Renormalizationgroup improved predictions for topquark pair production at hadron colliders
Abstract
Precision predictions for phenomenologically interesting observables such as the tbar{t} invariant mass distribution and forwardbackward asymmetry in topquark pair production at hadron colliders require control over the differential cross section in perturbative QCD. In this paper we improve existing calculations of the doubly differential cross section in the invariant mass and scattering angle by using techniques from softcollinear effective theory to perform an NNLL resummation of threshold logarithms, which become large when the invariant mass M of the topquark pair approaches the partonic centerofmass energy sqrt {{hat{s}}} . We also derive an approximate formula for the differential cross section at NNLO in fixedorder perturbation theory, which completely determines the coefficients multiplying the singular plus distributions in the variable left( {1  {{{{M^2}}} left/ {{hat{s}}} right.}} right) . We then match our results in the threshold region with the exact results at NLO in fixedorder perturbation theory, and perform a numerical analysis of the invariant mass distribution, the total cross section, and the forwardbackward asymmetry. We argue that these are the most accurate predictions available for these observables at present. Using MSTW2008NNLO parton distribution functions (PDFs) along with α _{ s }( M _{ Z }) = 0 .117 and m _{ t } = 173 .1 GeV, we obtain for the inclusive production cross sections at the Tevatron and LHC the values {{{σ }}_{text{Tevatron}}} = left( {6.30± 0.19_{  0.23}^{ + 0.31}} right){text{pb}} and σ _{LHC} = (149 ± 7 ± 8) pb, where the first error results from scale variations while the second reflects PDF uncertainties.
 Publication:

Journal of High Energy Physics
 Pub Date:
 September 2010
 DOI:
 10.1007/JHEP09(2010)097
 arXiv:
 arXiv:1003.5827
 Bibcode:
 2010JHEP...09..097A
 Keywords:

 Hadronic Colliders;
 Renormalization Group;
 QCD;
 High Energy Physics  Phenomenology
 EPrint:
 61 pages, 18 figures, version to appear in JHEP