Log 21
Justin
Vandenbroucke
justinv@hep.stanford.edu
Stanford
University
10/16/03
This file contains log entries summarizing the results of various small subprojects of the AUTEC study. Each entry begins with a date, a title, and the names of any relevant programs (Labview .vi files or Matlab .m files – if an extension is not given, they are assumed to be .m files).
Note: Higher-resolution versions of the figures are
available. If a log has URL
dirname/logLL.html, Figure FF of the log should be at URL dirname/FF.jpg.
10/16/03
filterNeutrino.m
Not knowing the exact
transfer function of the AUTEC hydrophone + amplifiers system, we do not know the
expected neutrino signal after it’s been through the system. We do know that frequencies from 7.5
kHz to 50 kHz pass the sytem. So
we can get some idea of the effect on the neutrino signal by passing it through
a simple Butterworth bandpass filter.
The effect is shown in figures 1-10 below. The neutrino signal used is a simple bipolar pulse, S(t) =
(-t/tau)*exp(-t^2/(2*tau^2)), with tau = 10 us.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Unfortunately, the filtered signal looks similar
to the multipolar signals we have been seeing. Figure 6 gives a multipolar signal, reproduced from Figure
11 of Log 19. It looks like there
are perhaps 4-5 poles, more than in the filtered signals above, but the two do
seem uncomfortably similar.
Figure 6
10/16/03
Rate
of 5-fold and 7-fold coincidences
find5Coincidences.m
find7Coincidences.m
plot5Coincidences.m
Figure
7 gives the rate of 5-fold coincidences.
The upper panel gives the number of combinations, the lower the number
of singles, in 5-fold coincidence.
The difference between the two panels is the effect of combinatorics due
to phone-to-phone matching ambiguity.
Figure
8 gives the same plot for 7-fold coincidences. The rate decreases significantly. There is a period of several months when one phone was
down. So we may wish to use 6-fold
rather than 7. But
Figure 7
Figure 8
10/16/03
Rejection
of multipolar events by requiring 7-fold coincidence
plotCoincidenceWaveforms.m
Below
are 2 examples of 7-fold coincidence events. The first is what we believe are Navy pingers. The second is the diamond (dolphin)
signal. In most 7-phone events,
the waveforms do not even match in shape.
In the events I have looked through, there have been no 7-phone events
with all 7 waveforms being multipolar.
So apparently requiring 7 phones rejects multipolar events.
I
am still checking exactly how many, if any, multipolar events are not rejected by requiring 7
phones hit.
Figure 9
Figure 10