Oliver Brein

Durham University, Durham, England, United Kingdom

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Publications (28)37.31 Total impact

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    ABSTRACT: We describe the new developments in version 4 of the public computer code HiggsBounds. HiggsBounds is a tool to test models with arbitrary Higgs sectors, containing both neutral and charged Higgs bosons, against the published exclusion bounds from Higgs searches at the LEP, Tevatron and LHC experiments. From the model predictions for the Higgs masses, branching ratios, production cross sections and total decay widths - which are specified by the user in the input for the program - the code calculates the predicted signal rates for the search channels considered in the experimental data. The signal rates are compared to the expected and observed cross section limits from the Higgs searches to determine whether a point in the model parameter space is excluded at 95% confidence level. In this document we present a modification of the HiggsBounds main algorithm that extends the exclusion test in order to ensure that it provides useful results in the presence of one or more significant excesses in the data, corresponding to potential Higgs signals. We also describe a new method to test whether the limits from an experimental search performed under certain model assumptions can be applied to a different theoretical model. Further developments discussed here include a framework to take into account theoretical uncertainties on the Higgs mass predictions, and the possibility to obtain the $\chi^2$ likelihood of Higgs exclusion limits from LEP. Extensions to the user subroutines from earlier versions of HiggsBounds are described. The new features are demonstrated by additional example programs.
    10/2013;
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    ABSTRACT: We report on recent developments in the public computer code HiggsBounds, which confronts arbitrary Higgs sector predictions with 95% C.L. exclusion limits from Higgs searches at the LEP, Tevatron and LHC experiments. We discuss in detail the performance of the Standard Model (SM) likeness test as implemented in the latest version HiggsBounds-3.8.0, whose outcome decides whether a search for a SM Higgs boson can be applied to a model beyond the SM. Furthermore, we give a preview of features in the upcoming version HiggsBounds-4.0.0 and the new program HiggsSignals, which performs a chi-squared test of Higgs sector predictions against the signal rate and mass measurements from Higgs boson analyses at the Tevatron and LHC. This is illustrated with an example where the heavier CP-even Higgs boson of the Minimal Supersymmetric Standard Model (MSSM) is considered as an explanation of the LHC Higgs signal at ~126 GeV.
    01/2013;
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    ABSTRACT: A numerical program for the evaluation of the inclusive cross section for associated Higgs production with a massive weak gauge boson at hadron colliders is described, sigma(pp/pbar p -> HV), V=W,Z. The calculation is performed in the framework of the Standard Model and includes next-to-next-to-leading order QCD as well as next-to-leading order electro-weak effects.
    Computer Physics Communications 10/2012; 184(3). · 3.08 Impact Factor
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    ABSTRACT: Novel contributions to the total inclusive cross section for Higgs-Strahlung in the Standard Model at hadron colliders are evaluated. Although formally of order $\alpha_s^2$, they have not been taken into account in previous NNLO predictions. The terms under consideration are induced by Higgs radiation off top-quark loops and thus proportional to the top-quark Yukawa coupling. At the Tevatron, their effects to HW production are below 1% in the relevant Higgs mass range, while for HZ production, we find corrections between about 1% and 2%. At the LHC, the contribution of the newly evaluated terms to the cross section is typically of the order of 1%-3%. Based on these results, we provide updated predictions for the total inclusive Higgs-Strahlung cross section at the Tevatron and the LHC.
    European Physical Journal C 11/2011; · 5.25 Impact Factor
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    ABSTRACT: HiggsBounds 2.0.0 is a computer code which tests both neutral and charged Higgs sectors of arbitrary models against the current exclusion bounds from the Higgs searches at LEP and the Tevatron. As input, it requires a selection of model predictions, such as Higgs masses, branching ratios, effective couplings and total decay widths. HiggsBounds 2.0.0 then uses the expected and observed topological cross section limits from the Higgs searches to determine whether a given parameter scenario of a model is excluded at the 95% C.L. by those searches. Version 2.0.0 represents a significant extension of the code since its first release (1.0.0). It includes now 28/53 LEP/Tevatron Higgs search analyses, compared to the 11/22 in the first release, of which many of the ones from the Tevatron are replaced by updates. As a major extension, the code allows now the predictions for (singly) charged Higgs bosons to be confronted with LEP and Tevatron searches. Furthermore, the newly included analyses contain LEP searches for neutral Higgs bosons (H) decaying invisibly or into (non flavour tagged) hadrons as well as decay-mode independent searches for neutral Higgs bosons, LEP searches via the production modes tau+ tau- H and b b-bar H, and Tevatron searches via t t-bar H. Also, all Tevatron results presented at the ICHEP'10 are included in version 2.0.0. As physics applications of HiggsBounds 2.0.0 we study the allowed Higgs mass range for model scenarios with invisible Higgs decays and we obtain exclusion results for the scalar sector of the Randall-Sundrum model using up-to-date LEP and Tevatron direct search results.
