https://doi.org/10.1051/epjconf/201920604001
PYTHIA and the preoccupied proton
University of Washington, Seattle, Washington, USA
* e-mail: ttrainor99@gmail.com
Published online: 19 April 2019
The PYTHIA Monte Carlo (PMC) has been applied broadly to simulations of high-energy p-p and p- 
collisions. The PMC is based on several assumptions, such as that most hadrons result from jet production (multiple par-ton interactions or MPIs), that p-p centrality is relevant and that color reconnection (CR) strongly influences fragmentation to jets. An alternative description is provided by the two-component (soft + hard) model (TCM) of hadron production. TCM analysis of p-Pb ensemble-mean-pt data reveals centrality trends quite different from those estimated via a geometric Glauber model based on the eikonal approximation. Glauber estimates of binary-collision number are three times TCM estimates. Detailed study of p-Pb data conflicts with a basic Glauber assumption – that a projectile proton may interact simultaneously with multiple target nucleons. Instead, in both p-p and p-A collisions, a p-N collision once initiated is exclusive of other possible interactions (during that collision), and within the collision any pair of participant partons may interact –a p-N collision is thus “all or nothing.” In this presentation the PMC is challenged by an assortment of contradictory data, and evidence for p-N exclusivity is reviewed to make a case for the “preoccupied proton” of the title.
© The Authors, published by EDP Sciences, 2019
This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
