Impact of CMS dijets in 5.02 TeV pPb and pp collisions on EPPS16 nuclear PDFs
K. Eskola, P. Paakkinen,* H. Paukkunen
*corresponding author
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Pre-published on: 2019 January 12
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Abstract
The CMS measurement of dijet pseudorapidity distributions in pPb versus pp collisions at 5.02 TeV provides a direct probe on nuclear gluon PDFs. We show that while the predicted pPb pseudorapidity distributions suffer from sizable free-proton PDF uncertainties, the ratios of the pPb and pp distributions are practically insensitive to scale and free-proton PDF choices. We find the CMS data on pPb to pp ratios to be in good agreement with the EPPS16 nuclear modifications. Using a non-quadratic extension of the Hessian PDF reweighting method, we study the impact of these data on the EPPS16 nuclear PDFs. Relative to EPPS16, we find stronger evidence for mid-$x$ gluon antishadowing as well as indication for larger gluon shadowing at small $x$. The data are also able to further constrain the gluon PDF in the EMC region.
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