UC Davis Particle Physics Seminars 2013

Searching for Supersymmetry with Final State Photons at ATLAS Nov 06, 2012

Bruce Schumm describes the ATLAS search for SUSY using photons.

Boosted Multijet Resonances and New Color-Flow Variables Nov 13, 2012

We use modern jet-substructure techniques to propose LHC searches for multijet-resonance signals without leptons or missing energy. We focus on three-jet resonances produced by R-parity-violating decays of boosted gluinos, showing that shape analyses searching for a mass peak can probe such gluinos up to masses of 750 GeV (650 GeV) with 20/fb (5/fb) at the LHC at 8 TeV. This complements existing search strategies, which also include counting methods that are inherently more prone to systematic uncertainties. Since R-parity-violating gluinos lighter than all squarks hadronize before decaying, we introduce new color-flow variables, "radial pull" and "axis contraction", which are sensitive to the color structure of the R-hadron's decay. The former measures the inward pull of subjets in a fat jet, while the latter quantifies the inward drift of the N-subjettiness axes when changing the distance measure. We show that they can dramatically improve the discrimination of a boosted gluino signal.

Metaphor for Dark Energy Nov 16, 2012

Thinking about dark energy using 3D gravity as a toy model.

Mini-Split Nov 19, 2012

An update on mini-split supersymmetry.

Searches for 0-nu-beta-beta Decay & WIMP Dark Matter Nov 20, 2012

Xenon is increasingly popular for both direct WIMP and 0-nu-beta-beta decay searches. Although the current trend has exploited the liquid phase, gas phase xenon offers some remarkable performance advantages for energy resolution, topology visualization, and discrimination between electron and nuclear recoils. I will describe recent results with small prototypes, indicating that NEXT-100 can provide about 0.5% FWHM energy resolution at the decay Q-value, as well as topological rejection of gamma-rays.

Resurgence, transseries, and towards a continuum definition of QFT Nov 26, 2012

Resolving the problems with instantons and renormalons.

How to Unlock the Hidden Photon Collider in the LHC Nov 27, 2012

The physics reach of the LHC can be extended by detecting events in which the beam protons interact via the gamma-gamma or gluon-gluon process and remain intact. Since there is no "underlying event" background from the breakup of the protons, which occurs in typical proton interactions, this central exclusive production (CEP) mode can be used as an experimentally clean way to observe many new physics channels, such as a low-mass SUSY lepton, the Higgs boson, and anomalous production of W and Z boson pairs and to study hard-diffractive QCD physics. I will describe the upgrade effort of the CMS detector at the LHC to detect the off-momentum protons produced by these exclusive events and the expected physics performance.

Solitons and the microscopic entropy of hairy black holes in three dimensions Dec 03, 2012

One of the strongest evidences of the AdS/CFT correspondence is provided by three-dimensional gravity with a negative cosmological constant, whose asymptotic symmetry group is the conformal one. As a further example, one can consider gravity coupled to self-interacting scalar field having a slow fall-off at infinity. In these cases, the metric describes an asymptotically AdS spacetime in a relaxed sense as compared with the one of Brown and Henneaux. Nevertheless, the asymptotic symmetry group remains to be the same as in pure gravity. In this talk we show a wide class of scalar hairy black holes, including spinning ones, which fit in these asymptotic conditions.

Keeping Gd-Loaded Water Crystal Clear...Indefinitely! Dec 04, 2012

Loading a water Cherenkov detector with a water soluble gadolinium compound makes possible the detection of thermal neutrons, dramatically improving such an enhanced detector's sensitivity to anti-neutrinos fluxes from both nuclear reactors and supernova explosions. But how can the Gd-loaded water be continuously repurified, maintaining its excellent optical properties, without also removing the dissolved gadolinium? A new technology - the molecular band-pass filter - has recently been developed and is currently being industrialized. The zen and the art of Gd-loaded water - including some of the more entertaining bumps encountered along the way to a viable system - will be discussed by the inventor of this technology.

Poincare Invariance and Charges in Shape Dynamics Dec 10, 2012

Shape dynamics is a theory of gravity that is generically dynamically equivalent to general relativity and yet sheds refoliaiton invariance in favor of spatial Weyl invariance. The different invariance groups has caused some puzzlement regarding the theory. In this talk, we will show how shape dynamics reproduce Poincare symmetry for a Minkowski-like curve in phase space. The asymptotic algebra is the same, but the charges for this theory acquire a new contribution to the energy that makes it Weyl invariant. The boundary conditions that allow for Poincare symmetry do not allow for a remaining conformal symmetry.

Higgs-like Dilatons in Particle Physics Jan 07, 2013

This lecture discusses how the Goldstone boson of spontaneously broken scale symmetry can mimic the behavior of the Higgs boson.

Time Delay in Classical and Quantum Gravity Jan 14, 2013

A class of diffeomorphism invariant, physical observables (so-called astrometric observables) is introduced. A particularly simple example, the time delay, which expresses the difference between two initially synchronized proper time clocks in relative inertial motion, is analyzed in detail. It is found to satisfy some interesting inequalities related to the causal structure of classical Lorentzian space times. Some potential applications of astrometric observables in quantum gravity are discussed.

Recent Developments in the Search for Dark Matter Jan 25, 2013

This lecture offers a careful look at dark matter searches, especially focusing on problems in the DAMA analysis of the annual modulation in the dark matter "signal."

Time Dependence of Hawking Radiation Entropy Jan 28, 2013

If a black hole starts in a pure quantum state and evaporates completely by a unitary process, the von Neumann entropy of the Hawking radiation initially increases and then decreases back to zero when the black hole has disappeared. Here numerical results are given for an approximation to the time dependence of the radiation entropy under an assumption of fast scrambling, for large nonrotating black holes that emit essentially only photons and gravitons.

Hunting Asymmetric Stops Feb 11, 2013

Jessie Shelton describes how the LHC experiments can probe a model that explains the Tevatron anomaly in the forward-backward top asymmetry.

Black Holes: Complementarity or Firewalls? Feb 25, 2013

Joe Polchinksi argues that the following three statements cannot all be true: (i) Hawking radiation is in a pure state, (ii) the information carried by the radiation is emitted from the region near the horizon, with low energy effective field theory valid beyond some microscopic distance from the horizon, and (iii) the infalling observer encounters nothing unusual at the horizon. Perhaps the most conservative resolution is that the infalling observer burns up at the horizon. Alternatives would seem to require novel dynamics that nevertheless cause notable violations of semiclassical physics at macroscopic distances from the horizon.

Effective Theory in a Time Dependent World Mar 04, 2013

Richard Holman describes how to calculate processes in time-dependent effective theories.

The Once and Future Higgs Mar 06, 2013

Nathaniel Craig discusses general search strategies for new physics in the Higgs sector.

Effective Theory of a Light Dilaton Mar 11, 2013

Zackaria Chacko discusses light dilators and how one could mimic the Higgs boson.

Goldstone Meets Higgs at the LHC Mar 18, 2013

After the recent discovery at the LHC of a Higgs-like particle with mass around 125 GeV, it is mandatory to reassess the viability of the proposed solutions to the hierarchy problem of the electroweak scale. In this talk, Javi Serra focuses on compositeness as the fundamental idea, with the Higgs arising as a Goldstone boson of the new strong dynamics and discuss its exciting phenomenological implications, including the prospect of non-minimal scalar sectors and its significance for Higgs couplings.