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Register a new userSearch for the lightest scalar top quark in R-parity violating decays at the LHC
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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.
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The $R$-parity violating decays of Bino neutralino LSPs are analyzed within the context of the $B-L$ MSSM heterotic standard model. These LSPs correspond to statistically determined initial soft supersymmetry breaking parameters which, when evolved using the renormalization group equations, lead to an effective theory satisfying all phenomenological requirements; including the observed electroweak vector boson masses and the Higgs mass. The explicit RPV decay channels of these LSPs into standard model particles, the analytic and numerical decay rates and the associated branching ratios are presented. The analysis of these quantities breaks into two separate calculations; first, for Bino neutralino LSPs with mass larger than $M_{W^{pm}}$ and, second, when the Bino neutralino mass is smaller than the electroweak scale. The RPV decay processes in both of these regions is analyzed in detail. The decay lengths of these RPV interactions are discussed. It is shown that for heavy Bino neutralino LSPs the vast majority of these decays are prompt, although a small, but calculable, number correspond to displaced decays of various lengths. The situation is reversed for light Bino LSPs, only a small number of which can RPV decay promptly. The relation of these results to the neutrino hierarchy--either normal or inverted--is discussed in detail.
The flavor-changing top-quark decay $tto c h$, where $h$ is the lightest CP-even Higgs boson in the minimal supersymmetric standard model, is examined in the R-parity-violating supersymmetric model. Within the existing bounds on the relevant R-parity-violating couplings, the branching fraction for $tto c h$ can be as large as about $10^{-5}$ in some part of the parameter space.
The $R$-parity violating decays of both Wino chargino and Wino neutralino LSPs are analyzed within the context of the $B-L$ MSSM heterotic standard model. These LSPs correspond to statistically determined initial soft supersymmetry breaking parameters which, when evolved using the renormalization group equations, lead to an effective theory satisfying all phenomenological requirements; including the observed electroweak vector boson and Higgs masses. The explicit decay channels of these LSPs into standard model particles, the analytic and numerical decay rates and the associated branching ratios are presented. The decay lengths of these RPV interactions are discussed. It is shown that the vast majority of these decays are prompt, although a small, but calculable, number correspond to displaced vertices of various lengths. It is demonstrated that for a Wino chargino LSP, the NLSP is the Wino neutralino with a mass only slightly higher than the LSP-- and vice-versa. As a consequence, we show that both the Wino chargino and Wino neutralino LSP/NLSP $R$-parity violating decays should be simultaneously observable at the CERN LHC.
We consider the case where supersymmetry with broken R-parity is embedded in the minimal supergravity model (mSUGRA). This alters the standard mSUGRA spectrum and opens a wide range in parameter space, where the scalar tau is the lightest supersymmetric particle, instead of the lightest neutralino. We study the resulting LHC phenomenology. Promising signatures would be detached vertices from long-lived staus, multi lepton final states and multi-tau final states. We investigate in detail the corresponding cross sections and decay rates in characteristic benchmark scenarios.
We study the collider phenomenology of bilinear R-parity violating supergravity, the simplest effective model for supersymmetric neutrino masses accounting for the current neutrino oscillation data. At the CERN Large Hadron Collider the center-of-mass energy will be high enough to probe directly these models through the search for the superpartners of the Standard Model (SM) particles. We analyze the impact of R-parity violation on the canonical supersymmetry searches - that is, we examine how the decay of the lightest supersymmetric particle (LSP) via bilinear R-parity violating interactions degrades the average expected missing momentum of the reactions and show how this diminishes the reach in the usual channels for supersymmetry searches. However, the R-parity violating interactions lead to an enhancement of the final states containing isolated same-sign di-leptons and trileptons, compensating the reach loss in the fully inclusive channel. We show how the searches for displaced vertices associated to LSP decay substantially increase the coverage in supergravity parameter space, giving the corresponding reaches for two reference luminosities of 10 and 100 fb$^{-1}$ and compare with those of the R-parity conserving minimal supergravity model.
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