NLO predictions for t-channel production of single top and fourth generation quarks at hadron colliders

Abstract

We present updated NLO predictions for the electroweak t-channel production of heavy quarks at the Tevatron and at the LHC. We consider production of single top and fourth generation t ′ starting from both 2 → 2 and 2 → 3 Born processes. Predictions for tb ′ and t ′ b ′ cross sections at NLO are also given for the first time. A thorough study of the theoretical uncertainties coming from parton distribution functions, renormalisation and factorisation scale dependence and heavy quark masses is performed. Keywords: Top quark, Standard Model, Beyond the Standard Model, Tevatron, LHC. * On leave of absence from CP3, Université catholique de Louvain.

On the interpretation of Top Partners searches

“…As we will explain in section 3.1, the X 5/3 single-production is closely related to the single production of a charge −1/3 top partner in association with a Top quark. We can thus use the latter process, which can be implemented in the MCFM code [50][51][52][53], to extract a reliable estimate of the X 5/3 single production cross-section. The results are reported in table 2 and encode the effect of the QCD interactions up to NLO, the integration over the phase-space and the convolution with the parton distribution functions.…”

“…The efficiencies at each mass point can thus be obtained JHEP12(2014)097 Table 2. NLO single production cross sections for the W t fusion for a unit coupling, at √ s = 8, 13 TeV (the LO values are in brackets) computed with MCFM [50][51][52][53] by considering the closely related process of single production of a charge −1/3 Top Partner pp → Bt (see main text for more details). The results were obtained by using the MSTW2008 parton distribution functions.…”

“…The MCFM code [50][51][52][53] is designed to compute QCD corrections to the SM single-Top production process, however it can also be used for BSM studies as it allows to change freely the mass of the Top and of the Bottom quark. By setting m t to M X we can compute σ W + b and σ W − b , obtaining the results reported, together with the LO estimate within brackets, in table 5.…”

Single production of an exotic bottom partner at LHC

“…This allow us to use the results of the ref. [45] where the NLO K-factor of the single production of heavy quarks between 1.3 TeV and 2.5 TeV range over 1.26-1.49. This leads to a cross-section of 1-10 fb which yields 100-1000 of single production events in the first 100 fb −1 of the 14 TeV LHC run II.…”

“…We have used NLO K-factor of ref. [45] for the normalization of the signal and the ones of ref. [51,52] for the backgrounds.…”