paul scherrer institut
CH-5232 Villigen PSI, Switzerland



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The KARMEN Time Anomaly: Search for a Neutral Particle of Mass 33.9 MeV in Pion Decay

M. Daum1, M. Janousch2, P.-R. Kettle1,
J. Koglin1,3, D. Pocanic3, J. Schottmüller1,
C. Wigger1, Z. G. Zhao4

1PSI, Paul-Scherrer-Institut, CH-5232 Villigen-PSI, Switzerland
2IPP, Institut für Teilchenphysik der ETHZ , CH-5232 Villigen-PSI, Switzerland
3 Physics Department, University of Virginia, Charlottesville, Virginia 22901,USA.
4Institute of High Energy Physics, Chinese Academy of Science, Beijing 100039, The People's Republic of China


We have searched for the rare pion-decay p+ ®  m+ X where X is a neutral particle of mass 33.9 MeV, a process suggested by the KARMEN Collaboration [1] to explain an anomaly seen in their time spectrum of neutrino induced reactions. By measuring the muon momentum spectrum of charged pions decaying in flight using the pE1 high intensity pion channel at PSI, we were able to place an upper limit on the branching fraction h of such decays, at the level of h < 6.0·10-10 with a 95% confidence level.


NewHeavns PublicationsNewHeavns

Jason Koglin's Dissertation, May 2000 (postscript)
PSI Scientific Report 1998 / Volume I
Neutrino `98 Contribution
PSI Annual Report 1997 / Annex I
PSI Annual Report 1995 / Annex I
Phys. Lett. B 361 (1995) 179-183.

Related Information and Links

Publications Related to the KARMEN Anomaly
KARMEN Homepage
Information on the pE1 Beamline

Created by J. Koglin.

Last updated on 17th December 2001.
by P.-R. Kettle