[en] We report on the development and performance of a high-sensitivity purity-analysis technique for gaseous xenon. The gas is sampled at macroscopic pressure from the system of interest using a UHV leak valve. The xenon present in the sample is removed with a liquid-nitrogen cold trap, and the remaining impurities are observed with a standard vacuum mass-spectroscopy device. Using calibrated samples of xenon gas spiked with known levels of impurities, we find that the minimum detectable levels of N₂, O₂, and methane are 1x10^-9, 160x10^-12, and 60 x10^-12 g/g, respectively. This represents an improvement of about a factor of 10 000 compared to measurements performed without a cold trap.

[en] We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance

[en] The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D((rvec e), e'γ)X cross section measured at Q²=1.9 GeV² and x_B=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_q, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced

[en] We report the most precise measurement to date of a parity-violating asymmetry in elastic electron-proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle <θ_lab> = 6.0 degrees, with the result A_PV = -1.14 ± 0.24 (stat) ± 0.06 (syst) parts per million. From this we extract, at Q² = 0.099 GeV², the strange form factor combination G_E^s + 0.080 G_M^s = 0.030 ± 0.025 (stat) ± 0.006 (syst) ± 0.012 (FF) where the first two errors are experimental and the last error is due to the uncertainty in the neutron electromagnetic form factor. The measurement significantly improves existing constraints on G_E^s and G_M^s at Q² ∼0.1 GeV². A consistent picture emerges from all measurements at this Q². A combined fit shows that G_E^s is consistent with zero while G_M^s prefers positive values though G_E^s = G_M^s = 0 is compatible with the data at 95% C.L