    Computer Physics Communications 02/2011; 182(12). · 3.08 Impact Factor
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    ABSTRACT: This Report summarizes the results of the first 10 months' activities of the LHC Higgs Cross Sections Working Group. The main goal of the working group was to present the status-of-art on Higgs Physics at the LHC integrating all new results that have appeared in the last few years. The Report is more than a mere collection of the proceedings of the general meetings. The subgroups have been working in different directions. An attempt has been made to present the first Report from these subgroups in a complete and homogeneous form. The subgroups' contributions correspondingly comprise the main parts of the Report. A significant amount of work has been performed in providing higher-order corrections to the Higgs-boson cross sections and pinning down the theoretical uncertainty of the Standard Model predictions. This Report comprises explicit numerical results on total cross sections, leaving the issues of event selection cuts and differential distributions to future publications. The subjects for further study are identified.
    01/2011;
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    ABSTRACT: We introduce version 2.0.0 of the computer program HiggsBounds. The program tests neutral and charged Higgs sectors of new models against the current exclusion bounds from LEP and the Tevatron. As input, it requires a selection of model predictions, such as Higgs masses, branching ratios, effective couplings and total decay widths. The program then uses the expected and observed topological cross section limits from the Higgs searches to determine whether a given parameter scenario of a model is excluded at the 95% C.L. by those searches. Version 2.0.0 includes 39/53 LEP/Tevatron Higgs search analyses, compared to 13/36 in the previous release (1.2.0). Among the newly included analyses are LEP searches for neutral Higgs bosons (H) decaying invisibly or into hadrons, LEP searches via the production modes (tau+ tau- H) and (b b-bar H), Tevatron searches via (t t-bar H), and LEP and Tevatron searches for charged Higgs bosons. Also, all Tevatron results presented at the ICHEP'10 are included in version 2.0.0. In this talk, we explain the basic ideas behind the implementation of HiggsBounds and provide a list of search topologies implemented in version 2.0.0. Furthermore, we apply HiggsBounds 2.0.0 to (a) determine the allowed Higgs mass range for a simple 4th generation model, (b) update/reproduce LEP/Tevatron Higgs exclusion plots for the MSSM m_h-max benchmark scenario, and (c) show exclusion results for the scalar sector of the Randall-Sundrum model.
    Red Report (2010),. 12/2010;
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    Oliver Brein
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    ABSTRACT: This paper presents predictions for jet pseudorapidity (eta) and transverse momentum (p_T) distributions for the production of the Standard Model Higgs boson in association with a high-p_T hadronic jet. We discuss the contributions of electroweak loops and of bottom-quark parton processes to the cross section. The latter arise in the five-flavour scheme. Predictions for the Tevatron and the Large Hadron Collider with 10 TeV collision energy are presented. For Higgs boson masses of 120 GeV, 160 GeV and 200 GeV, we find the maximal effects of the electroweak contributions to the Higgs plus jet p_T and eta distribution to be -14 % and -5.3 %, respectively, for the Tevatron, and -3 % and -2 %, respectively, for the LHC. For the maximal contribution of bottom-quark parton processes to the p_T and eta distribution, we find +3 % and + 2.5 %, respectively, for the Tevatron, and +3.5 % and +3 %, respectively, for the LHC. A separate study of the Higgs + b-jet cross section demonstrates that a calculational approach which respects the hierarchies of Yukawa couplings yields a leading order cross section prediction which is more accurate in the high-p_T regime than conventional approaches. Comment: 25 pages, 14 figures
    Physical review D: Particles and fields 03/2010;
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    ABSTRACT: HiggsBounds is a computer code that tests theoretical predictions of models with arbitrary Higgs sectors against the exclusion bounds obtained from the Higgs searches at LEP and the Tevatron. The included experimental information comprises exclusion bounds at 95% C.L. on topological cross sections. In order to determine which search topology has the highest exclusion power, the program also includes, for each topology, information from the experiments on the expected exclusion bound, which would have been observed in case of a pure background distribution. Using the predictions of the desired model provided by the user as input, HiggsBounds determines the most sensitive channel and tests whether the considered parameter point is excluded at the 95% C.L. HiggsBounds is available as a Fortran 77 and Fortran 90 code. The code can be invoked as a command line version, a subroutine version and an online version. Examples of exclusion bounds obtained with HiggsBounds are discussed for the Standard Model, for a model with a fourth generation of quarks and leptons