The differential cross section for the gamma +n --> pi- + p and the gamma + p --> pi+ n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50 degree to 110 degree. The pi- and pi+ photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing pi+ data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.
Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 5.614 GeV.
Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 4.236 GeV.
Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 3.400 GeV.
The reaction γ⊥,∥p→π+n has been studied with linearly polarized photons of energy 3.0 GeV at −t values between 0.15 and 1.2 (GeVc)2. The asymmetry A+=(dσ⊥−dσ∥)(dσ⊥+dσ∥) is found to be positive throughout this four-momentum-transfer range, implying the dominance of natural parity exchange in the t channel. Comparison of dσ⊥(γ⊥p→π+n) and dσ⊥p→π−p) from a previous experiment indicates strong interference between the isoscalar and isovector photon amplitudes for photons polarized perpendicular to the production plane.
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Total and differenial cross sections of the reaction γ +n→p+ π − have been determined for photon-energies between 0.2 and 2.0 GGeV. Below 500 MeV the differential cross sections are compared with theoretical predictions derived from fixed-momentum-transfer dispersion relations.
Axis error includes +- 0.0/0.0 contribution (5 TO 8////).
Axis error includes +- 0.0/0.0 contribution (5 TO 8////).
Axis error includes +- 0.0/0.0 contribution (5 TO 8////).
Differential cross sections for the photoproduction of single charged pions from deuterium and hydrogen have been measured at pion center-of-mass angles between 30° and 90° and at photon energies between 3.0 and 3.7 GeV. The ratio of π− to π+ cross sections from deuterium is found to be appreciably smaller than 1.
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