Research

Research

My research interests lie at the intersections of the fields of high energy particle physics, dark matter physics, particle astrophysics and cosmology.

There are two specific problems that my current research tries to address:

  • Understanding the nature of electroweak symmetry breaking (EWSB).

  • Finding the properties of the dark matter particle(s) and exploring its interactions.

Collider Physics

My main motivation to study collider physics is to understand the nature of EWSB. The Standard Model (SM) describes all known physics up to the ~100 GeV scale extremely well. However, the SM itself cannot be a complete description of nature at extremely high energies because it does not explain quantum gravity, dark matter, inflation/reheating, the baryon asymmetry of the universe, the strong CP problem etc., all of which are extremely well motivated by observations. In the SM, the Higgs boson is the remnant of the EWSB mechanism. Its mass is generally sensitive to new physics at higher energies and must be fine tuned to agree with the apparent, observed value of 125 GeV, unless some new physics is found at TeV scale. Generically, such new physics models predict a modification of the simple EWSB mechanism of the SM and lead to some generic predictions at the LHC:

    1. Deviations in Higgs boson interactions as compared to the SM.

    2. New resonances of the electroweak W and Z gauge bosons.

    3. Extra Higgs multiplets.

    4. Partners to SM particles from models such as supersymmetry and extra dimensions.

My expertise in collider physics is in the creation of new techniques for experimentalists to discern such new physics. With several different collaborators, I have proposed many novel techniques and search strategies that will allow us to discover new particles and to study their detailed properties.

I am currently working on a boosted object tagger using wavelets.

A H->ZZ event at CMS

Dark Matter

The evidence for existence of dark matter (DM) is overwhelming from cosmological and astrophysical observations. This is the clearest experimental indication that we have of new particles beyond the Standard Model. However, we are completely clueless as to the particle nature of dark matter. The goal of the dark matter particle physics program is to find evidence for non-gravitational interactions of dark matter as well as to determine the properties of the dark matter particle(s). An explanation for the production of dark matter in the early universe, with the observed relic abundance, demands such non-gravitational interactions.

This field is highly interdisciplinary and draws from particle physics, nuclear physics, cosmology and astrophysics. I will discuss below some of the important questions that drive my research in dark matter physics.

The WIMP paradigm: One of the extremely well motivated candidates for dark matter is weakly interacting massive particles or WIMPs. This is based upon the so called ``WIMP miracle'': the observation that a particle with a weakly interacting cross-section (~pb) and mass around the TeV scale would give the right relic abundance due to freeze-out. This ties in neatly with our expectation of new physics models to explain the hierarchy problem that generally predict such particles at the weak scale. Crossing-symmetry suggests three strategies for the detection of WIMPs: direct (through the WIMP wind in the solar system colliding with underground detectors), indirect (through annihilations or decays of WIMPs in high density regions of dark matter) and collider searches. For a review, see for e.g. this.

The LHC is a machine well suited to directly producing WIMPs, either through cascades in new physics theories such as SUSY, or direct production with a corresponding recoil object (typically a jet).

I have just completed a study in which we were able to identify contact interactions of WIMP-like Dark Matter in monojet searches at the LHC.

Bullet cluster.

Others

I have worked in related areas such as early universe cosmology, dynamical SUSY breaking etc. I am also interested in formal properties of QFTs and RG flows.

I strongly believe that a balance of both experimental and theoretical approaches are needed to make headway past some of the formidable problems that we face in particle physics today. I have had the luxury of starting my career in a data rich-era with data from the LHC, neutrino experiments, dark matter terrestrial and astrophysical experiments and precision cosmological surveys. The insights that we have drawn from each of these experiments has shaped my research and the view of BSM physics and they will continue to provide guidance over the next few decades with the next-generation of experiments.