Ramona Gröber

The measurement of the Higgs self-coupling at the LHC: theoretical status

A bstractNow that the Higgs boson has been observed by the ATLAS and CMS experiments at the LHC, the next important step would be to measure accurately its properties to establish the details of the electroweak symmetry breaking mechanism. Among the measurements which need to be performed, the determination of the Higgs self-coupling in processes where the Higgs boson is produced in pairs is of utmost importance. In this paper, we discuss the various processes which allow for the measurement of the trilinear Higgs coupling: double Higgs production in gluon fusion, vector boson fusion, double Higgs-strahlung and associated production with a top quark pair. We first evaluate the production cross sections for these processes at the LHC with center-of-mass energies ranging from the present

NLO QCD Corrections to Higgs Pair Production including Dimension-6 Operators

\sqrt{s}=8

NMSSMCALC: A program package for the calculation of loop-corrected Higgs boson masses and decay widths in the (complex) NMSSM☆

TeV to

Higgs mass predictions of public NMSSM spectrum generators

\sqrt{s}=100

Accidental matter at the LHC

TeV, and discuss their sensitivity to the trilinear Higgs coupling. We include the various higher order QCD radiative corrections, at next-to-leading order for gluon and vector boson fusion and at next-to-next-to-leading order for associated double Higgs production with a gauge boson. The theoretical uncertainties on these cross sections are estimated. Finally, we discuss the various channels which could allow for the detection of the double Higgs production signal at the LHC and estimate their potential to probe the trilinear Higgs coupling.

On the two-loop virtual QCD corrections to Higgs boson pair production in the Standard Model

A bstractNew Physics that becomes relevant at some high scale Λ beyond the experimental reach, can be described in the effective theory approach by adding higher-dimensional operators to the Standard Model (SM) Lagrangian. In Higgs pair production through gluon fusion, which gives access to the trilinear Higgs self-coupling, this leads not only to modifications of the SM couplings but also induces novel couplings not present in the SM. For a proper prediction of the cross section, higher order QCD corrections that are important for this process, have to be taken into account. The various higher-dimensional contributions are affected differently by the QCD corrections. In this paper, we provide the next-to-leading order (NLO) QCD corrections to Higgs pair production including dimension-6 operators in the limit of large top quark masses. Depending on the dimension-6 coefficients entering the Lagrangian, the new operators affect the relative NLO QCD corrections by several per cent, while modifying the cross section by up to an order of magnitude.

Signs of Composite Higgs Pair Production at Next-to-Leading Order

Abstract We present the program package NMSSMCALC for the calculation of the loop-corrected NMSSM Higgs boson masses and decay widths in the CP-conserving and CP-violating NMSSM. The full one-loop corrections to the Higgs boson masses are evaluated in a mixed renormalisation scheme of on-shell and DR ¯ conditions. The Higgs decay widths include the dominant higher order QCD corrections, and the decays into bottom quarks, strange quarks and τ leptons are supplemented by higher order SUSY corrections through effective couplings. All relevant off-shell decays into two massive gauge bosons, gauge and Higgs boson and Higgs pair final states as well as into heavy quark pairs are computed. The input and output files feature the SUSY Les Houches Accord so that the program can easily be linked with existing computer tools. Program summary Program title: NMSSMCALC Catalogue identifier: AEUE_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEUE_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 53070 No. of bytes in distributed program, including test data, etc.: 329132 Distribution format: tar.gz Programming language: Fortran77. Computer: Any with a Fortran77 system. Operating system: Linux, Unix. RAM: 0.5MB Classification: 11.1. Nature of problem: Computation of the NMSSM Higgs mass spectrum including higher order corrections in a mixed renormalisation scheme of on-shell and DRbar conditions, and numerical calculation of the decay widths and branching ratios, both in the CP-conserving and in the CP-violating NMSSM. The decay widths include the dominant higher order QCD corrections and, for the neutral Higgs boson decays into a bottom quark pair, the higher order SUSY–QCD and the approximate SUSY–electroweak (elw) corrections up to one-loop accuracy. The decays into a strange quark pair include the dominant resummed SUSY–QCD corrections and the one into a τ pair the dominant resummed SUSY–elw corrections. Analogously for the charged Higgs boson the higher order SUSY corrections have been implemented for the decays into fermion pairs. In the real NMSSM, the decays into stop and sbottom pairs, respectively, contain the SUSY–QCD corrections. All relevant off-shell decays into massive gauge bosons, into gauge and Higgs bosons, into Higgs pairs and into heavy quark pairs have been taken into account. The input and output files feature the SUSY Les Houches Accord (SLHA). Solution method: The necessary input values are set in the two input files inp.dat (in the SLHA format) and bhdecay.in . The file inp.dat , where the choice between the real and the complex NMSSM can be made, is read in by CalcMasses.F , which calculates the one-loop corrected NMSSM Higgs mass spectrum. CalcMasses.F writes out all necessary parameters, masses and mixing angles in an SLHA format file slha.in , which is read in by bhdecay.f (by bhdecay c.f in the complex case). This Fortran routine then computes the decay widths and branching ratios and writes them out in an SLHA format file slha decay.out . Furthermore it writes out all parameters and mixing angles. Restrictions: At present the NMSSM Higgs spectrum is calculated at one-loop accuracy, the Higgs self-couplings at leading order, and no renormalisation group running of the input parameters is included. However, we are about to implement the two-loop corrections to the NMSSM Higgs boson masses and the Higgs self-couplings. Furthermore, the renormalisation group equations for the input parameters shall be provided in the near future. The program does not provide any distributions. Running time: Less than one second per point

NLO-QCD corrections to Higgs pair production in the MSSM

The publicly available spectrum generators for the NMSSM often lead to different predictions for the mass of the standard model-like Higgs boson even if using the same renormalization scheme and two-loop accuracy. Depending on the parameter point, the differences can exceed 5 GeV, and even reach 8 GeV for moderate superparticle masses of up to 2 TeV. It is shown here that these differences can be traced back to the calculation of the running standard model parameters entering all calculations, to the approximations used in the two-loop corrections included in the different codes, and to different choices for the renormalization conditions and scales. In particular, the importance of the calculation of the top Yukawa coupling is pointed out.

Maxi-sizing the trilinear Higgs self-coupling: how large could it be?

A bstractWe classify weak-scale extensions of the Standard Model which automatically preserve its accidental and approximate symmetry structure at the renormalizable level and which are hence invisible to low-energy indirect probes. By requiring the consistency of the effective field theory up to scales of Λeff ≈ 1015 GeV and after applying cosmological constraints, we arrive at a finite set of possibilities that we analyze in detail. One of the most striking signatures of this framework is the presence of new charged and/or colored states which can be efficiently produced in high-energy particle colliders and which are stable on the scale of detectors.

Searches for vector-like quarks at future colliders and implications for composite Higgs models with dark matter

We compute the next-to-leading order virtual QCD corrections to Higgs-pair production via gluon fusion. We present analytic results for the two-loop contributions to the spin-0 and spin-2 form factors in the amplitude. The reducible contributions, given by the double-triangle diagrams, are evaluated exactly while the two-loop irreducible diagrams are evaluated by an asymptotic expansion in heavy top-quark mass up to and including terms of