EIC/EPIC ZDC development with NP-HEP cooperation in Japan

Forward nucleon and spectator tagging in ep/eA scattering is a detector system playing crucial role in the EIC physics program. The ePIC detector will be equipped with three forward detectors: the Roman Pot and off-momentum tagger for tracking fast charged particles, the large-acceptance tracking and EMCAL detector in front of the first accelerator “B0” magnet for measuring large-angle spectators, and the Zero-Degree Calorimeter (ZDC) for measuring neutrals. The ZDC measures very forward neutrons produced in ep collisions for understanding the forward baryon production mechanism such as one-pion exchange, as well to tag spectator neutrons in eA collisions. It also tags photons, either from π⁰’s to measure the forward meson yield and also to veto incoherent eA scattering through gamma emission from the deexcitation of nuclei.

The ZDC is required to measure the energy and position of photons and neutrons in high precision in order to achieve these goals. Challenges are: high resolution measurement of photons of as low as 100 MeV; and very high radiation dose during the highest luminosity operation for several years. To cope with them, the ZDC is divided into three parts. The first layer consists of crystal scintillators for measuring low-energy photons with good resolution. The second part is highly granular silicon-pad sandwich calorimeter, serving for the second EM section and the first the hadronic calorimeter, to provide very good position resolution and immunity to high radiation field at the hadron shower maximum. The last section, the second half of the HadCal, is based on plastic scintillator sandwich. Alternative options are being considered for cost reduction.

The ZDC development is being performed by a joint effort of NP and HEP researchers worldwide, including Asian countries and Japan. This talk reviews the physics at EIC with ZDC that are of common interest to both NP and HEP communities and present the status of the development.