Department of Physics, Panjab University, Chandigarh, India

### Department seminar

Date and time: 12 October 2015 (Monday), 4:00 pm
Venue: Seminar Hall

Title: Demystifying nucleons using lattice QCD: from gA to neutron EDM

Speaker: Prof. Rajan Gupta, Los Alamos National Laboratory, Los Alamos, New Mexico, USA

Abstract: Understanding the decay of neutrons led to the modern theory of weak interactions. Precise measurements of the small helicity-flip parameters $b$ and $b_\nu$ in the neutron decay distribution can, in a very similar way, be used to probe novel scalar and tensor interactions at the TeV scale, while the neutron EDM is a very sensitive probe of new CP violation. I will describe lattice QCD calculations of the matrix elements of the iso-vector scalar and tensor bilinear quark operators within the ground state nucleon needed to constrain novel scalar and tensor interactions at the TeV scale, and of flavor diagonal tensor operators needed to quantify the contributions of the $u,\ d, \ s$ quark electric dipole moments to the neutron electric dipole moment (nEDM) and their impact on setting bounds on new sources of CP violation. The talk will cover our latest lattice QCD results with a focus on providing an understanding of, and leve of control over, all sources of systematic errors in these calculations.