The CMS Muon Detector

VCI 21 conference 19-23/2/21 The CMS Muon Detector Paolo Giacomelli INFN Sezione di Bologna Univ. of California, Riverside General Overview Drift Tubes Cathode Strip Chambers Resistive Plate Chambers Global Muon Trigger Conclusions

The CMS Muon Detector FORWARD CALORIMETER CMS A Compact Solenoidal Detector for LHC MUON CHAMBERS TRACKER CRYSTAL ECAL HCAL Z Y X AIR PADS Total weight : 12,5 t. Overall diameter : 15. m Overall length : 21.6 m Magnetic field : 4 Tesla SUPERCONDUCTING COIL RETURN YOKE CMS-PARA-1-24/11/97 JLB.PP / pg.gm.hr The CMS Muon detector is made of 3 different sub-detectors to ensure redundancy and robustness: Drift Tubes (DT) in the barrel region Cathod Strip Chambers (CSC) in the endcap region and Resistive Plate Chambers (RPC) as dedicated trigger detectors in both the barrel and the endcap 2

The CMS Muon Detector µ Trasverse view 5 wheels in the Barrel MB/Z/4/6 YB/Z/3/6 MB/Z/3/6 YB/Z/2/6 MB/Z/2/6 YB/Z/1/6 MB/Z/4/5 YB/Z/3/5 MB/Z/3/5 YB/Z/2/5 MB/Z/2/5 YB/Z/1/5 TC MB/Z/1/6 MB/Z/1/5 TC MB/Z/4/4 YB/Z/3/4 MB/Z/3/4 YB/Z/2/4 MB/Z/2/4 YB/Z/1/4 MB/Z/1/4 TC COIL HB EB YB/Z/2/3 MB/Z/2/3 YB/Z/1/3 MB/Z/1/3 TC YB/Z/3/3 MB/Z/3/3 MB/Z/4/3 YB/Z/2/2 MB/Z/2/2 YB/Z/1/2 MB/Z/1/2 TC MB/Z/3/2 YB/Z/3/2 MB/Z/4/2 3 (φ) sectors MB/Z/4/7 YB/Z/3/7 MB/Z/3/7 YB/Z/2/7 MB/Z/2/7 YB/Z/1/7 MB/Z/1/7 TC MB/Z/4/1 YB/Z/3/1 MB/Z/3/1 YB/Z/2/1 MB/Z/2/1 YB/Z/1/1 MB/Z/1/1 TC MB/Z/4/8 YB/Z/3/8 MB/Z/3/8 YB/Z/2/8 MB/Z/2/8 YRB/Z/1/8 MB/Z/1/8 TC MB/Z/4/9 YB/Z/3/9 MB/Z/3/9 YB/Z/2/9 MB/Z/2/9 YB/Z/1/9 TC MB/Z/1/9 TC MB/Z/1/1 YB/Z/3/1 MB/Z/3/1 YB/Z/2/1 MB/Z/2/1 YB/Z/1/1 MB/Z/2/11 YB/Z/1/11 MB/Z/1/11 TC YB/Z/2/11 MB/Z/3/11 YB/Z/3/11 MB/Z/4/11 MB/Z/1/12 TC MB/Z/2/12 YB/Z/1/12 YB/Z/2/12 MB/Z/3/12 YB/Z/3/12 MB/Z/4/12 Z+ Y ϕ X Towards Center of LHC MB/Z/4/1 Z = -2, -1,, 1, 2 according to the Barrel wheel concerned 4 layers of Muon chambers covering up to η =2.4, providing 3 track segments along a muon track 3

/pg/hr Muon Detector Requirements Z 1.23 % g Y C.M.S. Compact Muon Solenoid Longitudinal View 7.43 m 6.955 m h = 1.479 ME/4/2 h = 1.1 ME/3/2 ME/2/2 ME/1/3 movement with field on:.5 cm, distributed 6.61 m 3.954 m h =1 h =.5 YB/2/3 YB/2/2 MB/2/4 MB/2/3 MB/2/2 YB/2/1 Field off YB/1/3 YB/1/2 MB/1/4 MB/1/3 MB/1/2 YB/1/1 1.268 m MB//4 YB//3 MB//3 YB//2 MB//2 YB//1 4.95 m h = 5.31 HF/1 1.86 m ME/4/1 YE/3 1.83 m 1.63 m ME/3/1 9.75 m YE/2 8.495 m ME/2/1 7.24 m 6.66 m 6.45 m 5.68 m 4.2 m 2.95 m 1.811 m 1.29 m.44 m. m 14.96 m 14.56 m 14.53 m 1.91 m ME/1/2 YE/1 ME/1/1 HE/1 1.711 m EE/1 SB/1 SE/1 4.332 m 3.9 m. m 7.38 m 7. m 5.975 m h = 3. h = 2.4 MB/2/1 2.7 m MB/1/1 MB//1 CB/ HB/1 1.9415 m EB/1 3.8 m 2.864 m 1.185 m 2.935 m. m Field off movement with field on: 1 cm All dimensions are indicated with field off CMS - PARA- 3-14/1/97 PP Muon ID with at least 16 λ down to η =2.4 Standalone transverse momentum res. 8-15% δp t /p t (at 1 GeV), 2-4% δp t /p t (at 1 TeV) Global momentum resolution 1.-1.5 % δp t /p t Unambiguous BX identification Single and di-muon first level trigger with variable p t thresholds down to η =2.1 Correct charge assignment up to p=7 TeV Ability to withstand the highest radiation and interaction background foreseen at the LHC 4

