How Magnetic is the Dirac Neutrino?

We derive model-independent, "naturalness" upper bounds on the magnetic moments munu of Dirac neutrinos generated by physics above the scale of electroweak symmetry breaking. In the absence of fine-tuning of effective operator coefficients, we find that current information on neutrino mass implies that[EQUATION: SEE TEXT] bohr magnetons. This bound is several orders of magnitude stronger than those obtained from analyses of solar and reactor neutrino data and astrophysical observations.

Neutrinoless double Beta decay and lepton flavor violation

We point out that extensions of the standard model with low scale (approximately TeV) lepton number violation (LNV) generally lead to a pattern of lepton flavor violation (LFV) experimentally distinguishable from the one implied by models with grand unified theory scale LNV. As a consequence, muon LFV processes provide a powerful diagnostic tool to determine whether or not the effective neutrino mass can be deduced from the rate of neutrinoless double beta decay. We discuss the role of mu-->egamma and mu-->e conversion in nuclei, which will be studied with high sensitivity in forthcoming experiments.

Hadronic light-by-light contribution to muon g - 2 in chiral perturbation theory

We compute the hadronic light-by-light scattering contributions to the muon anomalous magnetic moment, a(LL)(mu)(had), in chiral perturbation theory that are enhanced by large logarithms and a factor of N(C). They depend on a low-energy constant constrained by eta-->mu(+) mu(-) and pi(0)-->e(+)e(-) branching ratios. However, the dependence of a(LL)(mu)(had) on nonlogarithmically enhanced effects cannot be constrained except through the measurement of the anomalous moment itself.

Charged current universality in the minimal supersymmetric standard model

We compute the complete one-loop contributions to low-energy charged current weak interaction observables in the minimal supersymmetric standard model (MSSM). We obtain the constraints on the MSSM parameter space which arise when precision low-energy charged current data are analyzed in tandem with measurements of the muon anomaly. While the data allow the presence of at least one light neutralino, they also imply a pattern of mass splittings among first and second generation sleptons and squarks which contradicts predictions of widely used models for supersymmetry-breaking mediation.

Parity-violating photoproduction of pi(+/-) on the delta resonance

We analyze the real-photon asymmetry A(gamma)(+/-) for the parity-violating (PV) pi(+/-) production on the Delta resonance via the reactions (-->)gamma + p --> Delta(+) --> pi(+) + n and (-->)gamma + d --> Delta(0) + p --> pi(-) + p + p. This asymmetry is nonvanishing due to a PV gamma N Delta coupling constant, d(Delta)(+/-). We argue that an experimental determination of this coupling would be of interest for hadron dynamics, possibly shedding light on the S-wave/ P-wave puzzle in the hyperon nonleptonic decays and the violation of Hara's theorem in weak radiative hyperon decays.

Anapole moment and other constraints on the strangeness conserving Hadronic weak interaction

Standard analyses of low-energy NN and nuclear parity-violating observables have been based on a pi-, rho-, and omega-exchange model capable of describing all five independent s-p partial waves. Here a parallel analysis is performed for the one-body, exchange-current, and nuclear polarization contributions to the anapole moments of 133Cs and 205Tl. The resulting constraints are not consistent, though there remains some degree of uncertainty in the nuclear structure analysis of the atomic moments.