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Robert V. Harlander

Publications and source records attributed to Robert V. Harlander.

52 records · Page 3Linked to original sources
arXiv2010

Hadronic Higgs Production and Decay in Supersymmetry at Next-to-Leading Order

Supersymmetric QCD corrections to the gluonic production and decay rate of a CP-even Higgs boson are evaluated at next-to-leading order. To this aim, we derive an effective Lagrangian for the gluon-Higgs coupling. We show that a consistent calculation requires the inclusion of gluino effects, in contrast to what has been done previously. The supersymmetric corrections to the gluon-Higgs coupling lead to a modification of the next-to-leading order K-factor for the Higgs production rate at the LHC by less than five percent.

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arXiv2009

Higgs production in gluon fusion at next-to-next-to-leading order QCD for finite top mass

The inclusive Higgs production cross section from gluon fusion is calculated through NNLO QCD, including its top quark mass dependence. This is achieved through a matching of the 1/mtop expansion of the partonic cross sections to the exact large s-hat limits which are derived from k_T-factorization. The accuracy of this procedure is estimated to be better than 1% for the hadronic cross section. The final result is shown to be within 1% of the commonly used effective theory approach, thus confirming earlier findings.

hep-ph↗
arXiv2009

Finite top mass effects for hadronic Higgs production at next-to-next-to-leading order

The first four terms of an expansion in mH^2/mt^2 of the total inclusive cross section for Higgs production in gluon fusion are evaluated through next-to-next-to-leading order QCD. A reliable and precise approximation of the full top mass dependence at NNLO is derived and compared to the frequently used heavy-top limit. It is found that both results agree numerically to better than 0.5% in the Higgs mass range of 100-300 GeV. This validates the higher order results for the inclusive Higgs cross section and justifies the heavy-top limit as a powerful tool for Higgs phenomenology at the LHC and the Tevatron.

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arXiv2009

The SUSY-QCD beta function to three loops

A number of DR-bar renormalization constants in softly broken SUSY-QCD are evaluated to three-loop level: the wave function renormalization constants for quarks, squarks, gluons, gluinos, ghosts, and epsilon-scalars, and the renormalization constants for the quark and gluino mass as well as for all cubic vertices. The latter allow us to derive the corresponding beta functions through three loops, all of which we find to be identical to the expression for the gauge beta function obtained by Jack, Jones, and North [Jack:1996vg] (see also Ref. [Pickering:2001aq]). This explicitely demonstrates the consistency of DRED with SUSY and gauge invariance, an important pre-requisite for precision calculations in supersymmetric theories.

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arXiv2009

Top mass effects in Higgs production at next-to-next-to-leading order QCD: virtual corrections

Top quark mass suppressed terms are calculated for the virtual amplitude for Higgs production in gluon fusion at three-loop level, i.e. O(α_s^3). The method of asymptotic expansions in its automated form is used to evaluate the first three non-vanishing orders in terms of M_H^2/M_t^2, where the first order corresponds to the known results of the effective Lagrangian approach.

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arXiv2006

Pseudo-scalar Higgs production at next-to-leading order SUSY-QCD

The production rate of the CP-odd Higgs boson in the Minimal Supersymmetric Standard Model is evaluated through next-to-leading order in the strong coupling constant. The divergent integrals are regulated using Dimensional Reduction, with a straightforward implementation of $γ_5$. The result is confirmed within Dimensional Regularization where $γ_5$ is implemented according to the Standard Model calculation of Chetyrkin et al. The well-known Standard Model result is recovered if the masses of the supersymmetric particles tend to infinity.

