Abstract
We have measured the quadratic slope parameter α for η → 3π 0 decay. Our final result is α=−0.031(4). We have also obtained the branching ratio (BR) for the double radiative decay η → π 0 γγ. Our preliminary result is BR(η → π 0 γγ=3.2(9)×10−4. These new measurements were performed using the recent (1998) high-statistics sample of 1.9 × 107 η produced at the AGS at BNL in π − p → nη close to threshold. The η decay into neutrals was detected with the Crystal Ball multiphoton spectrometer. Both measurements provide important tests of chiral perturbation theory (χPTh). Our result for α is four times more precise than the present world data and disagrees with current χPTh calculations by about four standard deviations. Our branching ratio for η → π 0 γγ is about half the current value and is in agreement with the χPTh predictions.
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From Yadernaya Fizika, Vol. 65, No. 12, 2002, pp. 2300–2304.
Original English Text Copyright © 2002 by Prakhov.
The author represents the Crystal Ball Collaboration
This article was submitted by the author in English.
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Prakhov, S. New measurement of the η → π 0 γγ branching ratio and the slope parameter for η → 3π 0 decay with the crystal ball. Phys. Atom. Nuclei 65, 2238–2242 (2002). https://doi.org/10.1134/1.1530307
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DOI: https://doi.org/10.1134/1.1530307