eRHIC Design Study: An Electron-Ion Collider at BNL

This document presents BNLs plan for an electron-ion collider, eRHIC, a major new research tool that builds on the existing RHIC facility to advance the long-term vision for Nuclear Physics to discover and understand the emergent phenomena of Quantum Chromodynamics (QCD), the fundamental theory of the strong interaction that binds the atomic nucleus. We describe the scientific requirements for such a facility, following up on the community-wide 2012 white paper, Electron-Ion Collider: the Next QCD Frontier, and present a design concept that incorporates new, innovative accelerator techniques to provide a cost-effective upgrade of RHIC with polarized electron beams colliding with the full array of RHIC hadron beams. The new facility will deliver electron-nucleon luminosity of 10^33-10^34 cm-1sec-1 for collisions of 15.9 GeV polarized electrons on either 250 GeV polarized protons or 100 GeV/u heavy ion beams. The facility will also be capable of providing an electron beam energy of 21.2 GeV, at reduced luminosity. We discuss the on-going R&D effort to realize the project, and present key detector requirements and design ideas for an experimental program capable of making the golden measurements called for in the EIC White Paper.

Beam-helicity asymmetry in associated electroproduction of real photons $ep to egamma pi N$ in the $Delta$-resonance region

The beam-helicity asymmetry in associated electroproduction of real photons, $epto egamma pi N$, in the $Delta$(1232)-resonance region is measured using the longitudinally polarized HERA positron beam and an unpolarized hydrogen target. Azimuthal Fourier amplitudes of this asymmetry are extracted separately for two channels, $epto egamma pi^0 p$ and $epto egamma pi^+ n$, from a data set collected with a recoil detector. All asymmetry amplitudes are found to be consistent with zero.

The RHIC Spin Program: Achievements and Future Opportunities

This document summarizes recent achievements of the RHIC spin program and their impact on our understanding of the nucleons spin structure, i.e. the individual parton (quark and gluon) contributions to the helicity structure of the nucleon and to understand the origin of the transverse spin phenomena. Open questions are identified and a suite of future measurements with polarized beams at RHIC to address them is laid out. Machine and detector requirements and upgrades are briefly discussed.