Jul 6 – 13, 2022
Bologna, Italy
Europe/Rome timezone

Search for sub-millicharged particles at J-PARC

Jul 7, 2022, 11:15 AM
Room 10 (Magenta B)

Room 10 (Magenta B)

Parallel Talk Beyond the Standard Model Beyond the Standard Model


Hoyong Jeong (Korea University)


Electric charge quantization is a long-standing question in particle physics. While fractionally charged particles (millicharged particles hereafter) have typically been thought to preclude the possibility of Grand Unified Theories (GUTs), well-motivated dark-sector models have been proposed to predict the existence of millicharged particles while preserving the possibility for unification. Such models can contain a rich internal structure, providing candidate particles for dark matter. A number of experiments have searched for millicharged particles ($\chi$s), but in the parameter space of the charge ($Q$) and mass ($m_\chi$), the region of $m_\chi > 0.1$ GeV/$\rm{c}^2$ and $Q < 10^{−3}e$ is largely unexplored.

SUB-Millicharge ExperimenT (SUBMET) has been proposed to search for sub-
millicharged particles 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 expected to be a random coincidence between the two layers due to dark counts in PMTs, which can be reduced significantly using the timing of the proton beam. With $\rm{N}_\rm{POT} = 5 × 10^{21}$, the experiment provides sensitivity to χs with the charge down to $7\times10^{−5}e$ in $m_\chi < 0.2$ GeV/$\rm{c}^2$ and $10^{-3}e$ in $m_\chi < 1.6$ GeV/$\rm{c}^2$. This is the regime largely uncovered by the previous experiments.

In-person participation Yes

Primary author

Hoyong Jeong (Korea University)


Jae Hyeok Yoo (Korea University (KR))

Presentation materials