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Events on Friday, April 25th, 2014

Theory Seminar (High Energy/Cosmology)
Soft R-Parity Violation
Time: 2:15 pm
Place: 5280 Chamberlin Hall
Speaker: Yuhsin Tsai, Univ. of California-Davis
Abstract: Supersymmetric (SUSY) models with R-parity generically predict sparticle decays with invisible neutralinos, which yield distinctive missing energy events at colliders. Since most LHC searches are designed with this expectation, the putative bounds on sparticle masses become considerably weaker if R-parity is violated so that squarks and gluinos decay to jets with large QCD backgrounds. In this talk I will introduce a scenario in which baryonic R-parity violation (RPV) arises effectively from soft SUSY-breaking interactions. The model features a global R-symmetry that initially forbids RPV interactions, a hidden R-breaking sector, and a heavy mediator that communicates this breaking to the visible sector. After R-symmetry breaking, the mediator is integrated out and an effective RPV A-term arises at tree leve. Although this mediator must be heavy compared to soft masses, the model introduces no new hierarchy since viable RPV can arise when the mediator mass is near the SUSY breaking scale. In generic regions of parameter space, a light thermally-produced gravitino is stable and can be a viable dark matter candidate.
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Physics Department Colloquium
Searching for new physics at the LHC: The story you haven't heard
Time: 3:30 pm
Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
Speaker: Michael Williams , MIT
Abstract: There are two ways to discover new particles: we can make them in the lab and observe their decays or we can observe discrepancies between precision measurements and theoretical predictions. Both methods are being employed by the LHCb experiment at CERN to search for what lies beyond the Standard Model (SM) of particle physics. The LHCb experiment has published over 170 papers since 2011. The core physics program involves making precise measurements of observables whose SM predictions are well known and that are expected to be extremely sensitive to a wide range of beyond the SM theories, e.g., supersymmetry. The magic of quantum mechanics permits particles that are too massive to be produced in the lab, even at the LHC, to make significant contributions to the observables measured at LHCb. If, in fact, the lightest new particles cannot be produced directly at the LHC, then our only hope for discovery at a collider in the coming decades is via such indirect observations. I will also discuss direct searches for light dark matter candidates and other future prospects for discovery.
Host: Westerhoff
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