Particle Physics

I will discuss cosmological, astrophysical and collider constraints on thermal dark matter with mass in the range 1 MeV to 10 GeV. CMB observations can be evaded if the DM relic density is sufficiently asymmetric, while collider constraints generally require sufficiently light mediators. These light mediators can give rise to significant DM self-interactions, and I will describe bounds on such interactions from dark matter halo shapes. Finally, I will describe how these constraints map onto the parameter space of DM-electron and DM-nucleon scattering cross sections for direct detection.

We propose that the fermionic superpartner of a weak-scale Goldstone boson can be a nat- ural WIMP candidate. The p-wave annihilation of this `Goldstone fermion' into pairs of Gold- stone bosons automatically generates the correct relic abundance, whereas the XENON100 direct detection bounds are evaded due to suppressed couplings to the Standard Model. Further, it is able to avoid indirect detection constraints because the relevant s-wave annihi- lations are small. The interactions of the Goldstone supermultiplet can induce non-standard Higgs decays and novel collider phenomenology.

We show that a baryon asymmetry can be generated by dissipative effects during warm inflation via a supersymmetric two-stage mechanism, where the inflaton is coupled to heavy mediator fields that then decay into light species through B- and CP-violating interactions. In contrast with thermal GUT baryogenesis models, the temperature during inflation is always below the heavy mass threshold, simultaneously suppressing thermal and quantum corrections to the inflaton potential and the production of dangerous GUT relics. This naturally gives a small baryon asymmetry close to the observed value, although parametrically larger values may be diluted after inflation along with any gravitino overabundance. Furthermore, this process yields baryon isocurvature perturbations within the range of future experiments, making this an attractive and testable model of GUT baryogenesis.

Both Tevatron experiments have recently reported an anomalous forward-backward asymmetry in top-antitop production. Their inclusive results are roughly 3 standard deviations larger than the standard model prediction and may be evidence of new physics that couples to the top quark. In this talk, I will present a weakly-coupled light axigluon model (< Mtop) with flavor universal couplings as a possible explanation. Surprisingly,a particle with these properties can generate a large ttbar asymmetry with model-parameters safe from dijet resonance searches, flavor changing neutral currents, and constraints from the Z pole.

In massive gravity the so-far-found black hole solutions on Minkowski space happen to convert horizons into a certain type of singularities. I will discuss whether these singularities can be avoided if space-time is not asymptotically Minkowskian. As an illustration, I will present an exact analytic black hole solution  which evades  the above problem by a transition at large scales to self-induced de Sitter space-time. The solution demonstrates that in massive GR, in the Schwarzschild coordinate system, a BH  metric has to be accompanied by the St\"uckelberg fields with nontrivial backgrounds to  prevent the horizons to convert into the singularities.

In this talk, I will discuss various aspects of UV-complete R-symmetric QFTs. In particular, I will focus on a small set of operators that are well-defined in many such theories, and I will argue that one can use these operators to get a (partial) non-perturbative handle on the deep IR physics, including, possibly, a handle on certain aspects of the emergent symmetries. Throughout, I will highlight applications to particle physics.

The full machinery of supergravity (SUGRA) is required to fully understand many supersymmetric models. For the purpose of understanding phenomenology at colliders and in cosmology, the main concern is to ascertain the effects of SUGRA on the vacuum structure and particle spectrum. Practical calculations often require cumbersome manipulations of component field terms involving the full gravity multiplet. In this talk I will present an alternative gauge fixing for conformal SUGRA which decouples these gravity complications from SUGRA computations. This yields a simplified tree-level action for the matter fields in SUGRA which can be expressed compactly in terms of superfields and a modified conformal compensator. As a concrete application I will finally show the example of the mass spectrum of goldstini arising from a general admixture of F-term, D-term, and almost no-scale supersymmetry breaking.

I will discuss how to construct a consistent effective field theory when the differing modes of the theory have the same invariant mass scale. I will sketch some phenomenological applications of the formalism relevant for the LHC.

After a short introduction to general gauge mediation, we use the operator product expansion (OPE) to explore the dynamics of the hidden sector of SUSY breaking, much like the OPE is used in e+e- scattering to hadrons in QCD. Along the way we derive consequences that the N=1 superconformal symmetry puts on three-point functions of two current superfields with an arbitrary superconformal primary operator. Using those constraints we construct a ``supermultiplet'' of OPEs. Finally, we give approximations to soft masses, which can be used even in strongly-coupled theories.  
References: arXiv:1107.1721, 1109.4940

I will present a class of models in which the dark matter particle carries flavor quantum numbers, and has renormalizable contact interactions with Standard Model fields. In particular, I will focus on models where the dark matter flavor is identified with lepton flavor in the Standard Model. The region of parameter space where the dark matter has the right abundance to be a thermal relic is accessible at current direct detection experiments. A full simulation of the signal and backgrounds, including detector effects, shows that in a significant part of parameter space these theories can be discovered above Standard Model backgrounds at the LHC. Further, flavor and charge correlations among the final state leptons might allow models of this type to be distinguished from theories where dark matter couples to leptons but does not carry flavor.