# Particle Physics

This series consists of talks in the areas of Particle Physics, High Energy Physics & Quantum Field Theory.

## Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

## Second-Order Relativistic Hydrodynamics

Friday Oct 29, 2010
Speaker(s):

Hydrodynamics is the universal theory describing the behavior of fluids when their spacetime variation is on scales longer than any microphysical scale in the fluid. Relativistic hydro has applications in heavy ion collisions and early Universe cosmology, and has seen a surge of interest due to heavy ion experiments and theoretical developments in AdS/CFT. I will explain what second order hydrodynamics is and why it is the minimum theory to study in the relativistic case.

Collection/Series:
Scientific Areas:

Friday Oct 22, 2010
Speaker(s):

We formulate a numerical procedure to calculate Hawking radiation during non-equilibrium black hole formation. The procedure is applied to a static string in thermal AdS and it is shown that for an arbitrary initial state, the final state is an equilibrated heavy quark string. The fluctuations in the quark string are transmitted from the horizon to the boundary leading to Brownian motion in the boundary theory.

Collection/Series:
Scientific Areas:

## Long-Lived Neutral Particles at the LHC

Friday Oct 15, 2010
Speaker(s):

I will discuss the collider signatures of heavy, long-lived, neutral particles that decay to charged particles plus missing energy. The focus will be the case of a neutralino NLSP decaying to Z and gravitino within the context of General Gauge Mediation (based on arXiv:1006.4575). I will show that the LHC has the potential for early discovery of such a long-lived particle if its lifetime (c tau) is between about 0.1 millimeters and 100 meters. I will also discuss the use of timing and pointing measurements to fully reconstruct kinematics in events with displaced decays.

Collection/Series:
Scientific Areas:

## The flavor puzzle : Why neutrinos are different ?

Friday Sep 24, 2010
Speaker(s):

Large mixing angles and a mild mass hierarchy are observed in neutrino oscillations, in stark contrast with the quarks and charged leptons sectors where very hierarchical masses come along with small mixings.
We review and discuss the neutrino mass patterns that are technically natural, in the context of the seesaw mechanism and with a quark-lepton unification perspective.

Collection/Series:
Scientific Areas:

## Topological defects and vacuum decay

Friday Aug 20, 2010
Speaker(s):

False vacua in QFT are liable to undergo spontaneous decay. Slowness of quantum tunneling can however allow a long lifetime to the false vacuum state. In supersymmetric theories this is a crucial criterion for obtaining a long lived universe with spontaneously broken supersymmetry. We have explored false vacua which admit topological defects, including in a supersymmetric model with O'Rafeartaigh type supersymmetry breaking. We show that the presence of topological defects significantly alters the stability of the false vacuum.

Collection/Series:
Scientific Areas:

## Cascade supersymmetry breaking and low scale gauge mediation

Friday Jul 16, 2010
Speaker(s):

The gauge mediation models with a gravitino mass in the eV range is a
quite attractive scenario which causes no cosmological/astrophysical problems.
The model construction with such a light gravitino is, however, quite challenging
and in most cases ends up with the problems with the suppressed gaugino mass,
the vacuum instability and the Landau pole problems of the Standard Model gauge
coupling constants.

Collection/Series:
Scientific Areas:

## Rescuing the Standard Model in the case the Higgs Boson is not found

Friday May 14, 2010
Speaker(s):

A plethora of Higgsless models have been proposed and we are in the peculiar situation where Fermilab & LHC results will be extremely interesting whether or not the Higgs boson is found. I present here a model where one of the sacred assumption of quantum field theory (renormalizability) is dropped. A precise prescription for the removal of the divergences guarantees both unitarity and predictivity. Interestingly the model is consistent if the Power counting criterion is enforced in a weak form (Weak Power Counting).

Collection/Series:
Scientific Areas:

## An Unparticle Solution to the Hierarchy Problem

Friday May 07, 2010
Speaker(s):

The Planck-weak hierarchy is investigated in an extradimensional, soft-wall model originally proposed by Batell and Gherghetta. In this model the soft-wall is dynamically generated by background ﬁelds that, in the Einstein frame, cause the metric factor to deviate from anti-de Sitter by a power-law of the conformal coordinate. This talk will demonstrate that in order to achieve the appropriate Planck-weak hierarchy, the power of the conformal coordinate must be less than one.

Collection/Series:
Scientific Areas:

## Boosting Higgs Discovery

Friday May 07, 2010
Speaker(s):

An enormous effort is underway to search for the Higgs boson at the LHC. One new development of the past couple of years is to look into the kinematic region where the Higgs boosted, which has led to the possibility to observe the dominant b-bar decay mode as a single "fat jet" when the Higgs is light. I'll discuss how this technique has great promise not only within the Standard Model, but potentially has even greater promise to find a light Higgs in new physics models such as supersymmetry.

Collection/Series:
Scientific Areas:

## WIMPless Dark Matter and Meson Decays with Missing Energy

Tuesday Apr 20, 2010
Speaker(s):

WIMPless dark matter offers an attractive framework in which dark matter can be very light. We investigate the implications of such scenarios on invisible decays of bottomonium states for dark matter with a mass less than around $5 {\rm GeV}$. We relate these decays to measurements of nucleon-dark matter elastic scattering. We also investigate the effect that a coupling to $s$ quarks has on flavor changing $b\to s$ processes involving missing energy.

Collection/Series:
Scientific Areas:

## RECENT PUBLIC LECTURE

### The Most Wanted Particle

Speaker: Jon Butterworth