LZ Veto + Offline Data Quality

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Ewan Fraser

LUX-ZEPLIN!

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• Dual Phase LXe TPC.

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• Looking for WIMPs. Dark Matter Candidate.

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• Surrounded by 2 vetoes. LXe Skin and an Gd-LS Outer Detector.

Offline Data Quality - PREM - Physics Readiness Monitor

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Motivation:

• Validate that LZ’s data Runs are ready for their respective physics analysis.
• Verify the stability of the LZ detectors.
• Identity and catalogue any defects in the data.

Components:

• Automatically run, data analysis modules (ALPACA).
• Data Quality Leads - write and coordinate these analysis. Outer Detector - Me.
• Shifters - monitoring of PREM.
• Website to display the results of these analysis.
• Database - store associated metadata.

ALPACA - LZ’s Analysis Package

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• Modify ALPACA to output JSON metadata files.

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• Analyse time varying parameters.
• Across multiple Runs.
• Within a Run.

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• Flag significant changes in time varying parameters.

PREMweb

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PREM Database:

• Store JSON Metadata files for each run.
• Semi-structured, MongoDB

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PREM Website:

• Frontend: Bootstrap CSS and Javascript.
• Backend: NodeJS App.
• Express + Mongoose to interact with DB.

PREM Stack deployed at NERSC

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PREM Stack deployed on SPIN2, viewed in Rancher2.

Contains frontend and backend.

MongoDB.

Hosts site and 2-factor authentication.

SPIN2:

• NERSC’s container-based platform for science gateways.
• Deploy each project using a Docker image.
• Creates a Kubernetes cluster.

Photos! Outer Detector installation

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Alice installing the OCS fibres to monitor scintillator and acrylic degradation.

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Harvey working on OCS and OD PMT installation.

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OD PMT QA: Analysis

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Motivation:

• Provide QA for the OD PMTs.
• Calibrate Improve our model of the OD.

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Simulations:

• SPE: 1k photons, 100k events.
• Afterpulsing: 10k photons, 500k events.

OD PMT QA: SPE

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• Measure the response of the OD PMTs to a single photoelectron (SPE).
• Spectra in LZ are measured in photons detected (phd).
• Calibrating this response is the first step towards energy calibration.

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Analysis Note - Qing He, Daya Bay

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chPulseArea (phd)

OD PMT QA: Afterpulsing

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• Photoelectron ionizes a molecule when travelling between photocathode and first dynode.
• The more molecules the more afterpulsing.
• Measure of the quality of the vacuum in a PMT.
• Has it degraded since production in Korea?

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Neutron Selection in the LZ Veto

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• Begun to look at extending the Neutron Selection analysis for the LZ Veto.
• Improve our understanding of the dominant background in the Veto, gammas from cavern rock.
• Simulating the U238, Th232 and K40 decay chains in the cavern Rock. CPU intensive, not many make it through the water shield.
• Use event biasing to improve the efficiency of the simulation.

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Diagram of surfaces in LZ used for event biasing, Andrew N - Sheffield.

Summary

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• Developed LZ’s Offline Data Quality tool PREM.
• Helped coordinate Data Quality analysis group and the various analysis modules produced.
• Responsible for the Data Quality analysis in the Outer Detector.
• OD PMT QA is about to begin!
• Developed an SPE analysis and Afterpulsing analysis for this effort.
• Begun work on looking at the neutron selection in the LZ Veto.
• Simulating the main veto backgrounds using an Event Biasing technique.

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• Analysis: Andrew S - Oxford - LZ
• Electron Lifetime: Measure of LXe purity - Important correction for analysis

Current Development for PREM

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Sam Woodford - Liverpool:

• Automation of analysis.
• Database Queries!

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Anna D - UCL:

• Creating a data structure.
• Handle calibration values for all PMTs.

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