and for the Minimal Supersymmetric Standard Model with and without CP-violation. The experimental information on the exclusion bounds currently implemented in HiggsBounds will be updated as new results from the Higgs searches become available.Program summaryProgram title: HiggsBoundsCatalogue identifier: AEFF_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFF_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 55 733No. of bytes in distributed program, including test data, etc.: 1 986 213Distribution format: tar.gzProgramming language: Fortran 77, Fortran 90 (two code versions are offered).Computer: HiggsBounds can be built with any compatible Fortran 77 or Fortran 90 compiler. The program has been tested on x86 CPUs running under Linux (Ubuntu 8.04) and with the following compilers: The Portland Group Inc. Fortran compilers (pgf77, pgf90), the GNU project Fortran compilers (g77, gfortran).Operating system: LinuxRAM: minimum of about 6000 kbytes (dependent on the code version)Classification: 11.1External routines: HiggsBounds requires no external routines/libraries. Some sample programs in the distribution require the programs FeynHiggs 2.6.x or CPsuperH2 to be installed (see “Subprograms used”).Subprograms used:View Within ArticleNature of problem: Determine whether a parameter point of a given model is excluded or allowed by LEP and Tevatron Higgs-boson search results.Solution method: The most sensitive channel from LEP and Tevatron searches is determined and subsequently applied to test this parameter point. The test requires as input model predictions for the Higgs-boson masses, branching ratios and ratios of production cross sections with respect to reference values.Restrictions: In the current version, results from decay-mode independent Higgs searches and results of searches for charged Higgs bosons are not taken into account.Running time: About 0.01 seconds (or less) for one parameter point using one processor of an Intel Core 2 Quad Q6600 CPU at 2.40 GHz for sample model scenarios with three Higgs bosons. It depends on the complexity of the Higgs sector (e.g. the number of Higgs bosons and the number of open decay channels) and on the code version.
    Computer Physics Communications 01/2010; · 3.08 Impact Factor
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    ABSTRACT: We review the program HiggsBounds that tests theoretical predictions of models with arbitrary Higgs sectors against the exclusion bounds obtained from the Higgs searches at LEP and the Tevatron. We explicitly list the bounds that have been added after the first release of HiggsBounds. Comment: 4 pages, talk given at SUSY09, Boston, June 2009
    09/2009;
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    Oliver Brein, Wolfgang Hollik
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    ABSTRACT: We present pseudorapidity and transverse momentum distributions for the cross section for the production of the lightest neutral Higgs boson in association with a high-p_T hadronic jet, calculated in the framework of the minimal supersymmetric standard model. We discuss the theoretical predictions for the differential cross sections at the Large Hadron Collider and the Tevatron. In particular, we present the differences in the distributions compared to the Standard Model.
    11/2007;
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    Oliver Brein, Terrance Figy
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    ABSTRACT: We present results of a calculation of the cross section for the production of a charged Higgs boson in association with an electron and a neutrino at electron-positron colliders (e+ e- -> H+ e- nu_e-bar, H- e+ nu_e). We study predictions for the cross section in the Minimal Supersymmetric Standard Model (MSSM) and the Two Higgs Doublet Model (THDM), highlighting possible differences. The process is effectively loop-induced in both models. Hence, the cross section is expected to be strongly model-dependent. Most notably, due to the presence of superpartners, the MSSM amplitude contains Feynman graphs of pentagon-type, which are not present in the THDM. This is the first complete one-loop calculation of the cross section for this process in the THDM and the MSSM. For both models, so far, only approximate results with limited ranges of validity were available. Our main aim here is to clarify several open questions in the existing literature on this process. Specifically, we will discuss the validity of the Heavy Fermion loop approximation in both models, and of the Fermion/Sfermion loop approximation in the MSSM.
    Physical review D: Particles and fields 11/2007;
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    Oliver Brein, Wolfgang Hollik
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    ABSTRACT: We present pseudorapidity and transverse momentum distributions for the cross section for the production of the lightest neutral Higgs boson in association with a high-p_T hadronic jet, calculated in the framework of the minimal supersymmetric standard model (MSSM). We discuss the theoretical predictions for the differential cross sections at the Large Hadron Collider and the Tevatron for the most common benchmark scenarios.
    Physical review D: Particles and fields 06/2007;
