Measurement of the Centrality Dependence of the Dijet Yield in p+Pb Collisions at $\sqrt{s_{NN}}$ = 8.16 TeV with the ATLAS Detector

ATLAS measured the centrality dependence of the dijet yield using 165 nb$^{-1}$ of p+Pb data collected at $\sqrt{s_{NN}}$ = 8.16 TeV in 2016. The event centrality, which reflects the p+Pb impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, R$_{CP}$, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The R$_{CP}$ shows a scaling with the Bjorken x of the parton originating from the proton, x$_p$, while no such trend is observed as a function of x$_{Pb}$. This analysis provides unique input to understanding the role of small proton spatial configurations in p+Pb collisions by covering parton momentum fractions from the valence region down to x$_p$∼10$^{-3}$ and x$_{Pb}$∼4×10$^{-4}$.