The LHCb Muon SystemBurkhard Schmidt / CERNon behalf of the LHCb collaboration

LHCb Muon Group:Cagliari, CERN, Ferrara, Frascati, Marseille, PNPI,

Potenza, Roma ‘La Sapienza’, Roma ‘Tor Vergata’, UFRJ

2nd International Symposium “LHC Physics and Detectors”JINR Dubna, 28-30 June 2000

28-30 June 2000 2B. Schmidt / CERN

LHCb Muon SystemOutline:

• Introduction– Physics Goals and Requirements– Background Conditions

• Overview of the Muon System– Detector Layout– Detector Technologies

• Performance Studies• FE-electronics

– FE-chip– Electronics Architecure

• Planning and Conclusions

28-30 June 2000 3B. Schmidt / CERN

IntroductionPhysics Goals:

• The Muon system of LHCb is primarily used as an identifier- and trigger system for muons produced in the decay of B-mesons: B X ;In particular: Bd J/(+-) Ks ; Bs J/(+-) ; Bs +-

• The muon momentum is measured precisely in the tracking system; the muon chambers are used to validate the muon candidate and match it with the track of the tracking system.

Requirements:• Modest momentum resolution (~25%) for a robust PT -selective trigger• Good time resolution (few ns) for reliable bunch-crossing identification• Good muon identification

28-30 June 2000 4B. Schmidt / CERN

IntroductionBackground sources in the LHC environment:

• Primary background:- hadron punch-through including muons generated in the hadron shower- ,K X decays

• Radiation background:Photon “gas” generated via n- processes by hadrons interacting in the absorber

• Machine background:Energetic muons produced in beam-gas interactions and in machine elements upstream of the experimental area

Requirements:• High rate capability of chambers and good ageing properties of

detector components• System layout of sufficient granularity to provide a redundant muon

trigger.

28-30 June 2000 5B. Schmidt / CERN

Overview

• 5 Muon stations with 2 layers/station

• 870m2 of detector area arranged in ~1500 chambers

• Hadron Absorber of 21 thickness

• Stations M1 and M2 are used for the PT-measurement• Stations M2, M3 (trigger seed), M4 and M5 for muon track finding

M1 M2 M3 M4 M5

28-30 June 2000 6B. Schmidt / CERN

Muon Detector LayoutTP-Layout Optimized Layout

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Station 1

28-30 June 2000 7B. Schmidt / CERN

Muon Detector LayoutOptimized Layout:• Stations are subdivided in 4 regions with different pad size

-> Region- and Pad-sizes scale by factor 2• Pad dimensions scale with station number

-> Projectivity to interaction point• Physical pads in stations M2-M5 are grouped to logical strips• Due to the high occupancy in M1 strips are not possible.

-> Significant reduction of channel number:Total number of physical channels: ~150 k

(TP: ~240k) Total number of logical channels: ~ 26k(TP: ~45k)

• Required resolution in the bending plane leads to an x/y aspect ratio of 1/4 in stations M2 and M3 and 1/2 in M1

28-30 June 2000 8B. Schmidt / CERN

Particle Rates in the Muon System

M1 M2 M3 M4 M5

R 17.010-3

560 kHz2.510-4

100 kHz2.010-4

80 kHz1.210-4

48 kHz1.210-4

48 kHz

R 24.0 10-3

320 kHz1.210-4

48 kHz2.010-5

8 kHz1.010-5

4 kHz8.010-6

3.2 kHz

R 31.010-3

80 kHz4.010-5

16 kHz4.010-6

1.6 kHz3.010-6

1.2 kHz3.010-6

1.2 kHz

R43.010-4

24 kHz5.010-6

2 kHz1.010-6

400 Hz7.510-7

300 Hz3.010-6

1.2 kHz

Applied Procedure:• LHCb peak Luminosity of 51032 cm2/s has been assumed• Estimation based on MARS as simulation package • Safety factor of 2.5 has been applied for M2-M5 and 2 for M1

dN/dA /cm2/int Required Rate Capability

Three areas can be distinguished:I) Rate 100 KHz II) 100 kHz Rate 1Khz III) Rate 1kHz

28-30 June 2000 9B. Schmidt / CERN

Muon System TechnologiesTechnology Choice:• In the outer part of M4 and M5 a technology with moderate rate capability can be used -> RPC

– covers 48% of muon system • For most of the regions MWPC with anode wire and/or cathode pad readout are the optimal

solution – covers 52% of the total area

• No technology has been chosen yet for the inner part of station 1– integrated charge in 108s in a MWPC would be ~ 2-5 C/cm– area size corresponds to < 1% of total muon system

