Transverse-momentum resummation for heavy-quark hadroproduction

Stefano Catani,Massimiliano Grazzini,Alessandro Torre

doi:10.1016/j.nuclphysb.2014.11.019

Stefano Catani, Massimiliano Grazzini + Show 1 more

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https://doi.org/10.1016/j.nuclphysb.2014.11.019

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Abstract

We consider the production of a pair of heavy quarks (QQ¯) in hadronic collisions. When the transverse momentum qT of the heavy-quark pair is much smaller than its invariant mass, the QCD perturbative expansion is affected by large logarithmic terms that must be resummed to all orders. This behavior is well known from the simpler case of hadroproduction of colorless high-mass systems, such as vector or Higgs boson(s). In the case of QQ¯ production, the final-state heavy quarks carry color charge and are responsible for additional soft radiation (through direct emission and interferences with initial-state radiation) that complicates the evaluation of the logarithmically-enhanced terms in the small-qT region. We present the all-order resummation structure of the logarithmic contributions, which includes color flow evolution factors due to soft wide-angle radiation. Resummation is performed at the completely differential level with respect to the kinematical variables of the produced heavy quarks. Soft-parton radiation produces azimuthal correlations that are fully taken into account by the resummation formalism. These azimuthal correlations are entangled with those that are produced by initial-state collinear radiation. We present explicit analytical results up to next-to-leading order and next-to-next-to-leading logarithmic accuracy.

Highlights

We consider the inclusive production of a QQpair of heavy quarks (Q) in hadron–hadron collisions
As in the case of simpler processes, such as the hadroproduction of a system of non-strongly interacting particles, the perturbative QCD computation of the qT cross section is affected by large logarithmic terms that need be resummed to all perturbative orders
We have discussed the new issues that arise in the case of heavy-quark production, and we have presented our all-order resummation formula (see Eq (5)) for the logarithmically-enhanced contributions

Summary

Introduction

We consider the inclusive production of a QQpair of heavy quarks (Q) in hadron–hadron collisions. Transverse-momentum resummation for these processes has an all-order universal (process-independent) structure [11, 6, 12, 13, 14], which has been explicitly worked out [14, 15, 16, 17] at NNLL accuracy and the next-to-next-to-leading order (NNLO) in the perturbative expansion This universality structure eventually originates from the underlying physical mechanism that produces the qT broadening of the system F at small qT : the transverse momentum of F is produced by (soft and collinear) QCD radiation from the initial-state colliding partons.

All-order resummation

D C C μ1ν1 μ2ν2 g a1 g a2

Explicit results for the resummation coefficients

Summary