Author/Authors :
KARMEN Collaboration، نويسنده , , B. Armbruster، نويسنده , , I. Blair، نويسنده , , B.A. Bodmann، نويسنده , , N.E. Booth، نويسنده , , G. Drexlin، نويسنده , , V. Eberhard، نويسنده , , J.A. Edgington، نويسنده , , K. Eitel، نويسنده , , E. Finckh، نويسنده , , H. Gemmeke، نويسنده , , J. H??l، نويسنده , , T. Jannakos، نويسنده , , M. Kleifges، نويسنده , , J. Kleinfeller، نويسنده , , W. Kretschmer، نويسنده , , R. Maschuw، نويسنده , , P. Plischke، نويسنده , , J. Rapp، نويسنده , , B. Seligmann، نويسنده , , et al.، نويسنده ,
Abstract :
Analysis of the charged and neutral current reactions 12C(νe, e−) 12N and 12C(ν, ν′) 12C∗ induced by neutrinos from π+- and μ+-decays at rest reveals an anomaly in the time distribution after all π+ have decayed: the measured time constant for subsequent events differs substantially from the value of 2.2 μs corresponding to the μ+ lifetime. This anomaly cannot currently be explained by background processes or errors in the experimental set-up. A satisfactory description of the time spectrum is achieved by assuming it has two components, one exponential with a 2.2 μs time constant, the other a Gaussian signal of 83±28 events at 3.6 μs after beam-on-target. A speculative explanation, but one fully consistent with all the data, is that these delayed events originate from the decay of a slowly moving (β∼0.02) massive neutral particle produced in the beam stop. Further measurements to improve statistical significance are necessary.
