Direct search for orthopositronium decay into two photons
- Department of Physics, Faculty of Science, University of Tokyo, Tokyo 113, Japan (JP)
We have performed the first direct search for orthopositronium decay into two photons in order to determine if this decay, forbidden by space-rotational invariance, is the cause of the reported discrepancy in the orthopositronium decay rate. A high-resolution measurement of the photon-energy spectrum by a germanium detector was used to discriminate the expected sharp peak of the two-photon decay from the broader peak of the pickoff annihilations, the magnitude of which was minimized by selecting a target of low-density silica powder and by placing it in vacuum. No evidence of such decay is observed, resulting in an upper limit on the branching ratio of 3.5{times}10{sup {minus}4}, a factor of 6 below the level that could explain the decay-rate discrepancy.
- OSTI ID:
- 5865598
- Journal Information:
- Physical Review Letters; (USA), Journal Name: Physical Review Letters; (USA) Vol. 66:10; ISSN PRLTA; ISSN 0031-9007
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Positronium
Muonium
& Muonic & Mesic Atoms & Molecules
645400 -- High Energy Physics-- Field Theory
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
74 ATOMIC AND MOLECULAR PHYSICS
ANNIHILATION
BASIC INTERACTIONS
DATA
ELECTRODYNAMICS
ELECTROMAGNETIC INTERACTIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
EXPERIMENTAL DATA
FIELD THEORIES
GAMMA RADIATION
GERMANIUM
INFORMATION
INTERACTIONS
IONIZING RADIATIONS
MASSLESS PARTICLES
MEASURING INSTRUMENTS
METALS
MULTI-PHOTON PROCESSES
NUMERICAL DATA
PHOTONS
POSITRONIUM
QUANTUM ELECTRODYNAMICS
QUANTUM FIELD THEORY
RADIATION DETECTORS
RADIATIONS
RESOLUTION
SEMICONDUCTOR DETECTORS
TESTING
VACUUM SYSTEMS