High Energy Physics Seminar

Abstract: In this talk, we discuss the Standard Model (SM) electroweak (EW) sector as a portal to the hidden sector, with EW bosons serving as mediators. We propose several UV complete models of the EW portal and explore their prospects in EW precision tests (EWPT). A rich phenomenology emerges when the hidden sector admits a confining gauge interaction, leading to a family of dark hadrons such as dark pions and rhos. These dark hadrons are generally long-lived if their mass is of the GeV scale. The primary signal in collider physics will be dark showers from exotic boson decays, generating multiple long-lived particles. We will cover current LHC searches and other facilities, as well as the cosmological implications.

Abstract: The flavor sector of the Standard Model contains most of its free parameters, and exhibits an interesting structure that currently lacks a satisfactory explanation. Moreover, when moving beyond the Standard Model, assumptions about the flavor structure of new physics are crucial to make predictions and design searches. In this talk, I will review how the typical flavor ansätze for BSM physics come about, and motivate the need to move beyond these “minimal” ideas. I will then introduce several new, non-minimal ansatz for physics beyond the Standard Model: the Froggatt-Nielsen mechanism with “wrinkles”, and Spontaneous Flavor Violation. These ansätze lead to new correlations between experiments at low-, medium- and high-energies, and novel signatures at the LHC such as enhanced Higgs decays to strange quarks, some of which provide interesting targets for future experiments at the energy frontier.

Abstract: Gravitational microlensing is one of the most sensitive methods we have to search for macroscopic dark matter. NASA’s upcoming Roman Space Telescope will dramatically advance this search by performing a comprehensive microlensing survey of the Galactic Bulge at sensitivities orders of magnitude stronger than existing telescopes. Its unprecedented sensitivity will provide the opportunity to search for dark matter across a wide range of unexplored parameter space; however, it will also pose new challenges, including an irreducible astrophysical background in the form of free-floating planets. In this talk, I will discuss how population-level modeling can help mitigate this background and open the potential for Roman to make a first discovery of primordial black holes or other macroscopic dark matter in our galaxy.

Abstract: Dark Matter (DM) remains mysterious. Despite decades of experimental and theoretical efforts, its microscopic identity is still unknown to us. In this talk, I will walk you through how a variety of celestial objects can be utilised as powerful DM detectors. This astrophysical probe, complementary to the terrestrial and cosmological probes, covers a significant portion of the DM parameters (DM mass and its interaction strength with nucleons) which otherwise remains elusive.

Abstract: The WIMP may not be dead, but its decline has opened a number of new frontiers in the search for dark matter, spanning a vast range of scales. This is problematic for traditional direct detection searches: decades of development have produced detectors that are extremely sensitive to weak-scale dark matter, but nearly blind to other important targets. The growing scope of our search thus calls for new experimental ideas. I will describe a new conceptual framework for the treatment of dark matter--electron interaction rates in which the capabilities of detectors are determined by their dielectric properties. This language makes it possible to leverage the complicated condensed matter physics of detector materials to probe dark matter at masses several orders of magnitude below existing bounds. This novel formalism is already enabling new approaches to the detection of light dark matter, and I will share recent results including new constraints on sub-MeV dark matter and prospects for directional sensitivity with off-the-shelf dielectric targets. The future prospects promise to transform direct detection from a surgical instrument at the weak scale to a robust tool in the search for new physics across the scales.

Abstract: In this talk, I will discuss new probes of neutrino/non-photon interactions using cosmology, specifically the cosmic microwave background (CMB) data. A phase shift in the acoustic oscillations of CMB spectra is a characteristic signature for the presence of neutrinos (non-photon radiation) propagating differently compared to photons. Focusing on dark matter neutrino interaction and neutrino self-interaction, we will show how these interactions imprint changes in the acoustic phase shift and be probed using data. In the case of dark matter-neutrino interaction, the scattering between dark matter and neutrinos further amplifies the phase shift due to `dark matter' loading. For neutrino self-interaction, we find that the CMB dataset favors strong self-interaction if only one or two of the three active neutrino flavors interact relative to the flavor-universal scenario. Flavor non-universal interaction also helps to avoid the stringent constraints on new secret interactions among electron and muon neutrinos from several laboratory experiments. Finally, I will discuss how a tower of neutrino states, that appear in BSM scenarios, can be probed using cosmology. I will discuss the relevance of the tower of neutrino states in light of the latest bound on neutrino mass from cosmological data.