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Main review page

Minutes of 2008-Feb-14 S5 QPipeline Review Teleconference


Shourov Chatterji, Jonah Kanner, Isabel Leonor, Dave Reitze

Minutes by Jonah Kanner.



S5 H1H2 scatterplots and significance

An investigation on a modified definition of H1H2 significance suggest that correlated energy, or perhaps a more complicate cut in the correlated vs. coherent energy plane may be a useful definition of significance.

S5 H1H2 1 year triggers

Updated distributions for time-lagged H1H2 triggers from the full 1st year analysis have been posted. Note that the zero lag triggers on this page are only from the 1 day playground.


As decided last week, the timeline has been rearranged to focus first on the triple coincident analysis in the context of the 1 day playground. At the same time, trigger production will continue for the H1H2 full 1 year analysis.

S5 H1H2L1 1 day playground analysis

A first look at the distribution of triple "coincident" triggers is posted here.


Dave: Why don't we walk through the plots that are passed around on e-mail

Shourov: We'll start with scatter plots of H1H2 energies


These are plotted in terms of energy instead of energy: snr = sqrt(2*energy)

Dave: The blue lines are isocontours?

Shourov: It's a family of curves parametrized by a single value to define a
significance We can see why correlated energy has been doing well as a statistic
- in the plots a cut on correlated energy does about as well separating glitches
and injections as can be done.

This ellipse cut behaves about the same as a cut on correlated energy, but I
thought the downward curve would be useful when adding L1.

In the correlated-coherent plane, the injections tend to follow a line

Isabel: When you calculate the significance, do you actually use the

Shourov: No.  For me significance is just a number.  As long as its
monotonically increasing, that's all that matters here.

Dave: Let me ask about S4 data.  I'm looking at this outlier, and it should be
followed up

Shourov: Yes, it is clearly an outlier.  You can find qscans linked off the S4
page ~shourov/s5qreview/s4_results

If you look at the difference between S4 and the S5 playground, you'll see that
S5 playground day has a very serious outlier.  That may mean that S5 is not like
S4.  Then again, looking at the S5 1-year background, there are events louder
than the outlier from the playground day.

Dave: You'll do something like 200 time shifts?

Shourov: No.  It's too expensive.  So far I've done 6.  I'm hoping to do at
least 10.  But, with the H1H2 data set, you can't gaurentee that zero-lag is
like the background.

Dave: Why a nice binary sequence of time lags?  Why not pick pi seconds of time

Shourov: That's a good idea.  I'll run a weird number as well.

Let's go to ~shourov/s5qreview/s5_results.  Here, the red is playground day.
It's one time lag in background, but it's for the whole year.

Let's go to /playground_withveto/H1H2L1

H1H2 triggers are tested for time frequency coincidence with L1.  Here, time
lags are cheap, because you are just moving triggers around.  The black have
H1H2 in zero lag, just L1 is moving

There's no null veto on Livingston, so the L1 significance can go quite high

Vertical features in these plots are when a Hanford trigger lines up with
different L triggers

Dave: Are there data quality flags applied here?

Shourov: Only cat. 1 data quality flags have been applied here - vetoes are not
yet ready One of the main advantages of the null stream test is that it quickly
cleaned up the data, without these labor issues.

Dave: I'll be really interested to see how much this is going to be cleaned up
when you apply vetos and category 2 DQ

Isabel: These are coincident in time and frequency?

Shourov: Yes, these are coincident with a window of 15 ms.  The center of the
tile has to overlap with some portion of the other tile.

If we look at the top left plot, we can see how much the L1 test has cleaned up
this plot.  This is with L1 significance threshold at 10 - if you move the L1
significance up to 100.  What I had hoped was to combine these statistics in one
measure of significance - but that looks to be daunting.  So, what I could do is
threshold on L1, and then just use the ellipsoid cuts from the H1H2 to rank
events.  So, L1 is acting only as a veto process.

Action Items

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