Backward-angle photoproduction of $\pi^0$ mesons on the proton at $E_\gamma$ = 1.5--2.4 GeV

TL;DR

This study measures differential cross sections and photon beam asymmetries for $b0$ meson photoproduction on protons at energies 1.5 to 2.4 GeV, revealing backward-angle enhancements and angular dependencies suggestive of $u$-channel effects and high-mass resonances.

Contribution

First measurement of photon beam asymmetries at backward angles in $b0$ photoproduction, providing new insights into resonance contributions and reaction mechanisms.

Findings

Backward-angle enhancement observed above 2.0 GeV.

Strong angular dependence of asymmetries at high energies.

Energy-dependent slope of differential cross sections determined.

Abstract

Differential cross sections and photon beam asymmetries for $\pi^0$ photoproduction have been measured at $E_\gamma$ = 1.5--2.4 GeV and at the $\pi^0$ scattering angles, --1 $<$ cos$\Theta_{c.m.} <$ --0.6. The energy-dependent slope of differential cross sections for $u$-channel $\pi^0$ production has been determined. An enhancement at backward angles is found above $E_\gamma$ = 2.0 GeV. This is inferred to be due to the $u$-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 $E_\gamma >$ 2.0 GeV, which may be due to the unknown high-mass resonances.