Drift Tubes layout MB1,2,3 = 8 φ-layers + 4 θ-layers MB4 = 8 φ-layers 25 chambers 2 channels Cell Layers RPC RPC wire pitch = 4.2 cm max. drift time = 38 ns SuperLayer DT chamber RPC RPC 5

DT basic cell design New design: 18 V - 12 V Nominal voltages Gas mixture Ar(85%) + CO 2 (15%) 36 V Requirements Single cell space resolution 25 µm Chamber space resolution ~ 1 µm BX tagging efficiency 99%, trigger space res. 1-2 mm 6

DT time resolution Drift Time Simulation test beam 2 7 6 5 4 3 2 1 HV: 36/18/-12 V Time Spectrum from TDC 1 2 3 4 5 6 ns 2 175 15 125 1 75 5 25 225 2 175 15 125 1 75 5 25 Meantimer run 842 87.9 / 21 Constant 1899. Mean 368.1 Sigma 4.585 Preliminary: MT1 83.43 / 2 Constant 1997. Mean 368.7 Sigma 4.362 vdrift = 57mm/ns Resol.= 28 mm (all cells together) 32 33 34 35 36 37 38 39 4 MT2 ns 32 33 34 35 36 37 38 39 4 ns 7

DT test beam results Q4: Single wire resolution (test beam 1999) 8

B perp = B cos (φ) B par = B sin (φ) DT magnetic field effects v drift apparent efficiency resolution Drift velocity (mm/ns) 58 57 56 55 Phi = deg. Phi = 1 deg. Phi = 15 deg. Cell efficiency (%) 1 99.5 99 98.5 98 Resolution (mm) 6 5 4 Phi = deg. Phi = 1 deg. Phi = 15 deg. 54 97.5 3 53 52 51 97 96.5 96 95.5 Phi = deg. Phi = 1 deg. Phi = 15 deg. 2 1 5.2.4.6.8 1 1.2 1.4 Magnetic field (T) 95.2.4.6.8 1 1.2 1.4 Magnetic field (T).2.4.6.8 1 1.2 1.4 Magnetic field (T) 9

DT Local Trigger BTI h 1 2 3 4 5 6 7 8 x 9 A B C D x 32 BTI BTI TRACO TRACO TRACO TRACO sel 9 5 TSS previews 2 9+2 Server Board TSMS full tracks 25 TSMD sel 3 bit TRACO Out Out 1 Out 2 Out 3 Out 4 Out 5 Out 6 Out 7 Out 8 Out 9 Out 1 Out 11 Outer Layer Phi Trigger Board 1 2 3 4 5 6 7 previews 16 TSMD 25 full tracks 2 bit To Sector Collector D = 23.7 cm Xcor Kcor In In 1 In 2 In3 Inner Layer x 32 BTI 2 TST BTI Theta Trigger Board 1 2 Outer SL θ TRIGGER SERVER Inner SL 1

track clas selector Assignment Unit Barrel track finder Pairwise Matching - Extrapolation muon station 4 Track Assembler Assignment Unit extrapolation window track segment muon station 3 muon station 2 muon station 1 track found (TS1, TS2, TS3, TS4) pt f h quality f2 -f1 extrapolation result "1/" TS1, TS2, TS3, TS4 11

CSC layout 54 Chambers 4, readout channels Sensitive area 6, m 2 (all planes) Offline spatial resolution ~1 mm Trigger spatial precision ~1-2 mm Trigger bunch-tagging efficiency ~99% 12

