Search For Nuclear Stopping using Bremsstrahlung Photons Emitted from Ultra-central Pb+Pb Collision at the Large Hadron Collider (CERN)

The Large Hadron Collider (LHC) enables the study of high-energy collisions, recreating early-universe conditions. This project investigates bremsstrahlung photons—produced by decelerated ultra-relativistic particles—in lead-lead collisions at √s = 5.36 TeV, using 2024 CMS heavy-ion data. These photons are essential for probing nuclear stopping and gluon saturation, key to understanding collision dynamics. Despite skepticism within the CMS community, we demonstrate that the Zero Degree Calorimeter (ZDC), located 140 m from the interaction point, can detect bremsstrahlung photons. Angular distributions were simulated via Monte Carlo (inverse sampling), and detector response was validated against real data. Simulations show ~43 ± 3% of photons reach the ZDC. The ZDC exhibits linear response, and ultra-central collisions have been identified to optimize photon yield. This is the first time bremsstrahlung photons have been experimentally verified at the ZDC—a novel and potentially transformative result.