Abstract
We calculate the two-loop QCD corrections to gg → ZZ involving a closed top-quark loop. We present a new method to systematically construct linear combinations of Feynman integrals with a convergent parametric representation, where we also allow for irreducible numerators, higher powers of propagators, dimensionally shifted integrals, and subsector integrals. The amplitude is expressed in terms of such finite integrals by employing syzygies derived with linear algebra and finite field techniques. Evaluating the amplitude using numerical integration, we find agreement with previous expansions in asymptotic limits and provide ab initio results also for intermediate partonic energies and non-central scattering at higher energies.
Highlights
Accounts for O(60%) [14] of the total NNLO correction owing to the high gluon luminosity at the LHC
The amplitude is expressed in terms of such finite integrals by employing syzygies derived with linear algebra and finite field techniques
To improve our numerical performance, we choose a basis of finite integrals, where we allow for linear combinations of divergent integrals
Summary
Accounts for O(60%) [14] of the total NNLO correction owing to the high gluon luminosity at the LHC. Due to the Goldstone boson equivalence theorem [28, 29], top-quark corrections at two-loops could be significant as well, especially for longitudinally polarised Z bosons at high invariant mass. This configuration is of particular interest, since it provides unique opportunities for measurement of an anomalous ttZ coupling [30, 31]. We calculate the two-loop QCD corrections to on-shell gg → ZZ production which involve a closed top-quark loop, keeping the dependence on the top-quark mass exact.
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