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.

We propose a new method to discover light top squarks (stops) in the co-annihilation region at the Large Hadron Collider (LHC). The bino-like neutralino is the lightest supersymmetric particle (LSP) and the lighter stop is the next-to-LSP. Such scenarios can be consistent with electroweak baryogenesis and also with dark matter constraints. We consider the production of two stops in association with two b−quarks, including pure QCD as well as mixed electroweak-QCD contributions. The stops decay into a charm quark and the LSP. For a higgsino-like light chargino the electroweak contributions can exceed the pure QCD prediction. We show the size of the electroweak contributions as a function of the stop mass and present the LHC discovery reach in the stop-neutralino mass plane.

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We investigate the prospects for indirect detection of right-handed sneutrino dark matter at the IceCube neutrino telescope in a Uð1Þ BÀL extension of the minimal supersymmetric standard model. The capture and annihilation of sneutrinos inside the Sun reach equilibrium, and the flux of produced neutrinos is governed by the sneutrino-proton elastic scattering cross section, which has an upper bound of 8 Â 10 À9 pb from the Z 0 mass limits in the B À L model. Despite the absence of any spin-dependent contribution, the muon event rates predicted by this model can be detected at IceCube since sneutrinos mainly annihilate into leptonic final states by virtue of the fermion B À L charges. These subsequently decay to neutrinos with 100% efficiency. The Earth muon event rates are too small to be detected for the standard halo model irrespective of an enhanced sneutrino annihilation cross section that can explain the recent PAMELA data. For modified velocity distributions, the Earth muon events increase substantially and can be greater than the IceCube detection threshold of 12 events km À2 yr À1 . However, this only leads to a mild increase of about 30% for the Sun muon events. The number of muon events from the Sun can be as large as roughly 100 events km À2 yr À1 for this model.

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. 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 minimal supergravity 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 dijet data.