4 research outputs found
Target and double spin asymmetries of deeply virtual pi(0) production with a longitudinally polarized proton target and CLAS
The target and double spin asymmetries of the exclusive pseudoscalar channel
were measured for the first time in the
deep-inelastic regime using a longitudinally polarized 5.9 GeV electron beam
and a longitudinally polarized proton target at Jefferson Lab with the CEBAF
Large Acceptance Spectrometer (CLAS). The data were collected over a large
kinematic phase space and divided into 110 four-dimensional bins of ,
, and . Large values of asymmetry moments clearly indicate a
substantial contribution to the polarized structure functions from transverse
virtual photon amplitudes. The interpretation of experimental data in terms of
generalized parton distributions (GPDs) provides the first insight on the
chiral-odd GPDs and , and complement previous measurements
of unpolarized structure functions sensitive to the GPDs and .
These data provide necessary constraints for chiral-odd GPD parametrizations
and will strongly influence existing theoretical handbag models
Exclusive electroproduction on transversely polarized protons
AbstractThe exclusive electroproduction of ρ0 mesons was studied with the hermes spectrometer at the Desy laboratory by scattering 27.6 GeV positron and electron beams off a transversely polarized hydrogen target. Spin density matrix elements for this process were determined from the measured production- and decay-angle distributions of the produced ρ0 mesons. These matrix elements embody information on helicity transfer and the validity of s-channel helicity conservation in the case of a transversely polarized target. From the spin density matrix elements, the leading-twist term in the single-spin asymmetry was calculated separately for longitudinally and transversely polarized ρ0 mesons. Neglecting s-channel helicity changing matrix elements, results for the former can be compared to calculations based on generalized parton distributions, which are sensitive to the contribution of the total angular momentum of the quarks to the proton spin
Single-spin azimuthal asymmetry in exclusive electroproduction of mesons on transversely polarized protons
Exclusive electroproduction of pi+ mesons was studied by scattering 27.6 GeV
positrons or electrons off a transversely polarized hydrogen target. The
single-spin azimuthal asymmetry with respect to target polarization was
measured as a function of the Mandelstam variable t, the Bjorken scaling
variable x_B, and the virtuality Q^2 of the exchanged photon. The extracted
Fourier components of the asymmetry were found to be consistent with zero,
except one that was found to be large and that involves interference of
contributions from longitudinal and transverse virtual photons.Comment: 7 pages, 2 figure