Corrections to the elastic proton-proton analyzing power parametrization at high energies

A A Poblaguev

doi:10.1103/physrevd.100.116017

Abstract

The HJET Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) polarimeter was designed to measure the absolute polarization of the proton beams at the Relativistic Heavy Ion Collider. In these measurements, the small scattering angle elastic $pp$ single $A_N(t)$ and double $A_{NN}(t)$ spin analyzing powers can be precisely determined. The experimental accuracy achieved at HJET requires corrections to the $A_N(t)$ parametrization, conventionally used for such studies. In this paper we evaluate the corrections to the analyzing powers due to (i) the differences between the electromagnetic and hadronic form factors and (ii) the $m_p^2/s$ terms in the elastic spin-flip $pp$ electromagnetic amplitude. The corresponding alterations of the evaluated hadronic spin-flip amplitudes are about the same as the experimental uncertainties of the HJET measurements. The proposed corrections may have implications for the elastic $pp$ forward real-to-imaginary amplitude ratios $\rho$ determined in unpolarized $pp$ experiments.

Highlights

The Polarized Atomic Hydrogen Gas Jet Target [1]polarimeter (HJET) is employed to measure the absolute polarization of proton beams at the Relativistic Heavy IonCollider (RHIC)
An update [6] for the Relativistic Heavy IonCollider (RHIC) spin program provided a parametrization of ANðs; tÞ, which was used in all previous experimental evaluations [7,8,9] of the hadronic spin-flip amplitudes in high energy near-forward elastic pp scattering
A dependence of the measured r5 on the absorptive corrections could be readily estimated if the corresponding modification of the electromagnetic form factor F emðtÞ of an elastic pp amplitude can be approximated in the Coulomb-nuclear interference (CNI) region by a linear function of t, F emðtÞ → F emðtÞ × 1⁄21 þ aðsÞt=tc: ð51Þ

Summary

INTRODUCTION

Polarimeter (HJET) is employed to measure the absolute polarization of proton beams at the Relativistic Heavy Ion. An update [6] for the RHIC spin program provided a parametrization of ANðs; tÞ, which was used in all previous experimental evaluations [7,8,9] of the hadronic spin-flip amplitudes in high energy near-forward elastic pp scattering. It was pointed out [10] that analyzing power ANðtÞ given in Ref. It was found that the discussed corrections may be important for experimental determination of the real-to-imaginary ratio ρ of the pp forward elastic scattering amplitude

PARAMETRIZATION OF THE CNI ANALYZING POWERS AT HIGH ENERGIES

ANALYZING POWER MEASUREMENTS AT HJET

CORRECTIONS TO THE ANALYZING POWERS

NUMERICAL ESTIMATES OF THE CORRECTIONS

POSSIBLE EFFECT OF THE ABSORPTIVE CORRECTION

CONCLUSIONS