[NT/RBRC seminar] Statistical analysis of pQCD energy loss across system size, flavor, sqrt(s), and p_T

by William Horowitz (University of Cape Town)

Friday 27 Jun 2025, 11:00 → 13:00 US/Eastern

CFNS library ( https://bnl.zoomgov.com/j/1614715193?pwd=WkwxODVWdzZzb29zQnZRVGp3VTBDQT09)

We present suppression predictions from our pQCD-based energy loss model, which receives small system size corrections, for high-p_T pi, D and B meson R_{AB} as a function of centrality, flavor, sqrt(s), and p_T from large to small collision systems at RHIC and LHC.

 

A statistical analysis constrains the effective strong coupling in our model to available high-p_T suppression data from central heavy-ion collisions at RHIC and LHC, yielding good agreement with all available data. We estimate two important theoretical uncertainties in our model, stemming from: the transition between vacuum and hard thermal loop propagators in the collisional energy loss, and from the angular cutoff on the radiated gluon momentum.

The model uncertainties lead to significant uncertainties in the extracted alpha_s^{eff.} of ~30%, much larger than the uncertainties associated with the extraction procedure; however, the final uncertainty on the constrained R_{AB} and on extrapolations of R_{AB} to regions where it was not constrained of is only ~20%.

We make predictions from our large-system-constrained model for small systems and find good agreement with the photon-normalized R^\pi_{d Au} ~ 0.75 in 0-5% central d+Au collisions by PHENIX. We argue that our significant disagreement with LHC R_{pA} data is due in large part to experimental centrality bias and provide predictions for measurements to disentangle initial from final state effects for understanding suppression measurements at RHIC and LHC.