New results on a search for a 33.9 MeV/c2 neutral particle from π+ decay in the NOMAD experiment

P. Astier, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, M. Banner, G. Bassompierre, K. Benslama, N. Besson, I. Bird, B. Blumenfeld, F. Bobisut, J. Bouchez, S. Boyd, A. Bueno, S. Bunyatov, L. Camilleri, A. Cardini, P. W. Cattaneo, V. Cavasinni, A. Cervera-VillanuevaG. Collazuol, G. Conforto, C. Conta, M. Contalbrigo, R. Cousins, D. Daniels, H. Degaudenzi, T. Del Prete, A. De Santo, T. Dignan, L. Di Lella, E. Do Couto E Silva, J. Dumarchez, M. Ellis, T. Fazio, G. J. Feldman, R. Ferrari, D. Ferrère, V. Flaminio, M. Fraternali, J. M. Gaillard, E. Gangler, A. Geiser, D. Geppert, D. Gibin, S. N. Gninenko, A. Godley, M. C. Gonzalez-Garcia, J. J. Gomez-Cadenas, J. Gosset, C. Gößling, M. Gouanère, A. Grant, G. Graziani, A. Guglielmi, C. Hagner, J. Hernando, D. Hubbard, P. Hurst, N. Hyett, E. Iacopini, C. Joseph, F. Juget, M. M. Kirsanov, O. Klimov, J. Kokkonen, A. V. Kovzelev, N. V. Krasnikov, A. Krasnoperov, S. Lacaprara, C. Lachaud, B. Lakić, A. Lanza, L. La Rotonda, M. Laveder, A. Letessier-Selvon, J. M. Levy, L. Linssen, A. Ljubičić, J. Long, A. Lupi, A. Marchionni, F. Martelli, X. Méchain, J. P. Mendiburu, J. P. Meyer, M. Mezzetto, S. R. Mishra, G. F. Moorhead, D. Naumov, P. Nédélec, Yu Nefedov, C. Nguyen-Mau, D. Orestano, F. Pastore, L. S. Peak, E. Pennacchio, H. Pessard, R. Petti, A. Placci, G. Polesello, D. Pollmann, A. Polyarush, B. Popov, C. Poulsen, P. Rathouit, J. Rico, C. Roda, A. Rubbia, F. Salvatore, K. Schahmaneche, B. Schmidt, M. Sevior, D. Sillou, F. J.P. Soler, G. Sozzi, D. Steele, U. Stiegler, M. Stipčević, Th Stolarczyk, M. Tareb-Reyes, G. N. Taylor, V. Tereshchenko, A. N. Toropin, A. M. Touchard, S. N. Tovey, M. T. Tran, E. Tsesmelis, J. Ulrichs, L. Vacavant, M. Valdata-Nappi, V. Valuev, F. Vannucci, K. E. Varvell, M. Veltri, V. Vercesi, G. Vidal-Sitjes, J. M. Vieira, T. Vinogradova, F. V. Weber, T. Weisse, F. F. Wilson, L. J. Winton, B. D. Yabsley, H. Zaccone, K. Zuber, P. Zuccon

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10 Scopus citations


We report on a direct search in NOMAD for a new 33.9 MeV/c2 neutral particle (X) produced in pion decay in flight, π → μX followed by the decay X → ve+e-. Both decays are postulated to occur to explain the time anomaly observed by the KARMEN experiment. From the analysis of the data collected during the 1996-1998 runs with 4.1 × 1019 protons on target, a single candidate event consistent with background expectations was found. The search is sensitive to a pion branching ratio BR(π → μX) > 3.7 × 10-15, significantly smaller than previous experimental limits.

Original languageEnglish (US)
Pages (from-to)23-28
Number of pages6
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1-2
StatePublished - Feb 14 2002
Externally publishedYes


  • Neutrino decay
  • Neutrino mixing

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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