Probing Novel Scalar and Tensor Interactions from (Ultra)Cold Neutrons to the LHC
Scalar and tensor interactions were once competitors to the now well-established V-A structure of the Standard Model weak interactions. We revisit these interactions and survey constraints from low-energy probes (neutron, nuclear, and pion decays) as well as collider searches. Currently, the most stringent limit on scalar and tensor interactions arise from 0+ -> 0+ nuclear decays and the radiative pion decay pi -> e nu gamma, respectively. For the future, we find that upcoming neutron beta decay and LHC measurements will compete in setting the most stringent bounds. For neutron beta decay, we demonstrate the importance of lattice computations of the neutron-to-proton matrix elements t…
Lattice QCD calculations of transverse momentum-dependent parton distributions (TMDs)
An ongoing program of evaluating TMD observables within Lattice QCD is reviewed, summarizing recent progress with respect to several challenges faced by such calculations. These lattice calculations are based on a definition of TMDs through hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections. A parametrization of the matrix elements in terms of invariant amplitudes serves to cast them in the Lorentz frame preferred for a lattice calculation. Data on the naively T-odd Sivers and Boer-Mulders effects as well as the transversity TMD are presented.
Parton distributions and lattice QCD calculations: A community white paper
Progress in particle and nuclear physics 100, 107 - 160 (2018). doi:10.1016/j.ppnp.2018.01.007
Isovector charges of the nucleon from 2+1-flavor QCD with clover fermions
Physical review / D 95(7), 074508 (2017). doi:10.1103/PhysRevD.95.074508