Search

A number of LHC searches now display intriguing excesses. Most prominently, the measurement of the $W^+W^-$ cross-section has been consistently $\sim 20\%$ higher than the theoretical prediction across both ATLAS and CMS for both 7 and 8 TeV runs. More recently, supersymmetric searches for final states containing two or three leptons have also seen more events than predicted in certain signal regions. We show that a supersymmetric model containing a light stop, winos and binos can consistently match the data. We perform a fit to all measurements and searches that may be sensitive to our model and find a reduction in the log-likelihood of 15.4 compared to the Standard Model which corresponds to 3.5-$\sigma$ once the extra degrees of freedom in the fit are considered., Comment: 19 pages, 5 Figures. v3: minor corrections, to appear at JHEP

We consider light higgsinos and singlinos in the next-to-minimal supersymmetric Standard Model at the Large Hadron Collider. We assume that the singlino is the lightest supersymmetric particle and that the higgsino is the next-to-lightest supersymmetric particle with the remaining supersymmetric particles in the multi-TeV range. This scenario, which is motivated by the flavor and CP issues, provides a phenomenologically viable dark matter candidate and improved electroweak fit consistent with the measured Higgs mass. Here, the higgsinos decay into on (off)-shell gauge boson and the singlino. We consider the leptonic decay modes and the resulting signature is three isolated leptons and missing transverse energy which is known as the trilepton signal. We simulate the signal and the Standard Model backgrounds and present the exclusion region in the higgsino-singlino mass plane at the Large Hadron Collider at $\sqrt{s}=14$ TeV for an integrated luminosity of 300 fb$^{-1}$., Comment: 12 pages, overall changes, conclusion unchanged, matches published version

In the first three years of running, the LHC has delivered a wealth of new data that is now being analysed. With over 20 fb$^{-1}$ of integrated luminosity, both ATLAS and CMS have performed many searches for new physics that theorists are eager to test their model against. However, tuning the detector simulations, understanding the particular analysis details and interpreting the results can be a tedious task. CheckMATE (Check Models At Terascale Energies) is a program package which accepts simulated event files in many formats for any model. The program then determines whether the model is excluded or not at 95% C.L. by comparing to many recent experimental analyses. Furthermore the program can calculate confidence limits and provide detailed information about signal regions of interest. It is simple to use and the program structure allows for easy extensions to upcoming LHC results in the future. CheckMATE can be found at: http://checkmate.hepforge.org, Comment: Version submitted to CPC. Updated versions of this manual will now be available at: http://www.hepforge.org/downloads/checkmate

The ATLAS and CMS collaborations have recently reported tantalizing hints of the existence of a 125 GeV Higgs--like particle, whose couplings appear to match well the Standard Model (SM) expectations. In this work, we study implications of this observation for the neutralino sector of supersymmetric models, assuming that the Higgs signal gets confirmed. In general, the Higgs decay into neutralinos can be one of its dominant decay channels. Since a large invisible Higgs decay branching ratio would be in conflict with the data, this possibility is now constrained. In particular, we find that most of the region mu < 170 GeV, M_1 < 70 GeV at tan beta ~ 10 and mu < 120 GeV, M_1 < 70 GeV at tan beta ~ 40 is disfavored., Comment: 9 pages, 4 figures; to appear in PLB

We consider light top squarks (stops) in the minimal supersymmetric Standard Model at the Large Hadron Collider. Here, we assume that the lightest neutralino is the lightest supersymmetric particle (LSP) and the lighter stop is the next-to-LSP. Stop pair production is difficult to probe at the Large Hadron Collider for small stop-LSP mass splitting. It has been shown previously that even in this case stop detection is possible if one considers stop pair production in association with one hard jet. We reconsider this supersymmetric monojet signature and go beyond previous works by including the full Standard Model background and optimizing the cuts, working at the hadron level and including detector effects. As a result, a larger portion of the stop-LSP mass plane becomes accessible to monojet searches., Comment: 12 pages

In the framework of minimal flavor violation (MFV), we discuss the decay properties of a supersymmetric scalar top (stop) in the presence of a light gravitino. Given a small mass difference between the lighter stop and lightest neutralino and an otherwise sufficiently decoupled spectrum, the stop may be long-lived and thus can provide support to MFV at hadron colliders. For a bino-like lightest neutralino, we apply bounds from searches in the gamma gamma plus missing transverse energy channel (ATLAS with 1 fb^-1 and D0 with 6.3 fb^-1) and give a 5 fb^-1 projection for the ATLAS search., Comment: 9 pages, 6 figures

It has been shown that very light or even massless neutralinos are consistent with all current experiments, given non-universal gaugino masses. Furthermore, a very light neutralino is consistent with astrophysical bounds from supernov{\ae} and cosmological bounds on dark matter. Here we study the cosmological constraints on this scenario from Big Bang nucleosynthesis taking gravitinos into account and find that a very light neutralino is even favoured by current observations., Comment: 9 pages, 3 figures