Endcap Muon System Large 1 o (3.4x1.5 m 2 ): 72 ME2/2 chambers 72 ME3/2 chambers (72 ME4/2 chambers) Small 1 o (1.8x1.1 m 2 ): 72 ME1/1 chambers 72 ME1/2 chambers 72 ME1/3 chambers h = 3. h = 2.61 h = 2.85 h = 2.436 h = 1.218 h = 1.35 h = 1.392 h = 1.479 h = 1.566 h = 1.653 h = 1.74 h = 1.827 h = 1.914 h = 2.1 h = 2.88 h = 2.262 CMS DETECTOR ME / 1/3 6.66 m h = 1.131 h = 1.44 h =.957 h =.87 h =.783 h =.696 h =.69 h =.522 h =.435 h =.348 h =.261 h =.174 h =.87 h =. ME / 4/2 ME / 4/1 YE / 3 ME / 3/2 ME / 3/1 YE / 2 ME / 2/2 ME / 2/1 YE / 1 ME / 1/2 NOSE ME / 1/1 4.4 m MB / 2/4 MB / 1/4 YB / 2/3 MB / 2/3 YB / 2/2 MB / 2/2 YB / 2/1 MB / 2/1 HE / 1 YB / 1/3 MB / 1/3 YB / 1/2 MB / 1/2 YB / 1/1 MB / 1/1 Coil 1.268 m HB / 1 EB / 1 MB / /4 YB / /3 MB / /3 YB / /2 MB / /2 YB / /1 MB / /1 7.38 m 7.1 m 5.975 m 4.885 m 4.2 m 3.8 m 2.95 m 2.864 m 1.93 m 1.41 m 1.31 m Small 2 o (1.9x1.5 m 2 h =5.31 ): 36 ME2/1 chambers 36 ME3/1 chambers (36 ME4/1 chambers) 14.98 m 14.58 m 14.55 m.5 1. (meters) HF / 1 1.88 m 1.6 m 9.77 m 8.515 m 8.26 m 6.7 m 6.5 m 5.7 m 3.88 m EE / 1 3.22 m 3. m Tracker D_D_141c CMS-RRB 15 April 97 4 Environment random hit rates up to 1 Hz/cm 2 2 khz/channel 4 times larger than mip signals punch-through rates up to 1 Hz/cm 2 penetrate through all six planes of a chamber B-field 3.5 T and uniform in ME1/1-1 T and very non-uniform in some others 13

CSC conceptual design CSCs will satisfy the performance requirements, while operating in the CMS/LHC environment muon cathode wires cathode induced charge avalanche cathode with strips wires plane cathode Conceptual design of a CMS EMU CSC Wires trapezoidal chambers length up to 3.4 m width up to 1.5 m 6 planes per chamber 9.5 mm gas gap (per plane) Strips 6.7 to 16. mm strip width strips run radially to measure f-coordinate with ~1 mm precision 5 µm wires spaced by 3.2 mm 5 to 16 wires ganged in groups wires measure r-coordinate gas Ar(4%)+CO 2 (5%)+CF 4 (1%) HV~3.6 kv (Q cathode ~11 fc, Q anode ~14 fc) 14

BX Tagging Efficiency (4th time in LCT) CSC time and space resolution Bunch tagging ID efficiency ~99% at maximum LHC rates Spatial resolution <1 mm even for very wide strips: - strip width = 16 mm - o strip width = 12 mm Rates expected at LHC 92% efficiency requirement 4 3 2 1 - D strip width = 8 mm six plane chamber resolution (MC).2.4.6.8 1 Hit coordinate across strip (x/w) single-plane resolution Rate, Hz/(wire group) 15

CSC Anode Trigger 25 ns Time spread per plane is broad: drift, noise, fluctuations in cluster formations "Dr ift" time per plane (ns) A pattern of anode hits, or LCT for Local Charged Track, consistent with a muon track (i.e., pointing back to IP) is searched for (to ensure time overlap, signals are shaped to last 15 ns) 2nd (or 3rd) earliest hit in LCT has a much narrower distribution and can be used for reliable bunch crossing tagging sigma = 3.9 ns 3rd hit in LCT 16

CSC Cathode trigger Q C First, hits are localized with precision of a half-strip: Q > threshold Q >Q right Q >Q left Q right >Q left Q L Q R _ + _ + Threshold _ + _ + Then, a track-like pattern of half-strips is searched for (LCT-- local charged track). Expected precision: (w/2)/sqrt(12)=.14*w for normal incidence for wide-spread angles it should be even better 17

