Baryon number in proton-proton and proton-nucleus high energy collisions

Marek Jeżabek,Andrzej Rybicki

doi:10.1140/epjp/s13360-021-01956-1

Abstract

New analyses of baryon spectra in proton-proton and proton-carbon collisions at sqrt{s}_mathrm {_{NN}}=17.3 GeV, made in the framework of two phenomenological models are presented. The first model in question is the classic Dual Parton Model by Capella and Tran Thanh Van, the second is the Gluon Exchange Model very recently proposed by the authors. For both studies, the usage of modern experimental data from the CERN SPS eliminates several of the most important limitations inherent to earlier studies of this type. In both studies, the standard mechanism of baryon stopping with preservation of the diquark, proposed by Capella and Tran Thanh Van fails to describe the distribution of non-strange baryons in collisions of the projectile proton with more than one nucleon from the carbon target obtained from experimental data, and the upper limit for the contribution of this mechanism can be established. In both cases, the conclusion is that the projectile diquark must be very often disintegrated. This opens new diagrams not available in proton-proton collisions which lead to the transport of baryon number over long distances in rapidity. The present limitations, and possibility of improvement in both approaches are discussed. The implications of our findings for new measurements are addressed, in particular using antiproton beams.

Highlights

The process of transport of baryon number from the initial to the final state plays a special role in studies of non-perturbative (“soft”) processes, induced by the strong interaction
Both studies were based on modern experimental data on proton and neutron sp√ectra in pp and pC collisions obtained at the CERN SPS at beam energy of 158 GeV ( s =17.3 GeV) [8,9]. These analyses were made in the framework of two phenomenological models (1) the Dual Parton Model (DPM) proposed by Capella and Tran Thanh Van [4], which makes it partially similar to earlier studies made by one of us [5,10], and (2) the Gluon Exchange Model (GEM) which we proposed very recently and which can be considered, technically, as an extension of the DPM with a natural, even if very significant, broadening of the available Fock space
The analysis presented was a direct application of the Dual Parton Model, in its formulation dedicated to baryon studies from Ref. [5], to modern and far more complete

Summary

Introduction

The process of transport of baryon number from the initial to the final state plays a special role in studies of non-perturbative (“soft”) processes, induced by the strong interaction. Baryon number conservation implies that at least at not too high collision energies where baryonantibaryon pair production is reasonably limited, baryon spectra can provide a cleaner way to investigate the fate of quarks in the reaction than, e.g., spectra of produced particles They give a better tool to constrain the inherent dynamical scenarios. In heavy ion collisions, baryon number transport plays a fundamental role as it lies at the basis of the energy deposit necessary to create a deconfined quark-gluon plasma [1] Seen in this context, the state of the art knowledge on the dynamics of this process appears as quite incomplete, and not exempt from spectacular controversies [2]. This situation we attribute at least partially to the limitations inherent to experimental data which originally served to build the core of the present understanding of baryon stopping phenomena, see e.g

Objectives

Results

Conclusion