Search for fractionally charged particles as lightly ionizing particles using public data from an underground direct detection experiment

TL;DR

This study searches for fractionally charged particles using underground electron recoil data from XENON-nT, setting new limits on their charge, mass, and flux, and advancing the field of lightly ionizing particle detection.

Contribution

It provides the first direct detection constraints on relativistic FCPs from supernova shocks and sets new, more stringent limits across a wide parameter space compared to previous experiments.

Findings

Excluded FCP charge range from 3.6×10^{-9}e to 1.0×10^{-2}e for masses 1 keV–556 GeV.

Set the most stringent flux limits for FCPs across a broad parameter space.

Achieved limits far surpass previous results in underground direct detection experiments.

Abstract

Approximately 60 years after the Milligan oil drop experiment in 1909, fractionally charged particles (FCPs) were reported to have been discovered in air-shower cores, and the search for FCPs continues to the present day in space, terrestrial and underground experiments. In this letter, relativistic FCPs are examined as lightly ionizing particles in underground direct detection on the basis of electron recoil data from XENON-nT. For FCPs from supernova shocks, the best results are obtained via direct detection, excluding the FCP charge of $\left(3.6\times10^{-9} - 1.0\times10^{-2}\right)\cdot e$ corresponding to an FCP mass of 1 keV--556 GeV. For FCPs from general sources, the best limit is achieved, which is far ahead of other results in almost the entire parameter space, by excluding the FCP flux of $\left(4.0\times10^{-4} - 4.0\times10^{-16}\right)$ cm$^{-2}\cdot$ s$^{-1}\cdot$ sr$^{-1}$ corresponding to the FCP charge of $\left(1\times10^{-6} - 1\right)\cdot e$.