Comparison of spectrum models as applied to single-particle $\bf p_t$ spectra from high-energy p-p collisions and their physical interpretations

Abstract

A parametrized mathematical model is required to extract the information carried by transverse momentum $p_t$ spectra from high-energy nuclear collisions and subject it to physical interpretation in terms of possible hadron production mechanisms. The importance of proper model construction and implementation has increased with the emergence of claims for ``collectivity'' (flows) associated with small collision systems (e.g. $p$-$p$ and $p$-Pb). A two-element spectrum model, denoted herein as the Bylinkin model, includes an exponential element and a ``power-law'' element interpreted by the authors to represent emission from a thermalized source and from jet production respectively. Application of the Bylinkin model to various collision systems has led to conclusions about achievement of thermalization and other characteristics of nuclear dynamics. In connection with the Bylinkin model there has emerged theoretical conjecture that the thermalization mechanism signaled by the exponential element is hard processes interacting with quantum entanglement within projectile protons. Predating the Bylinkin model is a two-component (soft+hard) model (TCM) derived empirically from the evolution of $p$-$p$ spectrum data with event multiplicity as a form of data compression. The TCM has been applied to many collision systems and hadron species from which a systematic description of high-energy nuclear collisions has emerged. The Bylinkin model can be seen as a limiting case of the TCM model functions that is unsuited to represent underlying production mechanisms. The present study provides detailed comparisons of the two models for a variety of situations and contrasts two very different data interpretations that result.