Abstract

Precise measurements of transverse spin asymmetries in proton-proton elastic scattering at very small values of four-momentum transfer squared, [Formula: see text], have been performed using the Relativistic Heavy Ion Collider (RHIC) polarized proton beams. The measurements of both single and double spin asymmetries were made at the center-of-mass energy [Formula: see text] GeV and in the region [Formula: see text] [Formula: see text], which was accessed using Roman Pot devices incorporated into the STAR experimental setup. The obtained set of asymmetries is sensitive to the poorly known hadronic contribution to the spin-flip amplitudes and provide significant constraints for the theoretical descriptions of the reaction mechanism of proton-proton elastic scattering at high energies.

Highlights

  • Asymmetries and Helicity AmplitudesMeasurements of the transverse spin asymmetries AN , ANN and ASS provide important information on the spin dependence of the hadronic interactions at high energies and low momentum transfer

  • SubtractionMany stability tests were performed to proof the highest accuracy of the double spin asymmetry result

  • The Roman Pot detectors were incorporated into the STAR infrastructure giving full advantage of using other STAR subsystems for crosschecks and precise luminosity monitoring

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Summary

Asymmetries and Helicity Amplitudes

Measurements of the transverse spin asymmetries AN , ANN and ASS provide important information on the spin dependence of the hadronic interactions at high energies and low momentum transfer. Where φ+ = (φ1 + φ3)/2 is the half-sum of dominating non-spin-flip amplitudes. For each amplitude, both electromagnetic and nuclear parts should be taken into. Both electromagnetic and nuclear parts should be taken into This is an Open Access article published by World Scientific Publishing Company. To quantify the spin-dependent hadronic contributions, the relative amplitudes are introduced: r2. The relative amplitudes include main kinematic factors and their dependence on momentum transfer is usually neglected in narrow t-ranges

Experimental Setup
Single Spin Asymmetry AN
Relative Luminosity
Background
Background asymmetry
Double Spin Asymmetries
Conclusions

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