M1 M2 M3 M4 M5R 1 ? MWPC MWPC MWPC MWPCR 2 ? MWPC MWPC MWPC MWPCR 3 MWPC MWPC MWPC RPC RPCR 4 MWPC MWPC MWPC RPC RPC

28-30 June 2000 10B. Schmidt / CERN

RPC Detector: OverviewCharacteristics:• Provides excellent timing (time resolution < 2ns) • Robust and flexible: electrodes and detector are independent

several configurations possible (single-, double-gap) • Cheap and simple to construct -> Produced in Industry Requirements:• Rate capability: 1.2 kHz/cm2

-> Avalanche mode operation with C2H2F4/C4H10/SF6 95/4/1 gas mixture-> Use low-resistive Bakelite ( < 1010 Ohm cm )

• Redundant spatial efficiency: > 99% / station -> Use two gaps (DRPC or OR-ed SRPC)

• Average cluster size < 1.2 strips (M3) and < 2 strips in M4/M5 • Max. radiation dose (10 y) 100 Gy

Activities: Carried out by Firenze and Roma ‘Tor Vergata’ groups

28-30 June 2000 11B. Schmidt / CERN

RPC Detector: LayoutSchematic Layout for Regions 3+4:• 1 chamber: 2 gas gaps (2 SRPC with independent FE-chips or DRPC)• Each electrode measures space points (no x-y coincidence required!)

29-31cm

Total region 3 : • 48 chambers/station• 4.6k-9.2k FE-ch./station Total region 4 : • 96-192 chambers/station• 9.2k FE-ch./station

split strips in region 3with 96-192 strips/chamber

140-150cm

28-30 June 2000 12B. Schmidt / CERN

RPC Detector: PerformanceResults from tests at the CERN PS:

• Time resolution ~1.3 ns• Full efficiency within 10 ns time window

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28-30 June 2000 13B. Schmidt / CERN

RPC Detector: Cluster SizeContributions to the Cluster Size:• direct induction -> geometrical effect, largest between strips•cross-talk SRPC -> depends on electrical characteristics of strip planes Scan over adjacent strips

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DRPC(strips less shielded)

28-30 June 2000 14B. Schmidt / CERN

RPC Detector: Performance Cluster Size Studies:

• Cluster size decreases with increasing threshold• At a given efficiency OR of two SRPC allows lower cluster size

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SRPC

Two SRPCin OR

28-30 June 2000 15B. Schmidt / CERN

RPC Detector: Rate CapabilityResults from GIF-Tests: • GIF Photon rate:

R = 740 GBq 0.85(BR) 0.5/Att. 1/4r2

• Procedure:Determine R from measured plateau curve with photons

R = 3.1 (1/Att)0.76 kHz/cm2

Calculate photon sensitivity factor

~1/800

28-30 June 2000 16B. Schmidt / CERN

RPC Detector: Rate CapabilityResults from tests at GIF:

• Gamma Irradiation Facility allows to test muon chambers under conditions comparable to those expected at the LHC.

• Test of 3 SRPC with x and y planes

->Efficiencies of >95% have been obtained at 1.8 KHz/cm2

->RPC of low resistive material show good rate capability behavior

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x-planes y-planes

28-30 June 2000 17B. Schmidt / CERN

MWPC Detector: OverviewCharacteristics:

• MWPC with anode and/or cathode readout are very well known• Integrated charge in 10 LHC years (108s) is <1 C/cm in all regions considered• MWPC operated with Ar/CO2/CF4 40/50/10 mixture has good aging properties

Requirements:• Efficiency within 20 ns time window: > 95%

-> Two gaps, staggered, 1.5mm wire spacing • Redundant spatial efficiency: > 99% /station

-> Two independent double gap chambers Activities: Carried out by PNPI (proponent), CERN, Firenze, Ferrara, Roma I (Potenza) and UFRJ groups

28-30 June 2000 18B. Schmidt / CERN

Muon Detector LayoutChamber arrangement:Frontview Sideview

28-30 June 2000 19B. Schmidt / CERN

MWPC : PerformanceTiming Properties: time distribution

Time resolution <3ns at operating point

Time resolution at 3.15kV (ASDQ) y = 0.0075x + 1.1609

0

1

2

3

4

5

6

0 100 200 300 400 500 600

Threshold (x10) (mV)

RM

S (n

s)

Time resolution

01234567

2.8 3 3.2 3.4 3.6

HV (kV)

RM

S (n

s)PNPI (4x8, Cdet=60pF)

ASDQ (2x8, Cdet=40pF)

28-30 June 2000 20B. Schmidt / CERN

MWPC: PerformanceMWPC test at CERN PS:

Gas Mixture:Ar/CO2/CF4 40/50/10FE-electronics:Custom made (SMD) peaking time ~10ns

