Real data in the Muon Spectrometer Bernardo RESENDE and a lot of other people not named here NIKHEF Jamboree, December 2008

Our goals for momentum precision: GeV, 1 TeV  Needs excellent chambers, alignment and reconstruction Precision tracking in magnetic field: – Monitored Drift Tubes (MDT) – 1150 stations with 6-8 tube layers, 354k channels – Cathode Strip Chambers (CSC) – 32 chambers, channels Muon specific trigger: – Resistive Plate Chambers (RPC) – 606 chambers, 373k channels – Thin Gap Chambers (TGC) – 3588 chambers, 318k channels ATLAS Muon Spectrometer 11/07/2016 B. Resende - ATLAS Muon Spectrometer 2/20 Three layers of muon chambers (inner, middle, outer) MDT + RPC MDT + TGC CSC MDT magnets

Where we stood in December 2007 Spectrometer almost ready –85% chambers –94 % alignment, DCS (barrel) 1/3 of ATLAS commissioned –O(10 M) cosmics in partial detector –Combined: only during “milestone” weeks Cosmic track reconstruction starting to develop –Testing specific configuration 11/07/2016 B. Resende - ATLAS Muon Spectrometer Enter 2008… 3/20

Last piece… Installation of last chambers –“Small Wheels”: last pieces of ATLAS puzzle in February-March 11/07/2016 B. Resende - ATLAS Muon Spectrometer 4/20

11/07/2016 B. Resende - ATLAS Muon Spectrometer 5/20 … and last connection

The completion of the Spectrometer All scheduled chambers in 1088 of 1150 MDT chambers installed, 99.8% included in read-out –1.7% dead channels Total Aim: 0.2% after shutdown –Gas system OK DCS very advanced – all chambers connected –T-sensors: 12184, 99.4 % working –B-sensors: 1646, 99.3 % working –Database storage stable; alignment entries: ! Other technologies also up and running 11/07/2016 B. Resende - ATLAS Muon Spectrometer 6/20

Alignment requirements Important contribution of chamber alignment to resolution 11/07/2016 B. Resende - ATLAS Muon Spectrometer  Optical alignment system to monitor MDT displacements 1 TeV muon  measure sagitta of 500 μm with 50 μm accuracy  Alignment better than nominal resolution of 40 μm 7/20 Contribution to resolution in % total misalignment E loss tube resolution P T (GeV/c) multiple scattering 1000

Alignment: RASNIK image analysis Optical setup with “mask”: 11/07/2016 B. Resende - ATLAS Muon Spectrometer Fourier transform  Factor 7 gain in RMS of longitudinal magnification PC Improved image analysis algorithm: Foam2 8/20 (fast Fourier transform)

~ optical sensors, 99.6% ok –Validated in test beam and installation Alignment status and results 11/07/2016 B. Resende - ATLAS Muon Spectrometer Bar ProjectivePolar ProximityPraxial BIL BML BOL EI EE EM EO  Impact on cosmic tracks –O(mm) shifts down by factor 10 Also track-based alignment –Straight cosmic tracks : determine initial geometry (without field)  Statistical error: 10 microns 9/20 No correction Optical alignment Track-based alignment

Magnetic field sensors ~ 1600 sensors in MDT system 11/07/2016 B. Resende - ATLAS Muon Spectrometer 10/20 First beam ! |B| values and RMS (BOL)  Stable field (and read-out) for the beams! |B| RMS (|B|)  Constant supervision in ATLAS pit Nominal current for first beams ( I = A)

MDT twin tubes Special configuration for regions with limited trigger coverage (no φ information) –Two tubes connected, 2 read-outs No change in DAQ software needed –Time difference  position along tube 11/07/2016 B. Resende - ATLAS Muon Spectrometer 11/20 Check with data: comparing x (relative coordinate) from Twin Tubes and RPC chambers –Recent cosmic data, uncalibrated –Good correlation  Twin Tube measurement OK

Reconstructing muon tracks Muon stand-alone track reconstruction: –Find patterns among the hits –Fit segments in each station –Fit tracks though the different stations Stand-alone reco algorithm: Moore –Improvements, specially on background –Satisfactory performance in all simulations Good performance on real data (cosmics) –More than 99.5 % segment finding efficiency (middle/outer layer) –About 95 % track finding efficiency (w.r.t. inner detector) 11/07/2016 B. Resende - ATLAS Muon Spectrometer MDT hits: drift time, converted to drift radius segment 12/20

Commissioning with data ATLAS ready for collisions Crucial for detector understanding –Extract calibration –Exercise reconstruction 11/07/2016 B. Resende - ATLAS Muon Spectrometer recent cosmic event beam halo event 13/20 beam halo event

First beams from the LHC! Beam splashes : collimators closed (~200 m from ATLAS) 11/07/2016 B. Resende - ATLAS Muon Spectrometer 14/20  Stand-alone reconstruction resisted (well) this test!

