High Energy Physics Seminars This Term

I will discuss an agnostic, model-independent analysis of baryon number violating nucleon decay using the power of Effective Field Theory. In my presentation, I explore the contributions of dimension-six and -seven effective operators to ∣Δ(B−L)∣=0, 2 nucleon decays, incorporating the effects of the Renormalisation Group Equations. This analysis includes deriving lower limits on the energy scale of each operator as well as exploring correlations between different decay modes. Additionally, I will discuss a few simple UV models that generate proton decay at dimension six and seven in the SMEFT, highlighting their connection with the generation of Majorana neutrino masses.

A core-collapse Supernova in our own galaxy would be close enough to be seen with neutrinos in many of the world's neutrino and dark matter detectors. Those neutrinos exit the star promptly, while the electromagnetic fireworks appear ~hours later after the explosion's shock reaches the star's surface. This signal will teach us a lot both about the birth of a neutron star and neutrinos themselves when seen in detail with large, high resolution experiments such as DUNE. It will also be used as an automated early warning by SNEWS, a network of detectors around the world, to facilitate early observations of this rare (~1.5 per century) event using electromagnetic and gravitational wave messengers.

The SM has provided a powerful description of elementary particle physics, and it can explain most experimental findings with high precision. However, it is challenged by some recent experiments and theoretical considerations such as (g − 2)µ, Gauge Hierarchy Problem, etc. The vector-like quarks (VLQs) are well motivated in many new physics models and can be a key to solving the challenges that the SM left us. While all spin-½ particles have left- and right-handed components, the weak force only interacts with the left-handed components of Standard Model particles. However, vector-like quarks would have “ambidextrous” interactions with the weak force, giving them a bit more freedom in how they decay. In my analysis, I will be looking for channels with pair produced VLQs with top like properties decaying fully hadronically using a new boosted jet reclustering technique and cut based approach.

The weak-field limit of black hole scattering is an important problem in gravitational physics. In recent years, the high energy community has been contributing new and efficient methods to compute quantities of interest such as the post-Minkowskian expansion (i.e, expansion in GM/r (where c is set to one)) of the effective gravitational potential. In this talk, we will discuss some formal developments regarding two different methods from the high energy side, namely the eikonal method and the worldline method. We will see what these methods are, and show that they are actually equivalent. This equivalence allows us to prove a conjecture about the eikonal method (known as the "exponentiation of the eikonal phase") to all orders in the GM/r expansion.

A search for long-lived particles (LLPs) using final states including a soft displaced vertex, significant missing transverse momentum, and a jet from initial state radiation is reported. This search aims to be sensitive to soft LLPs that not only can travel 20cm before decay, but also carries very little energy that is less than 25 GeV.
Starting in 2026, LHC will begin a 2.5 years long shutdown and upgrade to High Luminosity LHC (HL-LHC). In HL-LHC, the number of interactions during each beam crossing will rise to 140-200, and the increased luminosity will improve the sensitivity of the search for “Beyond the standard model (BSM)” physics. However, the current Phase-1 CMS detector was designed to handle approximately only 50 pileup interactions. Therefore, MIP timing detector (MTD) is included in the upgrade plan to help solve this. MTD will give timing information of particles with 30-40 ps resolution at the start of operation, which helps the identification and reconstruction of the interactions and is necessary for maintaining the current excellent performance of the CMS detector.

Modern cosmology tells us that there are three species of neutrinos. In terms of a commonly used cosmological observable, it is Neff=3.045. Why 3.045? Why not an integer? Can this observable really be measured so precisely? How likely could this be affected by BSM physics related to neutrinos? In this talk, I will provide a brief introduction to neutrino cosmology, with a focus on one of its most important observables, Neff. I will demonstrate, through some of my recent work, that precision measurements of Neff in next-generation CMB experiments may be able to answer crucial questions such as whether neutrinos are Dirac or Majorana fermions, and how they may interact with dark matter and other dark sector particles.

Talk based on 2312.1715, 2307.13967, 2211.04669, 2110.09883, 2011.13059, and 2005.01629.

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LIGO and other large gravitational-wave detectors have now detected signals from over 200 merging binary black hole systems, and from a few merging binary neutron star systems.  Along with testing the fundamental physics of gravity (GR), I will point out the ways in which these observations are providing information about nuclear and particle astrophysics.  I will also summarize searches for ultralight boson states that could be revealed through distinctive gravitational wave emission or through direct interaction with gravitational-wave detectors.

Dark matter self-interactions is a fascinating concept that could help explain some of the universe's mysteries, such as the distribution of dark matter near galactic centers. If such interactions occur in nature, dark matter could form bound states, which might be observable in LHC collisions. In this search for self-interacting dark matter (SIDM), the dark matter particles produced at the LHC form a heavy bound state, which subsequently decays into a pair of boosted, long-lived dark photons. The decays of these dark photons could produce clusters of displaced and collimated leptons, which are reconstructed as "displaced lepton jets". The first part of the talk focuses on the reconstruction efficiency and displacement of these lepton jets. For the High Luminosity-LHC, the CMS detector is undergoing a massive upgrade, which involves the addition of an MIP Timing Detector (MTD). The central part of the MTD, the barrel timing layer (BTL), is designed to measure the arrival time of charged particles with a precision of 30ps. At UVA, we are making one-fourth of the total BTL. In the second part of the talk, I will talk about the components of the BTL and the progress we have made in its production.

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