Speaker
Description
Gluons are responsible for binding quarks inside protons and neutrons through the strong interaction (QCD). Understanding how gluons are arranged spatially provides insight into how nucleons interact and how nuclear matter is held together. The investigation of near-threshold J/ψ meson photoproduction is unique opportunity to probe the gluonic structure of the nucleon and light nuclei. In particular, the reaction γd→J/ψd provides direct sensitivity to the transverse gluon distribution and gluon-mediated interaction mechanisms inside the deuteron. The transverse gluon distributions are essential for mapping the 3D internal structure of nucleons and nuclei, particularly at high energy collisions. This research aims to determine the differential and total cross sections for coherent J/ψ meson photoproduction off deuteron near threshold using untagged quasi-real photons from Jefferson Lab experiment E12-11-003B. The CLAS12 detector, located in Hall B at Jefferson Lab, operates with a 11 GeV continuous electron beam incident on a fixed liquid deuterium target. J/ψ is then produced via the exchange of a quasi-real photon and decays to a lepton pair. The J/ψ meson is identified through its leptonic decay channel, while final state particles are reconstructed and identified using particle identification (PID) methods. The four-vector of the quasi-real photon is reconstructed through four-momentum conservation. The cross-section extraction further requires background subtraction, determination of luminosity, and CLAS12 acceptance for the coherent process. The expected outcome of the proposed project will be the first determination of the near-threshold coherent J/ψ photoproduction cross section on the deuteron. This work has been supported in part by NSF PHY-2412777.