Probing the Pomeron spin structure with Coulomb-nuclear interference

Abstract

Polarized pp elastic scattering at small angles in the Coulomb-nuclear interference (CNI) region offers a unique opportunity to study the spin structure of the Pomeron. Electromagnetic effects in elastic amplitude can be equivalently treated either as Coulomb corrections to the hadronic amplitude (Coulomb phase), or as absorption corrections to the Coulomb scattering amplitude. We perform the first calculation of the Coulomb phase for the spin-flip amplitude and found it significantly exceeding the widely used non-flip Coulomb phase. The alternative description in terms of absorption corrections, though equivalent, turned out to be a more adequate approach for the Coulomb corrected spin-flip amplitude. Inspired by the recent high statistics measurements of single-spin asymmetry in the fixed-target HJET experiment at the BNL, we also performed a Regge analysis of data, aiming at disentangling the Pomeron contribution. However, in spite of an exceptional accuracy of the data, they do not allow to single out the Pomeron term, which strongly correlates with the major sub-leading Reggeons. A stable solution can be accessed only by making additional ad hoc assumptions, e.g. assuming the Pomeron to be a simple Regge pole, or fixing some unknown parameters. Otherwise, in addition to the STAR data at $\sqrt{s}=$200 GeV new measurements, say at 100 GeV or 500 GeV, could become decisive.

arXiv comment18 pages, 3 figures, version published in Phys. Lett. B

References in corpus (9)

• The spin dependence of high energy proton scattering
• Nonperturbative Gluon Radiation and Energy Dependence of Elastic Scattering
• Soft QCD Dynamics of Elastic Scattering in Impact Parameter Representation
• Single Spin Asymmetry $A_N$ in Polarized Proton-Proton Elastic Scattering at $\sqrt{s}=200$ GeV
• The Coulomb Phase Revisited
• Measurements of Single Diffraction at sqrt(s) = 630 GeV; Evidence for a Non-Linear alpha(t) of the Pomeron
• Polarized Proton Nucleus Scattering
• Precision Small Scattering Angle Measurements of Elastic Proton-Proton Single and Double Spin Analyzing Powers at the RHIC Hydrogen Jet Polarimeter
• Energy Dependence of the Pomeron Spin-Flip

Cited by in corpus (4)

• Coulomb phase corrections to the transverse analyzing power $A_N(t)$ in high energy forward proton-proton scattering
• Feasibility study for precisely measuring the EIC ${}^3$He beam polarization with the Polarized Atomic Hydrogen Gas Jet Target polarimeter at RHIC
• Polarization Measurements of $p^{\uparrow }$ and ${}^3$He${}^{\uparrow }$ Beams at RHIC and Future EIC Using the Polarized Atomic Hydrogen Gas Jet Target
• Absorptive corrections to the electromagnetic form factor in high-energy elastic proton-proton scattering