I am interested in understanding what may lie beyond the Standard Model of Particle Physics. Over the last year, evidence has been mounting in the ATLAS and CMS experiments at the Large Hadron Collider at CERN that the Higgs boson exists and has a mass of about 125 GeV. This discovery had been anticipated not only because the Higgs boson is needed to make the Standard Model complete, but also because of indirect hints from previous experiments. This discovery is a tremendous success and 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.
Recently, I have been interested in some curious anomalies in the data from experiments at the LHC and the Tevatron. The older and more established anomaly is an asymmetry in the direction in which top quarks are produced in the CDF and D0 experiments at the Tevatron. Measurements from both experiments seem to indicate an asymmetry of order 20% whereas the Standard Model can account for at most 10% 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 currently being tested. Here are slides from a seminar I gave on the top quark asymmetry in 2012.
A more recent anomaly is an apparent discrepancy between prediction and measurements in the Higgs production and decay rates at the LHC. While current data does not yet allow us to conclude anything other than the existence of the Higgs with sufficient statistical certainty, it does appear (at the 2 sigma level) that several of the decay branching fractions of the Higgs boson may be different from predictions. Such discrepancies, if they are real, point towards the existence of other states which interfere in the Higgs decay channels and which might also be directly accessible at the LHC if we know how to look for them. I am currently exploring possibilities for what these other states might be, and what experiments could be done to discover them.