Measurement of the branching ratio of π0 → e+e- using KL → 3π0 decays in flight

A. Alavi-Harati, I. F. Albuquerque, T. Alexopoulos, M. Arenton, K. Arisaka, S. Averitte, A. R. Barker, L. Bellantoni, A. Bellavance, J. Belz, R. Ben-David, D. R. Bergman, E. Blucher, G. J. Bock, C. Bown, S. Bright, E. Cheu, S. Childress, R. Coleman, M. D. CorcoranG. Corti, B. Cox, M. B. Crisler, A. R. Erwin, R. Ford, A. Golossanov, G. Graham, J. Graham, K. Hagan, E. Halkiadakis, K. Hanagaki, S. Hidaka, Y. B. Hsiung, V. Jejer, J. Jennings, D. A. Jensen, R. Kessler, H. G.E. Kobrak, J. La Due, A. Lath, A. Ledovskoy, P. L. Mc Bride, A. P. Mc Manus, P. Mikelsons, E. Monnier, T. Nakaya, U. Nauenberg, K. S. Nelson, H. Nguyen, V. O’dell, M. Pang, R. Pordes, V. Prasad, C. Qiao, B. Quinn, E. J. Ramberg, R. E. Ray, A. Roodman, M. Sadamoto, S. Schnetzer, K. Senyo, P. Shanahan, P. S. Shawhan, W. Slater, N. Solomey, S. V. Somalwar, R. L. Stone, I. Suzuki, E. C. Swallow, R. A. Swanson, S. A. Taegar, R. J. Tesarek, G. B. Thomson, P. A. Toale, A. Tripathi, R. Tschirhart, Y. W. Wah, J. Wang, H. B. White, J. Whitmore, B. Winstein, R. Winston, J. Y. Wu, T. Yamanaka, E. D. Zimmerman

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20 Scopus citations


The branching ratio of the rare decay π0 → e+e- has been measured in E799-II, a rare kaon decay experiment using the KTeV detector at Fermilab. We observed 275 candidate π0 → e+e- events, with an expected background of 21.4 ± 6.2 events which includes the contribution from Dalitz decays. We measured B[π0 → e+e-,(me+e-/mπ0)2 > 0.95] = (6.09 ± 0.40 ± 0.24) × 10-8, where the first error is statistical and the second systematic. This result is the first significant observation of the excess rate for this decay above the unitarity lower bound.

Original languageEnglish (US)
Pages (from-to)922-925
Number of pages4
JournalPhysical review letters
Issue number5
StatePublished - Jan 1 1999

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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