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

Effect of bandpass filter on neutrino signal

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