Constraining gluon distributions in nuclei using dijets in proton-proton and proton-lead collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV

Understand

The pseudorapidity distributions of dijets as a function of their average transverse momentum ($p_\mathrm{T}^\text{ave}$) are measured in proton-lead (pPb) and proton-proton (pp) collisions.

• The data samples were collected by the CMS experiment at the CERN LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV.
• A significant modification of the pPb spectra with respect to the pp spectra is observed in all $p_\mathrm{T}^\text{ave}$ intervals investigated.
• The ratios of the pPb and pp distributions are compared to next-to-leading order perturbative quantum chromodynamics calculations with unbound nucleon and nuclear parton distribution functions (PDFs).