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Single Spin Asymmetry $A_N$ in Polarized Proton-Proton Elastic Scattering at $\sqrt{s}=200$ GeV

The collaboration
Phys.Lett.B 719 (2013) 62-69, 2013.

Abstract
We report a high precision measurement of the transverse single spin asymmetry $A_N$ at the center of mass energy $\sqrt{s}=200$ GeV in elastic proton-proton scattering by the STAR experiment at RHIC. The $A_N$ was measured in the four-momentum transfer squared $t$ range $0.003 \leqslant |t| \leqslant 0.035$ $\GeVcSq$, the region of a significant interference between the electromagnetic and hadronic scattering amplitudes. The measured values of $A_N$ and its $t$-dependence are consistent with a vanishing hadronic spin-flip amplitude, thus providing strong constraints on the ratio of the single spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated by the Pomeron amplitude at this $\sqrt{s}$, we conclude that this measurement addresses the question about the presence of a hadronic spin flip due to the Pomeron exchange in polarized proton-proton elastic scattering.

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Data from Figure 3

10.17182/hepdata.102952.v1/t1

The asymmetry $\varepsilon(\varphi)/(P_B + P_Y)$ for various $t$-intervals.

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Data from Figure 4

10.17182/hepdata.102952.v1/t2

The measured single spin asymmetry $A_N$ for five $-t$ intervals.

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Data from Figure 5

10.17182/hepdata.102952.v1/t3

Fitted value of $r_5$.