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CHRETIEN 1962

Chretien, M. et al.
Evidence for Spin Zero of the η from the Two Gamma-Ray Decay Mode
Phys. Rev. Lett. 9 (1962) 127;

Motivation
Recent experiments by Pevsner et al. (Phys. Rev. Lett. 7 (1961) 421) and others (Bastien et al., Phys. Rev. Lett 8 (1962) 114) report the existence of a mass 546 MeV particle (called the η) which has both charged and neutral modes of decay. The charged mode of decay is η → π⁺ π^– π^o. Present experimental evidence assigns isotopic-spin zero to this particle.
The original work was done in the reaction π⁺ d → p p η.(1) The proton in the deuteron plays a spectator role, hence the primary reaction is π⁺ n → p η. The cross section reported for the charged mode of decay of the η is 0.22 ± 0.06 mb and the cross section measured for the neutral modes of decay is 0.8 ± 0.2 mb. The experiment of reference 4 reports a flat plateau for the cross section in the region from 1700-1850 MeV, total energy in the center-of-mass system. The experiment reported here makes use of the reaction π^– p → n η.(2) From charge symmetry, reaction (2) will have the same cross section as reaction (1) at the same energy. This experiment covers an energy band from 1707-1740 MeV and thus one expects a production cross section for the η of about 1 mb. (Extracted from the introductory part of the paper.).

Accelerator BNL-COSMOTRON Detectors HLBC-50LIT

Related references
Analyse data from
A. Pevsner et al., Phys. Rev. Lett. 7 (1961) 421;
D. D. Carmony, A. H. Rosenfeld, and R. T. van de Walle, Phys. Rev. Lett. 8 (1962) 117;
P. Bastien et al., Phys. Rev. Lett. 8 (1962) 114;

Reactions

	π– p n 2γ	1140 MeV (Plab)	mass
	π– p n η	1140 MeV (Plab)	cs
	η 2γ

Particles studied

η

qn

Record comments
Confirmation of the existence and evidence for spin zero of the η meson.

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