UC Davis Particle Physics Seminars

Latest Episodes:

Searching for New Physics in Multilepton Events with the ATLAS Experiment Oct 30, 2012

Show notes

Events with three or more prompt leptons are rare at hadron colliders. At the LHC, where high interaction energies and rates create extremely busy final states, such multilepton events are well suited as a probe for new physics beyond the Standard Model (BSM). Mike Hance describes some recent analyses from ATLAS based on multilepton signatures. In particular, focusing on new model-independent limits for anomalous production of multilepton events that can be used to test a variety of BSM scenarios.

Higgs Identification Oct 29, 2012

Show notes

The July 4th announcement of the discovery of a Higgs-like particle at CERN LHC is only the beginning of a challenging program of "Higgs Identification" to establish the quantum numbers and couplings of the new particle, and to reveal its relationship, if any, to electroweak symmetry-breaking and fermion mass generation. Ian Low discusses preliminary efforts in this direction and explore implications of current measurements on future searches at the LHC and beyond.

Qjets: A Non-deterministic Approach to Tree-based Jet Substructure Oct 23, 2012

Show notes

Jet substructure is typically studied using clustering algorithms, such as kT, which arrange the jets' constituents into trees. Instead of considering a single tree per jet, Tuhin Roy proposes that multiple trees should be considered, weighted by an appropriate metric. Then each jet in each event produces a distribution for an observable, rather than a single value. Advantages of this approach include: 1) observables have significantly increased statistical stability; and, 2) new observables, such as the variance of the distribution, provide new handles for signal and background discrimination. For example, we find that employing a set of trees substantially reduces the observed fluctuations in the pruned mass distribution, enhancing the likelihood of new particle discovery for a given integrated luminosity. Furthermore, we introduce a new quantity 'volatility', a cut on which reduces the luminosity needed for a given significance requirement by a factor of two.

Goldstone Fermion Dark Matter Oct 22, 2012

Show notes

Nonlinear realizations describe the low-energy degrees of freedom of strongly coupled theories with spontaneously broken symmetry. When combined with SUSY, the Goldstone bosons of these theories are complex fields with "Goldstone fermion" super-partners. These, in turn, offer novel weakly interacting massive particle (WIMP) dark matter candidates. Flip Tanedo discusses how these can be used in realistic models of dark matter.

Unwinding Inflation Oct 16, 2012

Show notes

Guido D'Amico describes a new model of inflation using branes unwrapping from extra dimensions.