Searches for Neutral Higgs Boson and Interpretations in the MSSM at LEP

This paper discusses recent publications of the LEP collaborations DELPHI, L3 and OPAL on searches for Higgs bosons motivated by MSSM scenarios as well as their interpretation in the MSSM. With the final publication of the LEP collaborations available or awaited, more and more interpretations in different MSSM models, including both CP conserving and CP violating, become available. Also specialized analyses close open areas in the parameter space. In the same time, better theoretical calculations with an increased maximal mass of the Higgs boson were presented. Both the new scenarios as well as the new theoretical limit on $m_{\mathrm{h}}$ has consequences for the limits from LEP. The searches, the models in which they are interpreted and the implications of the LEP results for future SUSY searches, especially on the $\tan\beta$ limit, are presented here.Comment: 3 pages, 2 figures, contribution to the proceedings of the EPS HEP Conference Aachen (2003), Version 2: added reference to section

Search for CP Violating neutral Higgs bosons in the MSSM at LEP

The LEP collaborations ALEPH, DELPHI, L3 and OPAL have searched for the neutral Higgs bosons which are predicted within the framework of the Minimal Supersymmetric Standard Model (MSSM). The data of the four collaborations are statistically combined and show no signicant excess of events which would indicate the production of Higgs bosons. The search results are thus used to set upper bounds on the cross sections of various Higgs-like event topologies and limits on MSSM benchmark models, including CP-conserving and CP-violating scenarios. Here, the limits on the model parameters of the CP-violating benchmark scenario CPX and derivates of this scenario are shown.Comment: 5 pages, 4 figures, contribution to the proceedings of the International Europhysics Conference on High Energy Physics, Lisbon, 200

Extracting SUSY parameters from LHC measurements using Fittino

We show that presently available precision data are in good agreement with supersymmetry at a mass scale below 1 TeV. Using a SUSY point close to the best fit to present data, we give a projection of the capabilities of the LHC to constrain SUSY models and their parameters as function of the accumulated luminosity.Comment: 4 pages, contribution to the proceedings of the 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions (SUSY09), Northeastern University, Boston, MA, USA, June 200

Fittino, a program for determining MSSM parameters from collider observables using an iterative method

Provided that Supersymmetry (SUSY) is realized, the Large Hadron Collider (LHC) and the future International Linear Collider (ILC) may provide a wealth of precise data from SUSY processes. An important task will be to extract the Lagrangian parameters. On this basis the goal is to uncover the underlying symmetry breaking mechanism from the measured observables. In order to determine the SUSY parameters, the program Fittino has been developed. It uses an iterative fitting technique and a Simulated Annealing algorithm to determine the SUSY parameters directly from the observables without any a priori knowledge of the parameters, using all available loop-corrections to masses and couplings. Simulated Annealing is implemented as a stable and efficient method for finding the optimal parameter values. The theoretical predictions can be provided from any program with SUSY Les Houches Accord interface. As fit result, a set of parameters including the full error matrix and two-dimensional uncertainty contours are obtained. Pull distributions can automatically be created and allow an independent cross-check of the fit results and possible systematic shifts in the parameter determination. A determination of the importance of the individual observables for the measurement of each parameter can be performed after the fit. A flexible user interface is implemented, allowing a wide range of different types of observables and a wide range of parameters to be used.Comment: 32 pages, 6 figures, accepted by Comp. Phys. Com

SUSY Parameter Measurements with Fittino

This article presents the results of a realistic global fit of the Lagrangian parameters of the Minimal Supersymmetric Standard Model with no assumptions on the SUSY breaking mechanism using the fit program Fittino. The fit is performed using the precision of future mass measurements of superpartners at the LHC and mass and polarized topological cross-section measurements at the ILC. Higher order radiative corrections are accounted for wherever possible to date. Results are obtained for a modified SPS1a MSSM benchmark scenario (general MSSM without assumptions on the breaking mechanism) and for a specific mSUGRA scenario. Exploiting a simulated annealing algorithm, a stable result is obtained without any {\it a priori} assumptions on the fit parameters. Most of the Lagrangian parameters can be extracted at the percent level or better if theoretical uncertainties are neglected. Neither LHC nor ILC measurements alone will be sufficient to obtain a stable result.Comment: 3 pages, presented at the 2005 International Linear Collider Physics And Detector Workshop, Snowmass, CO, 14.-27. August 200