Beam halo and cosmic tracks Beam halo : particles parallel to the proton beam First studies of spatial distributions 11/07/2016 B. Resende - ATLAS Muon Spectrometer Beam Cosmics 15/20  Beam halo tracks along the beam axis  Small cosmics contribution

Recent cosmic data Most sub-detectors running in continuous combined data taking 11/07/2016 B. Resende - ATLAS Muon Spectrometer  Combined tracking: good matching, high efficiencies 16/20  Centralized reprocessing soon with recent calibration and reconstruction

Tagging the Inner Detector tracks Instead of full track reconstruction in Spectrometer, “tag” Inner Detector tracks: MuTagIMO  Extrapolate track to I nner, M iddle, O uter layers  Search for close segments, then precise matching  Multiple segment/track matchings: ambiguity solving BI BM BO High (> 99 %) efficiencies on simulation Robust performance 11/07/2016 B. Resende - ATLAS Muon Spectrometer 17/20

Example of MuTagIMO tagged track Recent cosmics event –Moore segments available, track reconstruction failed 11/07/2016 B. Resende - ATLAS Muon Spectrometer 18/20

MuTagIMO performance Cosmics efficiency estimation –Sample: 4792 events with ID track and segments to tag – 96.4 % tagged 98.8 % with silicon 11/07/2016 B. Resende - ATLAS Muon Spectrometer 19/20 Cross-check with Moore tracks: robust efficiency estimate  Nice performance on cosmics Black: all “taggable” tracks Red: tagged tracks Black: all “taggable” tracks Red: tagged tracks

Where we stand in December 2008 Spectrometer almost ready –85% chambers –94 % alignment, DCS (barrel) 1/3 of ATLAS commissioned –O(10 M) cosmics in partial detector –Combined: “milestone” weeks Cosmic track reconstruction starting to develop –Testing specific configuration 11/07/2016 B. Resende - ATLAS Muon Spectrometer Spectrometer ready ! –99.8% chambers, Twin Tubes in –99.6% alignment, with cosmics –All DCS connected ATLAS fully commissioned –O(100 M) cosmics in entire detector –Continuous combined running Cosmic track reconstruction mature –Performant reco and tagging Beam events! –We were ready, we want more! 20/20

Spare slides

ATLAS cavern From K. Black, ATLAS Week Dec /07/2016 B. Resende - ATLAS Muon Spectrometer 22

Reconstructing beam tracks Beam splashes: collimators closed (~200 m from ATLAS)  Stand-alone reconstruction resisted (well) this test! Beam halo: particles parallel to the proton beam 11/07/2016 B. Resende - ATLAS Muon Spectrometer Beam 2 – trigger: beam pickup  Longer tracks for beam halo Cosmics – trigger: RPC chambers 23 MDT hits only, no trigger hits MDT hits RPC hits no TGC hit

Beam halo and cosmic tracks Beam halo : particles parallel to the proton beam First studies of spatial distributions  Beam halo tracks along the beam axis 11/07/2016 B. Resende - ATLAS Muon Spectrometer Beam Cosmics Beam direction Cosmics : symmetric z Beam: asymmetric z 24

MuTagIMO performance on cosmics 11/07/2016 B. Resende - ATLAS Muon Spectrometer Efficiency: 96.4 % Efficiency with silicon: 98.8 % 4792 recent cosmic events –With ID track & segments to tag Cross-check with Moore  Stable efficiencies in selected sub- samples Fake search: top-bottom tags match > 93% Efficiency: 97 % Efficiency with silicon: 99.2 % Efficiency: 94.9 % Efficiency with silicon: 94.8 % Efficiency: 95.4 % Efficiency with silicon: 95.1 % 25

1 2 X Y Z Matching tagged segments, top & bottom How to estimate quality and look for fakes ? Looking for opposite tags: matching top and bottom –Projective matching criteria between Y > 0 and Y< 0 tags 11/07/2016 B. Resende - ATLAS Muon Spectrometer Lone tags quite common –Top alone : 1 event out of 8 –Bottom alone : 1 out of 36 Top  bottom: 93.6 % Bottom  top: 96.6 %  Track scattering from top to bottom + fakes ? 8 regions in 4 pairs: 1/5, 2/6, 3/7, 4/8 26

Efficiency at station level Efficiency: extrapolate track from 2 other layers and look for –Segments –Hits on track 11/07/2016 B. Resende - ATLAS Muon Spectrometer 27 LayerHit on track eff (%) barrelendcap Inner Middle Outer LayerSegment eff (%) barrelendcap Inner Middle Outer Good overall efficiencies Timing problems  lower efficiencies