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    ABSTRACT: We discuss the radiative corrections to charged and neutral current deep-inelastic neutrino--nucleon scattering in the minimal supersymmetric standard model (MSSM). In particular, we study deviations, delta_R^nu(nu-bar), from the Standard Model prediction for the ratios of neutral- to charged-current cross sections, taking into account all sources for deviations in the MSSM, i.e. different contributions from virtual Higgs bosons and virtual superpartners. Our calculation includes the full q^2 dependence of the one-loop amplitudes, parton distribution functions and a NuTeV-inspired process kinematics. We present results of a scan of delta_R^nu(nu-bar) over the relevant MSSM parameter space.
    12/2006;
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    Oliver Brein, Thomas Hahn
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    ABSTRACT: We present a calculation of the cross section for the process e+ e- --> W+/- H-/+ in the minimal supersymmetric standard model (MSSM) and the Two Higgs Doublet Model (THDM). We study the basic features of the MSSM prediction for some distinctive parameter scenarios. We find large effects from virtual squarks for scenarios with large mixing in the stop sector which can lead to a cross section vastly different from a THDM with identical Higgs sector parameters. We investigate this interesting behaviour in more detail by thoroughly scanning the MSSM parameter space for regions of large cross section. For a charged Higgs boson too heavy to be pair-produced at such a machine, it turns out that a large MSSM cross section with a good chance of observation is linked to a squark mass scale below 600 GeV and a considerable amount of mixing in either the stop and sbottom sector. Comment: 25 pages, 10 figures (two in colour). Substantially improved on the MSSM parameter restrictions taken into account. Added some references
    European Physical Journal C 10/2006; · 5.25 Impact Factor
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    Oliver Brein
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    ABSTRACT: A method is presented to exploit adaptive integration algorithms using importance sampling, like VEGAS, for the task of scanning theoretical predictions depending on a multi-dimensional parameter space. Usually, a parameter scan is performed with emphasis on certain features of a theoretical prediction. Adaptive integration algorithms are well-suited to perform this task very efficiently. Predictions which depend on parameter spaces with many dimensions call for such an adaptive scanning algorithm.
    Computer Physics Communications 07/2005; · 3.08 Impact Factor
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    Eri Asakawa, Oliver Brein, Shinya Kanemura
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    ABSTRACT: We discuss the associated W{sup {+-}}H{sup {+-}} production at the CERN large hadron collider. The dependence of the hadronic cross section on the Higgs sector parameters is investigated in detail in the framework of the general two Higgs doublet model (THDM). We study the possible enhancement of the THDM prediction for the cross section compared to the prediction of the minimal supersymmetric standard model (MSSM). We find regions in the THDM parameter space where the THDM prediction can exceed the one of the MSSM by 2 orders of magnitude. These regions of large cross section are in agreement with theoretical bounds on the model, derived from the requirement of vacuum stability and perturbative unitarity, and are not excluded by experimental constraints.
    Physical review D: Particles and fields 01/2005; 72(5):055017-055017.
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    O. Brein, B. Koch, W. Hollik
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    ABSTRACT: We discuss the radiative corrections to charged and neutral current deep-inelastic neutrino--nucleon scattering in the minimal supersymmetric standard model (MSSM). In particular, deviations from the Standard Model prediction for the ratios of neutral- to charged-current cross sections, $R^\nu$ and $R^{\bar\nu}$, are studied, and results of a scan over the MSSM parameter space are presented.
    09/2004;
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    ABSTRACT: Theoretical progress in Higgs boson production and background processes is discussed with particular emphasis on QCD corrections at and beyond next-to-leading order as well as next-to-leading order electroweak corrections. The residual theoretical uncertainties of the investigated processes are estimated in detail. Moreover, recent investigations of the MSSM Higgs sector and other extensions of the SM Higgs sector are presented. The potential of the LHC and a high-energy linear e+e- collider for the measurement of Higgs couplings is analyzed. Comment: 169 pages, Proceedings 3rd Les Houches Workshop: Physics at TeV Colliders, Les Houches, France, 26 May - 6 Jun 2003
    06/2004;
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    Oliver Brein, Wolfgang Hollik
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    ABSTRACT: The cross section prediction for the production of the lightest neutral Higgs boson in association with a high-p_T hadronic jet is presented in the framework of the minimal supersymmetric standard model (MSSM) and compared to the SM case. Prospects for the CERN Large Hadron Collider (LHC) are discussed.
    03/2004;

Publication Stats

392 Citations
37.31 Total Impact Points

Institutions

  • 2006–2010
    • Durham University
      • Institute for Particle Physics Phenomenology "IPPP"
      Durham, England, United Kingdom
  • 2004
    • CERN
      Genève, Geneva, Switzerland
  • 2003–2004
    • Max Planck Institute of Physics
      München, Bavaria, Germany
  • 1999–2001
    • Karlsruhe Institute of Technology
      • Institute of Theoretical Physics
      Karlsruhe, Baden-Wuerttemberg, Germany