Factorization of Hard Processes in QCD

Within the framework of generalized collinear factorization in perturbative QCD (pQCD), we study the effect of initial multiple parton scattering and induced parton energy loss in DrellYan (DY) process in proton-nucleus collisions. We express the contribution from multiple parton scattering and induced gluon radiation to the DY dilepton spectra in terms of nuclear modified effective beam quark distribution functions. The modification depends on the quark transport parameter in nuclear medium. This is similar to the final-state multiple parton scattering in deeply inelastic scattering (DIS) off large nuclei and leads to the suppression of the Drell-Yan cross section in p + A relative to p + p collisions. With the value of quark transport parameter determined from the nuclear modification of single-inclusive DIS hadron spectra as measured by the HERMES experiment, we calculate DY spectra in p + A collisions and find the nuclear suppression due to beam parton energy loss negligible at the Fermilab energy E lab =800 GeV in the kinematic region as covered by the E866 experiment. Most of the observed nuclear suppression of DY spectra in E866 experiment can be described well by parton shadowing in target nuclei as given by the EPS08 parameterization. The effect of beam parton energy loss, however, becomes significant for DY lepton pairs with large beam parton momentum fraction x ′ or small target parton momentum fraction x. We also predict the DY cross section in p + A collisions at lower beam proton energy E lab =120 GeV and show significant suppression due to initial state parton energy loss at moderately large x ′ where the effect of parton shadowing is very small.

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“…According to the collinear factorization [47], the Drell-Yan cross section in h+A collisions can be expressed,…”

Section: Leading Twist Contributionsmentioning

confidence: 99%

Parton energy loss and modified beam quark distribution functions in Drell–Yan process in collisions

et al. 2012

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“…From a phenomenological viewpoint, perhaps the most interesting result is the calculation of D (3) , which contributes to resummation for EW annihilation at the N 3 LL level. In fact, the only missing contribution in order to resum exactly to that accuracy is the four-loop cusp anomalous dimension γ (4) K , which in principle lies close the current boundaries of computability.…”

Section: Perspectivementioning

confidence: 99%

“…Soft and collinear gluon radiation in perturbative QCD is well-known to have special properties of universality and factorization, which are related to its semiclassical nature [1,2] and strongly tied to gauge invariance [3]. These properties are at the heart of our understanding of strong interactions at high energies, as they allow us to define infrared and collinear safe quantities to all orders in perturbation theory, and lead to factorization of long distance contributions in hadronic processes.…”

Section: Introductionmentioning

confidence: 99%

Refining threshold resummations

Laenen

Magnea

2006

Nuclear Physics B - Proceedings Supplements

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We describe some recent refinements of the techniques of threshold resummation, with emphasis on the usefulness of dimensional regularization when applied to nonabelian exponentiation. Threshold resummation is now under theoretical control for DIS and electroweak annihilation cross sections all the way to the fourth tower of logarithms and up to corrections suppressed by powers of the threshold variable.

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“…Factorization theorems [1] assert that for many such cross sections mass divergences may be subtracted, or mass-factorized, in a process-independent way, with any additional finite subtraction constants defining the mass-factorization scheme.…”

Section: Introductionmentioning

confidence: 99%

Exponentiation of the Drell-Yan cross section near partonic threshold in the DIS and MS-bar schemes

Eynck

Laenen

Magnea

2003

J. High Energy Phys.

132

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It has been observed that in the DIS scheme the refactorization of the DrellYan cross section leading to exponentiation of threshold logarithms can also be used to organize a class of constant terms, most of which arise from the ratio of the timelike Sudakov form factor to its spacelike counterpart. We extend this exponentiation to include all constant terms, and demonstrate how a similar organization may be achieved in the MS scheme. We study the relevance of these exponentiations in a two-loop analysis.

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Factorization of Hard Processes in QCD

Abstract: I briefly review: (a) some recent developments in the theory of hard scattering in QCD with polarized beams, and (b) coherent hard diffraction (that is, hard scattering in diffractive events, with the Pomeron behaving in an apparently point-like fashion).

Cited by 1,153 publications

References 58 publications

Parton energy loss and modified beam quark distribution functions in Drell–Yan process in collisions

Parton energy loss and modified beam quark distribution functions in Drell–Yan process in collisions

Refining threshold resummations

Exponentiation of the Drell-Yan cross section near partonic threshold in the DIS and MS-bar schemes

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