Muon Data Quality and Performance A. Belloni - G. Zevi Della Porta for the ATLAS Harvard Group DOE Site Visit

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 5/12/2015Harvard - ATLAS Group2

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 cm -2 s -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) 5/12/2015Harvard - ATLAS Group3 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 5/12/2015Harvard - ATLAS Group4

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 5/12/2015Harvard - ATLAS Group5

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) 5/12/2015Harvard - ATLAS Group6 Old Firmware: 32-counts gap New Firmware (BCR blocking): all drift times digitized correctly TDC 16

Between DQ and Performance Beam-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 5/12/2015Harvard - ATLAS Group7

Between DQ and Performance Beam-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 –Small corrections (ns) still applied to drift time of individual hits for each track segment using refitting technique developed by Harvard group In-situ t 0 calibration for MDT segments, ATL-COM-MUON /12/2015Harvard - ATLAS Group8 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 5/12/2015Harvard - ATLAS Group9

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: –Charge asymmetry in cosmic rays Measurement of the Cosmic Ray Muon Charge Ratio using the ATLAS Muon Spectrometer, ATL-COM-MUON /12/2015Harvard - ATLAS Group10

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 5/12/201511Harvard - ATLAS Group ATLAS

Performance: collisions Efforts continued in the context of the W/Z analysis: –Definition of high-p T muon (used for all Atlas high-p T analyses) –Data-driven calculation of muon reconstruction efficiency Muon Reconstruction Performance, ATLAS-CONF –Cosmic rejection currently used by Atlas (T. Lazovich, undergraduate) –Momentum resolution maps in  accounting for detector effects 5/12/2015Harvard - ATLAS Group12 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 5/12/2015Harvard - ATLAS Group13

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” 5/12/2015Harvard - ATLAS Group14

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 5/12/2015Harvard - ATLAS Group15

Backup 5/12/2015Harvard - ATLAS Group16

5/12/2015Harvard - ATLAS Group17 MDT/CSC ACR Shifter (7am-3pm) RPC ACR Shifter (7am-3pm) TGC ACR Shifter (7am-3pm) Verbal report Daily Muon Operations +DQ Meeting Experts in Attendance Calib Center Shifter Verbal / Slide report All Muon ACR Shifters Morning + Evening + Night Shift Summaries Shift Summaries Filled and 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 presentation on Thursdays 17