Comparison of electron and muon neutrino events

Muons make Cherenkov rings with sharp edges, electrons make rings with fuzzy edges.

The following two images show similar electron and muon events. This is real data, not Monte-Carlo simulation.

The color scale is time of arrival of light to a phototube. Bottom of the scale (violet and blue) corresponds to early time. Top of the scale (orange, red) corresponds to late time.

A time of flight (residual) cut 30 ns wide has been applied to eliminate noise and scattered and reflected light.

The histogram on the right shows time charge distribution before the time of flight cut.

Size of the square representing a PMT corresponds to amount of light observed. There is a maximum size cutoff, so that a PMT does not get larger than distance between PMTs, to avoid PMT overlap.

The reason why colors of the rings are somewhat different is that the electron direction is close to the view direction, while the muon traveled somewhat more sideways, from upper left to lower right. Diamond shows where track extended from the vertex in the forward direction would intersect detector wall, cross shows the same in backwards direction. X-marks show projections of the vertex to top, side and bottom walls.


This event occurred at 1998-04-04 08:35:22. It was reconstructed as a muon with momentum of 603 MeV. The time scale width is 162 ns. This event was followed by another event (not shown) 4 us later which was caused by an electron produced by the decay of the stopped muon. This gives us an additional confirmation that this is a muon.

Muon neutrino produces a muon that produces a Cherenkov ring
in the Super-Kamiokande neutrino detector.


This event occurred at 1998-04-04 21:26:08. It was reconstructed as an electron with momentum of 492 MeV. The time scale width is 130 ns.

Electron neutrino produces an electron that produces a Cherenkov ring
in the Super-Kamiokande neutrino detector.

How these images were made

Scripts used to produce these images.

Back to tscan.


Tomasz Barszczak