arXiv subjects

S. Heinemeyer

Publications and source records attributed to S. Heinemeyer.

At least 127 records · Page 7Linked to original sources

arXiv2012

Interpreting the LHC Higgs Search Results in the MSSM

Recent results reported by the ATLAS and CMS experiments on the search for a SM-like Higgs boson both show an excess for a Higgs mass near 125 GeV, which is mainly driven by the γγ and ZZ^* decay channels, but also receives some support from channels with a lower mass resolution. We discuss the implications of this possible signal within the context of the minimal supersymmetric Standard Model (MSSM), taking into account previous limits from Higgs searches at LEP, the Tevatron and the LHC. The consequences for the remaining MSSM parameter space are investigated. Under the assumption of a Higgs signal we derive new lower bounds on the tree-level parameters of the MSSM Higgs sector. We also discuss briefly an alternative interpretation of the excess in terms of the heavy CP-even Higgs boson, a scenario which is found to be still viable.

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arXiv2012

Searches for New Physics: Les Houches Recommendations for the Presentation of LHC Results

We present a set of recommendations for the presentation of LHC results on searches for new physics, which are aimed at providing a more efficient flow of scientific information between the experimental collaborations and the rest of the high energy physics community, and at facilitating the interpretation of the results in a wide class of models. Implementing these recommendations would aid the full exploitation of the physics potential of the LHC.

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arXiv2012

Benchmark Models, Planes, Lines and Points for Future SUSY Searches at the LHC

We define benchmark models for SUSY searches at the LHC, including the CMSSM, NUHM, mGMSB, mAMSB, MM-AMSB and p19MSSM, as well as models with R-parity violation and the NMSSM. Within the parameter spaces of these models, we propose benchmark subspaces, including planes, lines and points along them. The planes may be useful for presenting results of the experimental searches in different SUSY scenarios, while the specific benchmark points may serve for more detailed detector performance tests and comparisons. We also describe algorithms for defining suitable benchmark points along the proposed lines in the parameter spaces, and we define a few benchmark points motivated by recent fits to existing experimental data.

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arXiv2012

Chargino Decays in the Complex MSSM: A Full One-Loop Analysis

We evaluate two-body decay modes of charginos in the Minimal Supersymmetric Standard Model with complex parameters (cMSSM). Assuming heavy scalar quarks we take into account all decay channels involving charginos, neutralinos, (scalar) leptons, Higgs bosons and Standard Model gauge bosons. The evaluation of the decay widths is based on a full one-loop calculation including hard and soft QED radiation. Special attention is paid to decays involving the Lightest Supersymmetric Particle (LSP), i.e. the lightest neutralino, or a neutral or charged Higgs boson. The higher-order corrections of the chargino decay widths involving the LSP can easily reach a level of about \pm 10%, while the corrections to the decays to Higgs bosons are slightly smaller, translating into corrections of similar size in the respective branching ratios. These corrections are important for the correct interpretation of LSP and Higgs production at the LHC and at a future linear e+e- collider. The results will be implemented into the Fortran code FeynHiggs.

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arXiv2012

Progress for Higgs Bosons Physics at the LC

A linear e+e- collider (LC) could go into operation in the next decade. The LHC is currently exploring the Higgs sector of the SM, various supersymmetric extensions and other models. The LC is necessary to complete the profile of a Higgs boson of any model. Experimental analyses and theory calculations for Higgs physics at the LC are currently performed. We review recent progress, as presented at the LCWS 2011 in Granada, Spain.

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arXiv2012

Flavour Les Houches Accord: Interfacing Flavour related Codes

We present the Flavour Les Houches Accord (FLHA) which specifies a unique set of conventions for flavour-related parameters and observables. The FLHA uses the generic SUSY Les Houches Accord (SLHA) file structure. It defines the relevant Standard Model masses, Wilson coefficients, decay constants, bag parameters, flavour observables, etc. The accord provides a universal and model-independent interface between codes evaluating and/or using flavour-related observables.

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arXiv2012

Implications of SUSY Searches at the LHC for the ILC

Global frequentist fits to the CMSSM and NUHM1 using the MasterCode framework are updated to include the public results of searches for supersymmetric signals using \sim 1/fb of LHC data recorded by ATLAS and CMS and \sim 0.3/fb of data recorded by LHCb. We also include the constraints imposed by the electroweak precision and B-physics observables, the cosmological dark matter density and the XENON100 search for spin-independent dark matter scattering. Finally we also investigate the impact of a possible Higgs signal around 125 GeV. The various constraints set new bounds on the parameter space of the CMSSM and the NUHM1. We discuss the impact of the new results from SUSY and Higgs searches for these bounds and analyze the impact for a future liner e^+e^- collider.

