Backward single-pion production in the $\boldsymbol{pd\rightarrow {}^3\textrm{He}\,\pi^0}$ reaction with WASA-at-COSY

TL;DR

This paper reports new measurements of neutral pion production in the $pd ightarrow{}^3 extrm{He}\, extrm{pi}^0$ reaction at specific proton beam momenta, revealing detailed angular distributions and their evolution with energy, extending previous collinear data.

Contribution

It provides the first detailed differential cross sections for this reaction over a wide angular range at these energies, significantly expanding existing data beyond collinear kinematics.

Findings

Significant changes in angular distributions with small beam momentum variations.

Extension of data to large fractions of the backward hemisphere.

New insights into pion production mechanisms above threshold.

Abstract

New data on the production of single neutral pions in the $pd\rightarrow{}^3\textrm{He}\,\pi^0$ reaction are presented. For fifteen proton beam momenta between $p_p=1.60\;\textrm{GeV}/c$ and $p_p=1.74\;\textrm{GeV}/c$, differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.