We discuss how the experimental neutrino oscillation data can be realized in the framework of the baryon triality ($B_3$) constrained supersymmetric Standard Model (cSSM). We show how to obtain phenomenologically viable solutions, which are compatible with the recent WMAP observations. We present results for the hierarchical, inverted and degenerate cases which illustrate the possible size and structure of the lepton number violating couplings. We work with a new, as yet unpublished version of SOFTSUSY, where we implemented full one--loop neutrino masses. Finally, we shortly discuss some phenomenological implications at the LHC., Comment: 25 pages, 17 figures

We investigate the prospects to extract supersymmetric couplings from a decay length measurement at the LHC. Specifically, we exploit the opportunity of a light and long-lived stop which is pair-produced through gluinos in association with like-sign top quarks. Any observed finite value of the stop decay length strongly supports models in which flavor is broken in a minimal way solely by the Standard Model Yukawa couplings. We find that a 1 picosecond stop lifetime, dominated by t~ -> c chi^0 decays, yields macroscopic transverse impact parameters of about 180 microns. If the lightest neutralino is predominantly higgsino or very close in mass to the light stop, the stop lifetime even increases and allows to observe stop tracks and possibly secondary vertices directly. Measuring squark flavor violation with the stop decay length works also with a gravitino LSP if the neutralino is the NLSP. For this case, opportunities from t~ -> c chi^0 -> c gamma G~ decays for very light gravitinos with mass <= keV are pointed out., Comment: 8 pages, 9 figures; references and minor clarifications added

The exchange of electroweak gauginos in the $t-$ or $u-$channel allows squark pair production at hadron colliders without color exchange between the squarks. This can give rise to events where little or no energy is deposited in the detector between the squark decay products. We discuss the potential for detection of such rapidity gap events at the Large Hadron Collider (LHC). We present an analysis with full event simulation using PYTHIA as well as Herwig++, but without detector simulation. We analyze the transverse energy deposited between the jets from squark decay, as well as the probability of finding a third jet in between the two hardest jets. For the mSUGRA benchmark point SPS1a we find statistically significant evidence for a color singlet exchange contribution., Comment: 4 pages, 2 figures. To be published in the proceedings of SUSY09, Northeastern University, Boston, MA

The exchange of electroweak gauginos in the $t-$ or $u-$channel allows squark pair production at hadron colliders without color exchange between the squarks. This can give rise to events where little or no energy is deposited in the detector between the squark decay products. We discuss the potential for detection of such rapidity gap events at the Large Hadron Collider (LHC). Our numerical analysis is divided into two parts. First, we evaluate in a simplified framework the rapidity gap signal at the parton level. The second part covers an analysis with full event simulation using PYTHIA as well as Herwig++, but without detector simulation. We analyze the transverse energy deposited between the jets from squark decay, as well as the probability of finding a third jet in between the two hardest jets. For the mSUGRA benchmark point SPS1a we find statistically significant evidence for a color singlet exchange contribution. The systematical differences between current versions of PYTHIA and HERWIG++ are larger than the physical effect from color singlet exchange; however, these systematic differences could be reduced by tuning both Monte Carlo generators on normal QCD di--jet data., Comment: 23 pages, 10 figures

We make a simple ansatz for the supersymmetric lepton-number violating Yukawa couplings, by relating them to the corresponding Higgs Yukawa couplings. This reduces the free B$_3$ parameters from 36 to 6. We fit these parameters to solve the solar and atmospheric neutrino anomalies in terms of neutrino oscillations. The resulting couplings are consistent with the stringent low-energy bounds. We investigate the resulting LHC collider signals for a stau LSP scenario.

We compute electroweak contributions to the production of squark pairs at hadron colliders. These include the exchange of electroweak gauge bosons in the $s-$channel as well as electroweak gaugino exchange in the $t-$ and/or $u-$channel. In many cases these can interfere with the dominant QCD contributions. As a result, we find sizable contributions to the production of two SU(2) doublet squarks. At the LHC, they amount to 10 to 20% for typical mSUGRA (or CMSSM) scenarios, but in more general scenarios they can vary between -40 and $+55%$, depending on size and sign of the SU(2) gaugino mass. The electroweak contribution to the total squark pair production rate at the LHC is about 3.5 times smaller., Comment: Submitted for the SUSY07 proceedings, 4 pages, LaTeX, 3 eps figures

In this paper we compute electroweak contributions to the production of squark pairs at hadron colliders. These include the exchange of electroweak gauge bosons in the s-channel as well as electroweak gaugino exchange in the t- and/or u-channel. In many cases these can interfere with the dominant QCD contributions. As a result, we find sizable contributions to the production of two SU(2) doublet squarks. At the LHC, they amount to 10 to 20% for typical mSUGRA (or CMSSM) scenarios, but in more general scenarios they can vary between -40 and +55%, depending on size and sign of the SU(2) gaugino mass. The electroweak contribution to the total squark pair production rate at the LHC is about 3.5 times smaller., Comment: 28 pages, 9 figures

We generalize the notion of the Jarlskog invariant to supersymmetric models with right--handed neutrinos. This allows us to formulate basis--independent necessary and sufficient conditions for CP conservation in such models., Comment: 10 pages, no figures