Factorization at the LHC: From parton distribution functions to initial state jets
Factorization at the LHC: From parton distribution functions to initial state jets
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DOI：
10.1103/physrevd.81.094035
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发表时间：
2010-05
影响因子：
5
通讯作者：
I. Stewart;F. Tackmann;W. Waalewijn
中科院分区：
文献类型：
--
作者：
I. Stewart;F. Tackmann;W. Waalewijn
We study proton-(anti)proton collisions at the LHC or Tevatron in the presence of experimental restrictions on the hadronic final state and for generic parton momentum fractions. At the scale Q of the hard interaction, factorization does not yield standard parton distribution functions (PDFs) for the initial state. The measurement restricting the hadronic final state introduces a new scale {mu}{sub B}<<Q and probes the proton prior to the hard collision. This corresponds to evaluating the PDFs at the scale {mu}{sub B}. After the proton is probed, the incoming hard parton is contained in an initial-state jet, and the hard collision occurs between partons inside these jets rather than inside protons. The proper description of such initial-state jets requires ''beam functions''. At the scale {mu}{sub B}, the beam function factorizes into a convolution of calculable Wilson coefficients and PDFs. Below {mu}{sub B}, the initial-state evolution is described by the usual PDF evolution which changes x, while above {mu}{sub B} it is governed by a different renormalization group evolution that sums double logarithms of {mu}{sub B}/Q and leaves x fixed. As an example, we prove a factorization theorem for 'isolated Drell-Yan', pp{yields}Xl{sup +}l{sup -} where X is restricted to have no central jets.more » We comment on the extension to cases where the hadronic final state contains a certain number of isolated central jets.« less
