General Minimal Supersymmetric Standard Model Research Articles

Flavor anomalies in supersymmetric scenarios with nonminimal flavor violation

Motivated by tensions between experimental measurements and SM predictions in $b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ transitions, we present the first study of nonminimal flavor-violating minimal supersymmetric Standard Model (MSSM) scenarios contributing to the relevant Wilson coefficients to address the observed anomalies using SuperIso and MARTY. We calculate the full one-loop analytical contributions of the general MSSM to Wilson coefficients relevant for flavor anomalies, together with the anomalous muon magnetic dipole moment $(g\ensuremath{-}2{)}_{\ensuremath{\mu}}$. We show that, after imposing theoretical constraints on the flavor-violating parameters, we can find scenarios in agreement with the experimental measurements that can address at the same time the tensions in flavor observables and in $(g\ensuremath{-}2{)}_{\ensuremath{\mu}}$.

First steps towards the reconstruction of the squark flavour structure

Assuming the observation of a squark at the Large Hadron Collider, we investigate methods to access its flavour content and thus gain information on the underlying flavour structure of the theory. Based on simple observables, we apply a likelihood inference method to determine the top-flavour content of the observed particle. In addition, we employ a multivariate analysis in order to classify different flavour hypotheses. Both methods are discussed within a simplified model and the more general Minimal Supersymmetric Standard Model including most general squark mixing. We conclude that the likelihood inference may provide an estimation of the top-flavour content if additional knowledge, especially on the gaugino sector is available, while the multivariate analysis identifies different flavour patterns and can accommodate a more minimalistic set of observables.

Non-relativistic pair annihilation of nearly mass degenerate neutralinos and charginos III. Computation of the Sommerfeld enhancements

This paper concludes the presentation of the non-relativistic effective field theory formalism designed to calculate the radiative corrections that enhance the pair-annihilation cross sections of slowly moving neutralinos and charginos within the general minimal supersymmetric standard model (MSSM). While papers I and II focused on the computation of the tree-level annihilation rates that feed into the short-distance part, here we describe in detail the method to obtain the Sommerfeld factors that contain the enhanced long-distance corrections. This includes the computation of the potential interactions in the MSSM, which are provided in compact analytic form, and a novel solution of the multi-state Schr\"odinger equation that is free from the numerical instabilities generated by large mass splittings between the scattering states. Our results allow for a precise computation of the MSSM neutralino dark matter relic abundance and pair-annihilation rates in the present Universe, when Sommerfeld enhancements are important.

Constraining supersymmetry using the relic density and the Higgs boson

Recent measurements by Planck, LHC experiments, and Xenon100 have significant impact on supersymmetric models and their parameters. We first illustrate the constraints in the mSUGRA plane and then perform a detailed analysis of the general minimal supersymmetric Standard Model (MSSM) with 13 free parameters. Using SFitter, Bayesian and profile likelihood approaches are applied and their results compared. The allowed structures in the parameter spaces are largely defined by different mechanisms of dark matter annihilation in combination with the light Higgs mass prediction. In mSUGRA the pseudoscalar Higgs funnel and stau coannihilation processes are still avoiding experimental pressure. In the MSSM stau coannihilation, the light Higgs funnel, a mixed bino-Higgsino region including the heavy Higgs funnel, and a large Higgsino region predict the correct relic density. Volume effects and changes in the model parameters impact the extracted mSUGRA and MSSM parameter regions in the Bayesian analysis.

General MSSM signatures at the LHC with and withoutR-parity

We present the possible signatures appearing in general realizations of the minimal supersymmetric standard model based on 14 unrelated mass parameters at the supersymmetry scale. The parameters of the general minimal supersymmetric standard model are reduced by assuming a degeneracy of the sfermions of the first two generations with the same quantum numbers. We also assume no mass splitting between neutral and charged Higgsinos. We do allow for separate soft breaking terms for the third-generation sfermons. We consider all possible resulting $14!\ensuremath{\approx}9\ifmmode\times\else\texttimes\fi{}{10}^{10}$ relevant mass orderings and check for the dominant decay cascades and the corresponding collider signatures. In determining the dominant decay modes we assume that mixing between sparticles is subdominant. As preferred signatures, we consider charged leptons, missing transverse momentum, jets, and $W$, $Z$ or Higgs bosons. We include also the cases of bi- and trilinear $R$-parity violation and show that specific signatures can be used to distinguish the different scenarios.

