Probable SNO Solar-Neutrino Signals:
When a neutrino strikes the heavy water of the SNO detector, a faint
cone of light spreads out from that point to SNO's light sensors which
surround the spherical vessel of heavy water.
one event and a second
We use gamma rays from a Nitrogen-16 source to create Cerenkov
light for calibration purposes. This image shows
one such event. The similarity to the solar-neutrino signals shown
above indicates just how useful a calibration tool this is.
A Double-Ring Event: This is arguably our
prettiest event to date. In this event a
muon entered the SNO detector and exited through the pink region at
the top of the detector. (The pink indicates these photomultiplier
tubes detected a great deal of light.) This is typical of muons. What
is not so typical, is that the muon interacting in the detector
produced a secondary electron. This electron produced the large ring
just below the exit point of the muon.
A contained muon: Some of the muons detected in
SNO are created by interaction of an atmospheric neutrino in the heavy
water. These muons often decay in the detector rather than travel
right through it. This muon is an
example. The electron which resulted from the decay of the muon also
generated an event in SNO. From the
time stamp on the two images. You can see that the events both
occurred at 6:19 AM and 22 seconds. Looking at the decimal places
after the seconds in the time, we see the electron event occurred 0.9
microseconds after the muon event.
The event pictures above are taken from screen captures of
XSNOED (the X-windows SNO Event Display).