Abstract
It is known that multiple partonic scatterings in high-energy proton-proton () collisions must happen in parallel. However, a rigorous parallel scattering formalism, taking energy sharing properly into account, fails to reproduce factorization, which on the other hand is the basis of almost all event generators. In addition, binary scaling in nuclear scatterings is badly violated. These problems are usually “solved” by simply not considering strictly parallel scatterings, which is not a solution. I will report on new ideas (leading to EPOS4), which allow recovering perfectly factorization, and also binary scaling in collisions, in a rigorous unbiased parallel scattering formalism. In this new approach, dynamical saturation scales play a crucial role, and this seems to be the missing piece needed to reconcile parallel scattering with factorization. From a practical point of view, one can compute within the EPOS4 framework parton distribution functions (EPOS PDFs) and use them to compute inclusive cross sections. So, for the first time, one may compute inclusive jet production (for heavy or light flavors) at very high transverse momentum () and at the same time in the same formalism study flow effects at low in high-multiplicity events, making EPOS4 a full-scale “general purpose event generator”. I discuss applications, essentially multiplicity dependencies (of particle ratios, mean , charm production) which are very strongly affected by the saturation issues discussed in this paper.
30 More- Received 16 March 2023
- Revised 10 July 2023
- Accepted 19 September 2023
DOI:https://doi.org/10.1103/PhysRevC.108.064903
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Published by the American Physical Society