LBNL, Livermore, Los Alamos and four University of California campuses – Davis, Riverside, UCLA and UC Berkeley – have joined together to form the EIC “California Coalition,” banding together to pursue several specific physics and detector topics. The coalition has had several in-person meetings to find common ground, and recently, received funding from the University of California Office of the President (UCOP) to cement this multi-institution initiative.

The coalition is focusing on three physics topics – jets in ep/eA collisions, polarized proton parton distributions, and vector meson photo & electroproduction. The jet work builds on studies done at STAR and ALICE, where jet energy loss in hot and cold nuclear matter is of great interest; the nucleon spin work follows polarized parton studies with the STAR detector; and the vector meson studies follow naturally from current work on ultra-peripheral collisions at RHIC and the LHC.

Figure 1. An Υ->ee event from the eSTARlight Monte Carlo in the simulated silicon detector. Each red dot is a hit in one of the silicon barrel layers, which are not shown here; the forward and backward disks are shown.

One common feature of these reactions is that they rely on charged-particle tracking. Accordingly, the group has chosen as a hardware focus a large-acceptance silicon tracking detector, which will likely have a central barrel, plus forward and backward disks. Figure 1 shows one possible arrangement, showing an Υ(1S)->ee event from the eSTARlight Monte Carlo in the simulated detector. The technology flows from the Monolithic Active Pixel Detector (MAPS) sensors developed for the STAR (at RHIC) Heavy Flavor Tracker (HFT) and ALICE (at the LHC) Inner Tracking System (ITS). Improvements in both chip and overall detector design are being actively studied; some of this work will be in cooperation with the effort within the ALICE Collaboration to develop a replacement for the two inner ITS layers, with improved performance, and, critically, a smaller material budget.

This work has naturally led to a heavy involvement in the nascent EIC “Yellow Report,” with group members becoming co-convenors for several of the working groups: Ernst Sichtermann (jets, heavy quarks), Spencer Klein (exclusive, diffractive and forward tagging) and Leo Greiner (tracking including vertexing). These efforts should position California to play key roles in an EIC detector.