New measurement of the η → π0 γγ branching ratio and the slope parameter for η → 3π0 decay with the crystal ball

S. Prakhov, E. Berger, M. Clajus, A. Marušić, S. McDonald, B. M.K. Nefkens, N. Phaisangittisakul, J. W. Price, M. Pulver, A. Starostin, W. B. Tippens, D. Isenhower, M. Sadler, C. Allgower, H. Spinka, J. Comfort, K. Craig, T. Ramirez, T. Kycia, J. PetersonW. Briscoe, A. Shafi, H. M. Staudenmaier, D. M. Manley, J. Olmsted, D. Peaslee, V. Bekrenev, A. Koulbardis, N. Kozlenko, S. Kruglov, I. Lopatin, G. M. Huber, N. Knecht, G. J. Lolos, Z. Papandreou, I. Slaus, I. Supek, D. Grosnick, D. Koetke, R. Manweiler, S. Stanislaus

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


We have measured the quadratic slope parameter a for η → 3π0 decay. Our final result is α = -0.031(4). We have also obtained the branching ratio (BR) for the double radiative decay η → π0 γγ. Our preliminary result is BR(η → π0) = 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 a 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 → π0γγ is about half the current value and is in agreement with the χPTh predictions.

Original languageEnglish (US)
Pages (from-to)2238-2242
Number of pages5
JournalPhysics of Atomic Nuclei
Issue number12
StatePublished - Dec 2002
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Nuclear and High Energy Physics


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