A Measurement of Atomic X-ray Yields in Exotic Atoms and Implications for an Antideuteron-Based Dark Matter Search

TL;DR

This paper measures atomic X-ray yields in exotic atoms relevant for GAPS, a novel dark matter detection method using antideuterons, and develops a cascade model to predict yields for various materials, enhancing detection sensitivity.

Contribution

It provides the first precise measurements of X-ray yields in antiprotonic exotic atoms and introduces a comprehensive cascade model applicable to any exotic atom and target material.

Findings

X-ray yields for Al and S targets are approximately 75%.

The cascade model accurately predicts X-ray yields and is validated against experimental data.

Predicted antideuteron X-ray yields suggest GAPS has high sensitivity for dark matter detection.

Abstract

The General AntiParticle Spectrometer (GAPS) is a novel approach for the indirect dark matter search that exploits cosmic antideuterons. GAPS utilizes a distinctive detection method using atomic X-rays and charged particles from the exotic atom as well as the timing, stopping range and dE/dX energy deposit of the incoming particle, which provides excellent antideuteron identification. In anticipation of a future balloon experiment, an accelerator test was conducted in 2004 and 2005 at KEK, Japan, in order to prove the concept and to precisely measure the X-ray yields of antiprotonic exotic atoms formed with different target materials [1]. The X-ray yields of the exotic atoms with Al and S targets were obtained as ~ 75%, which are higher than were previously assumed in [2]. A simple, but comprehensive cascade model has been developed not only to evaluate the measurement results but also to predict the X-ray yields of the exotic atoms formed with any materials in the GAPS instrument. The cascade model is extendable to any kind of exotic atom (any negatively charged cascading particles with any target materials), and it was compared and validated with other experimental data and cascade models for muonic and antiprotonic exotic atoms. The X-ray yields of the antideuteronic exotic atoms are predicted with a simple cascade model and the sensitivity for the GAPS antideuteron search was estimated for the proposed long duration balloon program [3], which suggests that GAPS has a strong potential to detect antideuterons as a dark matter signature. A GAPS prototype flight (pGAPS) was launched successfully from the JAXA/ISAS balloon facility in Hokkaido, Japan in summer 2012 [4, 5] and a proposed GAPS science flight is to fly from Antarctica in the austral summer of 2017-2018.