CSC Trigger m m m m m j q 18

R (cm) RPC layout 8 7 6 5 4 3 h 2 1 2 4 6 8 1 12 Z (cm) 19

RPC double gap design HV HV Bakelite Gas Bakelite Bakelite Gas Bakelite Frontend strips strip pitch = η x φ ~.1 x 5/16 = 2-1 cm x 1-4 cm 2 mm double gap bakelite resistivity: 2-5 x 1 1 Wcm bakelite thickness: 2 mm gas mixture: 95.5% C 2 H 2 F 4 + 4.5% iso-c 4 H 1 operating voltage: ~9 kv 1.5-2.5 m RPC3.8-1.25 m RPC4 Lateral C bar Front-end electronics 2-3 chamb. 256 mm CMS barrel CMS endcap 12 mm indentation Front-end plate Trapezoidal strips and chambers 2

Efficiency (%) RPC efficiency and cluster size 98.5% HV=1.4 kv 95% HV=1.1 kv Cluster size < 2.3 strip 93% HV=1.5 kv Cluster with more than 7 strips<5% Source off Source off, random trigger Source off, muon trigger Abs 1, random trigger Abs1, muon trigger Abs5, random trigger Abs 5, muon trigge 21

RPC time resolution ABS 1 σ < 1.6 ns Events/1 ns 22

RPC Trigger algorithm MS 4 4 L 2T 5 1 6 3 MS 3 MS 2 A T C H E S 8 5... 9 8 7 6 5 4 3 2 1 MS 1 4T LATCHES p t coding 23

R (cm) 8 7 Muon Trigger geometry DriftTubes h=.8 h=1. h=1.2 RPC 6 5 4 3 2 h=2.1 h=2.4 1 CSC 2 4 6 8 1 12 Z (cm) 4 Stations in the barrel and each endcap 24

Global Muon Trigger (f, df, h, dh) (f, df, h, dh) h f h f h f h f 25

Trigger Rate (Hz) Trigger Rate (Hz) 1 6 1 5 Muon Trigger rates vs. p t Barrel: h < 1.4 Endcap: 1.4 < h < 2.4 1 6 1 5 1 4 1 4 1 3 1 3 1 2 1 Generated DT RPC GMT-opt GMT-and GMT-or 1 2 1 Generated CSC RPC GMT-opt GMT-and GMT-or 1 1 1 1 cut muon p T (GeV/c) 1 1 cut muon p T Curves show individual DT, RPC & CSC & 3 Global Muon Trigger Combinations: OR, AND, & optimized selection based on track quality & p t information Single muon trigger rate is 8.1 khz for a threshold of 25 GeV (9% efficient) Dimuon muon trigger rate is 2.8 khz for thresholds of 8, 5 GeV (9% efficient) (GeV/c) 26

Efficiency (%) Global Muon Trigger Efficiency 1 8 6 4 DTBX CSC DTBX or CSC 2 RPC GMT.5 1 1.5 2 (units) 2.5 h gen 27

CSC Efficiency (%), h >1.4 RPC Efficiency (%), 1.4< h <2.1 GMT Efficiency (%), 1.4< h <2.4 DT Efficiency (%), h <1.4 RPC Efficiency (%), h <1.4 GMT Efficiency (%), h <1.4 Muon trigger rates turn-on curves DTBX brlrpc brlgmt 1 8 6 4 2 1 GeV/c 2 GeV/c 3 GeV/c 4 GeV/c 5 GeV/c 6 GeV/c 1 8 6 4 2 1 GeV/c 2 GeV/c 3 GeV/c 4 GeV/c 5 GeV/c 6 GeV/c 1 8 6 4 2 1 GeV/c 2 GeV/c 3 GeV/c 4 GeV/c 5 GeV/c 6 GeV/c barrel 2 4 6 8 1 (GeV/c) p T,gen 2 4 6 8 1 (GeV/c) 7 p T,gen 2 4 6 8 1 (GeV/c) p T,gen CSC fwdrpc fwdgmt 1 8 6 4 2 1 GeV/c 2 GeV/c 3 GeV/c 4 GeV/c 5 GeV/c 6 GeV/c 1 8 6 4 2 1 GeV/c 2 GeV/c 3 GeV/c 4 GeV/c 5 GeV/c 6 GeV/c 1 8 6 4 2 1 GeV/c 2 GeV/c 3 GeV/c 4 GeV/c 5 GeV/c 6 GeV/c endcap 2 4 6 8 1 (GeV/c) p T,gen 2 4 6 8 1 p T,gen (GeV/c) 2 4 6 8 1 (GeV/c) p T,gen 28

Conclusions The CMS Muon detector will provide good muon identification with 4 independent measurements down to η =2.4 The Muon detector will provide unambiguous BX identification and single and di-muon first level triggers with very high efficiency Test-beam results have proven that the CMS Muon detector will be able to meet the requirements even at the highest LHC luminosities The production of DTs, CSCs and RPCs has started and the detectors will be operational for the first physics runs of LHC, foreseen in the summer of 26 29