arXiv subjects

S. Heinemeyer

Publications and source records attributed to S. Heinemeyer.

At least 253 records · Page 14Linked to original sources

arXiv2004

Extracting Higgs boson couplings from LHC data

We show how LHC Higgs boson production and decay data can be used to extract gauge and fermion couplings of Higgs bosons. We show that very mild theoretical assumptions, which are valid in general multi-Higgs doublet models, are sufficient to allow the extraction of absolute values for the couplings rather than just ratios of the couplings. For Higgs masses below 200 GeV we find accuracies of 10-40% for the Higgs boson couplings and total width after several years of LHC running. Slightly stronger assumptions on the Higgs gauge couplings even lead to a determination of couplings to fermions at the level of 10-20%. We also study the sensitivity to deviations from SM predictions in several supersymmetric benchmark scenarios as a subset of the analysis.

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arXiv2004

Electroweak Precision Observables in the MSSM with Non-Minimal Flavor Violation

The leading corrections to electroweak precision observables in the MSSM with non-minimal flavor violation (NMFV) are calculated and the effects on M_W and sin^2 theta_eff are analyzed. The corrections are obtained by evaluating the full one-loop contributions from the third and second generation scalar quarks, including the mixing in the scalar top and charm, as well as in the scalar bottom and strange sector. Furthermore the leading corrections to the mass of the lightest MSSM Higgs boson, m_h, is obtained. The electroweak one-loop contribution to M_W can amount up to 140 MeV and up to 70x10^{-5} for sin^2 theta_eff, allowing to set limits on the NMFV parameters. The corrections for m_h are not significant for moderate generation mixing.

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arXiv2004

Precision SUSY Physics

We review the theoretical status and the future perspectives of the most important electroweak precision observables in the MSSM. This comprises the mass of the W boson, M_W, the effective leptonic mixing angle, sin^2(theta_eff), the mass of the lightest MSSM Higgs boson, m_h, and the anomalous magnetic moment of the muon, a_μ. The impact of the parametric uncertainties from the experimental errors of the input parameters is studied, and an estimate for the remaining uncertainties from unknown higher-order corrections is given. The need for future improvements in the theory predictions is investigated.

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arXiv2004

The Higgs Working Group: Summary Report 2003

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.

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arXiv2004

Two-Loop SUSY Corrections to the Anomalous Magnetic Moment of the Muon

We calculate supersymmetric two-loop corrections to the anomalous magnetic moment of the muon, consisting of diagrams with a closed scalar fermion or fermion loop and gauge and/or Higgs boson exchange. We discuss the numerical impact of each subclass of diagrams and determine the leading contributions. We analyze in detail constraints from experimental information on the Higgs boson mass, Delta(rho), and the branching ratios of B -> X_s gamma and B_s -> mu^+ mu^-. If these constraints are taken into account, the largest possible contributions are reduced from more than 2 sigma (in terms of the current experimental error) to ~0.3 sigma. The only exceptions arise in rather extreme parameter scenarios with a strong non-universality between the soft breaking parameters in the stop and sbottom sectors.

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arXiv2004

Les Houches "Physics at TeV Colliders 2003" Beyond the Standard Model Working Group: Summary Report

The work contained herein constitutes a report of the ``Beyond the Standard Model'' working group for the Workshop "Physics at TeV Colliders", Les Houches, France, 26 May--6 June, 2003. The research presented is original, and was performed specifically for the workshop. Tools for calculations in the minimal supersymmetric standard model are presented, including a comparison of the dark matter relic density predicted by public codes. Reconstruction of supersymmetric particle masses at the LHC and a future linear collider facility is examined. Less orthodox supersymmetric signals such as non-pointing photons and R-parity violating signals are studied. Features of extra dimensional models are examined next, including measurement strategies for radions and Higgs', as well as the virtual effects of Kaluza Klein modes of gluons. An LHC search strategy for a heavy top found in many little Higgs model is presented and finally, there is an update on LHC $Z'$ studies.

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arXiv2004

Finite Unified Theories and the Higgs mass prediction

Finite Unified Theories (FUTs) are N=1 supersymmetric Grand Unified Theories, which can be made all-loop finite, both in the dimensionless (gauge and Yukawa couplings) and dimensionful (soft supersymmetry breaking terms) sectors. This remarkable property provides a drastic reduction in the number of free parameters, which in turn leads to an accurate prediction of the top quark mass in the dimensionless sector, and predictions for the Higgs boson mass and the supersymmetric spectrum in the dimensionful sector. Here we examine the predictions of two FUTs taking into account a number of theoretical and experimental constraints. For the first one we present the results of a detailed scanning concerning the Higgs mass prediction, while for the second we present a representative prediction of its spectrum.

