DVCS in Hall A @ JLab

Hall A experiment E00-110 measured the Q ² dependence of the helicity dependent H( e ,e'γ)p cross section at x _Bj =0.36 and Q ² = 1.5, 1.9, and 2.3 GeV ² . The results are consistent with dominance of the leading twist Im[BH*DVCS] term. The experiment also measured the helicity independent cross section at Q ² = 2.3 GeV ² . The latter results show evidence for strong contributions from both the Real part of the BH*DVCS interference and the pure |DVCS| ² terms (as well as the |BH| ² term).

The expansion of the existing calorimeter is required for a new series of DVCS experiments at 6 and 12 GeV. The Hall A 12 GeV DVCS experiment, E12-06-114 was approved by PAC30 in August, 2006 (J.Roche, C.E. Hyde-Wright, co-spokespersons). With the new calorimeter, we will extend DVCS and deep virtual π ⁰ measurements in x _Bj ,Q ² ) to (0.7,9.0 GeV ² ). In E07-007, we propose DVCS measurements at fixed Q ² , x _Bj and two different beam energies (6 and 4 GeV). The kinematic structure of the ep\rightarrow epγ cross section will allow us to separate the Real part of the BH*DVCS interference from the pure |DVCS| ² term at all three Q ² values of the previous E00-110. We will also obtain Rosenbluth L/T separations of the $ep\rightarrow epπ ⁰ cross section, which is crucial to testing factorization in this channel.