Optimized Probes of the CP Nature of the Top Quark Yukawa Coupling at Hadron Colliders

We summarize our recent proposals for probing the CP-odd iκ˜t¯γ5th interaction at the LHC and its projected upgrades directly using associated on-shell Higgs boson and top quark or top quark pair production. We first recount how to construct a CP-odd observable based on top quark polarization in Wb→th scattering with optimal linear sensitivity to κ˜. For the corresponding hadronic process pp→thj we then present a method of extracting the phase-space dependent weight function that allows to retain close to optimal sensitivity to κ˜. For the case of top quark pair production in association with the Higgs boson, pp→tt¯h, with semileptonically decaying tops, we instead show how one can construct manifestly CP-odd observables that rely solely on measuring the momenta of the Higgs boson and the leptons and b-jets from the decaying tops without having to distinguish the charge of the b-jets. Finally, we introduce machine learning (ML) and non-ML techniques to study the phase-space optimization of such CP-odd observables. We emphasize a simple optimized linear combination α·ω that gives similar sensitivity as the studied fully fledged ML models. Using α·ω we review sensitivity projections to κ˜ at HL-LHC, HE-LHC, and FCC-hh.

Three-particle system in a finite volume: formalism, quantization condition, spectrum and energy shift

Lattice QCD calculations provide an ab initio access to hadronic process. These calculations are usu ally performed in a small cubic volume with periodic boundary conditions. The infinite volume extrapolations for three-body systems are indispensable to understand many systems of high current interest. We derive the three-body quantization condition in a finite volume using an effective field theory in the particle-dimer picture. Our work shows a powerful and transparent method to read off three-body physical observables from lattice simulations. In this paper, we review the formalism, quantization condition, spectrum analysis and energy shifts calculation both for 3-body bound states and scattering states.

On the hadronic γ-ray emission from Tycho's Supernova Remnant

Tycho is one of nearly a dozen Galactic supernova remnants which are suggested to emit hadronic γ-ray emission. Among them, however, it is the only one in which the hadronic emission is proposed to arise from the interaction with low-density ambient medium. Based on the multi-band observations, we suggest that Tycho is encountering dense cloud at the northeastern boundary. The γ-ray emissions can be explained by hadronic process with self-consistent parameters, such as a modest energy conversion efficiency. In this SNR-cloud association scenario, the distance can be estimated as ~2.5 kpc.