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arXiv2012

Neutralinos from Chargino Decays in the Complex MSSM

We review the evaluation of two-body decay modes of charginos in the Minimal Supersymmetric Standard Model with complex parameters (cMSSM). Assuming heavy scalar quarks we take into account all decay channels involving charginos, neutralinos, (scalar) leptons, Higgs bosons and SM gauge bosons. The evaluation of the decay widths is based on a full one-loop calculation including hard and soft QED radiation. Here we focus on the decays involving the Lightest Supersymmetric Particle (LSP), i.e. the lightest neutralino, or a heavier neutralino and a W boson. The higher-order corrections of the chargino decay widths can easily reach a level of \pm 10%, translating into corrections of similar size in the respective branching ratios. These corrections are important for the correct interpretation of LSP and heavier neutralino production at the LHC and at a future linear e+e- collider.

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arXiv2012

Mh in the MSSM-seesaw scenario with ILC precision

We review the computation of the one-loop radiative corrections from the neutrino/ sneutrino sector to the lightest Higgs boson mass, Mh, within the context of the so-called MSSM-seesaw scenario. This model introduces right handed neutrinos and their supersymmetric partners, the sneutrinos, including Majorana mass terms. We find negative and sizeable corrections to Mh, up to -5 GeV for a large Majorana scale, 10^{13}-10^{15} GeV, and for the lightest neutrino mass in a range 0.1-1 eV. The corrections to Mh are substantially larger than the anticipated ILC precision for large regions of the MSSM-seesaw parameter space.

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arXiv2012

MSSM Higgs Bosons from Stop and Chargino Decays

The Higgs bosons of the MSSM can be produced from the decay of SUSY particles. We review the evalulation of two decay modes in the MSSM with complex parameters (cMSSM). The first type is the decay of the heavy scalar top quark to a lighter scalar quark and a Higgs boson. The second type is the decay of the heavy chargino to a lighter chargino/neutralino and a Higgs boson. The evaluation is based on a full one-loop calculation including hard QED and QCD radiation. We find sizable contributions to many partial decay widths and branching ratios. They are roughly of O(10%) of the tree-level results, but can go up to 30% or higher. These contributions are important for the correct interpretation of scalar top quark decays at a future linear e+e- collider.

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arXiv2012

The Higgs sector of the NMFV MSSM at the ILC

We calculate the one-loop corrections to the Higgs boson masses within the context of the MSSM with Non-Minimal Flavor Violation in the squark sector. We take into account all the relevant restrictions from BR(B -> X_s gamma), BR(B_s -> mu^+ mu^-) and ΔM_{B_s}. We find sizable corrections to the lightest Higgs boson mass that are considerably larger than the expected ILC precision for acceptable values of the mixing parameters deltas. We find delta^{LR}_{ct} and delta^{RL}_{ct} specially relevant, mainly at low tan beta.

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arXiv2012

Heavy Majorana neutrino effects on MSSM-Mh

We study the effects of heavy Majorana neutrinos on the Higgs sector of the MSSM via radiative corrections. We work within the SUSY context where the MSSM particle content is enlarged with right handed neutrinos and their corresponding SUSY partners, the sneutrinos, and where compatibility with neutrino data is required. We compute the one-loop corrections to the mass of the lightest MSSM CP-even neutral Higgs boson from Majorana neutrinos and their SUSY partners and assume a seesaw mechanism of type I for neutrino mass generation. A negative and sizeable Higgs mass correction of up to -5 GeV is found for a heavy Majorana mass of up to 10^{15} GeV. This negative correction can grow up to several tens of GeV if the soft SUSY breaking mass associated to their sneutrino partners is simmilarly heavy as the Majorana mass.

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arXiv2012

Handbook of LHC Higgs Cross Sections: 2. Differential Distributions

This Report summarises the results of the second year's activities of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. The first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) focuses on predictions (central values and errors) for total Higgs production cross sections and Higgs branching ratios in the Standard Model and its minimal supersymmetric extension, covering also related issues such as Monte Carlo generators, parton distribution functions, and pseudo-observables. This second Report represents the next natural step towards realistic predictions upon providing results on cross sections with benchmark cuts, differential distributions, details of specific decay channels, and further recent developments.

