CBM workshop on Muon ID B.Schmidt Muon Identification in LHCb Workshop on Muon Detection in the CBM Experiment Outline: Introduction –Physics requirements –Background conditions Overview of the Muon System Physics Performance –Muon trigger –Muon identification MWPC Detector –Performance and aging studies –Detector construction Triple Gem Detector –Performance and aging studies

CBM workshop on Muon ID B.Schmidt Introduction Physics Goals: The Muon system of LHCb is primarily used to trigger on muons produced in the decay of b-hadrons: b   X ; In particular: B  J/  (  +  - ) K s ; B s  J/  (  +  - )  ; B s   +  - The muon momentum is measured precisely in the tracking system The muon system identifies muons from tracks in the tracking system Requirements: Modest momentum resolution (~20%) for a robust P T -selective trigger Good time resolution (a few ns) for reliable bunch-crossing identification Good muon identification (~90%); small pion-misidentification (~1%) 0 0 0

CBM workshop on Muon ID B.Schmidt Introduction Background sources in the LHC environment: ,K   X decays –main background for L0 muon trigger Shower particles –hadron punch-through including shower muons Low-energy background induced by n-  processes –contributes significant to chamber hit rate Machine background, in particular high energy beam-halo muons Requirements: High rate capability of chambers Good ageing properties of detector components Detector instrumentation with sufficient redundancy

CBM workshop on Muon ID B.Schmidt Overview of the LHCb Muon Detector 435m 2 of detector area with 1380 chambers Hadron Absorber of 20 thickness in total 5 Muon stations, with 2 independent layers/station -> redundancy Layers are logically ORed -> high station efficiency M1 M2 M3 M4 M5 -> Projectivity to interaction point

CBM workshop on Muon ID B.Schmidt Detector status: snapshot from the pit Muon System Calorimeters RICH2 Magnet Tracking system Vertex Detector RICH1 In the pit To be installed

CBM workshop on Muon ID B.Schmidt Muon Detector Layout Space point measurement 4 Regions with granularity variable with distance from beam axis - 0.6cm x 3.1cm in Region 1, - 5cm x 25cm in Region4 Particle flux varies between MHz/cm 2 (M1 Region 1) kHz/cm 2 (M5 Region 4) Chamber Detector Technology : - MWPC will be used in most regions - triple GEMs are used for M1R1 Electronics: - System has 126k FE-channels, reduced to 26k readout channels

CBM workshop on Muon ID B.Schmidt Muons in LHCb

CBM workshop on Muon ID B.Schmidt Muon Trigger Algorithm Level 0 Muon Trigger: Muon track finding: Find seed pad in station M3 Find pads within opened search windows (FOI) in stations M2, M4 and M5 Use pads found in M2 and M3 to extrapolate to M1 and find pad in M1 within FOI Stations M1 and M2 are used for the P T - measurement -> Muon Trigger exploits multiple scattering in the muon shield by applying tight search windows

CBM workshop on Muon ID B.Schmidt Background Simulation

CBM workshop on Muon ID B.Schmidt Particle Rates in the LHCb Muon System

CBM workshop on Muon ID B.Schmidt Level 0 Muon Trigger Trigger Performance: Muon system includes realistic chamber geometry and detector response -> Muon System is robust

CBM workshop on Muon ID B.Schmidt Level 0 Muon Trigger Beam halo muons: Distribution of energy and radial position of halo muons 1m upstream of IP travelling in the direction of the muon system Muons entering the experimental hall behind M5 give hits in different BX in the muon stations ->No significant effect Halo muons are present in ~1.5% of the bunch crossings About 0.1% of them cause a L0 muon trigger

CBM workshop on Muon ID B.Schmidt Muon Identification Algorithm: Extrapolate reconstructed tracks with p > 3GeV/c and first hits in Velo from T10 to the muon system (M2 etc.) Define a field of interest (FOI) around extrapolation point and Define minimum number of stations with hits in FOIs M2+M3 for 3  p  6 GeV/c M2+M3+(M4 or M5) for 6  p  10 GeV/c M2+M3+M4+M5 for p  10 GeV/c

