David Wellmann

Information Institute: TTP Building: 30.23 Room: 11.18 Phone: +49 721 / 608 47023 Email: david.wellmann#kit.edu Responsibilities: IT Administrator

• J. Davies, G. Mishima, M. Steinhauser, D. Wellmann
  gg->ZZ: analytic two-loop results for the low- and high-energy regions
  2020, [arXiv]
Abstract: We compute next-to-leading order virtual two-loop corrections to the process gg->ZZ in the low- and high-energy limits, considering the contributions with virtual top quarks. Analytic results for all 20 form factors are presented including expansion terms up to 1/m12t and m32t. We use a Padé approximation procedure to extend the radius of convergence of the high-energy expansion and apply this approach to the finite virtual next-to-leading order corrections.

• J. Davies, G. Heinrich, S. P. Jones, M. Kerner, G. Mishima, M. Steinhauser, D. Wellmann
  Double Higgs boson production at NLO: combining the exact numerical result and high-energy expansion
  JHEP, 2019, [DOI], [arXiv]
Abstract: We consider the next-to-leading order QCD corrections to Higgs boson pair production, using our recent calculation of the form factors in the high-energy limit. We compute the virtual corrections to the partonic cross section, applying Padé approximations to extend the range of validity of the high-energy expansion. This enables us to compare to the exact numerical calculation in a significant part of the phase space and allows us to extend the virtual matrix element grid, based on the exact numerical calculation, to larger values of the (partonic) transverse momentum of the Higgs boson, which is important for boosted Higgs studies. Improved predictions for hadron colliders with centre-of-mass energies of 14 TeV and 100 TeV are presented. The updated grid is made publicly available.

• J. Davies, G. Mishima, M. Steinhauser, D. Wellmann
  Double Higgs boson production at NLO in the high-energy limit: complete analytic results
  JHEP, 2019, [DOI], [arXiv]
Abstract: We compute the NLO virtual corrections to the partonic cross section of gg->HH, in the high energy limit. Finite Higgs boson mass effects are taken into account via an expansion which is shown to converge quickly. We obtain analytic results for the next-to-leading order form factors which can be used to compute the cross section. The method used for the calculation of the (non-planar) master integrals is described in detail and explicit results are presented.

• J. Davies, G. Mishima, M. Steinhauser, D. Wellmann
  Double Higgs Production in the High Energy Limit
  PoS LL2018, 2018, [DOI],
Abstract: In this talk we summarize our work on NLO QCD corrections to the amplitude for double-Higgs boson production in the gluon fusion channel. We describe our setup to reduce the Feynman integrals of the amplitude to a minimal set of master integrals, and how we compute them. Finally we remark on how so-called uniformly transcendental integrals can be identified in the context of expansion by regions, which we have used extensively in our computation of boundary conditions for systems of differential equations for the master integrals.

• J. Davies, G. Mishima, M. Steinhauser, D. Wellmann
  Double-Higgs boson production in the high-energy limit: planar master integrals
  JHEP, 2018, [DOI], [arXiv]
Abstract: We consider the virtual corrections to the process gg->HH at NLO in the high energy limit and compute the corresponding planar master integrals in an expansion for small top quark mass. We provide details on the evaluation of the boundary conditions and present analytic results expressed in terms of harmonic polylogarithms.

• P. Marquard, A. V. Smirnov, V. A. Smirnov, M. Steinhauser, D. Wellmann
  (g-2)_μ at four loops in QED
  PHIPSI17, 2017, [DOI], [arXiv]
Abstract: We review the four-loop QED corrections to the anomalous magnetic moment of the muon. The fermionic contributions with closed electron and tau contributions are discussed. Furthermore, we report on a new independent calculation of the universal four-loop contribution and compare with existing results.

• J. Davies, M. Steinhauser, D. Wellmann
  Hadronic Higgs boson decay at order α_s⁴ and α_s⁵
  PoS DIS2017, 2018, [DOI], [arXiv]
Abstract: We compute corrections to the decay of the Standard Model Higgs boson to hadrons, to the fourth order in the strong coupling constant α. We use an effective theory in which the Higgs boson couples directly to bottom quarks and to gluons, via top quark-mediated effective couplings. Numerically, our results are of a comparable size to the previously-known "massless" contributions and complete the order α_s⁴ corrections to the hadronic decay of the Higgs boson. In these proceedings we also provide an independent cross check of the gluonic Higgs boson decay at order α_s⁵.

• J. Davies, M. Steinhauser, D. Wellmann
  Completing the hadronic Higgs boson decay at order α_s⁴
  Nucl. Phys. B920, 2017, [DOI], [arXiv]
Abstract: We compute four-loop corrections to the hadronic decay of the Standard Model Higgs boson which are induced by effective couplings to bottom quarks and gluons, mediated by the top quark. Our numerical results are comparable in size to the purely massless contributions which have been known for a few years. The results presented in this paper complete the order α_s⁴ corrections to the hadronic Higgs boson decay.

• P. Marquard, A. V. Smirnov, V. A. Smirnov, M. Steinhauser, D. Wellmann
  MS-on-shell quark mass relation up to four loops in QCD and a general SU(N) gauge group
  Phys. Rev. D 94, 2016, [DOI], [arXiv]
Abstract: We compute the relation between heavy quark masses defined in the modified minimal subtraction and the on-shell schemes. Detailed results are presented for all coefficients of the SU(Nc) color factors. The reduction of the four-loop on-shell integrals is performed for a general QCD gauge parameter. Altogether there are about 380 master integrals. Some of them are computed analytically, others with high numerical precision using Mellin-Barnes representations, and the rest numerically with the help of FIESTA. We discuss in detail the precise numerical evaluation of the four-loop master integrals. Updated relations between various short-distance masses and the MS quark mass to next-to-next-to-next-to-leading order accuracy are provided for the charm, bottom and top quarks. We discuss the dependence on the renormalization and factorization scale.