High-Energyπ0Photoproduction from Hydrogen with Unpolarized and Linearly Polarized Photons

Abstract

We have completed measurements of the differential cross section for y + prro + p , and the asymmetry with polarized photons, for incident photon energies from 4 to 18 GeV and momentum transfers between t = -0.1 and -1.4 (~e v / c ) ' . The experiment was performed at the Stanford Linear Accelerator Center, using the SLAC 1.6-GeV/c spectrometer to analyze protons recoiling from a hydrogen target. For the cross-section measurements a normal collimated bremsstrahlung beam was used. For the asymmetry measurements the polarized photons were produced by coherent bremsstrahlung from a diamond crystal, and a coincidence was required between the recoil proton and one of the TO decay photons in a shower counter.

Nuclear incoherent photoproduction ofπ0andηfrom 4 to 12 GeV

“…This result also shows for the first time that the proton data from DESY [34] and SLAC [36] are consistent with the complex nuclei data from Cornell. It is worth mentioning, however, that the Cornell data were sensitive to the Glauber corrections to the deuteron and additional cross section measurements with tagged photon beams are strongly encouraged for the verification of the MCMC cascade model.…”

“…The agreement between the calculations and the data is remarkable with our results reproducing both the energy (3.2 to 8.6 GeV) and target (Be to Pb) dependences of the data. Such result shows for the first time that the DESY [34] and SLAC [36] data for the elementary photoproduction cross sections are mutually consistent with the complex nuclei data from Cornell [29]. Figure 16 presents the differential cross sections ( dσ dt ) for carbon [ Fig.…”

“…The MCMC model, on the other hand, consists of an appropriate tool for the accurate determination of the Pauli blocking suppression factor. Equations (35) and (36) were derived using closure approximation without any specification about the photoproduction operator. The MCMC model also requires closure, since the NI amplitude for meson photoproduction from the nucleus is obtained as an incoherent sum of single nucleon amplitudes, but it is still possible to include the dynamical information for the elementary photoproduction during the evaluation of the Pauli-suppression factor.…”

“…1 and 2, respectively; where a nice agreement between the Regge model and the data is achieved. The forward-angle data included in our analysis are from DESY [34,35], SLAC [36,37], and Cornell [38]. The constructive interference between the strong and Coulomb amplitudes is highly favorable for π 0 photoproduction (F 1 → F 1 + F C ), while for η photoproduction the situation is opposite (F 1 → F 1 − F C ).…”

“…where [34] (squares) and SLAC [36] (triangles). The first data points from DESY [34] taken at θ π 0 * = 0 are omitted in our fitting due to the effects of angular resolution neglected in our analysis.…”