Pair production of neutralinos and charginos at the LHC: The role of Higgs bosons exchange

We analyze the effects of the s-channel Higgs bosons exchange on the charginos and neutralinos-pair production in proton-proton collision at the CERN Large Hadron Collider (LHC) in the following channels: $pp \to \Cha^+\Cha^-/\Neu^0\Neu^0 + X$, within the minimal supersymmetric standard model (MSSM). Assuming the usual GUT relation between $M_1$ and $M_2$ at the weak scale, we found that substantial enhancement can be obtained through s-channel Higgs bosons exchange in the mixed regime where $M_2 \sim |\mu|$ with moderate to large $\tan\beta$ at the resonance of the heavy Higgs bosons. By Combining the phenomenological constraints on neutralinos and charginos, we may still find regions of parameter space where charginos and neutralinos-pair production at the LHC from $b\bar b$ initial state can be large and observable at LHC. We also compute the full complete set of electroweak (EW) contributions to $pp\to gg\to \Cha^+\Cha^-/\Neu^0\Neu^0 + X$ at one loop level in the general MSSM. The analytical computation of the complete tree level amplitude for $b\bar{b} \to \Cha^+\Cha^-/\Neu^0\Neu^0 + X$, including s-channel Higgs exchange, is given.

Single Higgs-boson production at a photon–photon collider: General 2HDM versus MSSM

We revisit the production of a single Higgs boson from direct γγ-scattering at a photon collider. We compute the total cross-section σ(γγ→h) (for h=h0,H0,A0), and the strength of the effective gh0γγ coupling normalized to the Standard Model (SM), for both the general Two-Higgs-Doublet Model (2HDM) and the Minimal Supersymmetric Standard Model (MSSM). In both cases the predicted production rates for the CP-even (odd) states render up to 104 (103) events per 500 fb−1 of integrated luminosity, in full consistency with all the theoretical and phenomenological constraints. Depending on the channel the maximum rates can be larger or smaller than the SM expectations, but in most of the parameter space they should be well measurable. We analyze how these departures depend on the dynamics underlying each of the models, supersymmetric and non-supersymmetric, and highlight the possible distinctive phenomenological signatures. We demonstrate that this process could be extremely useful to discern non-supersymmetric Higgs bosons from supersymmetric ones. Furthermore, in the MSSM case, we show that γγ-physics could decisively help to overcome the serious impasse afflicting Higgs boson physics at the infamous “LHC wedge”.

A comprehensive approach to new physics simulations

We describe a framework to develop, implement and validate any perturbative Lagrangian-based particle physics model for further theoretical, phenomenological and experimental studies. The starting point is FeynRules, a Mathematica package that allows to generate Feynman rules for any Lagrangian and then, through dedicated interfaces, automatically pass the corresponding relevant information to any supported Monte Carlo event generator. We prove the power, robustness and flexibility of this approach by presenting a few examples of new physics models (the Hidden Abelian Higgs Model, the general Two-Higgs-Doublet Model, the most general Minimal Supersymmetric Standard Model, the Minimal Higgsless Model, Universal and Large Extra Dimensions, and QCD-inspired effective Lagrangians) and their implementation/validation in FeynArts/FormCalc, CalcHep, MadGraph/MadEvent, and Sherpa.

Long-lived slepton in the coannihilation region and measurement of lepton flavour violation at LHC

When the mass difference between the lightest slepton and the lightest neutralino is smaller than the tau mass, the lifetime of the lightest slepton in the constrained Minimal Supersymmetric Standard Model (MSSM) increases in many orders of magnitude with respect to typical lifetimes of other supersymmetric particles. In a general MSSM, the lifetime of the lightest slepton is inversely proportional to the square of the intergenerational mixing in the slepton mass matrices. Such a long-lived slepton would produce a distinctive signature at LHC and a measurement of its lifetime would be relatively simple. Therefore, the long-lived slepton scenario offers an excellent opportunity to study lepton flavour violation at ATLAS and CMS detectors in the LHC and an improvement of the leptonic mass insertion bounds by more than five orders of magnitude would be possible.

