Narrow Results

The mixing parameter ΔM_s is studied in the MSSM with large tan β. The recent Tevatron measurement of ΔM_s is used to constrain the MSSM parameter space. From this analysis the often neglected contribution to ΔM_s from the operator is found to be significant.

This paper is the completion of an earlier work arXiv:1207.4867 which involves the derivation of oblique corrections in the MSSM at one-loop. In terms of the two-component spinor formalism, which is new in comparison with those used in the literature, the contributions arising from the fermion superpartners, i.e. neutralino-chargino sector to self-energy of Standard Model electroweak gauge bosons are calculated. Corresponding descendants the S, T and U parameters are presented. The validity of our results is examined in two ways, which are then followed by detailed analysis on the results in the literature.

We study a Ramond–Neveu–Schwarz string with one end fixed on a D0-brane and the other end free as a qualitative guide to the spectrum of hadrons containing one very heavy quark. The mixed boundary conditions break half of the worldsheet supersymmetry and allow only odd α and even d modes in the Ramond sector, while the Neveu–Schwarz oscillators b's become odd-integer moded. Boson-fermion masses can still be matched if space–time is nine-dimensional; thus SO(8) triality still plays a role in the spectrum, although full space–time supersymmetry does not survive. We quantize the system in a temporal-like gauge where X⁰ ~ τ. Although the gauge choice eliminates negative-norm states at the outset, there are still even-moded Virasoro and even (odd) moded super-Virasoro constraints to be imposed in the NS(R) sectors. The Casimir energy is now positive in both sectors; there are no tachyons. States for α′ M² ≤ 13/4 are explicitly constructed and found to be organized into SO(8) irreps by (super)constraints, which include a novel "" operator in the Neveu–Schwarz and Γ⁰ ± I in the Ramond sectors. GSO projections are not allowed. The preconstraint states above the ground state have matching multiplicities, indicating space–time supersymmetry is broken by the (super)constraints. A distinctive physical signature of the system is a slope twice that of the open RNS string. When both ends are fixed, all leading and subleading trajectories are eliminated, resulting in a spectrum qualitatively similar to the J/ψ and ϒ particles.

We consider the λSUSY model, a version of the NMSSM with large λH₁H₂S coupling, relaxing the approximation of large singlet mass and negligible mixing of the scalar singlet with the scalar doublets. We show that there are regions of the parameter space in which the lightest pseudoscalar can be relatively light, with unusual consequences on the decay pattern of the CP-even Higgs bosons and thus on the LHC phenomenology.

We briefly review the status of motivated beyond-the-MSSM phenomenology in the light of the LHC searches to date. In particular, we discuss the conceptual consequences of the exclusion bounds, of the hint for a Higgs boson at about 125 GeV, and of interpreting the excess of direct CP violation in the charm sector as a signal of New Physics. We try to go into the various topics in a compact way while providing a relatively rich list of references, with particular attention to the most recent developments.

We analyze relevant signals expected at the LHC for a left sneutrino as the lightest supersymmetric particle (LSP). The discussion is carried out in the “$\mu$ from $\nu$” supersymmetric standard model $(\mu \nu \mathrm{\text{SSM}})$, where the presence of $R$-parity breaking couplings involving right-handed neutrinos solves the $\mu$ problem and reproduces neutrino data. The sneutrinos are pair produced via a virtual $W$, $Z$ or $\gamma$ in the $s$ channel. From the prompt decay of a pair of left sneutrinos LSPs of any family, a significant diphoton signal plus missing transverse energy (MET) from neutrinos can be present in the mass range 118–132 GeV, with 13 TeV center-of-mass energy and an integrated luminosity of 100 fb${}^{-1}$. In addition, in the case of a pair of tau left sneutrinos LSPs, given the large value of the tau Yukawa coupling diphoton plus leptons and/or multileptons can appear. We find that the number of expected events for the multilepton signal, together with properly adopted search strategies, is sufficient to give a significant evidence for a sneutrino of mass in the range 130–310 GeV, even with the integrated luminosity of 20 fb${}^{-1}$. In the case of the signal producing diphoton plus leptons, an integrated luminosity of 100 fb${}^{-1}$ is needed to give a significant evidence in the mass range 95–145 GeV. Finally, we discuss briefly the presence of displaced vertices and the associated range of masses.

