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S. Heinemeyer

Publications and source records attributed to S. Heinemeyer.

At least 271 records · Page 15Linked to original sources
arXiv2002

The Higgs Working Group: Summary Report (2001)

Report of the Higgs working group for the Workshop `Physics at TeV Colliders', Les Houches, France, 21 May - 1 June 2001. It contains 7 separate sections: A. Theoretical Developments B. Higgs Searches at the Tevatron C. Experimental Observation of an invisible Higgs Boson at LHC D. Search for the Standard Model Higgs Boson using Vector Boson Fusion at the LHC E. Study of the MSSM channel $A/H \to ττ$ at the LHC F. Searching for Higgs Bosons in $t\bar t H$ Production G. Studies of Charged Higgs Boson Signals for the Tevatron and the LHC

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arXiv2002

The Snowmass Points and Slopes: Benchmarks for SUSY Searches

The ``Snowmass Points and Slopes'' (SPS) are a set of benchmark points and parameter lines in the MSSM parameter space corresponding to different scenarios in the search for Supersymmetry at present and future experiments. This set of benchmarks was agreed upon at the 2001 ``Snowmass Workshop on the Future of Particle Physics'' as a consensus based on different existing proposals.

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arXiv2002

Physics Opportunities at mu+mu- Higgs Factories

We update theoretical studies of the physics opportunities presented by mu+mu- Higgs factories. Interesting measurements of the Standard Model Higgs decays into {\bar b}b, tau+tau- and WW* may be possible if the Higgs mass is less than about 160 GeV, as preferred by the precision electroweak data, the mass range being extended by varying appropriately the beam energy resolution. A suitable value of the beam energy resolution would also enable the uncertainty in the b-quark mass to be minimized, facilitating measurements of parameters in the MSSM at such a first mu+mu- Higgs factory. These measurements would be sensitive to radiative corrections to the Higgs-fermion-antifermion decay vertices, which may violate CP. Radiative corrections in the MSSM may also induce CP violation in Higgs-mass mixing, which can be probed via various asymmetries measurable using polarized mu+mu- beams. In addition, Higgs-chargino couplings may be probed at a second mu+mu- Higgs factory.

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arXiv2002

FeynHiggs1.2: Hybrid MSbar/on-shell Renormalization for the CP-even Higgs Boson Sector in the MSSM

An updated version is presented of the Fortran code FeynHiggs for the evaluation of the neutral CP-even Higgs sector masses and mixing angles. It differs from the previous version by a modification of the renormalization scheme concerning the treatment of subleading terms at the one-loop level; the two-loop corrections, for which the leading contributions of O(alpha_t alphas) and O(alpha_t^2) are implemented, are not affected by the modified renormalization prescription. Besides stabilizing the Higgs mass calculations and avoiding unphysically large threshold effects, the mass of the lightest MSSM Higgs boson, m_h, is increased by 1-2 GeV for most parts of the MSSM parameter space.

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arXiv2002

Suggestions for Benchmark Scenarios for MSSM Higgs Boson Searches at Hadron Colliders

The Higgs boson search has shifted from LEP2 to the Tevatron and will subsequently move to the LHC. Due to the different initial states, the Higgs production and decay channels relevant for Higgs boson searches were different at LEP2 to what they are at hadron colliders. We suggest new benchmark scenarios for the MSSM Higgs boson search at hadron colliders that exemplify the phenomenology of different parts of the MSSM parameter space. Besides the m_h^max scenario and the no-mixing scenario used in the LEP2 Higgs boson searches, we propose two new scenarios. In one the main production channel at the LHC, gg -> h, is suppressed. In the other, important Higgs decay channels at the Tevatron and at the LHC, h -> b \bar b and h -> tau^+ tau^-, are suppressed. All scenarios evade the LEP2 constraints for nearly the whole M_A-tan beta-plane.

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arXiv2002

Present and Future Electroweak Precision Measurements and the Indirect Determination of the Mass of the Higgs Boson

We discuss the experimental and theoretical uncertainties on precision electroweak observables and their relationship to the indirect constraints on the Higgs-boson mass, $\MH$, in the Standard Model (SM). The critical experimental measurements ($\MW$, $\sweff$, $\mt$, ...) are evaluated in terms of their present uncertainties and their prospects for improved precision at future colliders, and their contribution to the constraints on $\MH$. In addition, the current uncertainties of the theoretical predictions for $\MW$ and $\sweff$ due to missing higher order corrections are estimated and expectations and necessary theoretical improvements for future colliders are explored. The constraints from rare B decays are also discussed. Analysis of the present experimental and theoretical precisions yield a current upper bound on $\MH$ of $\sim 200$ GeV. Including anticipated improvements corresponding to the prospective situation at future colliders (Tevatron Run II, LHC, LC/GigaZ), we find a relative precision of about 25% to 8% (or better) is achievable in the indirect determination of $\MH$.