Analysis of Higgs Boson Mass Limit from LEP Experiment in General Minimal Supersymmetric Standard Model, and the Possibility of the Light Higgs Boson(Current Topics)

Analysis of Higgs Boson Mass Limit from LEP Experiment in General Minimal Supersymmetric Standard Model, and the Possibility of the Light Higgs Boson(Current Topics)

Measuring lepton flavor violation at LHC with a long-lived slepton in the coannihilation region

When the mass difference between the lightest slepton, the next to lightest supersymmetric particle, and the lightest neutralino, the lightest supersymmetric particle, is smaller than the tau mass, the lifetime of the lightest slepton increases in many orders of magnitude with respect to typical lifetimes of other supersymmetric particles. These small mass differences are possible in the minimal supersymmetric standard model (MSSM) and, for instance, they correspond to the coannihilation region of the constrained MSSM for ${M}_{1/2}\ensuremath{\gtrsim}700\text{ }\text{ }\mathrm{GeV}$. In a general gravity-mediated MSSM, where the lightest supersymmetric particle is the neutralino, the lifetime of the lightest slepton is inversely proportional to the square of the intergenerational mixing in the slepton mass matrices. Such a long-lived slepton would produce a distinctive signature at LHC and a measurement of its lifetime would be relatively simple. Therefore, the long-lived slepton scenario offers an excellent opportunity to study lepton flavor violation at ATLAS and CMS detectors in the LHC and an improvement of the leptonic mass insertion bounds by more than 5 orders of magnitude would be possible.

Gaugino-pair production in polarized and unpolarized hadron collisions

We present an exploratory study of gaugino-pair production in polarized and unpolarized hadron collisions, focusing on the correlation of beam polarization and gaugino/Higgsino mixing in the general minimal supersymmetric standard model. Helicity-dependent cross sections induced by neutral and charged electroweak currents and squark exchanges are computed analytically in terms of generalized charges, defined similarly for chargino-pair, neutralino-chargino associated, and neutralino-pair production. Our results confirm and extend those obtained previously for negligible Yukawa couplings and nonmixing squarks. Assuming that the lightest chargino mass is known, we show numerically that measurements of the longitudinal single-spin asymmetry at the existing polarized $pp$ collider RHIC and at possible polarization upgrades of the Tevatron or the LHC would allow for a determination of the gaugino/Higgsino fractions of charginos and neutralinos. The theoretical uncertainty coming from factorization scale and squark mass variations and the expected experimental error on the lightest chargino mass is generally smaller than the one induced by the polarized parton densities, so that more information on the latter would considerably improve on the analysis.

Electron electric dipole moment from Lepton Flavor Violation

The general Minimal Supersymmetric Standard Model introduces new sources for Lepton Flavor Violation (LFV) as well as CP-violation. In this paper, we show that when both sources are present, the electric dipole moment of the electron, $d_e$, receives a contribution from the phase of the trilinear $A$-term of staus, $\phi_{A_\tau}$. For $\phi_{A_\tau}=\pi/2$, the value of $d_e$, depending on the ratios of the LFV mass elements, can range between zero and three orders of magnitude above the present bound. We show that the present bound on $d_e$ rules out a large portion of the CP-violating and the LFV parameter space which is consistent with the bounds on the LFV rare decays. We show that studying the correlation between $d_e$ and the P-odd asymmetry in $\tau \to e\gamma$ helps us to derive a more conclusive bound on $\phi_{A_\tau}$ We also discuss the possibility of cancelation among the contributions of different CP-violating phases to $d_e$.

