Measurement of the resonance parameters of the X1(1(3)P(1)) and X2(1(3)P(2)) states of charmonium formed in antiproton-proton annihilations

We have studied the P-3(J) (chi(C)) states of charmonium in formation by antiproton-proton annihilations in experiment E835 at the Fermilab Antiproton Source. We report new measurements of the mass, width, and B(chi(cJ) -> (p) over barp)Gamma(chi(cJ) -> J/psi + anything) for the chi(c1) and chi(c2) by means of the inclusive reaction (p) over barp -> X-cJ -> J/psi + anything -> (e(+)e(-)) + anything. Using the sub-sample of events where chi(cJ) -> gamma + J/psi -> y + (e(+)e(-)) is fully reconstructed, we derive B(chi(cJ) -> (p) over barp)Gamma(chi(cJ) -> J/psi + gamma). We summarize the results of the E760 (updated) and E835 measurements of mass, width and B(chi(cJ) -> (p) over barp)Gamma(chi(cJ) -> J/psi + gamma) (J = 0, 1, 2) and discuss the significance of these measurements

Measurement of azimuthal asymmetries associated with deeply virtual Compton scattering on an unpolarized deuterium target

Azimuthal asymmetries in exclusive electroproduction of a real photon from an unpolarized deuterium target are measured with respect to beam helicity and charge. They appear in the distribution of these photons in the azimuthal angle φ{symbol} around the virtual-photon direction, relative to the lepton scattering plane. The extracted asymmetries are attributed to either the deeply virtual Compton scattering process or its interference with the Bethe-Heitler process. They are compared with earlier results on the proton target. In the measured kinematic region, the beam-charge asymmetry amplitudes and the leading amplitudes of the beam-helicity asymmetries on an unpolarized deuteron target are compatible with the results from unpolarized protons. © 2009 Elsevier B.V. All rights reserved

Measurement of the tensor structure function b(1) of the deuteron

The Hermes experiment has investigated the tensor spin structure of the deuteron using the 27.6 GeV/c positron beam of DESY HERA. The use of a tensor-polarized deuteron gas target with only a negligible residual vector polarization enabled the first measurement of the tensor asymmetry A(zz)(d) and the tensor structure function b(1)(d) for average values of the Bjorken variable 0.01 < 5 GeV2. The quantities A(zz)(d) and b(1)(d) are found to be nonzero. The rise of b(1)(d) for decreasing values of x can be interpreted to originate from the same mechanism that leads to nuclear shadowing in unpolarized scattering