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arXiv2011

Gluino Decays in the Complex MSSM: A Full One-Loop Analysis

We evaluate all two-body decay modes of the gluino, in the Minimal Supersymmetric Standard Model with complex parameters (cMSSM). This constitutes an important step in the cascade decays of SUSY particles at the LHC. The evaluation is based on a full one-loop calculation of all two-body decay channels, also including hard QED and QCD radiation. The dependence of the gluino decay to a scalar quark and a quark on the relevant cMSSM parameters is analyzed numerically. We find sizable contributions to the decay widths and branching ratios. They are, roughly of O(5%), but can go up to +-10% or higher, where the pure SUSY QCD contributions alone can give an insufficient approximation to the full one-loop result. Therefore the full corrections are important for the correct interpretation of gluino decays at the LHC. The results will be implemented into the Fortran code FeynHiggs.

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arXiv2011

Supersymmetry in Light of 1/fb of LHC Data

We update previous frequentist analyses of the CMSSM and NUHM1 parameter spaces to include the public results of searches for supersymmetric signals using ~1 /fb of LHC data recorded by ATLAS and CMS and ~0.3/fb of data recorded by LHCb in addition to electroweak precision and B-physics observables. We also include the constraints imposed by the cosmological dark matter density and the XENON100 search for spin-independent dark matter scattering. The LHC data set includes ATLAS and CMS searches for jets + missing ET events and for the heavier MSSM Higgs bosons, and the upper limits on B_s to mu^+ mu^- from LHCb and CMS. The absences of jets + missing ET signals in the LHC data favour heavier mass spectra than in our previous analyses of the CMSSM and NUHM1, which may be reconciled with (g-2)_mu if tan beta ~ 40, a possibility that is however under pressure from heavy Higgs searches and the upper limits on B_s to mu^+ mu^-. As a result, the p-value for the CMSSM fit is reduced to ~ 15 (38)%, and that for the NUHM1 to ~ 16 (38)%, to be compared with ~ 9 (49)% for the Standard Model limit of the CMSSM for the same set of observables (dropping (g-2)_mu), ignoring the dark matter relic density in both cases. We discuss the sensitivities of the fits to the (g-2)_mu and b to s gamma constraints, contrasting fits with and without the (g-2)_mu constraint, and combining the theoretical and experimental errors for b to s gamma linearly or in quadrature. We present predictions for m_gluino, B_s to mu^+ mu^-, M_h and M_A, and update predictions for spin-independent dark matter scattering, stressing again the importance of taking into account the uncertainty in the pi-nucleon sigma term, Sigma_{pi N}. Finally, we present predictions based on our fits for the likely thresholds for sparticle pair production in e^+e^- collisions in the CMSSM and NUHM1.

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arXiv2011

Standard Model Higgs-Boson Branching Ratios with Uncertainties

We present an update of the branching ratios for Higgs-boson decays in the Standard Model. We list results for all relevant branching ratios together with corresponding uncertainties resulting from input parameters and missing higher-order corrections. As sources of parametric uncertainties we include the masses of the charm, bottom, and top quarks as well as the QCD coupling constant. We compare our results with other predictions in the literature.

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arXiv2011

M_h in MSSM with Heavy Majorana Neutrinos

We review the main results of the one-loop radiative corrections from the neutrino/sneutrino sector to the lightest Higgs boson mass, M_h, within the context of the so-called MSSM-seesaw scenario where right handed neutrinos and their supersymmetric partners are included in order to explain neutrino masses. For simplicity, we have restricted ourselves to the one generation case. We find sizable corrections to M_h, which are negative in the region where the Majorana scale is large (10^{13} - 10^{15} GeV) and the lightest neutrino mass is within a range inspired by data (0.1 - 1 eV). For some regions of the MSSM-seesaw parameter space, the corrections to M_h are substantially larger than the anticipated LHC precision.

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arXiv2011

Exclusive production of the BSM Higgs bosons at the LHC

We review the prospects for Central Exclusive Production (CEP) of BSM Higgs bosons at the LHC using forward proton detectors proposed to be installed at 220 m and 420 m from the ATLAS and/ or CMS. Results are presented for MSSM in standard benchmark scenarios, in scenarios compatible with the Cold Dark Matter relic abundance and other precision measurements, and for SM with a fourth generation of fermions. We show that CEP can give a valuable information about spin-parity properties of the Higgs bosons.

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