Spin Density Matrix Elements in Exclusive rho^0 Electroproduction on 1H and 2H Targets at 27.5 GeV Beam Energy

Understand

Spin Density Matrix Elements (SDMEs) describing the angular distribution of exclusive rho^0 electroproduction and decay are determined in the HERMES experiment with 27.6 GeV beam energy and unpolarized hydrogen and deuterium targets.

• Eight (fifteen) SDMEs that are related (unrelated) to the longitudinal polarization of the beam are extracted in the kinematic region 1 GeV^2 < Q^2 < 7 GeV^2, 3.0 GeV < W < 6.3 GeV, and -t < 0.4 GeV^2.
• Within the given experimental uncertainties, a hierarchy of relative sizes of helicity amplitudes is observed.
• Kinematic dependences of all SDMEs on Q^2 and t are presented, as well as the longitudinal-to-transverse rho^0 electroproduction cross section ratio as a function of Q^2.