Anomaly in the time distribution of neutrinos from a pulsed beam stop source

• Published in: Physics letters. B 1995-03, Vol.348 (1), p.19-28
• Main Authors: Armbruster, B., Blair, I., Bodmann, B.A., Booth, N.E., Drexlin, G., Eberhard, V., Edgington, J.A., Eitel, K., Finckh, E., Gemmeke, H., Hößl, J., Jannakos, T., Kleifges, M., Kleinfeller, J., Kretschmer, W., Maschuw, R., Plischke, P., Rapp, J., Seligmann, B., Stumm, O., Wolf, J., Zeitnitz, B.
• Format: Article
• Language: English
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/0370-2693(95)00258-M

Analysis of the charged and neutral current reactions 12C (ν e, 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.