tension on physics at protodune eﬀects of wire

Adam Lister | DUNE APA Meeting | 26 Oct 2020

Effects of Wire

Tension on Physics at

ProtoDUNE

Adam Lister

DUNE / APA Meeting

26 October 2020

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Introduction

➔ This is mostly a repeat of what was shown back at the January collaboration meeting, with some newer, shinier plots◆ There’s now a technote on edms which outlines the full process:

https://edms.cern.ch/document/2425713/1

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https://edms.cern.ch/document/2425713/1


Why You Should Care

● ProtoDUNE tension specification: 5 N +/- 1 N● ~26.9% of wires out of spec at production sites

○ ~4.5% are under-tensioned○ ~22.4% are over-tensioned○ Wires also relax over time (5% effect on avg)

● Some expectation that looser wires leads to a higher noise rate, but no information on whether this can impact physics-level variables and analyses.

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Strategy

For this analysis we’re looking to see if energy deposition per unit length changes as a function of wire tension.

➔ Wire tension was measured at the production sites, and a subset was re-measured at CERN◆ We’re using the production-site values since all of the wires were measured

➔ We’re using stopping cosmic muons, which should have a well understood energy deposition

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Mapping Wire Numbers to DAQ Channels

The wire tension measurements are taken without any link to the DAQ channels, so we need to do some matching between “wire number” and “DAQ Channel”.

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➔ This was a nontrivial to set up --- see technote for details

➔ This has been validated by looking at the number of wire segments connected to each channel as per my mapping, and from the simulated geometry.

➔ There are ◆ 5760 channels that have 1 wire

attached (X Plane)◆ 1248 channels have 2 wires

attached (wrap once)◆ 8352 channels have 3 wires

attached (wrap twice)


Stopping Muon Selection

Stopping muons are a nice standard calibration for surface level LArTPCs

Not going to go into too many details here, but to summarise, tracks must:➔ start near the edge of the

detector, end in a fiducial volume defined by 50 cm;

➔ have a reconstructed interaction time (cross the cathode);

➔ meet some angular requirements;➔ meet some requirements which

target removal of broken tracks

Distribution of a subset of the selected tracks look reasonable - mostly start near the top and all cross the cathode.

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Based on Ajib Paudel’s work https://indico.fnal.gov/event/17467/contributions/43317/attachments/26783/33197/dEdx_calibration.pdf

https://indico.fnal.gov/event/17467/contributions/43317/attachments/26783/33197/dEdx_calibration.pdf

https://indico.fnal.gov/event/17467/contributions/43317/attachments/26783/33197/dEdx_calibration.pdf



We take a one meter section of the stopping muons one meter from the end of the track (grey lines), where there is a relatively constant dE/dx of ~2.1 MeV/cm (note only X plane properly calibrated - more on this later)

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There’s quite a bit of contamination at low dE/dx on the induction planes, no angular cuts seem to be able to remove these (see backup), so we just have to live with it.

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Calibration

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SCE Map - Mike Mooney

Drift-direction calibration YZ Calibration SCE Calibration

Accounts for drift-dependent effects.● Electron attenuation.● Electron diffusion

Accounts for variation in detector response across different APAs and planes

Accounts for E-field variations ● Impacts

conversion from dQ/dx to dE/dx

Wire tension changes as a function of wire number, i.e. in the YZ plane, so the drift-direction calibration should not correct for this, however both the YZ calibration and SCE calibration have components which change as a function of Y and Z position.

Mike Mooney

Adam Lister | DUNE APA Meeting | 26 Oct 2020 10

The YZ Calibration

For this analysis, we’re applying the SCE correction, but the YZ calibration is only applied to the X plane➔ When I did this work, the calibration was only available on the X plane and I haven’t

had chance to re-run the code since they were available on the U and V planes.➔ This means you should expect a smaller effect on the X plane than on the induction

planes➔ This will not completely calibrate out on the effect on the X plane, since we

calibrate in 5 cm bins --- ~10 wires at a time.

APA 3 APA 2 APA 1 APA 5 APA 6 APA 4


Results

Here showing the mean hit dE/dx as a function of wire tension.

The dE/dx values reduce significantly under 4 N. Out of an abundance of caution I’d suggest not letting wire tensions go below 4.5 N.

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So What’s Happening Here?

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As the tension is reduced

➔ there are small shifts in the dE/dx peak ;➔ there is a large increase in the number of

very low dE/dx values, and this is likely what drives most of the effect;

The first I think could be calibrated out, the second is more difficult to deal with


Summary

Having low wire tensions reduces the measured dE/dx values

➔ After calibration, X plane wires in the 3-3.5 N bin have a reduction of > 20%!➔ Results on the U and V planes are consistent with the X plane, though no YZ

calibration has applied on those planes

This seems to be caused by two effects:

➔ There is a shift in the 2.1 MeV/cm peak dE/dx value to lower values➔ There is a significant increase in the low dE/dx peak

It is my suggestion that we keep wire tensions above 4.5 N.

➔ There is precedence for setting the nominal tension to be 7N (SBND), so I’d advocate for 7N ± 1 N. This would get us well away from any potential problem region.

➔ Still safe for the APAs, the UK APAs routinely had wire tensions near 8 N without any apparent issues

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Backup

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This gap is caused by slightly larger SCE effects in the -x TPCs --- the results are consistent across the different TPCs so I didn’t rerun the stopping muon filter.

tension on physics at protodune eﬀects of wire

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