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Register a new userSearch for top squarks in R-parity-violating supersymmetry using three or more leptons and b-tagged jets
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The CMS Collaboration
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A search for anomalous production of events with three or more isolated leptons and bottom-quark jets produced in pp collisions at sqrt(s) = 8 TeV is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 19.5 inverse femtobarns collected by the CMS experiment at the LHC in 2012. No excess above the standard model expectations is observed. The results are interpreted in the context of supersymmetric models with signatures that have low missing transverse energy arising from light top-squark pair production with R-parity-violating decays of the lightest supersymmetric particle. In two models with different R-parity-violating couplings, top-squarks are excluded below masses of 1020 GeV and 820 GeV when the lightest supersymmetric particle has a mass of 200 GeV.
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A search for stop production in R-parity-violating supersymmetry has been performed in $e^{+}p$ interactions with the ZEUS detector at HERA, using an integrated luminosity of 65 pb$^{-1}$. At HERA, the R-parity-violating coupling $lambda$ allows resonant squark production, $e^+dtotilde{q}$. Since the lowest-mass squark state in most supersymmetry models is the light stop, $tilde{t}$, this search concentrated on production of $tilde{t}$, followed either by a direct R-parity-violating decay, or by the gauge decay to $btilde{chi}^+_{1}$. No evidence for stop production was found and limits were set on $lambda_{131}$ as a function of the stop mass in the framework of the Minimal Supersymmetric Standard Model. The results have also been interpreted in terms of constraints on the parameters of the minimal Supergravity model.
We search for lepton-flavor-violating tau decays into three leptons (electron or muon) using 535 fb-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. No evidence for these decays is observed, and we set 90% confidence level upper limits on the branching fractions of (2.0-4.1)x10^-8. These results improve upon our previously published upper limits by factors of 4.9 to 10.
$R$-parity violating supersymmetric models (RPV SUSY) are becoming increasingly more appealing than its $R$-parity conserving counterpart in view of the hitherto non-observation of SUSY signals at the LHC. In this paper, we discuss RPV scenarios where neutrino masses are naturally generated, namely RPV through bilinear terms (bRPV) and the $mu$-from-$ u$ supersymmetric standard model ($mu u$SSM). The latter is characterised by a rich Higgs sector that easily accommodates a 125-GeV Higgs boson. The phenomenology of such models at the LHC is reviewed, giving emphasis on final states with displaced objects, and relevant results obtained by LHC experiments are presented. The implications for dark matter for these theoretical proposals is also addressed.
The scalar partner of the top quark (the stop) is relatively light in many models of supersymmetry breaking. We study the production of stops at the Large Hadron Collider (LHC) and their subsequent decays through baryon-number violating couplings such that the final state contains no leptons. A detailed analysis performed using detector level observables demonstrate that stop masses upto $sim 600 gev$ may be explored at the LHC depending on the branching ratios for such decays and the integrated luminosity available. Extended to other analogous scenarios, the analysis will, generically, probe even larger masses.
We propose a supersymmetric explanation for the anomalously high forward backward asymmetry in top pair production measured by CDF and D0. We suppose that it is due to the t-channel exchange of a right-handed sbottom which couples to d_R and t_R, as is present in the R-parity violating minimal supersymmetric standard model. We show that all Tevatron and LHC experiments t tbar constraints may be respected for a sbottom mass between 300 and 1200 GeV, and a large Yukawa coupling >2.2, yielding A_{FB} up to 0.18. The non Standard Model contribution to the LHC charge asymmetry parameter is Delta A_C^y=0.017-0.045, small enough to be consistent with current measurements but non-zero and positive, allowing for LHC confirmation in the future within 20 fb^-1. A small additional contribution to the LHC t tbar production cross-section is also predicted, allowing a further test. We estimate that 10 fb^-1 of LHC luminosity would be sufficient to rule out the proposal to 95% confidence level, if the measurements of the t tbar cross-section turn out to be centred on the Standard Model prediction.
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