We examine the role played in double-parton interactions (DPI) by the parton–parton correlations originating from perturbative QCD parton splittings. Also presented are the results of the numerical ...analysis of the integrated DPI cross sections at Tevatron and LHC energies. To obtain the numerical results the knowledge of the single-parton GPDs gained by the HERA experiments was used to construct the non-perturbative input for
generalized double-parton distributions
. The perturbative two-parton correlations induced by three-parton interactions contribute significantly to a resolution of the longstanding puzzle of an excess of multi-jet production events in the back-to-back kinematics observed at the Tevatron.
pQCD physics of multiparton interactions Blok, B.; Dokshitzer, Yu; Frankfurt, L. ...
The European physical journal. C, Particles and fields,
04/2012, Volume:
72, Issue:
4
Journal Article
Peer reviewed
Open access
We study production of two pairs of jets in hadron–hadron collisions in view of extracting contribution of
double hard interactions
of three and four partons (3→4, 4→4). Such interactions, in spite ...of being power suppressed at the level of the total cross section, become comparable with the standard hard collisions of two partons, 2→4, in the
back-to-back kinematics
when the transverse momentum imbalances of two pairing jets are relatively small.
We express differential and total cross sections for two-dijet production in double parton collisions through the generalized two-parton distributions,
2
GPDs (Block et al., Phys. Rev. D 83, 071501,
2011
), and treat them in the leading logarithmic approximation of pQCD that resums collinear logarithms in all orders.
A special emphasis is given to 3→4 double hard interaction processes which, being of the same order in
as the 4→4 process, turn out to be
geometrically enhanced
compared to the latter and should contribute significantly to four-jet production.
The framework developed here takes into systematic consideration perturbative
Q
2
evolution of
2
GPDs. It can be used as a basis for future analysis of NLO corrections to multiparton interactions (MPI) at LHC and Tevatron colliders, in particular for improving evaluation of QCD backgrounds to new physics searches.
We construct universal parton evolution equation that produces space- and time-like anomalous dimensions for the maximally super-symmetric N=4 Yang–Mills field theory model, and find that its kernel ...satisfies the Gribov–Lipatov reciprocity relation in three loops. Given a simple structure of the evolution kernel, this should help to generate the major part of multi-loop contributions to QCD anomalous dimensions, due to classical soft gluon radiation effects.
We consider propagation of heavy quarks in QCD matter. Because of large quark mass, the radiative quark energy loss appears to be qualitatively different from that of light quarks at all energies of ...practical importance. Finite quark mass effects lead to an in-medium enhancement of the heavy-to-light D/π ratio at moderately large (5–10 GeV) transverse momenta. For hot QCD matter a large enhancement is expected, whose magnitude and shape are exponentially sensitive to the density of colour charges in the medium.
This remark is part of an ongoing project to simplify the structure of the multi-loop anomalous dimensions for parton distributions and fragmentation functions. It answers the call for a “structural ...explanation” of a “very suggestive” relation found by Moch, Vermaseren and Vogt in the context of the x→1 behaviour of three-loop DIS anomalous dimensions. It also highlights further structure that remains to be fully explained.
Analytical study of the rapidity distribution of the final state particles in deep inelastic scattering at small x is presented. We separate and analyze three sources of particle production: ...fragmentation of the quark–antiquark pair that these an impact, accompanying coherent soft gluon radiation due to octet color exchange in the t-channel, and fragmentation of gluons that form parton distribution functions.
Connection to Catani–Ciafaloni–Fiorani–Marchesini (CCFM) equations and the role of gluon reggeization are also discussed.
We consider the bosonic
sl
(
2
)
sector of the maximally supersymmetric
N
=
4
SYM model and show that anomalous dimension of the twist-3 single-trace composite operators built of scalar fields, ...recently calculated up to the four-loop order, can be generated by a compact reciprocity respecting evolution kernel.
Logarithmically enhanced effects due to radiation of soft gluons at large angles in 2→2 QCD scattering processes are treated in terms of the “fifth form factor” that accompanies the four collinear ...singular Sudakov form factors attached to incoming and outgoing hard partons. Unexpected symmetry under exchange of internal and external variables of the problem is pointed out for the anomalous dimension that governs soft gluon effects in hard gluon–gluon scattering.
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