-> Efficiency >99% within 20ns time window-> Dark count rate below < 50Hz/pad

-> plateau length:~ 400V for WPC ~ 300V for CPC

MWPC, anode wire readout (Pad size 4x16cm)

0.8

0.85

0.9

0.95

1

1.05

2.85 2.95 3.05 3.15 3.25 3.35 3.45

HV (kV)

Effi

cien

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0

50

100

150

Noi

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ount

(Hz) 50ns

25ns

20ns

15ns

noise

MWPC, cathode pad readout (Pad size 4x8cm)

0.8

0.85

0.9

0.95

1

1.05

2.85 2.95 3.05 3.15 3.25 3.35 3.45

HV (kV)

Effi

cien

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010203040506070

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(Hz) 50ns

25ns

20ns

15ns

noise

28-30 June 2000 21B. Schmidt / CERN

MWPC: PerformanceHigh rate performance:• FE-chip: ASDQ (has baseline restoration)

Time resolution at 3.15kV

00.5

11.5

22.5

33.5

0 20 40 60 80 100

Intensity (kHz/cm^2)

RM

S (n

s)

Efficiency at 3.15kV

0.95

0.96

0.97

0.98

0.99

1

0 20 40 60 80 100

Intensity (kHz/cm^2)

Effi

cien

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20ns

15ns

-> Efficiency > 98% within 20ns time window-> No deterioration of timing properties

28-30 June 2000 22B. Schmidt / CERN

FE - Electronics FE-chip specifications:• Peaking time ~10ns• Rin: < 50 • Cdet: 10-250pF• Polarities: +/-• Rate: up to 1MHz• Dead time: < 50ns• Dose: up to 1Mrad• Sensitivity: ~10mV/fC (@Cdet =0)• Low noise . . .

( Less stringent requirements for RPC FE-chip)

->Try to find existing chip satisfying our requirements

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Inefficiency due to ASD pulse-width

28-30 June 2000 23B. Schmidt / CERN

FE - Electronics FE-chip candidates:MWPC:• PNPI SMD (only for prototype studies)• SONY ASD (Tested, radiation limit ~ 50krad, dead time ~90ns) • ASDQ (Rin = 280, requires slight modification.)

-> Performs in general very well• MINSK ASD (matches well specifications, to be tested)• CMP 16 (for anode readout of CMS-EMU-chambers, to be tested)• GaAs (to be tested) • CARIOCA (0.25 CMOS) (under development)

RPC:• GaAs (0.6 MFET) (ATLAS RPC chip, very fast, radiation hard)

-> Baseline option• Bari (0.8 BiCMOS) (CMS RPC chip)

28-30 June 2000 24B. Schmidt / CERN

FE-ArchitectureStatus: – Basic concept of the FE-Architecture has been developed– Data reduction from physical channels (~150k ) to logical channels (~26k) done in intermediate boards– Synchronization of data from the various stations (timing alignment of signals) with muons using a 3-bit TDC

-> (ASD-chip) -> digital signals (~6m)-> channel reduction, FE-control (~4m)-> Synchronization, Pipelines, Trigger interface

FE-boards

Intermediate boards

Off Detector boards

28-30 June 2000 25B. Schmidt / CERN

FE-Electronics LocationsBaseline Locations for FE-Electronics:• FE-boards with kind of ASD chip on the chambers• Intermediate boards on the sides of each station• Off detector Boards performing synchronization, Data Format+BC Id,

LO-Pipeline and L1-Buffer on the sides of each station• L0-Muon-Trigger-Electronics on the sides of station 3

28-30 June 2000 26B. Schmidt / CERN

Project Plan

Schedule: • Decision on optimized muon detector layout Jan. 2000• Choice of detector technologies Feb/May 2000• Finalization of chamber design End 2000 • Baseline choice of FE-chip End 2000 • Technical Design Report (TDR) Early 2001 • Preparation of Production lines 2001• Construction and test of muon chambers 2002-2003• Installation and commissioning of the muon system 2004

28-30 June 2000 27B. Schmidt / CERN

Conclusions Layout and Architecture:

• Optimized layout has been found, requiring less physical and logical channels

• Realistic data flow between chambers and the Trigger/DAQ System

Detector Technologies:• RPC: - Rate capability of ~ 3 kHz/cm2 has been obtained

- Time resolution of 1.3 ns with efficiency >99% in 10 ns time window• MWPC: - Chambers perform very well up to rates > 100 kHz/cm2

- Time resolution < 3 ns with efficiency > 99% in 20 ns time window - Good ageing properties for Ar/CO2/CF4 (local tests > 13C/cm)

Muon System is proceeding well towards the Technical Design Report