MicrOMEGAs: Version 1.3

We present the latest version of micrOMEGAs, a code that calculates the relic density of the lightest supersymmetric particle (LSP) in the minimal supersymmetric standard model (MSSM). All tree-level processes for the annihilation of the LSP are included as well as all possible coannihilation processes with neutralinos, charginos, sleptons, squarks and gluinos. The cross-sections extracted from CalcHEP are calculated exactly using loop-corrected masses and mixings as specified in the SUSY Les Houches Accord. Relativistic formulae for the thermal average are used and care is taken to handle poles and thresholds by adopting specific integration routines. The input parameters can be either the soft SUSY parameters in a general MSSM or the parameters of a SUGRA model specified at the GUT scale. In the latter case, a link with Suspect, SOFTSUSY, Spheno and Isajet allows one to calculate the supersymmetric spectrum, Higgs masses, as well as mixing matrices. Higher-order corrections to Higgs couplings to quark pairs including QCD as well as some SUSY corrections ( Δ m b ) are implemented. Routines calculating ( g − 2 ) μ , b → s γ and B s → μ + μ − are also included. In particular the b → s γ routine includes an improved NLO for the SM and the charged Higgs while the SUSY large tan β effects beyond leading-order are included. This new version also provides cross-sections for any 2 → 2 process as well as partial decay widths for two-body final states in the MSSM allowing for easy simulation at colliders. Program summary Program title:micrOMEGAs1.3 Catalogue identifier:ADQR_v1_3 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADQR_v1_3 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions:none Computer:PC, Alpha, Silicon graphics, Sun Programming language:C and Fortran Operating system:UNIX (Linux, OSF1, IRIX64, SunOS) RAM:20 MB depending on the number of processes required No of lines in distributed program, including test data, etc.:78 314 No. of bytes in distributed program, including test data, etc.:703 112 Distribution format:tar.gz Number of processors used:1 External routines/libraries:Library of Fortran functions, for example, -lg2c (platform dependent) Catalogue identifier of previous version:ADQR Journal reference of previous version:Comput. Phys. Comm. 149 (2002) 103 Does the new version supersede the previous version?:yes Nature of problem:Calculation of the relic density of the lightest supersymmetric particle in the MSSM. Solution method:In numerically solving the evolution equation for the density of dark matter, relativistic formulae for the thermal average are used. All tree-level processes for annihilation and coannihilation of SUSY particles are included. The cross-sections for all processes are calculated exactly with CalcHEP. Higher-order corrections to Higgs masses and Higgs couplings to quark pairs including QCD as well as some SUSY corrections are implemented. The input parameters can be either the soft SUSY parameters in a general MSSM or the parameters of a SUGRA model specified at the GUT scale. In the latter case, a link with Suspect, SOFTSUSY, Spheno and Isajet allows to calculate the supersymmetric spectrum, Higgs masses, as well as mixing matrices. Reasons for the new version:This new version contains a more accurate calculation of the relic density of dark matter as well as many new features both for interface with codes that calculate the supersymmetric spectrum as well as for computation of cross-sections and decays relevant for collider physics. Summary of revisions: • Interface with the main codes to calculate the supersymmetric spectrum: Suspect, Isajet, Spheno and SOFTSUSY in models defined at some high scale. • Includes loop corrected sparticle masses and mixing matrices. • Includes loop-corrected Higgs masses and widths. QCD corrections to the Higgs couplings to fermion pairs are included as well as, via an effective Lagrangian, the Δ m b correction relevant at large tan β . • Provides exact numerical solution of the Boltzmann equation by Runge–Kutta. • Outputs the relative contribution of each channel to 1 / Ω . • Computes cross-sections for any 2 → 2 process at the parton level. • Calculates decay widths for all particles at tree-level including all 1 → 2 decay modes. • Calculates constraints on MSSM: B s → μ + μ − and NLO corrections to b → s γ . Unusual features:Depending on the parameters of the model, the program generates additional new code for matrix elements, compiles it and loads it dynamically. Running time:0.2 sec.

Review Article

After an introduction recalling the theoretical motivation for low energy (100 GeV to TeV scale) supersymmetry, this review describes the theory and experimental implications of the soft supersymmetry-breaking Lagrangian of the general minimal supersymmetric standard model (MSSM). Extensions to include neutrino masses and nonminimal theories are also discussed. Topics covered include models of supersymmetry breaking, phenomenological constraints from electroweak symmetry breaking, flavor / CP violation, collider searches, and cosmological constraints including dark matter and implications for baryogenesis and inflation.

Statistical analysis of supersymmetric dark matter in the minimal supersymmetric standard model after WMAP

We study supersymmetric dark matter in the general flavor diagonal minimal supersymmetric standard model by means of an extensive random scan of its parameter space. We find that, in contrast with the standard minimal supergravity lore, the large majority of viable models features either a Higgsino or a winolike lightest neutralino, and yields a relic abundance well below the Wilkinson Microwave Anisotropy Probe (WMAP) bound. Among the models with neutralino relic density within the WMAP range, Higgsinolike neutralinos are still dominant, though a sizable fraction of binos is also present. In this latter case, coannihilations are shown to be essential in order to obtain the correct neutralino abundance. We then carry out a statistical analysis and a general discussion of neutralino dark matter direct detection and of indirect neutralino detection at neutrino telescopes and at antimatter search experiments. We point out that current data exclude only a marginal portion of the viable parameter space, and that models whose thermal relic abundance lies in the WMAP range will be significantly probed only at future direct detection experiments. Finally, we emphasize the importance of relic density enhancement mechanisms for indirect detection perspectives, in particular, at future antimatter search experiments.

