I am interested in understanding what new physical laws may be discovered beyond the Standard Model of Particle Physics. A couple of years ago, the ATLAS and CMS experiments at the Large Hadron Collider at CERN have confirmed that the Higgs boson is not just theorists' idle speculation, but that it exists and has a mass of 125.5 GeV. The Higgs discovery marks a milestone in our efforts to understand the Physics of electroweak symmetry breaking, but it does not close the chapter on the Higgs or on the Standard Model. The trouble is that even after the discovery we still do not understood why there are three generations of quarks and leptons, why they have their peculiar pattern of masses and mixing, what makes up the Dark Matter and Dark Energy in the Universe, and why CP symmetry is violated only in the weak interactions. And even the Higgs particle itself poses new questions because in the Standard Model the Higgs mass suffers from a quantum instability. Attempts at curing this instability have motivated much of my work in the past on Supersymmetry, Extra Dimensions and Little Higgs Theories.
In recent years, I have been interested in some curious anomalies in the data from experiments at the LHC and the Tevatron. One anomaly concerns the asymmetry in the direction in which top quarks were produced in the CDF and D0 experiments at the Tevatron. Measurements from both experiments indicated an asymmetry of order 15% whereas the Standard Model prediction is about 8% asymmetry. My student Gustavo and I proposed the existence of a new particle which interferes quantum mechanically with the Standard Model production of top quarks and explains the asymmetry. Our model makes predictions for particle jet productions at the LHC experiments which are being tested at the LHC. Here are slides from a seminar I gave on the top quark asymmetry in 2012.
Another anomaly concerns the decays of B-mesons into final states with elecron or muon pairs. In the Standard Model the rates for these processes are predicted to be equal because of lepton universality. However recent LHCb data suggest otherwise (at about 3 sigma). With Gudrun Hiller I investigated the implications of this measurement, proposed models which might explain the data, and suggested new observables which should be measured to confirm or refute the lepton universality.
Currently, Gustavo, my student Manuel Buen Abad Najar and I are working on a model for dark matter and dark radiation. Our "non-Abelian darkness" has interesting consequences for LHC dark matter searches, for CMB measurements at Fermi and for large scale structure formation.