Search for cosmic-ray antideuterons

Area of Science:

• * Particle astrophysics and cosmology
• * High-energy astrophysics
• * Cosmic ray physics

Background:

• * Cosmic rays are high-energy particles originating from outer space.
• * The search for antimatter in cosmic rays, such as antideuterons, provides insights into fundamental physics and potential dark matter signals.
• * Previous experiments have limited the sensitivity for detecting rare cosmic-ray antimatter species.

Purpose of the Study:

• * To search for cosmic-ray antideuterons using a large dataset from multiple balloon flights.
• * To establish an experimental upper limit on the differential flux of cosmic-ray antideuterons.
• * To constrain theoretical models of cosmic ray propagation and particle astrophysics.

Main Methods:

• * Analysis of data collected during four BESS (Balloon borne Experiment for Solar System studies) flights between 1997 and 2000.
• * Utilized a sensitive detector system to identify and count antideuteron candidates.
• * Calculated the flux upper limit based on the absence of candidate events and detector acceptance.

Main Results:

• * No cosmic-ray antideuteron candidates were detected in the analyzed dataset.
• * An upper limit for the differential flux of cosmic-ray antideuterons was determined to be 1.9 x 10^-4 (m^2 s sr GeV/nucleon)^-1 at the 95% confidence level.
• * This limit applies to the energy range of 0.17 to 1.15 GeV/nucleon at the top of the atmosphere.

Conclusions:

• * The non-detection of antideuterons provides stringent constraints on their abundance in cosmic rays.
• * The derived flux upper limit is a significant contribution to the field, impacting models of new physics and astrophysical sources.
• * Future experiments can build upon these results to further probe the cosmic ray composition and search for exotic particles.