Research Interests

Better theory for the intensity frontier

Particle physicists like to divide their research into“frontiers”, such as the “Energy Frontier” or the “Cosmic Frontier”.  The “Intensity Frontier” involves pushing the limits of how many particles we can produce so that extremely large statistical samples can be gathered. With a massive statistical sample as the goal, there is not always room for compromise to make the experiment theoretically clean. Complex nuclei are often used as targets, forcing a good theoretical  description to necessarily straddle the gap between nuclear and particle physics.

My current interests largely focus on neutrino-nucleus cross sections with an emphasis on QED effects, and on the process of radiative muon capture (relevant for Mu2e and COMET). Both of these problems involve an interplay between well established theory (QED) and non-trivial nuclear effects. I have previously worked on Standard Model calculations of neutrino trident production, a rare process that can be used to search for new physics.

Ongoing work 

  • Estimates of RMC spectra in the near end-point region for aluminum-27.
  • Coulomb corrections for internal pair-production in the vicinity of a nucleus.
  • Coulomb corrections to charged current neutrino-nucleus scattering.

Papers: 

Cosmic rays as a source of new physics

Cosmic rays are a natural and perpetual source of any particle that can be produced in a proton-proton collision. They consequently offer a probe of physics Beyond the Standard Model that compliments collider searches. Although the flux of cosmic rays falls of steeply with increasing kinetic energy, there still exists a non-zero flux even at very high incident energies.

Papers: 

BSM physics with neutrinos

In the absence of any observed signal of new physics we can conclude that any new particles, should they exist, must either be very heavy (above roughly the TeV scale)  or very weakly interacting. The second option permits one to consider new particles with masses in the MeV-GeV regime that are very weakly interacting. It turns out that neutrino experiments are a great place to look for these particles since they are optimized to study the Standard Model’s own “dark” particle.

I have worked on models of new physics involving “neutrino portals” (where new particles couple to neutrinos) and other feebly interacting particle scenarios. I am generally interested in the ability to re-purpose existing facilities to help shed light on models of a hypothetical dark sector, but also in using natural sources of neutrino beams such as atmospheric and solar neutrinos.

Papers: 

Point particle effective field theory and absorptive systems

PPEFT aims to systematize the analysis of “bulk” fields interacting with compact objects (or branes). In any field-theory in a finite domain some boundary-condition must be imposed on the system. The idea is to provide a localized action describing the “point particle’s” interaction with the bulk field and it is this action that completely determines the boundary condition to be applied to the bulk field (in coordinate space).  The action is ordered  via a power counting scheme which dictates which boundary conditions are “universal” at low energies.

A powerful, and insightful setting to understand features of PPEFT is the quantum mechanics of the inverse square potential. The inverse square potential is interesting because of a phenomena known as “fall to the centre” and has connections to

  • Near horizon physics of black holes
  • Efimov physics
  • Conformal symmetry breaking

This project has three basic goals

  1.  Identify how to parameterize the inverse square potential as a PPEFT, and identify a universal set of RG invariants.
  2.  Propose an explicit proposal to realize, and test this system in a lab.
  3. Connect the results of any future experiment to other physical systems such as black hole and Efimov physics by using the universal parameterization mentioned above.

Papers: 

Hamltonian mean field model in the quantum regime (Ph.D. Thesis)

The HMF model is the toy model of long-range interacting systems (in the way the Ising model is for critical phenomena). It describes N particles of mass m interacting on a ring of radius R by the following Hamiltonian

 \displaystyle H=\sum\limits_i \frac{L_i^2}{2mR^2} + \frac{\epsilon}{N} \sum\limits_{i<j} \cos(\theta_i-\theta_j)

where L_i  is the (angular) momentum conjugate to \theta_i , and \epsilon/N is the inter-particle coupling. The coupling is re-scaled to ensure a non-trivial limit as N\rightarrow \infty , this is known as the Kac prescription.

We have been studying the quantum version of the model. Our first result was to determine the fate of the so-called bi-cluster two of our main results are shown below. We managed to make  non-equilibrium phase diagram that demonstrates how quantum zero-point energy modifies the dynamics, resulting in the interference pattern shown below

        

phase-diagram

Non-equilibrium phase diagram that shows how quantum effects change the model’s non-eq. behaviour.

biclust

Bi-cluster seeded by  small spatial variations in the phase of \Psi

       

Papers: