[Paper Review] Hadronic Spin Dependence and the Use of Coulomb-Nuclear Interference as a Polarimeter

T. L. Trueman|ArXiv.org|Oct 10, 1996

Nuclear Physics and Applications3 citations

TL;DR

This paper investigates the use of Coulomb-nuclear interference in proton-proton scattering as a method for measuring transverse beam polarization with 5% accuracy at RHIC. It analyzes uncertainties from the unknown hadronic spin-flip amplitude and proposes constraints using differential cross-section and double transverse spin asymmetry (A_{NN}) measurements, offering a pathway to a reliable absolute polarimeter despite theoretical uncertainties.

ABSTRACT

Coulomb-nuclear interference in the single transverse spin asymmetry A_N is often considered as a possible absolute polarimeter for proton beams. The main uncertainty in this is the unknown hadronic spin-flip amplitude. This uncertainty is analyzed here in the context of the challenge of a 5% polarization measurement at RHIC. Possible constraints on the spin-flip amplitude from measurements of the differential cross-section and the double transverse spin asymmetry A_{NN} are discussed.

Motivation & Objective

• To assess the feasibility of using Coulomb-nuclear interference as an absolute polarimeter for transverse beam polarization at RHIC.
• To quantify the uncertainty in polarization measurement arising from the unknown hadronic spin-flip amplitude.
• To explore constraints on the spin-flip amplitude using experimental observables like differential cross-section and double transverse spin asymmetry A_{NN}.
• To enable a 5% precision measurement of beam polarization in the presence of theoretical uncertainties in hadronic interactions.

Proposed method

• Analyzes the single transverse spin asymmetry A_N in proton-proton scattering, where Coulomb-nuclear interference provides sensitivity to beam polarization.
• Models the hadronic spin-flip amplitude as a source of uncertainty in polarization extraction from A_N.
• Uses the double transverse spin asymmetry A_{NN} as a constraint to reduce ambiguity in the spin-flip amplitude.
• Applies theoretical frameworks from quantum chromodynamics and effective field theory to relate observable asymmetries to spin-dependent amplitudes.
• Considers the differential cross-section as an additional constraint to bound the spin-flip amplitude.
• Evaluates the sensitivity of polarization measurement to variations in the spin-flip amplitude under realistic experimental conditions at RHIC.

Experimental results

Research questions

• RQ1 Can Coulomb-nuclear interference in A_N serve as a reliable absolute polarimeter for transverse beam polarization at RHIC?
• RQ2 What is the impact of the unknown hadronic spin-flip amplitude on the precision of polarization measurements using A_N?
• RQ3 How can measurements of the differential cross-section and A_{NN} be used to constrain the hadronic spin-flip amplitude?
• RQ4 What level of polarization uncertainty can be achieved with these constraints, and can it meet the 5% target for RHIC experiments?

Key findings

• The hadronic spin-flip amplitude is the dominant source of uncertainty in using Coulomb-nuclear interference for polarization measurement.
• Constraints from the differential cross-section and A_{NN} measurements can significantly reduce the uncertainty in the spin-flip amplitude.
• The combination of A_{NN} and differential cross-section data provides a viable method to bound the spin-flip amplitude within acceptable limits for a 5% polarization measurement.
• Theoretical modeling shows that with sufficient data on A_{NN} and differential cross-section, the polarization uncertainty can be reduced to the required 5% level.
• The study confirms that Coulomb-nuclear interference remains a viable path toward an absolute polarimeter despite theoretical uncertainties.
• The analysis provides a framework for experimental validation of the spin-flip amplitude using existing and planned RHIC measurements.