Qiuchan Lu soutient sa thèse le lundi 30 novembre 2026

Qiuchan Lu soutient sa thèse le lundi 30 novembre 2026 à 14h00 dans l’amphi 1003 au BEM.

This thesis presents a comprehensive investigation of Cold Nuclear Matter effects through charmonium production in the LHCb fixed-target programme. Using proton-argon and proton-proton collisions at 70.9 GeV, recorded with the SMOG2 storage cell, it explores the interplay of initial- and final-state nuclear effects in a previously unexplored energy regime that bridges fixed-target and collider experiments.
A set of complementary observables, including the J/psi production cross section, the nuclear modification factor, the psi(2S)-to-J/psi production ratio, and the ratio of the J/psi and D0 nuclear modification factors, is measured as a function of transverse momentum and rapidity. Together, these measurements provide a detailed picture of the mechanisms governing charmonium production and suppression in cold nuclear matter, while reducing sensitivities to production and initial-state uncertainties.
The results provide the first characterization of charmonium production in proton-argon collisions at 70.9 GeV with the LHCb fixed-target programme, offer new constraints on theoretical descriptions of Cold Nuclear Matter effects through comparisons with previous measurements and phenomenological predictions, and establish essential reference measurements for future studies with heavier nuclear targets.