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arXiv2001

Implications of the Higgs Boson Searches on Different Soft SUSY-breaking Scenarios

We investigate the Higgs boson sector of the Minimal Supersymmetric Standard Model (MSSM) in the framework of the three most prominent soft SUSY-breaking scenarios, mSUGRA, MGMSB and mAMSB. For each scenario, we determine the parameters at the electroweak scale from the set of input variables at higher energy scales (depending on the specific scenario) and evaluate the Higgs boson properties. The latter are based on results obtained within the Feynman-diagrammatic approach by taking into account the complete one-loop and the dominant two-loop contributions. The maximum value of the mass of the lightest neutral CP-even MSSM Higgs boson, m_h, is determined in the three scenarios, and the behavior of the Higgs couplings to fermions and gauge bosons is investigated. Restrictions on tan beta and on the set of higher-energy scale parameters are derived from the lower limits arising from the Higgs search at LEP2. We furthermore discuss the regions of parameter space in the three scenarios compatible with interpreting the excess observed at LEP2 as a Higgs signal, with m_h = (115.0 + 1.3 - 0.9) GeV. The case where the events observed at LEP2 could originate from the production of the heavier neutral CP-even Higgs boson is also considered. The implications of a possible Higgs signal at 115 GeV for SUSY searches at future colliders are briefly discussed for each of the three scenarios.

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arXiv2001

Positron polarisation and low energy running at a Linear Collider

The physics potential of an e+e- linear collider can be significantly enhanced if both the electron and positron beams are polarised. Low energy running at the Z-resonance or close to the W-pair threshold is particularly attractive with polarised positrons. This note discusses the experimental aspects and physics opportunities of both low energy running and positron polarisation.

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arXiv2001

Theoretical and Experimental Status of the Indirect Higgs Boson Mass Determination in the Standard Model

The impact of theoretical and experimental uncertainties on the indirect determination of the Higgs boson mass, MH, in the Standard Model (SM) is discussed. Special emphasis is put on the electroweak precision observables MW (the W boson mass) and sin^2(theta_eff) (the effective leptonic mixing angle). The current uncertainties of the theoretical predictions for MW and sin^2(theta_eff) due to missing higher order corrections are conservatively estimated to delta MW \approx 7 MeV and delta sin^2(theta_eff) \approx 7 x 10^-5 . Expectations and necessary theoretical improvements for future colliders are explored. Results for the indirect MH determination are presented based on the present experimental and theoretical precisions as well as on improvements corresponding to the prospective situation at future colliders. The treatment of the different future colliders is done in a uniform way in order to allow for a direct comparison of the accuracies that can be reached. Taking all experimental, theoretical, and parametric uncertainties into account, a current upper bound on MH of \sim 200 GeV is obtained. Furthermore we find in a conservative approach that a Linear Collider with GigaZ capabilities can achieve a relative precision of about 8% (or better) in the indirect determination of MH.

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arXiv2001

The Higgs Boson Sector of the Complex MSSM in the Feynman-diagrammatic approach

In the Minimal Supersymmetric Standard Model with complex parameters (cMSSM) we calculate higher order corrections to the Higgs boson sector in the Feynman-diagrammatic approach using the on-shell renormalization scheme. The application of this approach to the cMSSM, being complementary to existing approaches, is analyzed in detail. Numerical examples for the leading fermionic corrections, including the leading two-loop effects, are presented. Numerical agreement within 10% with other approaches is found for small and moderate mixing in the scalar top sector. The leading fermionic corrections, supplemented by the full logarithmic one-loop and the leading two-loop contributions are implemented into the public Fortran code FeynHiggsFastC.

