Measurement of charge symmetry breaking by the comparison of π+d→pp η with π̄ d→ nn η

W. B. Tippens, V. Abaev, M. Batinic, V. Bekieiiev, W. J. Briscoe, R. E. Chrien, M. Clajus, D. Isenhower, N. Kozlenko, S. Kruglov, M. J. Leitch, A. Manisic, T. Moriwaki, T. Morrison, B. M.K. Nefkens, J. C. Peng, P. H. Pile, J. W. Price, D. Rigsby, M. E. SadlerR. Sawafta, I. Slaus, H. Seyfarth, A. Starostin, I. Supek, R. J. Sutler, A. Svarc, D. B. White

Research output: Contribution to journalArticlepeer-review


We report a measurement of charge symmetry breaking in the NN η system. We have measured the ratio of the differential cross sections of the charge-symmetric reactions π+d→ nn η and π-d →+nn η in the energy region of the η threshold. Our result is R=dδ(π+d-→ppη)/dδ(π-nn η)= 0.938±0.009 after a phasespace correction is made for the difference in the threshold energies of the two reactions. The deviation of R from unity is an indication of charge symmetry breaking, which is mostly due to ir°- ij mixing. A theoretical model for 77 production which includes 77°- -q mixing was used to fit the data and yields a mixing angle of (1.5±0.4)°. Our result is consistent with the mixing angle determined in particle decay and isospin-forbidden processes as well as predictions by several theoretical analyses which yield = 1 °and another which yields ≈2°.

Original languageEnglish (US)
Article number052001
Number of pages1
JournalPhysical Review D
Issue number5
StatePublished - 2001
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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