an offline look at tif data david stuart uc santa barbara may 2, 2007

An offline look at TIF data

David StuartUC Santa Barbara

May 2, 2007

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Introduction

• Last week I volunteered to look at data offline. I want to describe what I have done since.

• I’ve looked at two issues:– Comparing VR and ZS (motivated by discussions with Slawek).– Studying the Multi-Hit events (motivated by discussions with Patrizia et al).

• I am using a non-standard tool:– I use CMSSW to dump the raw data and then feed it to standalone-code.

• It is easier for me to use, since it is my old CDF code.– My code looks at all events in a single module (rather than all modules in a single event).

• That makes some things easier and some things harder.• This different approach may complement other studies.

David Stuart, UCSB, May 2, 2007

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Compare Virgin Raw and ZeroSuppressed

Ped run

VR cosmics

ZS cosmics

ADC - PED

Comparing Ped, VR and ZSfor one sample module.

Very small differences between ped and cosmics.


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ADC - PED

Low charge region not properly normalized.

My noise calculation may be different.

It might be shoulder strips from hits. I’ll look at low multiplicity modules; ZS peds might help.

Possible shape difference in signal region.

More apparent in some modules than others.To be investigated.

Compare Virgin Raw and ZeroSuppressedSimulating ZS gives qualitative agreement, but there is a quantitative difference that is still to be understood.


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Clusters

Cluster charge

Use thresholds of: 6*noise for 1 strip 4*noise for >=2 strip

Huge signal to noise.Thresholds could be tightened,but noise hits not significant.

Odd spikes…

TIBTOB

Looked at clusters in ZS Run 6505.


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Cluster Spikes?

The TIB spikes at 250, 380, and 4000 (off the plot)are all from one module, detector id 369264142.

That module has an odd region as shown here.

Those channels are at their pedestals.Virgin raw data looks fine.It gives normal hits otherwise.

Maybe the Zero Suppression is failing there?

Problem also present in Run6509. Will check other runs…


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TOB spike at 254 and 508 appears in many modules, e.g., below.

No specific position.

Investigating…

Cluster Spikes?David Stuart, UCSB, May 2, 2007

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High Multiplicity Events

Try to understand these high multiplicity events.Are they cosmic showers or evidence of a problem?


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Possible hypotheses:• Noise• Multiple events being merged in the DAQ• Multiple events being merged in the offline• Cosmic showers• Something else?

An interesting mystery. Hopefully we’ll have a related one next year…

High Multiplicity EventsDavid Stuart, UCSB, May 2, 2007

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They appear to be following a steep spectrum. No evidence of specific structure.


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They contain normal looking hits that are apparently from tracks.

So, not noise. Maybe many events getting overlain…


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To see if events were being overlaid in the offline, Vitaliano suggested comparing the number of clusters to the event size in the StorageManager file.

Used code provided by Kristian Hahn to dump the data and plot the event size.Correlation indicates that a purely offline overlay is not the culprit. Maybe the DAQ?

(Number of clusters)/100

(EventSize/1000)-53

?


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Multi-hit events

First, I checked a few things about the clusters:Cluster charge looks same.Cluster position looks same.Cluster length distribution “similar”.Events appear to have tracks.

Run 6507, Event 14907


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If events where being overlaid, not only would be see many hit clusters,we’d also see many “noise clusters”, I.e., channels that just randomly pass the zero suppression. Are there more of those in the busy events?

Check this by looking at strip pairs with (ADC-PED)/Noise between 2 and 3, requiring no latched channels within 2 strips on either side to suppress.

Hit cluster

Noise cluster


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The noise clusters are uniform with event number, indicating no overlays.

First events are noisy.


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High Multiplicity EventsAndrea Venturi pointed out that if they are cosmic showers, then they should contain particles that do not hit the trigger scintillators.

It is hard to discern the tracks, but the hit distribution should suffice.

The rare hits in the lower leftdon’t seem to be in the trigger acceptance.

Are those hits only present in the highmultiplicity events?


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Yes.


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They are outside the luminousregion for single track events.

So, they look like showers.

Yes.


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Summary•I’m comparing virgin raw and zero suppressed.

•Makes sense to 1st order.•More investigation needed to understand in detail.

•I started looking at clusters•At least one anomaly might be a ZS problem.

•Looked at multi-hit events•Not consistent with DAQ or offline overlaying events•Consistent with cosmic showers•One interesting next check is dE/dx.

•Do these showers have higher dE/dx, which would reveal very low momentum tracks? Andrea Giammanco is interested in applying his dE/dx.

•Next: •Understand ZS better.•Look at more recent runs.•Look at tracks.•Other?

Details at http://hepdhcpd.physics.ucsb.edu/cgi-bin/lgbk?user=stuart&ent=19794


an offline look at tif data david stuart uc santa barbara may 2, 2007

Documents

overlain david stuart

runs david stuart

noise multiple events

noise hits

daq multiple events

multihit events

data offline

noise calculation