Nuclear suppression from coherent $J/ψ$ photoproduction at the Large Hadron Collider

V. Guzey; E. Kryshen; M. Strikman; M. Zhalov

Paper

Nuclear suppression from coherent $J/ψ$ photoproduction at the Large Hadron Collider

Abstract

Using the data on coherent

photoproduction in Pb-Pb ultraperipheral collisions (UPCs) obtained in Runs 1 and 2 at the Large Hadron Collider (LHC), we determined with a good accuracy the nuclear suppression factor of

in a wide range of the momentum fraction

. In the small-

region

, our

fit favors a flat form of

with approximately a 5% accuracy for

and a 25% error at

. At the same time, uncertainties of the fit do not exclude a slow decrease of

in the small-

limit. At large

is constrained to better than 10% precision up to

and is also consistent with the value of

, which we extract from the Fermilab data on the

dependence of the cross section of coherent

photoproduction on fixed nuclear targets. The resulting uncertainties on

are small, which indicates the potential of the LHC data on coherent charmonium photoproduction in Pb-Pb UPCs to provide additional constraints on small-

nPDFs. We explicitly demonstrate this using as an example the EPPS16 and nCTEQ16 nuclear parton distribution functions, whose uncertainties decrease severalfold after the Bayesian reweighting of the discussed UPC data.