Abstract
In the 2001–2002 running period of the Relativistic Heavy Ion Collider (RHIC), transversely polarized protons were accelerated to 100 GeV for the first time, with collisions at s=200 GeV. We present results from this run for single transverse-spin asymmetries for inclusive production of neutral pions, photons and neutrons of the energy region 20–100 GeV for forward and backward production for angles between 0.3 mrad and 2.2 mrad with respect to the polarized proton direction. An asymmetry of AN=(−0.090±0.006±0.009)×(1.0−0.24+0.47) was observed for forward neutron production, where the errors are statistical and systematic, and the scale error is from the beam polarization uncertainty. The forward photon and π0, and backward neutron, photon, and π0 asymmetries were consistent with zero. The large neutron asymmetry indicates a strong interference between a spin–flip amplitude, such as one pion exchange which dominates lower energy neutron production, and remaining spin–non-flip amplitudes such as reggeon exchange.
Highlights
We present results from this run for single transverse spin asymmetries for inclusive production of neutral pions, photons and neutrons of the energy region 20 – 100 GeV for forward and backward production for angles between 0.3 mrad and 2.2 mrad with respect to the polarized proton direction
The large neutron asymmetry indicates a strong interference between a spin-flip amplitude, such as one pion exchange which dominates lower energy neutron production, and remaining spin non-flip amplitudes such as Reggeon exchange
We present results from an experiment at the 12 o’clock intersection point (IP12), for the single-spin asymmetry AN for collisions of transversely polarized protons with unpolarized protons, producing very forward neutral particles
Summary
We present results from this run for single transverse spin asymmetries for inclusive production of neutral pions, photons and neutrons of the energy region 20 – 100 GeV for forward and backward production for angles between 0.3 mrad and 2.2 mrad with respect to the polarized proton direction. We present results from an experiment at the 12 o’clock intersection point (IP12), for the single-spin asymmetry AN for collisions of transversely polarized protons with unpolarized protons, producing very forward (and very backward) neutral particles. The experimental apparatus at IP12 consisted of a pair of scintillator hodoscopes placed forward and backward of the collision point that identified proton-proton collisions, and detectors placed in the very forward directions, centered on a production angle of 0◦ downstream of the RHIC DX dipole magnets, which removed produced charged particles (Fig. 1). The preshower and EMCal arrays were built from PbWO4 crystals 2.0 ×
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