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arXiv2004

Single Charged MSSM Higgs-boson production at a Linear Collider

In the Minimal Supersymmetric Standard Model we present the calculation of the single charged Higgs-boson production in the gamma W- or Z W-fusion and the charged Higgs strahlung channel, e^+ e^- -> e nu H^\pm. The set of all O(alpha) corrections arising from loops of Standard Model fermions and scalar fermions are taken into account. Contrary to the case of single neutral heavy CP-even Higgs-boson production, for the charged Higgs boson we find for all the parameter space of the typical benchmark scenarios a cross section smaller than \sim 0.01 fb for sqrt(s)/2 \lessim M_H^\pm.

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arXiv2003

Physics Impact of a Precise Determination of the Top Quark Mass at an e+e- Linear Collider

At a prospective e+e- Linear Collider (LC) a very precise determination of the top quark mass with an accuracy of $δm_t <= 100 MeV$ will be possible. This is to be compared with the envisaged accuracy of $δm_t = 1-2 GeV$ at the Tevatron and the LHC. We discuss the physics impact of such a precise determination of m_t, focusing on the Standard Model (SM) and its minimal supersymmetric extension (MSSM). In particular, we show the importance of a precise knowledge of m_t for electroweak precision observables, and for Higgs physics and the scalar top sector of the MSSM. Taking the mSUGRA model as a specific example, we furthermore demonstrate the importance of a precise m_t value for the prediction of sparticle masses and for constraints on the parameter space allowed by the relic density. The uncertainty in m_t also significantly affects the reconstruction of the supersymmetric high scale theory. We find that going from hadron collider to LC accuracy in m_t leads to an improvement of the investigated quantities by up to an order of magnitude.

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arXiv2003

The lightest Higgs Boson of mSUGRA, mGMSB and mAMSB at Present and Future Colliders: Observability and Precision Analyses

We investigate the physics of the lightest CP-even MSSM Higgs boson at the Tevatron, the LHC, a linear e+e- collider, a gamma gamma collider and a mu+mu- collider. The analysis is performed in the three most prominent soft SUSY-breaking scenarios, mSUGRA, mGMSB and mAMSB. For all colliders the observability and parameter regions with suppressed production cross sections (compared to a SM Higgs boson with the same mass) are investigated. For the lepton and photon colliders the potential is analyzed of precision measurements of the branching ratios of the light CP-even Higgs boson for obtaining indirect bounds on the mass of the CP-odd Higgs boson and the high-energy parameters of the soft SUSY-breaking scenarios. In regions of the parameter space where the LHC can detect the heavy Higgs bosons, precision measurements of the properties of the light Higgs boson at the linear collider can provide valuable information for distinguishing between the mSUGRA, mGMSB and mAMSB scenarios.

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arXiv2003

The MSSM in the Light of Precision Data

The potential of present and anticipated future electroweak precision data, including the Higgs boson and top quark masses, for testing quantum effects of the electroweak theory is investigated in the context of the Minimal Supersymmetric Standard Model (MSSM). The present status of the theoretical predictions is analyzed. The impact of the parametric uncertainties from the experimental errors of the input parameters is studied, and an estimate for the remaining uncertainties from unknown higher-order corrections is given both in the Standard Model (SM) and the MSSM. Examples of electroweak precision tests in the mSUGRA scenario and the unconstrained MSSM are analyzed, and the status of the global fit to all data is discussed.

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arXiv2003

Towards High-Precision Predictions for the MSSM Higgs Sector

The status of the evaluation of the MSSM Higgs sector is reviewed. The phenomenological impact of recently obtained corrections is discussed. In particular it is shown that the upper bound on m_h within the MSSM is shifted upwards. Consequently, lower limits on tan beta obtained by confronting the upper bound as function of tan beta with the lower bound on m_h from Higgs searches are significantly weakened. Furthermore, the region in the M_A-tan beta-plane where the coupling of the lightest Higgs boson to down-type fermions is suppressed is modified. The presently not calculated higher-order corrections to the Higgs-boson mass matrix are estimated to shift the mass of the lightest Higgs boson by up to 3 GeV.

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arXiv2003

MSSM Higgs-Boson Production at the Linear Collider: Dominant Corrections to the WW-Fusion Channel

In the Minimal Supersymmetric Standard Model (MSSM) we calculate the corrections to neutral CP-even Higgs-boson production in the WW-fusion and Higgs-strahlung channel, e+e- -> \bar nu nu {h,H}, at a future Linear Collider, taking into account all O(alpha) corrections arising from loops of fermions and sfermions. For the production of the lightest MSSM Higgs boson, h, we find genuine loop corrections (beyond the universal Higgs propagator corrections) of up to -5%. For the heavy CP-even neutral Higgs boson, H, which shows decoupling behavior at tree level, we find non-negligible corrections that can enhance the cross section considerably in parts of the MSSM parameter space. At a center-of-mass energy of \sqrt{s} = 1000 GeV, heavy CP-even Higgs-boson masses of up to M_H <= 700 GeV are accessible at the Linear Collider in favorable regions of the MSSM parameter space.