CBM workshop on Muon ID B.Schmidt Muon Identification Performance: Nominal Maximal background background p>6GeV/c  Sx<0.053   94.0    0.6 M e 0.78    0.1 M  1.50    0.05 M K 1.65    0.1 M P 0.36    0.1 Additional cuts on slope difference  Sx between tracking and muon system and p  are required in case of large bkg. -> M  ~ 1%   ~ 90%

CBM workshop on Muon ID B.Schmidt Muonic Final States B 0  J/  (  +  - ) K s : Well established CP-violating decay from which angle  in the unitary triangle can be determined. J/  (  +  - ) reconstruction: - oppositely charged tracks identified as muons. - Mass of dimuon pair consistent with J/  mass -> More than 100k ev./year expected in LHCb B s   +  - : Decay involves FCNC and is strongly suppressed in the Standard Model -> B O mass resolution 18 MeV/c 2 -> ~10 signal events over 3 bkg expected per year LO performance for both decays: L0 trigger acceptance of fully reconstructed events is 98%. L0 muon acceptance is 95% with >70% triggered by muon trigger alone. 0

CBM workshop on Muon ID B.Schmidt MWPC Readout Types Region 4: Anode wire readout Region 3: Cathode pad readout Region 1+2: (in stations M2+M3) Combined anode and cathode readout -> Different readouts and variations in input capacitance pose special requirements on FE-chip

CBM workshop on Muon ID B.Schmidt MWPC Requirements and Layout 2 independent ASD ORed on FE Board (similar ORing scheme also applies to cathode pads) HV Requirements: High rate capability of chambers-> up to 0.2 MHz/cm 2 Good ageing properties of detector components: ->up to 1.6 C/cm 2 on cathodes and 0.3 C/cm on wires Detector instrumentation with good redundancy and time resolution ->each chamber has (generally) 4 layers ->99% station efficiency in 20ns time window Structural panel Cathode pads PCB 4 separate HV supplies to anode wires

CBM workshop on Muon ID B.Schmidt Geometry and Fields Volt /cm Pitch:2 mm Gap:5 mm Wire:30 µm HV:2650 V Cathode field:6.2 kV/cm Wire field:262 kV/cm Gain: 10 5 Total avalanche charge: 0.74pC cm

CBM workshop on Muon ID B.Schmidt Gas Properties Drift velocity of 90 µm/ns is ‘saturated’ meaning that a small change in electric field does not affect the time resolution. In Ar/CO 2 /CF 4 40/40/20 we expect for 10 GeV muons about: ~ 42 clusters/cm ~ 2.35 e-/cluster, -> 99 e-/cm

CBM workshop on Muon ID B.Schmidt Front-End Electronics 3x4mm prototype, (2.5x3mm final) FE-chip ‘CARIOCA’: –0.25  m CMOS technology –8 channel ASD –fully differential –10ns peaking time –30mW/channel UFRJ Rio, CERN FE-chip specifications: Peaking time ~ 10ns R in : < 50  C det : pF Noise:<2fC for C det =250pF Rate: up to 1MHz Pulse width: < 50ns Dose: up to 1Mrad

CBM workshop on Muon ID B.Schmidt Chamber Performance: Time resolution Optimum amplifier peaking time ~10ns Intrinsic time resolution is about 3ns 20ns

CBM workshop on Muon ID B.Schmidt Chamber Performance: Efficiency Cathode Efficiency:Anode Efficiency: WP -> Plateau length is about 350 – 450 V

CBM workshop on Muon ID B.Schmidt High rate behaviour 1.2 MHz/wire pad, 40kHz/cm 2 Time RMS is unchanged - no space charge effect, as expected 4% efficiency loss at 1MHz due to signal pileup, as expected

CBM workshop on Muon ID B.Schmidt Chamber Performance High rate performance: (old result obtained with 1.5mm pitch) Time resolution stable (no space charge effects) Small Efficiency drop due to pile up

CBM workshop on Muon ID B.Schmidt Comparison with Simulation Double gap chamber: 95% efficiency if the threshold is set to 30% of the average signal. 99% efficiency if the threshold is set to 20% of the average signal. In order to have a double gap chamber well within the plateau we want to be able to use a threshold of ~15% of the average signal. -> Good agreement, we understand our detector Full simulation: - Primary ionization (HEED) - Drift, Diffusion (MAGBOLTZ) - Induced Signals (GARFIELD)

