Gary Prezeau

New Contribution to Scattering of Weakly Interacting Massive Particles on Nuclei

A weakly-interacting massive particle (WIMP) is perhaps the most promising candidate for the dark matter in the Galactic halo. The WIMP detection rate in laboratory searches is fixed by the cross section for elastic WIMP-nucleus scattering. Here we calculate the contribution to this cross section from two-nucleon currents from pion exchange in the nucleus, and show that it may in some cases be comparable to the one-nucleon current that has been considered in prior work, and perhaps help resolve the discrepancies between the various direct dark-matter search experiments. We provide simple expressions that allow these new contributions to be included in current calculations.

Neutrinoless double beta decay and effective field theory

We analyze neutrinoless double beta decay (0nubetabeta decay) mediated by heavy particles from the standpoint of effective field theory. We show how symmetries of the 0nubetabeta-decay quark operators arising in a given particle physics model determine the form of the corresponding effective, hadronic operators. We classify the latter according to their symmetry transformation properties as well as the order at which they appear in a derivative expansion. We apply this framework to several particle physics models, including R-parity violating supersymmetry (RPV SUSY) and the left-right symmetric model (LRSM) with mixing and a right-handed Majorana neutrino. We show that, in general, the pion exchange contributions to 0nubetabeta decay dominate over the short-range four-nucleon operators. This confirms previously published RPV SUSY results and allows us to derive new constraints on the masses in the LRSM. In particular, we show how a nonzero mixing angle zeta in the left-right symmetry model produces a new potentially dominant contribution to 0nubetabeta decay that substantially modifies previous limits on the masses of the right-handed neutrino and boson stemming from constraints from 0nubetabeta decay and vacuum stability requirements.

Effective field theory dimensional regularization

A Lorentz-covariant regularization scheme for effective field theories with an arbitrary number of propagating heavy and light particles is given. This regularization scheme leaves the low-energy analytic structure of Greens functions intact and preserves all the symmetries of the underlying Lagrangian. The power divergences of regularized loop integrals are controlled by the low-energy kinematic variables. Simple diagrammatic rules are derived for the regularization of arbitrary one-loop graphs and the generalization to higher loops is discussed.

Hadronic parity violation and inelastic electron-deuteron scattering

We compute contributions to the parity-violating (PV) inelastic electron-deuteron scattering asymmetry arising from hadronic PV. While hadronic PV effects can be relatively important in PV threshold electrodisintegration, we find that they are highly suppressed at quasielastic kinematics. The interpretation of the PV quasielastic asymmetry is, thus, largely unaffected by hadronic PV.

ALGORITHM FOR THE EVALUATION OF REDUCED WIGNER MATRICES

Algorithms for the fast and exact computation of Wigner matrices are described and their application to a fast and massively parallel 4π convolution code between a beam and a sky is also presented.

Light neutrino and heavy particle exchange in 0νββ-decay

Abstract A simple and precise method is presented to compare contributions to neutrinoless double-beta decay ( 0 ν β β -decay) from heavy particle exchange and light Majorana neutrino exchange. This procedure makes no assumptions about the momentum transfer between the two nucleons involved in the 0 ν β β -decay process. It is shown that for a general particle physics model, the characteristic 0 ν β β -decay scale > 4.4 TeV when all the coupling constants are assumed to be natural and of O ( 1 ) .