Determination of the number of participating nucleons in p+p interactions at SPS energies

TL;DR

This paper investigates the actual number of participating nucleons in proton-proton collisions at SPS energies, revealing that fewer protons participate than previously assumed, and provides a method to estimate yields of various particles based on conservation laws.

Contribution

It introduces a novel analysis showing that on average only 1.89 protons participate in p+p interactions at 17.3 GeV, challenging previous assumptions and enabling yield estimations using conservation principles.

Findings

Average participating protons are 1.89 at 17.3 GeV.

Yields of neutrons, kaons, and hyperons can be estimated with high precision.

Conservation laws allow for accurate predictions of particle yields below tens of GeV.

Abstract

In the past the analyses of inelastic p+p collision for example in terms of the hadron gas model have assumed that always both protons participate in the interaction. In this article we show that (at sqrt(s) = 17.3 GeV ) on average only 1,89 protons are interacting. Measurements of the mean multiplicities of protons, neutrons, charged pions, charged kaons and {\Lambda} hyperons allow to compute the number of initial state nucleons using conservation of baryon number, strangeness, and isospin. We further argue that once the number of initial state nucleons is given and the mean multiplicities of protons and charged pions are known in p+p interactions at center-of-mass energies below a few tens of GeV, the yields of net neutrons, kaons, and hyperons can be estimated with a precision of a few percent using again baryon and isospin conservation.