K2K June/2000 Official Plots
Hitmaps of FC K2K Events Extracted by KINGFISH Online
These hitmaps were generated using the fully-contained events found
by KINGFISH, the online Super-K data monitor computer. When this computer
detects a fully-contained event it immediately queries another computer at KEK
to determine the time since the last beam spill. If the FC event is
in time with the spill (i.e., occurring within approximately 1
microsecond of the nearest spill time after time-of-flight and
other corrections are taken into account) then the event is kept.
Due to network traffic it is occasionally possible for
an event which is later found offline to be missed by this process,
but all retained online events are part of the official K2K SK data set.
Events found online should therefore be viewed as a fully
representative, largely overlapping sampling of the official set.
The hitmaps show the relative number of times a given photomultiplier
tube has seen light during all the intime FC K2K events observed online
since June, 1999. The colors and sizes of the spots autoscale, based
on the spread of the number of hits in all tubes. Naturally, one would
expect that many more inward-facing Super-K tubes on the
downstream side of the K2K neutrino beam would see Cherenkov light
than those on upstream side. These plots demonstrate this rather
dramatically, showing that the intime events are indeed coming
from the direction of KEK.
Hitmaps are available in two views - facing downstream, such that
the most often hit PMT's will be near the center of the screen, and rotated
some 45 degrees to better show the anti-beam direction. In the
rotated view the survey-based direction back to KEK is indicated with a line
drawn along the wall of the detector; light should, on average, radiate
from this direction against the opposite side of the Super-K tank.
Questions and comments about these figures should be directed to
Mark Vagins.
