Master Thesis Open Access

Impact of differential dijet cross section measurements on PDF fits at NNLO

Stark, Jakob

Thesis supervisor(s)

Rabbertz, Klaus; Quast, G√ľnter

Influence of triple differential dijet cross sections at √s = 8 TeV on fitted PDFs is studied. Inclusion of jet data into PDF fits mainly has impact on the gluon PDF. Compared to previous PDF fits of the CMS collaboration with dijet data included, this is done for the first time with NNLO theory calculations, that only became available in the last few years. By comparing PDF fits at NLO to NNLO one finds, that at NNLO the scale dependency and scale uncertainties of the resulting PDFs decrease significantly, which matches the expected behavior.

In addition, simultaneous fits of the PDFs and the strong coupling constant are presented. Here the results exhibit significantly smaller scale uncertainties at NNLO. The central fit results for αs(Mz) are, as expected, somewhat smaller at NNLO than at NLO.

At last, a double differential dijet cross section measurement at √s = 7 TeV is included into the PDF fits as well. While at NLO both dijet measurements lead to slightly different results, at NNLO these differences decrease drastically, such that a combined fit can be performed including both dijet datasets in a consistent way.

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