We study constrained versions of the minimal supersymmetric model and investigate the hierarchy between the electroweak scale and the scale of superpartners that can be achieved without relying on specifying model parameters by more than one digit (or with better than 10% precision). This approach automatically avoids scenarios in which a large hierarchy is obtained by special choices of parameters and yet keeps scenarios that would otherwise be disfavored by various sensitivity measures. We consider models with universal gaugino and scalar masses, models with nonuniversal Higgs masses or nonuniversal gaugino masses and focus on scenarios in which all the model parameters are either of the same order or zero at the grand unification scale. We find that the maximal hierarchy between the electroweak scale and stop masses, requiring that model parameters are not specified beyond one digit, ranges from a factor of $\sim$10–30 for the CMSSM up to $\sim$300 for models with nonuniversal Higgs or gaugino masses.

We study the loop-induced decays $h^0\to \gamma \gamma$ and $h^0\to gg$ in the Minimal Supersymmetric Standard Model (MSSM) with quark flavor violation (QFV), identifying $h^0$ with the Higgs boson with a mass of 125 GeV, where $\gamma$ and $g$ are photon and gluon, respectively. We perform a MSSM parameter scan and a detailed analysis around a fixed reference point respecting theoretical constraints from vacuum stability conditions and experimental constraints, such as those from $B$-meson data and electroweak precision data, as well as recent limits on Supersymmetric (SUSY) particle masses from LHC experiments. We find that (i) the relative deviation of the decay width $\mathrm{\Gamma }(h^0\to gg)$ from the Standard Model value, $\mathrm{\text{DEV}}(g)$, can be large and negative, $\lesssim -15\%$, (ii) the analogous deviation of $\mathrm{\Gamma }(h^0\to \gamma \gamma )$ is strongly correlated, $\mathrm{\text{DEV}}(\gamma )\simeq -1/4\mathrm{\text{DEV}}(g)$ for $\mathrm{\text{DEV}}(g)\lesssim -4\%$, (iii) the relative deviation of the width ratio $\mathrm{\Gamma }(h^0\to \gamma \gamma )/\mathrm{\Gamma }(h^0\to gg)$ from the SM value, $\mathrm{\text{DEV}}(\gamma /g)$, can be large (up to $\sim$20%), (iv) the deviations can be large due to the up-type squark loop contributions, (v) the SUSY QFV parameters can have a significant effect on these deviations. Such large deviations can be observed at a future $e^{+}{e}^{-}$ collider like ILC. Observation of the deviation patterns as shown in this study would favor the MSSM with flavor-violating squark mixings and encourage to perform further studies in this model.

The purpose of this paper is to examine the model dependence of the stringent constraints on the gluino mass obtained from the Large Hadron Collider (LHC) experiments by analyzing the Run II data using specific simplified models based on several ad hoc sparticle spectra which cannot be realized even in the fairly generic pMSSM models. We first revisit the bounds on the gluino mass placed by the ATLAS collaboration using the $1l+\mathrm{\text{jets}}+{∕E}_T$ data. We show that the exclusion region in the $M_{\tilde{g}}-M_{{\tilde{\chi }}_1^0}$ plane in the pMSSM scenario sensitively depends on the mass hierarchy between the left and right squarks and composition of the lighter electroweakinos and to a lesser extent, other parameters. Most importantly, for higgsino-type lighter electroweakinos (except for the LSP), the bound on the gluino mass from this channel practically disappears. However, if such models are confronted by the ATLAS $\mathrm{\text{jets}}+{∕E}_T$ data, fairly strong limits are regained. Thus, in the pMSSM, an analysis involving a small number of channels may provide more reliable mass limits. We have also performed detailed analyses on neutralino Dark Matter (DM) constraints in the models we have studied and have found that for a significant range of LSP masses, the relic density constraints from the WMAP/PLANCK data are satisfied and LSP-gluino coannihilation plays an important role in relic density production. We have also checked the simultaneous compatibility of the models studied here with the direct DM detection, and the LHC constraints.