MFV reductions of MSSM parameter space

Journal of High Energy Physics, Feb 2015

The 100+ free parameters of the minimal supersymmetric standard model (MSSM) make it computationally difficult to compare systematically with data, motivating the study of specific parameter reductions such as the cMSSM and pMSSM. Here we instead study the reductions of parameter space implied by using minimal flavour violation (MFV) to organise the R-parity conserving MSSM, with a view towards systematically building in constraints on flavour-violating physics. Within this framework the space of parameters is reduced by expanding soft supersymmetry-breaking terms in powers of the Cabibbo angle, leading to a 24-, 30- or 42-parameter framework (which we call MSSM-24, MSSM-30, and MSSM-42 respectively), depending on the order kept in the expansion. We provide a Bayesian global fit to data of the MSSM-30 parameter set to show that this is manageable with current tools. We compare the MFV reductions to the 19-parameter pMSSM choice and show that the pMSSM is not contained as a subset. The MSSM-30 analysis favours a relatively lighter TeV-scale pseudoscalar Higgs boson and tan β ∼ 10 with multi-TeV sparticles.

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MFV reductions of MSSM parameter space

S.S. AbdusSalam 1 2 5 7 8 9 C.P. Burgess 1 2 3 4 6 8 9 F. Quevedo 0 1 2 5 8 9 P.le A. Moro 1 2 8 9 I- 1 2 8 9 Roma 1 2 8 9 Italia 1 2 8 9 Hamilton ON 1 2 8 9 Canada 1 2 8 9 Cambridge 1 2 8 9 U.K. 1 2 8 9 0 DAMTP, Cambridge University 1 CH-1211 , Gen`eve 23 , Suisse 2 Waterloo , ON , Canada 3 Perimeter Institute for Theoretical Physics 4 Division PH -TH , CERN 5 The Abdus Salam ICTP 6 Department of Physics & Astronomy, McMaster University 7 INFN - Sezione di Roma 8 Open Access , c The Authors 9 [54] M.W. Cahill-Rowley , J.L. Hewett, A. Ismail and T.G. Rizzo, More energy, more searches The 100+ free parameters of the minimal supersymmetric standard model (MSSM) make it computationally difficult to compare systematically with data, motivating the study of specific parameter reductions such as the cMSSM and pMSSM. Here we instead study the reductions of parameter space implied by using minimal flavour violation (MFV) to organise the R-parity conserving MSSM, with a view towards systematically building in constraints on flavour-violating physics. Within this framework the space of parameters is reduced by expanding soft supersymmetry-breaking terms in powers of the Cabibbo angle, leading to a 24-, 30- or 42-parameter framework (which we call MSSM-24, MSSM-30, and MSSM-42 respectively), depending on the order kept in the expansion. We provide a Bayesian global fit to data of the MSSM-30 parameter set to show that this is manageable with current tools. We compare the MFV reductions to the 19-parameter pMSSM choice and show that the pMSSM is not contained as a subset. The MSSM-30 analysis favours a relatively lighter TeV-scale pseudoscalar Higgs boson and tan 10 with multi-TeV sparticles. 1 Introduction The models 2 3 Expansions in small mixing angles The MSSM-30 fit Conclusions and outlook (on the cover of The Hitchhikers Guide to the Galaxy [1]) Douglas Adams Supersymmetry, when linearly realised, requires the existence of superpartners to the known elementary particles, and robustly dictates their quantum numbers. Less robustly dictated are their masses and couplings once supersymmetry is spontaneously broken, as experiments demand it must be. A full description of these requires the more than 100 parameters of the supersymmetry-breaking sector of the R-parity conserving minimal supersymmetric Standard Model (MSSM). The challenge of confronting such a vast parameter space with data drives the development of various kinds of well-motivated benchmark models. The earliest of these, the cMSSM/mSUGRA [24], specialises to a restricted parameter space motivated by what would be generated if supersymmetry were broken in a flavour-blind hidden sector (as suggested by the earliest gravity-mediation models). This simple model is one of the main benchmarks against which LHC results are compared, with the result that it is in real tension with the data. But should this tension be regarded as evidence against supersymmetry, even if only in its linearly realised1 form? Answering this requires a more detailed exploration of the parameter space, yet a complete scan of the total parameters still remains beyond our current computational capabilities. What is needed is a more strategic survey of the possibilities, of which several approaches have emerged. One approach for example, Gauge-Mediated Supersymmetry 1See [5] for a well-motivated example where supersymmetry breaks at the electroweak scale but is nonlinearly realised in the Standard Model sector, and so doesnt require the existence of MSSM superpartners like squarks and sleptons. Breaking (GMSB) [6], or more sophisticated string-motivated gravity mediation mechanisms [7] is to explore alternative mechanisms of supersymmetry breaking whose low-energy implications differ from those of the minimal gravity-mediated picture. Another focusses less on surveying the parameter space and more on the generic features of the underlying production and decay mechanisms, such as appear in simplified models [8]. Comparison of such models to the data can quantify which of these mechanisms are favoured or disfavoured. A more specific simplified models approach instead focuses on those interactions that take part in the naturalness issues that underlie the motivation for supersymmetry in the first place [911]. A third approach is to try to broadly survey the allowed parameter space, but to use prior knowledge about other constraints (like limits on flavour and CP violations) to cut down the range of parameters examined at the LHC. Of course this would be simple if it were just a matter of removing couplings that are excluded by other constraints. How the parameters are best pruned is more of a judgement call when the couplings of interest are not directly forbidden by other observations. The phenomenological MSSM (pMSSM) [12] is one of the leading approaches along these lines which stakes out a 19-parameter subset of MSSM by removing all members of potentially dangerous families (...truncated)


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S. S. AbdusSalam, C. P. Burgess, F. Quevedo. MFV reductions of MSSM parameter space, Journal of High Energy Physics, 2015, pp. 73, Volume 2015, Issue 2, DOI: 10.1007/JHEP02(2015)073