Parity Violation in gamma proton Compton Scattering

A measurement of parity-violating spin-dependent gamma proton Compton scattering will provide a theoretically clean determination of the parity-violating pion-nucleon coupling constant $h_{\pi NN}^{(1)}$. We calculate the leading parity-violating amplitude arising from one-loop pion graphs in chiral perturbation theory. An asymmetry of ~5 10^{-8} is estimated for Compton scattering of 100 MeV photons.Comment: 6 pages, 1 figure, latex. Reference adde

Nuclear Anapole Moments

Nuclear anapole moments are parity-odd, time-reversal-even E1 moments of the electromagnetic current operator. Although the existence of this moment was recognized theoretically soon after the discovery of parity nonconservation (PNC), its experimental isolation was achieved only recently, when a new level of precision was reached in a measurement of the hyperfine dependence of atomic PNC in 133Cs. An important anapole moment bound in 205Tl also exists. In this paper, we present the details of the first calculation of these anapole moments in the framework commonly used in other studies of hadronic PNC, a meson exchange potential that includes long-range pion exchange and enough degrees of freedom to describe the five independent $S-P$ amplitudes induced by short-range interactions. The resulting contributions of pi-, rho-, and omega-exchange to the single-nucleon anapole moment, to parity admixtures in the nuclear ground state, and to PNC exchange currents are evaluated, using configuration-mixed shell-model wave functions. The experimental anapole moment constraints on the PNC meson-nucleon coupling constants are derived and compared with those from other tests of the hadronic weak interaction. While the bounds obtained from the anapole moment results are consistent with the broad ``reasonable ranges'' defined by theory, they are not in good agreement with the constraints from the other experiments. We explore possible explanations for the discrepancy and comment on the potential importance of new experiments.Comment: 53 pages; 10 figures; revtex; submitted to Phys Rev

Measurement of the Decay of the Y(1S) and Y(2S) Resonances To Muon Pairs

Using the Crystal Ball detector at the e+e-storage ring DORIS II, we have measured the branching fraction to muon pairs B(mu-mu) of the UPSILON(1S) and UPSILON(2S) resonances and for the first time the product of the muonic partial width GAMMA(mu-mu) and the branching fraction to electrons B(ee) for both resonances. We obtain B(mu-mu) (1S) = (2.31 +/- 0.12 +/- 0.10)%, GAMMA(mu-mu) (1S) . B(ee) (1S) = (31.2 +/- 1.6 +/- 1.7) eV, and B(mu-mu) (2S) = (1.22 +/- 0.28 +/- 0.19)%, GAMMA(mu-mu) (2S) . B(ee) (2S) = (6.5 +/- 1.5 +/- 1.0) eV. Inserting the present world average value of B(ee) (1S) = (2.52 +/- 0.17)%, we determine the muonic partial width of the UPSILON(1S) as GAMMA(mu-mu) (1S) = (1.24 +/- 0.06 +/- 0.11) keV. In addition, we present the first indication of the expected interference between mu-pair production in the continuum and in UPSILON(1S) decays