Measurement of exclusive photoproduction from protons in Pb collisions at

Area of Science:

• High-energy physics
• Nuclear physics
• Quantum chromodynamics

Background:

• Ultra--peripheral heavy-ion collisions provide a clean environment for studying photon-induced processes.
• The J/psi meson is a key probe for understanding the strong interaction and quark-gluon plasma.

Purpose of the Study:

• To measure the differential cross sections for exclusive J/psi photoproduction from protons in ultraperipheral Pb-Pb collisions.
• To compare the measured cross sections with theoretical predictions based on perturbative quantum chromodynamics.

Main Methods:

• Data collected by the CMS experiment at the Large Hadron Collider.
• Analysis of the J/psi -> mu+ mu- decay channel.
• Selection of events with low hadronic activity, characteristic of ultraperipheral collisions.

Main Results:

• Differential cross sections for J/psi photoproduction were extracted as a function of transverse momentum squared and rapidity.
• The J/psi photoproduction cross section was determined in a specific rapidity range, corresponding to a range of photon-proton center-of-mass energies.
• The results provide new experimental data on J/psi production in a high-energy, photon-dominated regime.

Conclusions:

• The study provides precise measurements of J/psi photoproduction, contributing to the understanding of strong interaction dynamics.
• Comparison with theoretical models will help refine predictions for exclusive vector meson production in heavy-ion collisions.