Inclusive Hadron Photoproduction from Longitudinally Polarized Protons and Deuterons

TL;DR

This study measures asymmetries in inclusive hadron production from polarized protons and deuterons using polarized photons, revealing small asymmetries for protons and null results for deuterons, challenging existing theoretical models.

Contribution

It provides new experimental data on hadron photoproduction asymmetries with polarized targets, highlighting discrepancies with current theoretical predictions.

Findings

Small non-zero asymmetries observed for protons

Deuteron asymmetries are consistent with zero

Data challenge recent theoretical calculations

Abstract

We report measurements of the asymmetry A_parallel for inclusive hadron production on longitudinally polarized proton and deuteron targets by circularly polarized photons. The photons were produced via internal and external bremsstrahlung from an electron beam of 48.35 GeV. Asymmetries for both positive and negative signed hadrons, and a subset of identified pions, were measured in the momentum range 10<P<30 GeV at 2.75 and 5.5 degrees. Small non-zero asymmetries are observed for the proton, while the deuteron results are consistent with zero. Recent calculations do not describe the data well.