C. Prescott

Parity Non-Conservation in Inelastic Electron Scattering

Abstract We have measured parity violating asymmetries in the inelastic scattering of longitudinally polarized electrons from deuterium and hydrogen. For deuterium near Q2 = 1.6 (GeV/c)2 the asymmetry is (−9.5 × 10−5)Q2 with statistical and systematic uncertainties each about 10%.

Search for Neutrinoless Double-Beta Decay in 136 Xe with EXO-200

We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for an exposure of 32.5 kg yr, with a background of ∼1.5×10(-3)  kg(-1) yr(-1)  keV(-1) in the ±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T(1/2)(0νββ)(136Xe)>1.6×10(25)  yr (90% C.L.), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.

Further measurements of parity non-conservation in inelastic electron scattering☆

Measurements of the y-dependence of the parity nonconserving asymmetries for inelastic electron scattering from deuterium. The measurements cover a range of y values from 0.15 to 0.36 and show only a small y-dependence. The results are in good agreement with the Weinberg-Salam model for sin/sup 2/theta/sub W/ = 0.224 +- 0.020. 20 references.

Measurements of the Proton and Deuteron Spin Structure Functions g1 and g2

Measurements are reported of the proton and deuteron spin structure functions g1 at beam energies of 29.1, 16.2, and 9.7 GeV and g2 at a beam energy of 29.1 GeV. The integrals of g1 over x have been evaluated at fixed Q**2 = 3 (GeV/c)**2 using the full data set. The Q**2 dependence of the ratio g1/F1 was studied and found to be small for Q**2>1 (GeV/c)**2. Within experimental precision the g2 data are well-described by the Wandzura-Wilczek twist-2 contribution. Twist-3 matrix elements were extracted and compared to theoretical predictions. The asymmetry A2 was measured and found to be significantly smaller than the positivity limit for both proton and deuteron targets. A2 for the proton is found to be positive and inconsistent with zero. Measurements of g1 in the resonance region show strong variations with x and Q**2, consistent with resonant amplitudes extracted from unpolarized data. These data allow us to study the Q**2 dependence of the first moments of g1 below the scaling region.

Measurements of the Q**2 dependence of the proton and neutron spin structure functions g(1)**p and g(1)**n

Abstract The ratio g 1 F 1 has been measured over the range 0.03 g 1 F 1 to be consistent with no Q2-dependence at fixed x in the deep-inelastic region Q2 > 1 (GeV/c)2. A trend is observed for g 1 F 1 to decrease at lower Q2. Fits to world data with and without a possible Q2-dependence in g 1 F 1 are in agreement with the Bjorken sum rule, but Δq is substantially less than the quark-parton model expectation.

Search for Neutrinoless Double-Beta Decay in 136Xe with EXO-200

We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for an exposure of 32.5 kg yr, with a background of ∼1.5×10(-3)  kg(-1) yr(-1)  keV(-1) in the ±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T(1/2)(0νββ)(136Xe)>1.6×10(25)  yr (90% C.L.), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.

Measurements of the Proton and Deuteron Spin Structure Function g2 and Asymmetry A2

We have measured proton and deuteron virtual photon-nucleon asymmetries A2p and A2d and structure functions g2p and g2d over the range 0.03<x<0.8 and 1.3<Q2<10 (GeV/c)2 by inelastically scattering polarized electrons off polarized ammonia targets. Results for A2 are significantly smaller than the positivity limit sqrt(R) for both targets. Within experimental precision, the g2 data are well-described by the twist-2 contribution g2WW. Twist-3 matrix elements have been extracted and are compared to theorectical predictions.

Measurement of the deuteron spin structure function g1d(x) for 1 (GeV/c)2 < Q2 < 40 (GeV/c)2

New measurements are reported on the deuteron spin structure function g_1^d. These results were obtained from deep inelastic scattering of 48.3 GeV electrons on polarized deuterons in the kinematic range 0.01<x<0.9 and 1<Q^2<40 (GeV/c)^2. These are the first high dose electron scattering data obtained using lithium deuteride (6Li2H) as the target material. Extrapolations of the data were performed to obtain moments of g_1^d, including Gamma_1^d, and the net quark polarization Delta Sigma.Abstract New measurements are reported on the deuteron spin structure function g1d. These results were obtained from deep inelastic scattering of 48.3 GeV electrons on polarized deuterons in the kinematic range 0.01 6 Li 2 H) as the target material. Extrapolations of the data were performed to obtain moments of g1d, including Γ1d, and the net quark polarization ΔΣ.

Measurements of R = σL/σT for 0.03 < x < 0.1 and Fit to World Data

Abstract Measurements were made at SLAC of the cross section for scattering 29 GeV electrons from carbon at a laboratory angle of 4.5°, corresponding to 0.03Measurements were made at SLAC of the cross section for scattering 29 GeV electrons from carbon at a laboratory angle of 4.5 degrees, corresponding to 0.03<x<0.1 and 1.3<Q^2<2.7 GeV^2. Values of R=sigma_L/sigma_T were extracted in this kinematic range by comparing these data to cross sections measured at a higher beam energy by the NMC collaboration. The results are in reasonable agreement with pQCD calculations and with extrapolations of the R1990 parameterization of previous data. A new fit is made including these data and other recent results.

Precision measurement of the proton and deuteron spin structure functions g2 and asymmetries A2

We have measured the spin structure functions g{sub 2}{sup p} and g{sub 2}{sup d} and the virtual photon asymmetries A{sub 2}{sup p} and A{sub 2}{sup d} over the kinematic range 0.02 {le} x {le} 0.8 and 0.7 {le} Q{sup 2} {le} 20 GeV{sup 2} by scattering 29.1 and 32.3 GeV longitudinally polarized electrons from transversely polarized NH{sub 3} and {sup 6}LiD targets. Our measured g{sub 2} approximately follows the twist-2 Wandzura-Wilczek calculation. The twist-3 reduced matrix elements d{sub 2}{sup p} and d{sub 2}{sup n} are less than two standard deviations from zero. The data are inconsistent with the Burkhardt-Cottingham sum rule if there is no pathological behavior as x {yields} 0. The Efremov-Leader-Teryaev integral is consistent with zero within our measured kinematic range. The absolute value of A{sub 2} is significantly smaller than the A{sub 2} < {radical}(R(1+A{sub 1})/2) limit.