Particle Physics

CRESST is a cryogenic dark matter search located at the Laboratori Nazionali del Gran Sasso in Italy. Scintillating CaWO4 crystals are operated as cryogenic calorimeters. The phonon (heat) signal measured with a tungten transition edge sensor on the surface of these crystals allows a precise determination of the energy deposited in the crystal, independent of the type of interaction. A light signal, simultaneously registered by a separate cryogenic detector, serves to identify the type of interaction. This phonon/light technique allows a discrimination of electron recoils induced by radioative backgrounds from the searched nuclear recoils with high efficiency ,and, to some extent, even to determine which type of nucleus was recoiling. I will present results from 564 kg-days of data of the presently still ongoing run, which reveal an unexpected excess of oxygen recoils. To shine some light on the nature of these events, I will discuss possible backgrounds in some detail.

The consequences of the fact that electroweak scale particles are often produced beyond threshold has been appreciated only recently. Decay products of boosted objects tend to be collimated and their final state radiation (FSR) might overlap. It has been shown that it can be advantageous to collect all FSR of a decaying resonance in a so-called 'fat jet' and apply subjet techniques to it to obtain a good mass reconstruction of the resonance and an improved background rejection. In my talk I would like to cover recent developments in this field and discuss applications to Higgs searches and top reconstruction within and beyond the Standard Model.

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.

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.

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. We show that a seesaw in six dimensions offers an elegant and unique solution to the flavor puzzle. An explicit model is constructed, with a vortex background on a sphere. It offers an explanation for the replication of families in the Standard Model, and predicts suppressed flavour violating interactions.

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. For some values of parameters, it also results in the putative false vacuum being rendered unstable. Finally I report a formula derived for instanton assisted tunneling applicable to metastable vacua with monopoles.

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. In this talk, I explain our proposal in which a gauge mediation model with the gravitino whose mass in the eV range is realized without having those problems.

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). Among the novel features one notices an extra parameter (the ratio M_W/M_Z) but also a consistent accommodation of the Majorana neutrino mass.

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. This in turn implies that the gravitational sector contains scalar fields that act like unparticles without a mass gap.

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.