Stephen Philip Jones

A bstract: In this article, we explore the selection of contour deformations for the numerical evaluation of Feynman integrals after sector decomposition. In existing codes, the contour of integration is determined heuristically for each individual phase-space point by sampling the integrand. In this work, we introduce two methods for selecting a valid contour deformation as a function of the kinematic variables in an entire phase-space region using only an initial sampling or training step. In addition to ensuring the validity of the contour, our method also minimises the variance of the resulting integrand, making it optimal for Monte Carlo integration. We investigate the suitability of these contours when used for Randomised Quasi-Monte Carlo integration and show that although the optimal contour for such integration rules depends on the specific generating vector used, one of our methods typically yields contours with better performance than existing heuristic methods. The a priori knowledge of the integration path obtained in this work can be used to improve the speed of conventional integration methods or be leveraged for integration using neural networks, where, crucially, it removes the need to retrain the neural network for each phase-space point. The techniques described in this work can be adapted to other problems where a non-trivial integration path has to be chosen subject to a set of constraints.

We present state-of-the-art predictions for the inclusive cross section of gluon-initiated ZH Z H production, following the recommendations of the LHC Higgs Working Group. In particular, we include NLO QCD corrections, where the virtual corrections are obtained from the combination of a forward expansion and a high-energy expansion, and the real corrections are exact. The expanded results for the virtual corrections are compared in detail to full numerical results. The updated predictions show a reduction of the scale uncertainties to the level of 15%, and they include an estimate of the top-mass-scheme uncertainty.

We present a major update of the one-loop generator GoSam, containing performance improvements as well as new features, in particular functionalities that facilitate calculations beyond the Standard Model in Effective Field Theory frameworks.

Constraining the Higgs boson self-interaction is one of the main goals for the high luminosity phase of the LHC. A promising channel to this aim is the simultaneous production of two Higgs bosons from gluon fusion. For the interpretation of the data, precise theoretical predictions, also for differential cross sections, are needed. Following current projections this requires electroweak corrections at next-to-leading order. We present the contributions of top-Yukawa and Higgs self- interaction-type, as well as the first steps towards inclusion of the complete NLO electroweak corrections.

Constraining the Higgs boson self-interaction is one of the main goals for the high luminosity phase of the LHC. A promising channel to this aim is the simultaneous production of two Higgs bosons from gluon fusion. For the interpretation of the data, precise theoretical predictions, also for differential cross sections, are needed. Following current projections this requires electroweak corrections at next-to-leading order. We present the contributions of top-Yukawa and Higgs self-interaction-type, as well as the first steps towards inclusion of the complete NLO electroweak corrections.

A bstract: We present a method for rewriting dimensionally regulated Feynman parameter integrals in the Minkowski regime as a sum of real, positive integrands multiplied by complex prefactors. This representation eliminates the need for contour deformation, allowing for direct numerical or analytic evaluation of the integrals. We develop an algorithm to construct such representations for a broad class of integrals and demonstrate its generalisation through selected examples. Our approach is applied to integrals up to three loops, including cases with internal masses and off-shell external legs. The resulting expressions are suitable for evaluation using existing techniques, such as sector decomposition, where we observe performance gains of up to four orders of magnitude in certain cases.

We present a major update of the one-loop generator GoSam, containing performance improvements as well as new features, in particular functionalities that facilitate calculations beyond the Standard Model in Effective Field Theory frameworks.

We present a method for rewriting dimensionally regulated Feynman parameter integrals in the Minkowski regime as a sum of real, positive integrands multiplied by complex prefactors. This representation eliminates the need for contour deformation, allowing for direct numerical or analytic evaluation of the integrals. We develop an algorithm to construct such representations for a broad class of integrals and demonstrate its generalisation through selected examples. Our approach is applied to integrals up to three loops, including cases with internal masses and off-shell external legs. The resulting expressions are suitable for evaluation using existing techniques, such as sector decomposition, where we observe performance gains of up to four orders of magnitude in certain cases.

We calculate the complete next-to-leading order (NLO) QCD corrections to loop-induced g g → Z Z production including full top-quark mass effects. The two-loop virtual corrections are obtained by combining analytic results for the massless, Higgs-mediated, and one-loop factorizable contributions with numerically computed amplitudes containing the top-quark mass. We show that the choice of subtraction scheme for the virtual contribution impacts the precision with which the virtual contribution must be evaluated in order to obtain sufficiently precise phenomenological predictions. For direct production through a massive top-quark loop, we observe that the relative NLO corrections are large. The direct massive and Higgs-mediated contributions individually increase relative to the massless production at high diboson invariant mass, but interfere destructively with each other. At the Large Hadron Collider, the NLO corrections to the gluon channel give a sizable contribution to the p p → Z Z + X cross section at N 3 LO .