The concept of colliding an intense 10 GeV electron beam with the hadron beams circulating in RHIC has been designated as e-RHIC. Such a facility would allow the investigation of e-A collisions at center of mass (COM) energies up to 63 GeV, more than a factor of two higher than at any previous facility. As the electron beam is to be polarized, collisions with polarized protons occur at COM energies up to 100 GeV; more than a factor of three higher than the SMC measurements. Thus values of x as low as 3x10-4 and 10-4 respectively can be investigated with Q2 greater than 1 GeV. In the case of e-A collisions, the low-x gluon distributions can be investigated with the possibility of observing saturation. In the case of polarized e on polarized p, the gluon spin can be measured down to x of 10-3. The e-e' virtual photon fluctuates into (q-qbar) pairs, creating a strongly interacting system of variable but known transverse size, determined by the momentum transfer (Q). The combined range in x, Q2, and A that can be achieved at e-RHIC is unprecedented. Further, the collider mode offers ready access to the final state of the nuclear target, a feature effectively unrealizable in fixed target experiments. Providing the desired luminosity of 1033 e-nucleon/cm2s is challenging, as is its integration into the RHIC program. An electron-hadron collider would greatly enhance our knowledge of QCD in both the perturbative and non-pertubative regimes of strong interactions. It is an essential element in the complement of facilities required by nuclear scientists for the investigation of strongly interacting matter at COM energies up to several hundred GeV.
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