Measurement of analyzing powers ofπ+andπ−produced on a hydrogen and a carbon target with a22−GeV/cincident polarized proton beam

Abstract

The analyzing powers of ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ were measured using an incident $22\ensuremath{-}\mathrm{GeV}/c$ transversely polarized proton beam at the Brookhaven Alternating Gradient Synchrotron. A magnetic spectrometer measured ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ inclusive asymmetries on a hydrogen and a carbon target. An elastic polarimeter with a ${\mathrm{CH}}_{2}$ target measured pp elastic-scattering asymmetries to determine the beam polarization using published data for the pp elastic analyzing power. Using the beam polarization determined from the elastic polarimeter and asymmetries from the inclusive spectrometer, analyzing powers ${A}_{N}$ for ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ were determined in the ${x}_{F}$ and ${p}_{T}$ ranges $(0.45--0.8)$ and $(0.3--1.2 \mathrm{GeV}/c),$ respectively. The analyzing power results are similar in both sign and character to other measurements at 200 and $11.7 \mathrm{GeV}/c,$ confirming the expectation that high-energy pion inclusive analyzing powers remain large and relatively energy independent. This suggests that pion inclusive polarimetry may be a suitable method for measuring future beam polarizations at BNL RHIC or DESY HERA. Analyzing powers of ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ produced on hydrogen and carbon targets are the same. Various models to explain inclusive analyzing powers are also discussed.