NNLL soft and Coulomb resummation for squark and gluino production at the LHC

Abstract

We present predictions for the total cross sections for pair production of squarks and gluinos at the LHC including a combined NNLL resummation of soft and Coulomb gluon effects. We derive all terms in the NNLO cross section that are enhanced near the production threshold, which include contributions from spin-dependent potentials and socalled annihilation corrections. The NNLL corrections at √ s = 13 TeV range from up to 20% for squark-squark production to 90% for gluino pair production relative to the NLO results and reduce the theoretical uncertainties of the perturbative calculation to the 10% level. Grid files with our numerical results are publicly available [1].

Reconstruction of top-quark mass effects in Higgs pair production and other gluon-fusion processes

“…In this section the computation of the non-analytic terms in the threshold expansion of the form factors defined in Section 2 is described. Factorization formulae for the inclusive production cross section of heavy-particle pairs near threshold have been developed in [51][52][53][54][55] and applied to a number of processes [56][57][58][59][60][61][62][63]. The approach is based on the factorization of forward-scattering amplitudes which are related to the inclusive cross section by the optical theorem.…”

Soft-gluon and Coulomb corrections to hadronic top-quark pair production beyond NNLO

“…where the labels collectively denote the spin and colour quantum numbers. This convention agrees with [55]. The four-fermion Lagrangian can be decomposed into contributions with definite spin and colour quantum numbers, analogously to (B.1) and (B.4) Here we have neglected imaginary parts, which contribute to toponium decay into light hadrons and should not be taken into account for the total cross section for pp → tt → bbW + W − .…”

“…In the Coulomb sector, using the NLO potential function quoted in [15] resums all corrections of the form (α s /β) k and α s × (α s /β) k . This was supplemented by a leading resummation of logarithms by using a running Coulomb scale, and the inclusion of the leading so-called non-Coulomb correction [15,27,55], which give rise to a tower of terms of the form α 2 s ln β × (α s /β) k .…”

“…All terms in (3.32) apart from the constant were obtained in [27], with the exception of the annihilation contribution which was added in [34,55]. As discussed in [38] this contribution is taken into account in the resummed calculation [15,18], which includes the resummed Coulomb corrections above threshold and the boundstate corrections below.…”

ColliderBit: a GAMBIT module for the calculation of high-energy collider observables and likelihoods

“…This is clearly unusable in a scan where the evaluation of a single parameter point must be done in times on the order of a few seconds. For strong production there exist pre-computed grids of NLO crosssections with added (N)NLL corrections, which in combination with fast interpolation routines allow accurate cross-sections to be obtained within fractions of a second [73][74][75][76][77][78][79]. However, these interpolations are limited to models where all squarks except the stops are mass degenerate.…”