Supersymmetry Parameter Analysis with Fittino

We present the results of a realistic global fit of the Lagrangian parameters of the Minimal Supersymmetric Standard Model to simulated data from ILC and LHC with realistic estimates of the observable uncertainties. Higher order radiative corrections are accounted for where ever possible to date. Results are obtained for a modified SPS1a MSSM benchmark scenario but they were checked not to depend critically on this assumption. Exploiting a simulated annealing algorithm, a stable result is obtained without any a priori assumptions on the fit parameters. Most of the Lagrangian parameters can be extracted at the percent level or better if theoretical uncertainties are neglected. Neither LHC nor ILC measurements alone will be sufficient to obtain a stable result. The effects of theoretical uncertainties arising from unknown higher-order corrections and parametric uncertainties are examined qualitatively. They appear to be relevant and the result motivates further precision calculations.Comment: 6 pages, 2 figures, presented at the Linear Collider Workshop 2005, Stanfor

Light pseudoscalar eta and H->eta eta decay in the simplest little Higgs mode

The SU(3) simplest little Higgs model in its original framework without the so-called mu term inevitably involves a massless pseudoscalar boson eta, which is problematic for b-physics and cosmological axion limit. With the mu term introduced by hand, the eta boson acquires mass m_eta ~ mu, which can be lighter than half the Higgs boson mass in a large portion of the parameter space. In addition, the introduced mu term generates sizable coupling of H-eta-eta. The Higgs boson can dominantly decay into a pair of eta's especially when mH below the WW threshold. Another new decay channel of H->Z+eta can be dominant or compatible with H -> WW for mH above the Z+eta threshold. We show that the LEP bound on the Higgs boson mass is loosened to some extent due to this new H->eta eta decay channel as well as the reduced coupling of H-Z-Z. The Higgs boson mass bound falls to about 110 GeV for f=3-4 TeV. Since the eta boson decays mainly into a bb pair, H-> eta eta -> 4b and H-> Z eta -> Z bb open up other interesting search channels in the pursuit of the Higgs boson in the future experiments. We discuss on these issues.Comment: major modification considering the simplest little Higgs model with the mu ter

Applying Exclusion Likelihoods from LHC Searches to Extended Higgs Sectors

LHC searches for non-standard Higgs bosons decaying into tau lepton pairs constitute a sensitive experimental probe for physics beyond the Standard Model (BSM), such as Supersymmetry (SUSY). Recently, the limits obtained from these searches have been presented by the CMS collaboration in a nearly model-independent fashion - as a narrow resonance model - based on the full 8 TeV dataset. In addition to publishing a 95% C.L. exclusion limit, the full likelihood information for the narrow resonance model has been released. This provides valuable information that can be incorporated into global BSM fits. We present a simple algorithm that maps an arbitrary model with multiple neutral Higgs bosons onto the narrow resonance model and derives the corresponding value for the exclusion likelihood from the CMS search. This procedure has been implemented into the public computer code HiggsBounds (version 4.2.0 and higher). We validate our implementation by cross-checking against the official CMS exclusion contours in three Higgs benchmark scenarios in the Minimal Supersymmetric Standard Model (MSSM), and find very good agreement. Going beyond validation, we discuss the combined constraints of the tau tau search and the rate measurements of the SM-like Higgs at 125 GeV in a recently proposed MSSM benchmark scenario, where the lightest Higgs boson obtains SM-like couplings independently of the decoupling of the heavier Higgs states. Technical details for how to access the likelihood information within HiggsBounds are given in the appendix. The program is available at http://higgsbounds.hepforge.org.Comment: 24 pages, 6 figures; The code can be downloaded from http://higgsbounds.hepforge.or