the experimental data at high multiplicities and has a deviation two orders of the magnitude at nch = 18 equal to (Fig. 1). We have refused from the quark model [7] (Fig. 1) because of some specific features which we cannot accept and that is why we have built a scheme of hadron interactions for MD description by means of the modified Two Stage Model (TSM) [8]. We consider that at the early stage of pp interactions initial quarks and gluons take part in the formation of QGS. They develop branch processes [9]. Also as in TSM we have used the hypothesis of soft decoloration at the second stage