49 research outputs found
Zero-jettiness beam functions at NLO
The zero-jettiness beam functions describe collinear emissions from initial
state legs and appear in the factorisation theorem for cross sections in the
limit of small zero-jettiness. They are an important building block for slicing
schemes for colour-singlet production at hadron colliders. We report on our
ongoing calculation of this quantity at next-to-next-to-next-to-leading order
(NLO) in QCD, highlighting in particular the aspects of partial fraction
relations and the calculation of master integrals.Comment: 12 pages, 2 figures, contribution to the proceedings of "Loops and
Legs in Quantum Field Theory - LL2022, 25-30 April, 2022, Ettal, Germany
Sector-improved residue subtraction: Improvements and Applications
We discuss two recent developments of the sector-improved residue subtraction
scheme for handling real radiation at NNLO in QCD. We present a new phase space
construction which minimizes the number phase space configurations for
subtraction terms and we rederive the four-dimensional formulation of the
scheme.Comment: Contribution to the proceedings of the Loops and Legs 2018
conference, St. Goar, German
Higgs decay into massive b-quarks at NNLO QCD in the nested soft-collinear subtraction scheme
We present a fully differential description of a decay of a scalar Higgs boson into massive b-quarks valid at next-to-next-to-leading order (NNLO) in perturbative quan- tum chromodynamics (QCD). We work within the nested soft-collinear subtraction scheme extended to accommodate massive partons. We include the loop-induced contribution in- volving a Higgs coupling to a top quark. We test our calculation against results existing in the literature, comparing the predictions for the total decay width and jet rates
Beam functions for N-jettiness at NLO in perturbative QCD
We present a calculation of all matching coefficients for N-jettiness beam functions at next-to-next-to-next-to-leading order (NLO) in perturbative quantum chromodynamics (QCD). Our computation is performed starting from the respective collinear splitting kernels, which we integrate using the axial gauge. We use reverse unitarity to map the relevant phase-space integrals to loop integrals, which allows us to employ multi-loop techniques including integration-by-parts identities and differential equations. We find a canonical basis and use an algorithm to establish non-trivial partial fraction relations among the resulting master integrals, which allows us to reduce their number substantially. By use of regularity conditions, we express all necessary boundary constants in terms of an independent set, which we compute by direct integration of the corresponding integrals in the soft limit. In this way, we provide an entirely independent calculation of the matching coefficients which were previously computed in ref. [1]
Beam functions for N-jettiness at NLO in perturbative QCD
We present a calculation of all matching coefficients for N-jettiness beam functions at next-to-next-to-next-to-leading order (NLO) in perturbative quantum chromodynamics (QCD). Our computation is performed starting from the respective collinear splitting kernels, which we integrate using the axial gauge. We use reverse unitarity to map the relevant phase-space integrals to loop integrals, which allows us to employ multi-loop techniques including integration-by-parts identities and differential equations. We find a canonical basis and use an algorithm to establish non-trivial partial fraction relations among the resulting master integrals, which allows us to reduce their number substantially. By use of regularity conditions, we express all necessary boundary constants in terms of an independent set, which we compute by direct integration of the corresponding integrals in the soft limit. In this way, we provide an entirely independent calculation of the matching coefficients which were previously computed in arXiv:2006.03056
Bottom quark mass effects in associated production with decay through NNLO QCD
We present a computation of NNLO QCD corrections to the production of a Higgs
boson in association with a boson at the LHC followed by the decay of the
Higgs boson to a pair. At variance with previous NNLO QCD studies of
the same process, we treat quarks as massive. An important advantage of
working with massive quarks is that it makes the use of flavor jet
algorithms unnecessary and allows us to employ conventional jet algorithms to
define jets. We compare NNLO QCD descriptions of the associated
production with massive and massless quarks and also
contrast them with the results provided by parton showers. We find differences in fiducial cross sections computed with massless and
massive quarks. We also observe that much larger differences between
massless and massive results, as well as between fixed-order and parton-shower
results, can arise in selected kinematic distributions.Comment: 30 pages, 9 figure
Quark beam function at next-to-next-to-next-to-leading order in perturbative QCD in the generalized large-approximation
We present the matching coefficient for the quark beam function at next-to-next-to-next-to-leading order
in perturbative QCD in the generalized large Nc-approximation, Nc ∼ Nf ≫ 1. Although several
refinements are still needed to make this result interesting for phenomenological applications, our
computation shows that a fully-differential description of simple color singlet production processes at a
hadron collider at N3LO in perturbative QCD is within reach