7 research outputs found
Forward coherent -meson photoproduction from deuterons near threshold
Differential cross sections and decay asymmetries for coherent -meson
photoproduction from deuterons were measured for the first time at forward
angles using linearly polarized photons at = 1.5-2.4 GeV. This
reaction offers a unique way to directly access natural-parity Pomeron dynamics
and gluon exchange at low energies. The cross sections at zero degrees increase
with increasing photon energy. The decay asymmetries demonstrate a complete
dominance of natural-parity exchange processes, showing that isovector
unnatural-parity -meson exchange is small. Nevertheless the deduced cross
sections of -mesons from nucleons contributed by isoscalar t-channel
exchange processes are not well described by the conventional Pomeron model.Comment: 14 pages, 6 figures. Final published versio
Backward-angle photoproduction of mesons on the proton at = 1.5--2.4 GeV
Differential cross sections and photon beam asymmetries for
photoproduction have been measured at = 1.5--2.4 GeV and at the
scattering angles, --1 cos --0.6. The
energy-dependent slope of differential cross sections for -channel
production has been determined. An enhancement at backward angles is found
above = 2.0 GeV. This is inferred to be due to the -channel
contribution and/or resonances. Photon beam asymmetries have been obtained for
the first time at backward angles. A strong angular dependence has been found
at 2.0 GeV, which may be due to the unknown high-mass resonances.Comment: 12 pages, 4 figures, submitted to PL
phi photo-production from Li, C, Al, and Cu nuclei at Egamma=1.5 - 2.4 GeV
The photo-production of mesons from Li, C, Al, and Cu at forward
angles has been measured at =1.5--2.4 GeV. The number of events for
incoherent phi photo-production is found to have a target mass number
dependence of in the kinematical region of
. The total cross section of the -nucleon interaction,
, has been estimated as mb using the
-dependence of the photo-production yield and a Glauber-type multiple
scattering theory. This value is much larger than in free
space, suggesting that the properties might change in the nuclear
medium.Comment: 12 pages 4 figures, submitted to Phys. Lett.
Measurement of the incoherent photoproduction near threshold
We report measurements of differential cross sections and decay asymmetries
of incoherent -meson photoproduction from the deuteron at forward angles
using linearly polarized photons at \Eg=1.5-2.4 GeV. The nuclear transparency
ratio for the deuteron shows a large suppression, and is consistent with the
A-dependence of the ratio observed in a previous measurement with nuclear
targets. The reduction for the deuteron cannot be adequately explained in term
of isospin asymmetry. The present results suggest the need of refining our
understanding of the -N interaction within a nucleus.Comment: 5 pages, 4 figures. Published in Physics Letters