LANSCE-mQ: Dedicated search for milli/fractionally charged particles at LANL

TL;DR

LANSCE-mQ is a proposed experiment at LANSCE to detect milli/fractionally charged particles using scintillation detectors, aiming to explore fundamental questions in particle physics and cosmology with high sensitivity in the 1-300 MeV mass range.

Contribution

This paper introduces the LANSCE-mQ experiment, a novel setup using scintillation detectors and detailed simulations to search for millicharged particles at LANSCE.

Findings

Preliminary background analysis identifies neutrons and dark current signals as dominant backgrounds.

Simulations suggest LANSCE-mQ has leading sensitivity for mCP masses between 1 MeV and 300 MeV.

The experiment could significantly advance understanding of charge quantization and dark sector physics.

Abstract

In this paper, we propose an experiment, LANSCE-mQ, aiming to detect fractionally charged and millicharged particles (mCP) using an 800 MeV proton beam fixed target at the Los Alamos Neutron Science Center (LANSCE) facility. This search can shed new light on numerous fundamental questions, including charge quantization, the predictions of string theories and grand unification theories, the gauge symmetry of the Standard Model, dark sector models, and the tests of cosmic reheating. We propose to install two-layer scintillation detectors made of plastic (such as EJ-200) or CeBr3 to search for mCPs. Dedicated Geant4 detector simulations and in situ measurements have been conducted to obtain a preliminary determination of the background rate. The dominant backgrounds are beam-induced neutrons and coincident dark current signals from the photomultiplier tubes, while beam-induced gammas and cosmic muons are subdominant. We determined that LANSCE-mQ, the dedicated mCP experiment, has the leading mCP sensitivity for mass between ~ 1 MeV to 300 MeV.