Non-resonant and electroweak NNLO correction to the e+e− top anti-top threshold

Abstract

Abstract:We determine the NNLO electroweak correction to the e + e − → bbW + W − X production cross section near the top-pair production threshold. The calculation includes non-resonant production of the final state as well as electroweak effects in resonant top anti-top pair production with non-relativistic resummation, and elevates the theoretical prediction to NNNLO QCD plus NNLO electroweak accuracy. We then study the impact of the new contributions on the top-pair threshold scan at a future lepton collider.

Electroweak and non-resonant corrections to top-pair production near threshold at NNLO

“…For the endpoint finite diagrams we use MadGraph [14] code from which we remove the contributions from the endpoint divergent diagrams. The details of this computation are given in [8].…”

“…They are currently not known at NLL. A detailed discussion of the corrections to the resonant part is given in [8].…”

“…At NNLO, we have to consider O(α EW ) corrections to the hard matching coefficients C (k) [15], which become complex because oftbW + and tbW − cuts [16,8]. Furthermore, there are corrections to the matrix element from the QED Coulomb potential −e 2 t α em /r and higher-order terms involving the top-quark width, e.g.…”

“…The subtraction terms are given by the singular terms in (1 − t) with the full ε dependence and have been determined in [13,8] using the expansion by regions [11,12]. The NNLO contributions contain endpoint singular terms scaling as (1 − t) −(a+bε) with a = 2, 3/2, 1.…”

“…We find, however, that non-QCD effects at NLO yield corrections up to 15% [6,7], which motivates the calculation of the full NNLO non-QCD corrections [8] presented in these proceedings. The extension of the calculation beyond pure QCD requires a systematic treatment of the instability of the top quark.…”