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arXiv2002

The Higgs Boson Masses of the Complex MSSM: A Complete One-Loop Calculation

In the Minimal Supersymmetric Standard Model with complex parameters (cMSSM) we perform a complete one-loop calculation for the Higgs boson masses (including the momentum dependence) and the mixing angles. These corrections are obtained in the Feynman-diagrammatic approach using the on-shell renormalization scheme. The impact of the newly evaluated corrections is analyzed numerically. The full one-loop result, supplemented by the leading two-loop contributions taken over from the real MSSM are implemented into the public Fortran code FeynHiggs2.0.

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arXiv2002

Very Heavy MSSM Higgs-Boson Production at the Linear Collider

In the Minimal Supersymmetric Standard Model (MSSM) we present the corrections to the heavy neutral CP-even Higgs-boson production in the WW-fusion and Higgs-strahlung channel, e+e- -> \bar nu nu H, taking into account all O(α) corrections arising from loops of fermions and sfermions. While the H boson shows decoupling behavior at the tree-level, we find non-negligible loop corrections that can enhance the cross section considerably. At a center-of-mass energy of \sqrt{s} = 1000 GeV, masses of up to M_H <= 750 GeV are accessible at the LC in favorable regions of the MSSM parameter space.

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arXiv2002

Leading Electroweak Two-Loop Corrections to Precision Observables in the MSSM

The leading electroweak MSSM two-loop corrections to the electroweak precision observables are calculated. They are obtained by evaluating the two-loop O(α_t^2), O(α_t α_b), O(α_b^2) contributions to the quantity Δρin the limit of heavy scalar quarks, i.e. we consider the contributions of a Two-Higgs-Doublet model with MSSM restrictions. The full analytic result for arbitrary values of the lightest CP-even Higgs boson mass is presented. The numerical effects of the leading electroweak MSSM two-loop corrections on the precision observables M_W and sin^2(theta_eff) are analyzed. The electroweak two-loop contribution to M_W amounts up to -12 MeV and up to +6 10^-5 for sin^2(theta_eff). The corrections from the bottom quark loops can become important for large values of tan beta. They enter with a different sign than the O(α_t^2) corrections. We furthermore investigate the current sensitivity of the electroweak precision observables to the top Yukawa coupling in the SM and the MSSM. The prospects for indirectly determining this coupling at the next generation of colliders are discussed.

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arXiv2002

The Higgs Boson Production Cross Section as a Precision Observable?

We investigate what can be learned at a linear collider about the sector of electroweak symmetry breaking from a precise measurement of the Higgs boson production cross section through the process e+e- -> hZ. We focus on deviations from the Standard Model arising in its minimal supersymmetric extension. The analysis is performed within two realistic future scenarios, taking into account all prospective experimental errors on supersymmetric particle masses as well as uncertainties from unknown higher order corrections. We find that information on tan beta and M_A could be obtained from a cross section measurement with a precision of 0.5 - 1 %. Alternatively, information could be obtained on the gaugino mass parameters M_2 and mu if they are relatively small, M_2, mu approximately 200 GeV.

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arXiv2002

The Beyond the Standard Model Working Group: Summary Report

Report of the "Beyond the Standard Model" working group for the Workshop `Physics at TeV Colliders', Les Houches, France, 21 May - 1 June 2001. It consists of 18 separate parts: 1. Preface; 2. Theoretical Discussion; 3. Numerical Calculation of the mSUGRA and Higgs Spectrum; 4. Theoretical Uncertainties in Sparticle Mass Predictions; 5. High Mass Supersymmetry with High Energy Hadron Colliders; 6. SUSY with Heavy Scalars at LHC; 7. Inclusive Study of MSSM in CMS; 8. Establishing a No-Lose Theorem for NMSSM Higgs Boson Discovery at the LHC; 9. Effects of Supersymmetric Phases on Higgs Production in Association with Squark Pairs in the Minimal Supersymmetric Standard Model; 10. Study of the Lepton Flavour Violating Decays of Charged Fermions in SUSY GUTs; 11. Interactions of the Goldstino Supermultiplet with Standard Model Fields; 12. Attempts at Explaining the NuTeV Observation of Di-Muon Events; 13. Kaluza-Klein States of the Standard Model Gauge Bosons: Constraints From High Energy Experiments; 14. Kaluza-Klein Excitations of Gauge Bosons in the ATLAS Detector; 15. Search for the Randall Sundrum Radion Using the ATLAS Detector; 16. Radion Mixing Effects on the Properties of the Standard Model Higgs Boson; 17. Probing Universal Extra Dimensions at Present and Future Colliders; 18. Black Hole Production at Future Colliders.

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