CP-sensitive observables in chargino production with transverse $e^{\pm}$ beam polarization

We consider the process $e^+e^-\to\ti\chi^+_i\ti\chi^-_j$ at a linear collider with transverse $e^{\pm}$ beam polarization. We investigate the influence of the CP phases on azimuthal asymmetries in $e^+e^-\to\ti\chi^+_i\ti\chi^-_j$ with subsequent two-body decays $\ti\chi^-_j\to \ti\nu_{\ell}\ell^-$ and $\ti\chi^-_j\to W^-\ti\chi^0_1$. We show that triple product correlations involving the transverse $e^{\pm}$ beam polarization vanish if at least one subsequent chargino decay is not observed. We derive this result within the Minimal Supersymmetric Standard Model (MSSM) with complex parameters, however, it holds also in the general MSSM with SUSY flavour violation.

Gluino annihilations and neutralino dark matter

We consider supersymmetric (SUSY) scenarios, compatible with all cosmological and phenomenological requirements, where the lightest SUSY particles (LSPs) are the neutralino and a quasidegenerate gluino. We study the neutralino relic abundance, focusing on gluino (co)annihilation effects. In case the neutralino is B-ino-like, in a wide mass window the relic abundance is naturally driven in the correct range for the LSP to be the main cold dark matter constituent. We show that the gluino is the strongest possible coannihilating partner of a B-ino-like neutralino in the general minimal supersymmetric standard model. Moreover, contrary to other coannihilation scenarios, gluino pair annihilations always dominate over coannihilation processes, even at relatively large gluino-neutralino mass splittings. Finally, we present prospects for neutralino dark matter detection in the outlined framework.

Trilepton+top signal from chargino-neutralino decays of MSSM charged Higgs bosons at the LHC

We perform for the Large Hadron Collider (LHC) a detailed study of charged Higgs boson production via the top-bottom quark associated mode followed by decays into a chargino and a neutralino, with masses and couplings as given by the general Minimal Supersymmetric Standard Model (MSSM). We focus our attention on the region of parameter space where the charged Higgs is heavier than the top quark, with intermediate values of tan beta. In this region, the identification of charged Higgs bosons via decays into Standard Model (SM) particles has proven to be ineffective. Modelling the CMS detector, we find that a signature consisting of three hard leptons accompanied by a hadronically reconstructed top quark plus substantial missing transverse energy, which may result from charged Higgs decays into neutralinos and charginos, can be made viable over a large variety of initially overwhelming SM and MSSM backgrounds, provided MSSM input parameters are favourable: notably, a small mu parameter and light sleptons are important prerequisites. We quantify these statements by performing a fairly extensive scan of the parameter space, including realistic hadron-level simulations, and delineate some potential discovery regions.

Upper and Lower Limits on Neutralino WIMP Mass and Spin–Independent Scattering Cross Section, and Impact of New (g−2)μMeasurement

We derive the allowed ranges of the spin--independent interaction cross section $\sigsip$ for the elastic scattering of neutralinos on proton for wide ranges of parameters of the general Minimal Supersymmetric Standard Model. We investigate the effects of the lower limits on Higgs and superpartner masses from colliders, as well as the impact of constraints from $\bsgamma$ and the new measurement of $\gmtwo$ on the upper and lower limits on $\sigsip$. We further explore the impact of the neutralino relic density, including coannihilation, and of theoretical assumptions about the largest allowed values of the supersymmetric parameters. For $\mu>0$, requiring the latter to lie below $1\tev$ leads to $\sigsip\gsim 10^{-11}\pb$ at $\mchi\sim100\gev$ and $\sigsip\gsim 10^{-8}\pb$ at $\mchi\sim1\tev$. When the supersymmetric parameters are allowed above $1\tev$, for $440\gev \lsim \mchi\lsim 1020 \gev$ we derive a {\em parameter--independent lower limit} of $\sigsip \gsim 2\times 10^{-12}\pb$. (No similar lower limits can be set for $\mu<0$ nor for $1020\gev\lsim\mchi\lsim2.6\tev$.) Requiring $\abundchi<0.3$ implies a {\em parameter--independent upper limit} $\mchi\lsim2.6\tev$. The new $\epem$--based measurement of $(g-2)_{\mu}$ restricts $\mchi\lsim 350\gev$ at $1 \sigma$ CL and $\mchi\lsim515\gev$ at $2 \sigma$ CL, and implies $\mu>0$. The largest allowed values of $\sigsip$ have already become accessible to recent experimental searches.