### Session J2: A High Luminosity Lepton Ion Collider to Study QCD

 Sunday, April 23, 2006 1:15PM - 1:51PM J2.00001: Design Considerations for a High Luminosity Lepton Ion Collider Invited Speaker: Manouchehr Farkhondeh Studies are underway in the US to design a lepton-ion collider (EIC) with high luminosity (10$^{-33}$ cm$^{-2}$s$^{-1})^{ }$and high center-of- mass energy centered around the existing nuclear physics accelerators at either BNL or Jefferson Lab. EIC will be optimized for studying of the formation and structure of hadrons in terms of their quark and gluon constituents. For the RHIC-based collider, eRHIC, two options are under consideration, a more mature option based on a ring-ring concept with e$^{-}$/e$^{+}$-p and e$^{-}$/e$^{+ }$-A collisions and a more ambitious design with a linac-ring architecture. Ions from the existing RHIC hadron ring will collide with 5-10 GeV electrons or positrons, either from a new electron/positron storage ring or a very high current cw electron linac. In both options, high current electron bunches in the polarized injector must be precisely synchronized with proton or ion bunches in the RHIC ring. The stacking option in the ring-ring design considerably reduces the required bunch charge from the polarized source. The polarized source requirements for the eRHIC linac-ring design are very demanding requiring sources capable of producing highly polarized cw currents of 200-300 mA. Another more futuristic option for Electron Ion Collider is being considered at Jefferson Lab (ELIC) based on the existing CEBAF superconducting linac, a new circulating electron ring and a hadron ring. The circulating figure-8 electron ring in this concept is intended to reduce the demanding high current injected polarized beam from the linac. In this paper, we present for the two options of eRHIC, the design considerations and requirements, and machine and polarized source parameters. The design considerations and machine parameters for ELIC will also be presented in this paper. Sunday, April 23, 2006 1:51PM - 2:27PM J2.00002: Study of spin structure of the nucleon using a lepton-ion collider Invited Speaker: Abhat Deshpande Construction of a high intensity, high energy polarized lepton beam facility to collide with the polarized proton beams of the existing Relativistic Heavy Ion Collider (RHIC), will allow polarized deep inelastic scattering off protons up to center of mass energies of $\sim$ 100 GeV. The physics potential of such a facility have been studied in various workshops over the years, and will be summarized in this talk. We show that several important and unique measurements in spin physics could only be possible using this facility, eRHIC. They include the spin structure function $g_{1}(x,Q^{2})$ of the proton at low x, precision measurement of the polarized gluon distribution through multiple processes such scaling violations, di-jet production over a large $x$ range, heavy quark and anti-quark flavor distributions using measurement of parity violating spin structure functions $g_{5}(x,Q^{2})$, parton distributions of the polarized photons and many more. Bjorken spin sum rule, one of the the most fundamental spin sum rules in QCD could also be addressed with unprecedented precision with eRHIC if the polarized 3He++ could accelerated and stored in the RHIC. As such eRHIC promises extremely significant leaps in our understanding of the nucleon spin structure and of QCD, complementary and often beyond what is possible with RHIC spin and the present fixed target polarized DIS experiments at CERN, DESY and Jlab. Sunday, April 23, 2006 2:27PM - 3:03PM J2.00003: The glue that binds us all: probing gluonic matter with an electron-ion collider Invited Speaker: Raju Venugopalan Very little is known about the gluonic content of nuclear matter. Answering this question is crucial to our picture of hadron and nuclear collisions at high energies. We discuss some ideas about the nature of gluonic matter and how these can be tested at a future electron-ion collider.