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arXiv2001

Observability of the Lightest CMSSM Higgs Boson at Hadron Colliders

We discuss the observability of the lightest neutral Higgs boson in the constrained MSSM (CMSSM), with universal soft supersymmetry-breaking parameters, at hadron colliders such as the Tevatron and the LHC. We take account of the constraints on parameter space provided by LEP, the measured rate of b to s gamma decay, the cosmological relic density Omega h^2, and the recent measurement of g_mu - 2. We normalize products of the expected CMSSM Higgs production cross sections and decay branching ratios (sigma B)_CMSSM relative to those expected for a Standard Model Higgs boson of the same mass. In the h to gamma gamma channel, we find that (sigma B)_CMSSM > 0.85 (sigma B)_SM. In the W/t tbar + h, h to b bbar channels, we find that (sigma B)_CMSSM \~ 1.05 (sigma B)_SM. We conclude that the lightest CMSSM Higgs boson should be almost as easy to see as the Standard Model Higgs boson: in particular, it should be discoverable with about 15/fb of luminosity at the Tevatron or 10/fb of luminosity at the LHC.

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arXiv2001

Do electroweak precision data and Higgs-mass constraints rule out a scalar bottom quark with mass of O(5 GeV)?

We investigate the phenomenological implications of a light scalar bottom quark, with a mass of about the bottom quark mass, within the minimal supersymmetric standard model. The study of such a scenario is of theoretical interest, since, depending on their production and decay modes, light sbottoms may have escaped experimental detection up to now and, in addition, may naturally appear for large values of \tanβ. In this article we show that such a light sbottom cannot be ruled out by the constraints from the electroweak precision data and the present bound on the lightest CP-even Higgs boson mass at LEP. It is inferred that a light sbottom scenario requires in general a relatively light scalar top quark whose mass is typically about the top-quark mass. It is also shown that under these conditions the lightest CP-even Higgs boson decays predominantly into scalar bottom quarks in most of the parameter space and that its mass is restricted to m_h ~< 123 GeV.

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arXiv2001

Precision Observables in the MSSM: Leading Electroweak Two-loop Corrections

The leading electroweak MSSM two-loop corrections to the $ρ$-parameter are calculated. They are obtained by evaluating the two-loop self-energies of the Z and the W boson at O(Gf^2 m_t^4) in the limit of heavy scalar quarks. A very compact expression is derived, depending on the ratio of the CP-odd Higgs boson mass, M_A, and the top quark mass, m_t. Expressions for the limiting cases M_A >> m_t and M_A << m_t are also given. The decoupling of the non-SM contribution in the limit M_A -> oo is verified at the two-loop level. The numerical effect of the leading electroweak MSSM two-loop corrections is analyzed in comparison with the leading corrections of O(Gf^2 m_t^4) in the SM and with the O(alpha alpha_s) corrections in the MSSM.

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arXiv2001

Two-loop Calculations in the MSSM with FeynArts

Recent electroweak two-loop corrections in the Minimal Supersymmetric Standard Model (MSSM) are reviewed. They have been obtained with the help of the programs FeynArts and TwoCalc, making use of the recently completed MSSM model file for FeynArts. Short examples of how to use the two codes together with the analytic result for the O(Gf^2 m_t^4) corrections to the $ρ$-parameter in the MSSM are presented.

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arXiv2001

Higgs Production and Decay in the MSSM: Status and Perspectives

The theoretical predictions in the MSSM for Higgs-boson production at a future e^+e^- Linear Collider and Higgs-boson decay processes are discussed focusing in particular on recent diagrammatic two-loop results in the MSSM Higgs sector. The present status of the theoretical predictions is briefly summarized, and it is emphasized that considerable improvements will be necessary in order to match the high experimental accuracy achievable at a future Linear Collider.

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arXiv2001

Neutral MSSM Higgs-boson production at e+e- colliders in the Feynman-diagrammatic approach

We calculate the cross sections for the neutral Higgs-boson production at e+e- colliders in the Minimal Supersymmetric Standard Model (MSSM) using the Feynman-diagrammatic approach and the on-shell renormalization scheme. We incorporate the Higgs-boson propagator corrections, evaluated up to two-loop order, into the prediction of the cross sections for the Higgs-boson production mechanism e+e- -> hZ, hA. The propagator corrections consist of the full one-loop contribution, including the effects of non-vanishing external momentum, and at the two-loop level of the dominant corrections of O(alpha alpha_s) and further sub-dominant contributions. The results are supplemented with the complete set of one-loop vertex and box corrections. The effects of the two-loop propagator corrections are investigated in detail. We briefly discuss also the effect of the box contributions for high $\sqrt{s}$. We compare our results with the case where only the corrections to the effective mixing angle, evaluated within the renormalization-group-improved one-loop Effective Potential approach, are taken into account. We find agreement better than 10% for LEP2 energies and deviations larger than 20% for $\sqrt{s}$ = 500 GeV.

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