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arXiv2004

Supersymmetric Higgs production in gluon fusion at next-to-leading order

The next-to-leading order (NLO) QCD corrections to the production and decay rate of a Higgs boson are computed within the framework of the Minimal Supersymmetric Standard Model (MSSM). The calculation is based on an effective theory for light and intermediate mass Higgs bosons. We provide a Fortran routine for the numerical evaluation of the coefficient function. For most of the MSSM parameter space, the relative size of the NLO corrections is typically of the order of 5% smaller than the Standard Model value. We exemplify the numerical results for two scenarios: the benchmark point SPS1a, and a parameter region where the gluon-Higgs coupling at leading order is very small due to a cancellation of the squark and quark contributions.

hep-ph↗
arXiv2003

Higgs boson production in bottom quark fusion at next-to-next-to-leading order

The total cross section for Higgs production in bottom-quark annihilation is evaluated at next-to-next-to-leading order (NNLO) in QCD. This is the first time that all terms at order alpha_s^2 are taken into account. We find a greatly reduced scale dependence with respect to lower order results, for both the factorization and the renormalization scales. The behavior of the result is consistent with earlier determinations of the appropriate factorization scale for this process of mu_F ~ M_H/4, and supports the validity of the bottom parton density approach for computing the total inclusive rate. We present precise predictions for the cross section at the Tevatron and the LHC.

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arXiv2003

Rhad: A program for the evaluation of the hadronic R-ratio in the perturbative regime of QCD

This paper describes the fortran program rhad which performs a numerical evaluation of the photon-induced hadronic R-ratio, R(s), related to the cross section for electron-positron annihilation, for a given center-of-mass energy \sqrt{s}. In rhad the state-of-the-art perturbative corrections to R(s) are implemented and the running and decoupling of the strong coupling constant and the quark masses is automatically treated consistently. Several options allow for a flexible use of the program.

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arXiv2002

Production of a pseudo-scalar Higgs boson at hadron colliders at next-to-next-to leading order

The production cross section for pseudo-scalar Higgs bosons at hadron colliders is computed at next-to-next-to-leading order (NNLO) in QCD. The pseudo-scalar Higgs is assumed to couple only to top quarks. The NNLO effects are evaluated using an effective lagrangian where the top quarks are integrated out. The NNLO corrections are similar in size to those found for scalar Higgs boson production.

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arXiv2002

Next-to-Next-to-Leading Order Higgs Production at Hadron Colliders

The Higgs boson production cross section at pp and p\bar{p} colliders is calculated in QCD at next-to-next-to-leading order (NNLO). We find that the perturbative expansion of the production cross section is well behaved and that scale dependence is reduced relative to the NLO result. These findings give us confidence in the reliability of the prediction. We also report an error in the NNLO correction to Drell-Yan production.

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arXiv2001

Inclusive Higgs Production at Next-to-Next-to-Leading Order

We describe the contributions of virtual corrections and soft gluon emission to the inclusive Higgs boson production cross section $pp\to H + X$ computed at next-to-next-to-leading order in the heavy top quark limit. We also discuss estimates of the leading non-soft corrections.

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arXiv2001

Soft and virtual corrections to pp -> H + X at NNLO

The contributions of virtual corrections and soft gluon emission to the inclusive Higgs production cross section pp -> H + X are computed at next-to-next-to-leading order in the heavy top quark limit. We show that this part of the total cross section is well behaved in the sense of perturbative convergence, with the NNLO corrections amounting to an enhancement of the NLO cross section by \sim 5% for LHC and 10-20% for the Tevatron. We compare our results with an existing estimate of the full NNLO effects and argue that an analytic evaluation of the hard scattering contributions is needed.

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arXiv2001

Pade approximation to fixed order QCD calculations

Pade approximations appear to be a powerful tool to extend the validity range of expansions around certain kinematical limits and to combine expansions of different limits to a single interpolating function. After a brief outline of the general method, we will review a number of recent applications and describe the modifications that have to be applied in each case. Among these applications are the MS-bar/on-shell conversion factor for quark masses and the top decay rate at NNLO in QCD.

hep-ph↗
arXiv2000

Virtual corrections to gg -> H to two loops in the heavy top limit

The virtual corrections to the production cross section of a Standard Model Higgs boson are computed up to order α_s^4. Using an effective Lagrangian for the limit M_t -> \infty, we evaluate the relevant massless two-loop vertex diagrams by mapping them onto three-loop two-point functions, following a method recently introduced by Baikov and Smirnov. As a result, we find a gauge-invariant contribution to the total Higgs production cross section at NNLO.

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