Afterpulse prediction for SUBMET experiment

TL;DR

This paper presents a method to predict afterpulse rates in the SUBMET experiment's detector, improving background understanding in searches for millicharged particles by accurately modeling delayed photomultiplier tube signals.

Contribution

The paper introduces a measurable-parameter-based prediction method for PMT afterpulses, enhancing background modeling in particle detection experiments.

Findings

Prediction reproduces observed afterpulse rates within 20% accuracy.

Method improves background estimation for millicharged particle searches.

Enhanced understanding of PMT afterpulses in scintillator detectors.

Abstract

The SUB-Millicharge ExperimenT (SUBMET) investigates an unexplored parameter space of millicharged particles with mass $m_\chi < $ 1.6 GeV/c$^2$ and charge $Q_\chi < 10^{-3}e$. The detector consists of an Eljen-200 plastic scintillator coupled to a Hamamatsu Photonics R7725 photomultiplier tube (PMT). PMT afterpulses, delayed pulses produced after an energetic pulse, have been observed in the SUBMET readout system, especially following primary pulses with a large area. We present a prediction method for afterpulse rates based on measurable parameters, which reproduces the observed rate with approximately 20\% precision. This approach enables a better understanding of afterpulse contributions and, consequently, improves the reliability of background predictions.