Search for sub-millicharged particles at J-PARC
Jeong Hwa Kim, In Sung Hwang, Jae Hyeok Yoo
Abstract
A bstract We studied the feasibility of an experiment searching for sub-millicharged particles ( χ s) using 30 GeV proton fixed-target collisions at J-PARC. The detector is composed of two layers of stacked scintillator bars and PMTs and is proposed to be installed 280 m from the target. The main background is a random coincidence between two layers due to dark counts in PMTs, which can be reduced to a negligible level using the timing of the proton beam. With N POT = 10 22 which corresponds to running the experiment for three years, the experiment provides sensitivity to χ s with the charge down to 5 × 10 − 5 in m χ < 0 . 2 GeV / c 2 and 8 × 10 − 4 in m χ < 1 . 6 GeV / c 2 . This is the regime largely uncovered by previous experiments. We also explored a few detector designs to achieve optimal sensitivity to χ s. The photoelectron yield is the main driver, but the sensitivity does not have a strong dependence on detector configuration in the sub-millicharge regime.