Imaging nuclear modifications on parton distributions with tripledifferential dijet cross sections in protonnucleus collisions
Abstract
Dijet production in protonnucleus (p A ) collisions at the LHC provides invaluable information on the underlying parton distributions in nuclei, especially the gluon distributions. Tripledifferential dijet cross sections enable a wellcontrolled kinematic scan (over momentum fraction x and probing scale Q^{2}) of the nuclear parton distribution functions (nPDFs), i.e., f_{i}^{A}(x ,Q^{2}). In this work, we study several types of tripledifferential cross sections for dijet production in protonproton and protonlead (p Pb ) collisions at the LHC, to nexttoleading order within the framework of perturbative quantum chromodynamics (pQCD). Four sets of nPDF parametrizations, EPPS16, nCTEQ15, TUJU19, and nIMParton16 are employed in the calculations for p Pb collisions. We show that the observable nuclear modification factor R_{p Pb} of such cross sections can serve as a nice image of the nuclear modifications on parton distributions, quantified by the ratio r_{i}^{A}(x ,Q^{2})=f_{i}^{A ,proton}(x ,Q^{2})/f_{i}^{proton}(x ,Q^{2}). Considerable differences among the R_{p Pb} predicted by the four nPDF sets can be observed and intuitively understood. Future measurements of such observables are expected to not only constrain the nPDF parametrizations, but also help confirm various nuclear effects, e.g., shadowing, antishadowing, EMC, and Fermi motion in different regions of x and their variations with probing scale Q^{2}.
 Publication:

Physical Review D
 Pub Date:
 May 2022
 DOI:
 10.1103/PhysRevD.105.096025
 arXiv:
 arXiv:2112.11819
 Bibcode:
 2022PhRvD.105i6025S
 Keywords:

 High Energy Physics  Phenomenology;
 Nuclear Theory
 EPrint:
 15 pages, 15 figures