Progress in the Glauber Model at Collider Energies

Abstract

We review the theoretical and experimental progress in the Glauber model of multiple nucleon and/or parton scatterings after the last 10–15 years of operation with proton and nuclear beams at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider. The main developments and the state of the art of the field are summarized. These encompass measurements of the inclusive inelastic proton and nuclear cross sections, advances in the description of the proton and nuclear density profiles and their fluctuations, inclusion of subnucleonic degrees of freedom, experimental procedures and issues related to the determination of the collision centrality, validation of the binary scaling prescription for hard scattering cross sections, and constraints on transport properties of quark–gluon matter from varying initial-state conditions in relativistic hydrodynamics calculations. These advances confirm the validity and usefulness of the Glauber formalism for quantitative studies of quantum chromodynamics matter produced in high-energy collisions of systems, from protons to uranium nuclei, of vastly different size. Expected final online publication date for the Annual Review of Nuclear and Particle Science, Volume 71 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

ALICE luminosity determination for Pb–Pb collisions at √s NN = 5.02 TeV

“…The measured cross section is in agreement with the prediction of (7.62 ± 0.15) b from ref. [48], based on a Monte Carlo implementation of the Glauber model with a nuclear radius of ∼ 6.7 fm, a nuclear skin depth for protons (neutrons) of ∼ 0.45 fm (∼ 0.56 fm), and an inelastic nucleon-nucleon cross section of ∼ 67 mb.…”

Predictions and postdictions for relativistic lead and oxygen collisions with Trajectum

“…Also theoretically it is not quite clear when a hadronic collision actually happened. This is usually determined by a Monte Carlo Glauber model that puts nucleons at fluctuating positions and then decides in a collision whether or not two nucleons collide or not [33,34]. A crucial ingredient herein is the nucleon-nucleon cross section, σ NN , which also features as a Trajectum parameter and is usually fixed by the measured value in pp collisions (at high energies the difference in cross section between protons and neutrons is negligible).…”

Further developments of a multi-phase transport model for relativistic nuclear collisions

“…In the second way, the initial transverse spatial condition including event-byevent sub-nucleon fluctuations is generated with a Glauber Monte Carlo method based on the constituent quark picture [236, [239][240][241][242][243]. By modeling the proton as three constituent quarks, the interaction of two protons can be interpreted as collisions between the constituent quarks from each incoming proton within the Glauber model framework [241,244]. The positions of the quark constituents are first sampled with the proton profile qðrÞ, and then the transverse coordinates of the excited strings are randomly assigned to the binary collision center of each interacting constituent pair.…”