Parton models of low momentum transfer processes

Abstract

In the last five years ample evidence has been found supporting the idea that the quark-parton structure of hadrons is relevant for multiple production in soft hadronic collisions. Starting from the experimental foundations, we compare the most successful models applying this idea. Implications are discussed on special type reactions like diffraction dissociation and collisions on nuclei, and the models are confronted with recent data leading to new insight and modifications. Relative yields of particles in the central region may be understood as reflecting their valence quark structure in the framework of quark combinatorics, and the comparison of the valence structure of initial and final hadrons allows us to understand yields in the fragmentation regions. From the structure functions of initial hadrons and/or the fragmentation functions of (di)quarks into final hadrons as seen in deep inelastic lepton-hadron or e+ecollisions, one can deduce the shape of fragmentation spectra in soft hadronic collisions. However, hadronic collisions also prove a very rich independent source of information on parton structure. Work to be done on the theoretical side is on a solid foundation of the two successful pictures of quark fragmentation and quark recombination as well as on an explanation of their apparent complementarity. On the experimental side, apart from further results from the pp collider, high statistics is needed on hydrogen and on heavier nuclei at Plab > 200 GeV/c in particular from strange beams.

Particle production and correlations in hadron-hadron collisions in the dual Monte-Carlo chain fragmentation model

“…In order to apply such a hadronization scheme also to soft hadron-hadron interactions, we have to make the basic assumption that quark and antiquark jets from e+e-annihilation or diquark jets from lepton-hadron scattering processes do not differ strongly from the ones produced in hadron-hadron collisions. This jet universality is not derived theoretically, but experimental data strongly suggest such an assumption, see [9] for a review.(iii) For chains of very low invariant mass we slightly modify the kinematics and create directly stable hadrons or hadron resonances.-2 -(iv) Transforming all created hadrons and hadron resonances back into the laboratory system, we obtain a complete final hadronic state.Since we use a Monte-Carlo method we are able to generate exclusive events conserving exactly energy momentum and all additive quantum numbers.(v) The subsequent decay of hadron resonances into stable final hadrons is realized using the Monte-Carlo code DECAY [10].Since we are only interested in multiparticle production in the energy range from 5 or 10 GeV up to 1 TeV, it is sufficient to consider two chains containing only the valence quarks in hadron-hadron collisions. This is not correct for larger energies, i.e.…”

Bubble chambers in high energy hadron collisions (and vice versa)

“…As is shown in Fig. 10, the average shape of the hadronic system is the same in all three types of collision at given hadronic energy [13], as is its quite dramatic change with energy. Of course, a higher energy hadronic point would be needed to see where flattening-off takes place, there.…”

“…The power ra of the (1 -ja:|)n parametrization of the invariant single-particle inclusive cross section, compared to the dimensional counting rules (lines). The broken lines are corrected for the sup pression of d-quarks in the proton structure function [13].…”

“…9, a compilation [13] is given of the power n for a large number of reactions in meson fragmentation (left) and baryon fragmentation (right). In general, the trend of the counting rules (lines) is reproduced by the data.…”

Neutral-strange-particle production in 200-Gev/cpπ+K+Brick1, Widgoff2, Beillière3 et al. 1992Phys. Rev. D10040View full textAdd to dashboardCite

“…Such a ratio for charged pions has often been fit to the form R = 1 +/3( vp -1 1. In the absence of rescattering, it is expected [20] that /3 should equal 0.5, and if rescattering does contribute significantly, than /3 should be greater. In our own previous work [ l l ] , we found that for charged pions, / 3 was consistent with 0.5 for each of our three beams.…”