Direct measurement of the branching ratio for the decay of the {eta} meson into two photons
- TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3
The first direct, precision measurement of the branching ratio for the decay of the {eta} meson into two photons, {ital B}({eta}{implies}{gamma}{gamma}){identical_to}{gamma}({eta}{implies}{gamma}{gamma})/{gamma}{sub t}{sub o}{sub t}({eta}), is presented. The systematic undertainties are quite different than in previous indirect measurements. Using the SATURNE II proton beam and a liquid-deuterium target, the {eta} mesons were produced in the reaction {ital pd}{implies}{sup 3}He {eta} at 1.5 MeV above threshold, and tagged by the detection of the recoil {sup 3}He in the magnetic spectrometer SPES2. The two decay photons were detected in two BGO electromagnetic calorimeters located at 65{degree} left and right of the beam axis. A lead collimator placed in front of the right calorimeter defined the detector acceptance. The analysis yielded {ital B}({eta}{implies}{gamma}{gamma})=0.3949{plus_minus}0.0017(stat){plus_minus}0.0 30(syst). {copyright} {ital 1995 The American Physical Society.}
- OSTI ID:
- 254920
- Journal Information:
- Physical Review, D, Journal Name: Physical Review, D Journal Issue: 1 Vol. 53; ISSN PRVDAQ; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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