# Measurements of Single and Double Spin Asymmetry in \textit{pp} Elastic Scattering in the CNI Region with Polarized Hydrogen Gas Jet Target

## TL;DR

This paper reports precise measurements of single and double spin asymmetries in proton-proton elastic scattering using a polarized hydrogen gas jet target at RHIC, providing new constraints on hadronic spin-flip amplitudes.

## Contribution

It introduces the first measurement of double spin asymmetry $A_{NN}$ in the CNI region at these energies, enhancing understanding of spin effects in elastic scattering.

## Key findings

- Measured $A_N$ and $A_{NN}$ in the CNI region at 24 and 100 GeV/$c$
- Provided constraints on hadronic spin-flip amplitudes
- Achieved first $A_{NN}$ measurement in this kinematic region

## Abstract

Precise measurements of the single spin asymmetry, $A_N$ and the double spin asymmetry, $A_{NN}$, in proton-proton (\textit{pp}) elastic scattering in the region of four-momentum transfer squared $0.001 < -t < 0.032 ({\rm GeV}/c)^2$ have been performed using a polarized atomic hydrogen gas jet target and the RHIC polarized proton beam at 24 GeV/$c$ and 100 GeV/$c$. The polarized gaseous proton target allowed us to achieve the measurement of $A_{NN}$ in the CNI region for the first time. Our results of $A_N$ and $A_{NN}$ provide significant constraints to determine the magnitude of poorly known hadronic single and double spin-flip amplitudes at this energy.