Muon Data Quality and Performance

A. Belloni - G. Zevi Della Portafor the ATLAS Harvard Group

DOE Site Visit - 2010

Outline

• Harvard group contributions cover many aspects of Muon Data Quality– Online monitoring of MDT chambers– Organization of DQ meetings and shifts– Offline problem-solving and commissioning

• and Muon Performance - Alberto– Measurements, studies and techniques with cosmic rays– Applied and re-designed for collision data– Momentum scale and resolution studies

04/18/23 Harvard - ATLAS Group 2

Online MDT Data Quality• Wrote MDT Online monitoring software

– Real-time automated checks on ~6000 raw-level histograms• Hit timing, charge, multiplicities, dataflow errors, noise

– Spotting problems from cosmic rays to 1031cm-2s-1 luminosities• Recent developments: charge and noise checks, graphical layout, mid-level

checks (after Level2 trigger decision)

• Taking up active role in histogram-producing software (GNAM)

04/18/23 Harvard - ATLAS Group 3

Single multilayer TDC spectrum

Muon DQ Coordination I

• Developed and implemented the current structure for DQ monitoring of the Muon Spectrometer– Unify results from online, offline, calibration centers– 4 sub-detectors (MDT, CSC, RPC, TGC)– Provide daily feedback to ATLAS for all physics runs

• Focused on:– Improving communication among 4 sub-detectors– Moving tasks from experts to shifters

04/18/23 Harvard - ATLAS Group 4

Muon DQ Coordination II

• To achieve these goals, we introduced:– Offline shift position (Muon Offline Data Quality shifter) – Daily meeting (Muon Data Quality and Operation meeting)

• “Which runs can be used for physics?”

• To implement this, we were given the (new) position of “Muon DQ Operation Coordinators”

• New structure is now fully in place: – We have led the DQ meeting every data-taking day since

first collisions in November 2009– Trained more than 50 offline shifters (8 in Athens)– Recently introduced training videos of sub-detector experts

04/18/23 Harvard - ATLAS Group 5

Offline MDT DQ• Follow up MDT issues spotted at various levels of DQ monitoring

and presented at the daily meeting– Located source of Atlas-wide coherent-noise events, with up to 50%

occupancy in MDT chambers– Traced “gaps” in drift-time spectrum to a mis-configuration of MDT

electronics with respect to Bunch Counter Reset signals – Correlated new features in hit-time and hit-charge distributions to

beam induced backgrounds (see talk by L. Jeanty)

04/18/23 Harvard - ATLAS Group 6

Old Firmware:32-counts gap

New Firmware (BCR blocking):all drift times digitized correctly

TDC TDC

1616 1616 1616

Between DQ and PerformanceBeam-splash: Flux

• Studied beam-splash events and used them for timing calibration– Beam-splash = 450 GeV proton beam colliding against closed

collimators ~140 m away from Atlas Interaction Point– Modeled flux through each tube using distance of closest particle to

wire• Measured fluxes of O(150,000) charged particles per beam-splash event• Consistent with Tile calorimeter estimates

04/18/23 Harvard - ATLAS Group 7

Between DQ and PerformanceBeam-splash: Timing

– Developed method to determine chamber-by-chamber timing offsets by averaging left- and right-moving splashes

• Timing calibrations currently used for muon-tracking• Beam Splash Studies with MDT Chambers: Timing and Flux, ATL-COM-

MUON-2010-006– Small corrections (ns) still applied to drift time of individual hits for

each track segment using refitting technique developed by Harvard group

• In-situ t0 calibration for MDT segments, ATL-COM-MUON-2009-006

04/18/23 Harvard - ATLAS Group 8

Average arrival time of the beam splash at each chamber layer using pre-beam-splash calibrations

The same plot using the new timing calibrations

Muon Performance

04/18/23 Harvard - ATLAS Group 9

Performance: cosmic rays• Harvard group has provided steady contributions to the Muon Run

Analysis Task Force– Leading studies on Endcap alignment, segment reconstruction– Muon tracking performance

• Commissioning of the ATLAS Muon Spectrometer with Cosmic Rays, arXiv:1006.4384

– Charge asymmetry in cosmic rays• Measurement of the Cosmic Ray Muon Charge Ratio using the ATLAS

Muon Spectrometer, ATL-COM-MUON-2010-012

04/18/23 Harvard - ATLAS Group 10

Cosmic Muon Charge Ratio• First physics measurement

used to drive performance and validation studies of muon reconstruction software– Massive validation campaign for

ATLAS track extrapolation tools– Developed L1 trigger simulation

• Fully data-driven analysis– Techniques invented for charge

ratio analysis re-utilized for first analyses with collision data

• Unique cosmic physics result for ATLAS– Albeit attention now devoted to

collision papers, muon community interested in publication of cosmic result

04/18/23 11Harvard - ATLAS Group

ATLAS

Performance: collisions• Efforts continued in the context of the W/Z analysis:

– Definition of high-pT muon (used for all Atlas high-pT analyses)– Data-driven calculation of muon reconstruction efficiency

• Muon Reconstruction Performance, ATLAS-CONF-2010-064– Cosmic rejection currently used by Atlas (T. Lazovich, undergraduate)– Momentum resolution maps in accounting for detector effects

04/18/23 Harvard - ATLAS Group 12

Timing based separation of cosmic and collision tracks

Performance: current status• Z to µµ invariant mass distribution allows to measure muon

momentum scale and resolution– Momentum scale found to be within 1%– Z peak width in data is larger than in MC: under investigation

• Currently this effect is taken into account by applying smearing factors to MC

04/18/23 Harvard - ATLAS Group 13

Performance: plans

• Define reconstructed muons for physics analyses– Use Z mass constraint to fit muon momentum resolution in

eta/phi bins• Study each identified region independently

– Tag and probe studies to define muon reco efficiency

• Work on fundamental aspects of muon performance– Calibration, alignment, tracking – Work within Muon Combined Performance group

• “Joint tracking/muon CP workshop: Z to µµ Performance”

04/18/23 Harvard - ATLAS Group 14

Summary

• Leading Muon Spectrometer data quality– Coordinate Muon DQ meetings and shifts– Write and maintain online DQ code for MDTs– Contact people for tracking down MDT issues

• Expertise in detector layout, cabling, electronics, raw-data format

• Important contributions to muon performance and physics analyses– Methods for calibration, track fitting, cosmic rejection

used Atlas-wide– Developed muon definition, reconstruction-efficiency

calculation– Ongoing studies of momentum scale and resolution

04/18/23 Harvard - ATLAS Group 15

Backup

04/18/23 Harvard - ATLAS Group 16

04/18/23 Harvard - ATLAS Group 17

MDT/CSC ACR Shifter(7am-3pm)

RPC ACR Shifter(7am-3pm)

TGCACR Shifter(7am-3pm)

Verbal report

Verbal report

Verbal report Daily Muon Operations +DQ Meeting

Experts in AttendanceCalib Center Shifter

Verbal / Slide report

All Muon ACR ShiftersMorning +

Evening + Night

Shift SummariesShift Summaries Filledand Placed on E-Log

(9 in total)

Muon DQ Shifter-Run Muon Daily Meeting-Get Evening/Night DQ

-Present Offline DQ status-Synthesize info from all sources-Present at ATLAS DQ meeting

ATLAS Daily DQ Meeting

Muon presentationon Thursdays

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