Measurement of analyzing powers ofπ+andπ−produced on a hydrogen and a carbon target with a

Abstract

The analyzing powers of ϩ and Ϫ were measured using an incident 22-GeV/c transversely polarized proton beam at the Brookhaven Alternating Gradient Synchrotron. A magnetic spectrometer measured Ϯ inclusive asymmetries on a hydrogen and a carbon target. An elastic polarimeter with a 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 Ϯ were determined in the x F and p T ranges (0.45-0.8) and (0.3-1.2 GeV/c), respectively. The analyzing power results are similar in both sign and character to other measurements at 200 and 11.7 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 ϩ and Ϫ produced on hydrogen and carbon targets are the same. Various models to explain inclusive analyzing powers are also discussed.

Nuclear Dependence of the Transverse Single-Spin Asymmetry in the Production of Charged Hadrons at Forward Rapidity in Polarized p+p , p+Al , and Aidala1, Akiba2, Alfred3 et al. 2019Phys. Rev. Lett.Self Cite

“…The first observations in pion production at large Feynmanx (x F ) [1] showed measured TSSAs that were considerably larger than early theoretical predictions (in collinear leading twist approach) [2]. Surprisingly large measured TSSAs continued to persist in hadronic collisions at high energies up to √ s = 500 GeV [3][4][5][6][7][8][9][10][11][12][13][14]. To explain these large TSSAs, two approaches were proposed within perturbative quantum chromodynamics (pQCD).…”

Cross section and transverse single-spin asymmetry of muons from open heavy-flavor decays in polarized p+p collisions at s=200 GeV

“…These results surprised the quantum-chromodynamics (QCD) community because they disagreed with the expectation from the naive perturbative QCD of very small spin asymmetries [2]. The large TSSA of pion production has been subsequently observed in hadronic collisions over a range of energies extending up to √ s = 500 GeV for π 0 ( √ s = 200 GeV for π ± ) [3][4][5][6][7][8][9][10][11][12]. Furthermore, TSSA in η meson production has also been studied at forward rapidity [13,14].…”

Twist-3 effect from the longitudinally polarized proton for A in hadron production from pp collisions

“…Well-known examples are the experimental observation of hyperons with large transverse polarization produced in unpolarized proton-proton collision, pp → Λ ↑ X [1][2][3][4][5], and the transverse single-spin (or left-right) asymmetry (SSA) A N of a produced hadron in the collision between a transversely polarized proton and an unpolarized proton, p ↑ p → h X (h = π, K, η, etc.) [6][7][8][9][10][11][12][13][14][15][16]. The magnitude of the asymmetries were as large as a few tens of percent in the forward direction.…”