Abstract
To obtain more precise parton distribution functions (PDFs) it is important to include data on inclusive high transverse energy jet production in the global parton analyses. These data have high statistics and the NNLO terms in the perturbative QCD (pQCD) description are now available. Our aim is to reduce the uncertainty in the comparison of the jet data with pQCD. To ensure the best convergence of the pQCD series it is important to choose the appropriate factorization scales, mu _mathrm{F}. We show that it is possible to absorb and resum in the incoming PDFs and fragmentation function (D) an essential part of the higher alpha _mathrm{s}-order corrections by determining the ‘optimal’ values of mu _mathrm{F}. We emphasize that it is necessary to optimize different factorization scales for the various factors in the cross section: indeed, both of the PDFs, and also the fragmentation function, have their own optimal scale. We show how the values of these scales can be calculated for the LO (NLO) part of the pQCD prediction of the cross section based on the theoretically known NLO (NNLO) corrections. After these scales are fixed at their optimal values, the residual factorization scale dependence is much reduced.
Highlights
With the availability of the complete QCD formulation of jet production to needed to avoid double counting of NLO (NNLO) [1] we are entering the precision era for extracting parton distribution functions (PDFs) from including these data [2,3] in the global PDF analyses
K factors, which reflect the ratio of NNLO/NLO perturbative QCD (pQCD) predictions, are used to correct the result obtained from the NLO Monte Carlo
To improve convergence of the pQCD series we have shown that three different factorization scales may be used for the LO part
Summary
From a formal point of view, factorization scales are unphysical quantities. The final result should not depend on their choice. They are introduced into pQCD just for convenience to separate the part of the cross section described by the hard matrix element for the partonic subprocess of interest from the part that can be described by PDFs or fragmentation functions which are universal and do not depend on the particular subprocess. Depending on the choice of factorization scales, a larger or smaller part of a fixed-order contribution is placed in the matrix element. It is advantageous to move a major part of the higher-order corrections into the universal PDFs and to minimize the remaining contribution in the matrix element
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