CBM workshop on Muon ID B.Schmidt Chamber Specifications Gas Gain variations: Working point should not move out of the plateau The gas gain should be for 95% of the area within 25% of G 0 For the remaining 5% of the area the gas gain should be within 50% of G 0 A gain change of a factor 1.25 (1.5) corresponds to a voltage change of ±34 (62)V around 2650 V, corresponding to ±1.25 (2.25)%. -> The gas gain changes by a factor 1.25 (1.5) if the wire surface field changes by ±1.25 (2.25)%. Resulting chamber specifications: Gap:95% in 90  m1%5% in 180  m2% Pitch: 95% in 50  m0.35%5% in 100  m0.7% Wire y-offset:95% in 100  m 0.1%5% in 200  m0.4% Wire plane y-offset:95% in 100  m 0.1%5% in 200  m0.4% -> Added in squares:1.07%2.2%

CBM workshop on Muon ID B.Schmidt Chamber Construction Production Program: Within two years ~1500 chambers had to be build in 6 production centres. Quality assurances (QA) is a key issue Example for QA: Measurement of wire pitch with CCD cameras using, telecentric lenses

CBM workshop on Muon ID B.Schmidt Wire Pitch Measurement Small pitch fluctuations mainly due to precision of combs -> 99% of wires within (2.00 ±0.05)mm Quality check of method: Reproducibility of result within 1.5  m (RMS) on average -> Method well adapted for reliable QA

CBM workshop on Muon ID B.Schmidt Example for Gas Gain Uniformity

CBM workshop on Muon ID B.Schmidt MWPC Aging studies Two long term aging tests have been performed: 1st test at GIF in 2001, where charges of 0.25 C/cm have been accumulated in 6 months. Open loop gas system has been used Gas mixture: Ar / CO2 / CF4 (40%, 50%, 10%) 2 nd test at ENEA Cassacia in June 2003, where charges of 0.5 C/cm have been accumulated in 1 month (using the 25kCi (!) Co source). One chamber has been in open loop, one in closed loop Gas mixture: Ar / CO2 / CF4 (40%, 40%, 20%) Parameters controlled : Relative gas gain: In both tests one gap was used as reference gap to avoid complicated corrections for P and T variations. The reference gap was only for very short periods per day under HV and always flashed with the fresh gas. Dark currents, including self-sustaining rest current following the beam off. The dark currents were measured with current monitors with a resolution of 1 nA.

CBM workshop on Muon ID B.Schmidt No signs for aging from the measured parameters: Relative currents did not change. Malter currents were not observed. No variations in current ratios after/before Casaccia from measurements with GIF and with an Am-source. Summary of Results from Casaccia ChamberGapIC (C/cm) M3R1A,C,D0.43 S/AS10.52 S/AS20.42 S/AA20.38 Accumulated charges:

Analysis of Surfaces Strong FR4 etching of open surfaces Bubbles under Kapton foil 1st the wires... CF 4 is a phantastic gas ! CF 4 is a terrible gas ! Detaching of the ground grid between the pads (due to FR4 etching)

CBM workshop on Muon ID B.Schmidt Conclusions Conclusions: Although no drop in gas gain was visible after the Casaccia aging test, the materials exposed to CF 4 show strong surface etching. The effects are very similar for the chambers in the two gas system used in Casaccia (vented and re-circulation gas-system). The effect has been stronger the 2 nd aging test, where the gas mixture contained 20% CF 4, than in 1 st test, where 10% CF 4 have been used. Plans: Repeat the test at GIF in the coming months, where the test takes however 5 times longer than in Casaccia (source strength 25kCi). New mixture with less/no CF 4. Both gas loops will be used. Control of O 2 and H 2 O and contamination is foreseen.

CBM workshop on Muon ID B.Schmidt

CBM workshop on Muon ID B.Schmidt

CBM workshop on Muon ID B.Schmidt

CBM workshop on Muon ID B.Schmidt

CBM workshop on Muon ID B.Schmidt

CBM workshop on Muon ID B.Schmidt

CBM workshop on Muon ID B.Schmidt

CBM workshop on Muon ID B.Schmidt

CBM workshop on Muon ID B.Schmidt