Speaker
Description
We present COMPASS results on the longitudinal double-spin asymmetry, Ap1, and the spin dependent structure function of the proton, gp1, in the quasi-real photoproduction regime. Data were collected by scattering a longitudinally polarised
muon beam off a longitudinally polarised proton target. Two data sets with a beam energy of respectively 160 and 200 GeV were taken, which improve, once combined, the statistical precision on Ap1 and gp1 by a factor of 12 compared to the previous SMC experiment covering a similar kinematic region.
The high statistical precision allows Ap1 and gp1 to be measured in several 2-D grids, (x, Q2), (ν, Q2), (x, ν) and (Q2, x) within the following kinematic domain: 4.0 × 10−5 ≤ x ≤ 4.0 × 10−2, 0.001 ≤ Q2 ≤ 1 (GeV/c)2 and 14 ≤ ν ≤ 194 GeV. The presented measurements provide inputs to better constrain non-perturbative models of electroproduction.
