1. Beam Test of a Large-Area GEM Detector Prototype for the Upgrade of the CMS Muon Endcap System Vallary Bhopatkar M. Hohlmann, M. Phipps, J. Twigger, A. Zhang Dept. of Physics and Space Sciences, Florida Institute of Technology (for the CMS GEM Collaboration) APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar

2. Outline Motivation Gas Electron Multiplier (GEM) Detectors Construction of GE1/1 Prototype III Large Area GEM Detector FNAL Test Beam Oct 2013: Setup and Measurements Detector performance in FNAL Test Beam  Uniformity, Cluster Size, Efficiency Preliminary Tracking Results  Correlation of GE 1/1 Detector with Trackers, Resolution Summary and Future Plans 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 2

3. Motivation 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 3  During the phase II upgrade process of CMS detector at CERN, we are planning to install large- area GEM detectors in the forward muon region.  This installation will help to restore redundancy for tracking and triggering in muon system.  GEM detector can sustain in high rate environment, provides precise tracking, which improves muon momentum resolution and helps to maintain the global muon trigger rate  The combination of GEM+CSC can provide an accurate measurement of the muon bending angle unaffected by multiple scattering, which can be used at the L1 trigger to reduce the soft muon rate.  Florida Tech is planning to contribute to this upgrade project by producing and commissioning approximately 40 detectors. We constructed a first large-area GE1/1 GEM detector and studied its characteristics at a test beam at Fermilab in Oct. 2013 CMS Upgrade Source: Worshop-Intro-Asharma-24-3-2014

4. Gas Electron Multiplier Detector  Micro Pattern Gas Detector (MPGD)  GEM foil is a kapton foil coated with copper on both sides that has an array of holes (typically 140µm pitch)  High voltage is applied across foils, which creates avalanche of electrons through holes  Provides good efficiency and spatial resolution Source: http://gdd.web.cern.ch/GDD/ Source: http://www.flc.desy.de/tpc/basicsgem.phpMurtas, F.: “Development of a gaseous detector based on Gas Electron Multiplier (GEM) Technology Triple GEM configuration: Most popular and reliable 04/08/2014 4  Typical gas gain of 10 4 with gas mixture of Ar/CO 2 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 140µm 70µm

5. Step I GEM foils assembly with inner frames Stack of GEM foils with inner frames ready to place on drift electrode Total assembly time 3 Hrs 40 mins with 2 people Step II Stretching GEM foils by providing tension Stretched GEM foils with inner and outer frames 04/08/2014 5 Step III Finished GEM detector w/ APV frontend hybrids connected Construction of GE1/1 Prototype III Large-Area GEM Detector at Florida Tech 1D readout board with 3,072 radial strips connected through 24 Panasonic connectors to 24 APV hybrids APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar  Internal gap configuration of the detector: 3/1/2/1mm  GEM foils produced by single mask etching technique at CERN  Active area: approximately 99×(28-45)cm 2  “Largest GEM detector in existence" Eta 8 7 6 54 3 2 1

6. FNAL Test Beam Oct 2013 Setup and Measurements 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 6  Gas mixture used in all detectors: Ar/CO 2 70:30  Beam Energies: 1.Mixed hadrons: 32 GeV 2.Proton: 120 GeV  3 (10cm x 10cm) & 1 (50cm x 50cm) GEM trackers with 2D readout area @ 4200V  DAQ with RD51 SRS  CMS detector tests: 1. High voltage scan from 2900V to 3300V 2. Position Scan at 3250V in 3 positions: Upper row APV Middle row APV Lower row APV CMS GE1/1-III Detector Trackers

7. Basic Performance Characteristics of Detector from FNAL Test Beam Data 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 7 Cluster Charge Distribution Cluster Size at 3250V Cluster Size vs. High Voltage Cluster size increases with voltage Charge Uniformity Detection Efficiency with Different Cuts on Pedestal Widths At 3250V Detection Efficiency is 97.8%  Average cluster size at operating voltage is 2.4 strips  At 3250V, most probable values for all 3 APV position are used to determine the charge uniformity across the detector:  Detection efficiency measured with this detector is 97.8% (with 5-sigma cut on pedestal width). Cluster charge distribution at 3250V fitted with Landau function

8. Preliminary Tracking Results Reference Tracker and Correlations with CMS GE1/1 Detector 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 8 Residuals of Tracker 1 in φ Beam Profile 32 GeV mixed-hadron120 GeV proton Inclusive σ = 21µrad Exclusive σ = 75µrad Correlation of GE1/1 detector hits with hits in first tracker detector: Reference Detector resolution in φ Tracker 1 Tracker 2 Tracker 3 Tracker 4

9. Preliminary Tracking Results Resolutions for CMS GEM Detector in Eta Sector 5 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 9 Exclusive ResidualInclusive Residual  This translates to residual widths of σ = 172 µm (inclusive) and σ = 217 µm (exclusive) in the azimuthal direction (at the center of the eta sector 5) using R=1874 mm.  Taking the geometric mean of exclusive and inclusive residual widths we find a resolution of σ = 103 µrad (22% of strip pitch) which corresponds to σ = 193 µm in the center of eta sector 5 when using the pulse-height sensitive analog readout Resolution of the detector: σ = (103 ± 1) µrad (22% of strip pitch) Preliminary σ = 92μrad in φσ = 116μrad in φ

10. Comparison of Resolution and Detection Efficiency 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 10 Efficiency Best resolution is obtained at the efficiency plateau (as expected) Resolution

11. Summary  The beam test at FNAL was successful as the performance of the GE1/1 prototype large area detector meets the expectation.  Detection efficiency of the detector is 97.8% in eta sector 5 and it is consistent with all other sectors.  Charge uniformity shows similar response for all three APV position.  Spatial resolution improves with high voltage and gives the best value when it reaches a plateau which corresponds to the efficiency plateau.  Spatial resolution at 3250V of eta sector 5 is (103 ± 1) μrad which is equivalent to 193 μm.  Future work:  Measure the spatial resolution of the other sectors of the GEM detector.  Measure eff. and res. with simulated binary-output electronics (as planned for CMS upgrade). 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 11

12. Thank You! 04/08/2014APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 12

13. Backup Slides 04/08/2014APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 13

14. Efficiency Measurement Studied the hit distribution, charge distribution and cluster size for HV scan and Position scan Evaluates the efficiency from cluster multiplicity(CM) Where, N1: No. of events with CM≥1 for given sector N: Total no. of events N2: sum of the no. of events with CM≥1 for other sectors 04/08/2014 14 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar

15. Tracking 04/08/2014 APS April Meeting 2014, Savannah, Georgia - Vallary Bhopatkar 15