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Particle Identification in the LHCb Experiment. Paul Soler University of Glasgow and Rutherford Appleton Laboratory (on behalf of LHCb RICH group). III LHC Symposium on Physics and Detectors Chia, Sardinia, Italy. 29 October 2001. Participating Institutes. Sezione di Milano. CERN.

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Particle Identification in the LHCb Experiment


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particle identification in the lhcb experiment

Particle Identification in the LHCb Experiment

Paul Soler

University of Glasgow and

Rutherford Appleton Laboratory

(on behalf of LHCb RICH group)

III LHC Symposium on Physics and Detectors

Chia, Sardinia, Italy.

29 October 2001.

participating institutes
Participating Institutes

Sezione di Milano

CERN

Sezione di Genova

University of Bristol

University of Edinburgh

University of Glasgow

University of Oxford

Imperial College

Rutherford Appleton

Laboratory

III LHC Symposium, Chia, Sardinia, 29 October 2001

lhcb experiment
LHCb Experiment
  • LHCb Detector: forward single arm spectrometer

Acceptance:

10-300 mrad bending

10-250 mrad non-bending

RICH1

RICH2

III LHC Symposium, Chia, Sardinia, 29 October 2001

particle identification
Particle Identification
  • Excellent Particle Identification (p-K separation) required from1 - 150 GeV/c

Momentum vs polar angle

Momentum

  • RICH system divided into 2 detectors and 3 radiators: aerogel, C4F10, CF4

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich system overview
RICH System Overview

RICH1

RICH2

Photo detectors

  • Acceptance
    • 300 mrad RICH 1
    • 120 mrad RICH 2
  • Radiators:thickness L, refractive index n, angle c, /K threshold

Aerogel C4F10 CF4

L 5 85 167 cm

n 1.03 1.0014 1.0005

qc 242 53 32 mrad

p 0.6 2.6 4.4 GeV

K 2.0 9.3 15.6 GeV

III LHC Symposium, Chia, Sardinia, 29 October 2001

photo detectors
Photo Detectors

C4F10

small rings

Aerogel

large rings

  • Photo detector area: 2.6 m2
  • Single photon sensitivity:200 - 600 nm, quantum efficiency > 20%
  • Goodgranularity: ~ 2.5 x 2.5 mm2
  • Large active area fraction:  73%
  • LHC speed read-out electronics: 40 MHz
  • LHCb environment: magnetic fields, charged particles

CF4

Hybrid Photodiodes (HPD) baseline

Multi-Anode PMT (backup)

III LHC Symposium, Chia, Sardinia, 29 October 2001

hybrid photo diodes hpd
Hybrid Photo Diodes (HPD)

Pixel HPD (baseline)

  • Quartzwindow, thin S20 photocathodeQE dE = 0.77 eV
  • 32 x 32 Si pixel array: 500 m

(Canberra)

  • ~450 tubes for RICH system
  • Cross-focusing optics
    • demagnification ~ 5
    • 50 m point-spread function
    • 20 kV operating voltage
  • Encapsulated binary electronics
  • Tube, encapsulation: industry (DEP)

-20 kV

61 pixel HPD

  • Existing prototype external read-out

 = 80 mm

III LHC Symposium, Chia, Sardinia, 29 October 2001

hpd r d results
HPD R&D Results

Testbeam

  • Testbeam Setup
    • RICH 1 prototype
    • 3 HPDs
  • Figure of merit
    • N0  202 cm-1 (~35 PE/ring)

Cherenkov

Photons

Single

photoelectron

spectra visible

III LHC Symposium, Chia, Sardinia, 29 October 2001

hpd electronics
HPD Electronics
  • ALICE / LHCbdevelopment

(0.25 m CMOS)

  • ALICE pixel size 50 m x 425 m
  • LHCb pixel size 62.5 m x 500 m

8 pixels = 1 LHCb super-pixel

500 m x 500 m

  • 40 MHz read-out clock
  • Bump bonding:chip-sensor

Pixel chip

Occupancy

Max Mean

RICH 1 8.2% 1.2%

RICH 2 2.6% 0.4%

50 mm

III LHC Symposium, Chia, Sardinia, 29 October 2001

pixel hpd chip status
Pixel HPD Chip Status
  • Chipsreceived: only operate up to 10 MHz(ALICE requirements)
  • Bump-bonding sensor-pixel chip: VTT Finland, good quality
  • Lab tests within LHCb requirements:
    • Threshold scans: ~700 e- (<2000 e-)
    • Noise: ~90 e- (<250 e-)
    • Signal: ~5000 e-
  • Wire bondingto ceramic carrier: Edgetek (Paris), good quality
  • LHCb chip redesign to achieve 40 MHz: submission IBM November
    • All current and voltage DACsredesigned and correctly layed-out
    • Improved uniformity of pulser
    • Clockskew being improved
  • HPD Pixel chip resubmission after October: review 31 October, 2001

HPD pixel chip assembly

with ceramic carrier

III LHC Symposium, Chia, Sardinia, 29 October 2001

magnetic field tests
Magnetic Field Tests
  • Prototype with a phosphor screen anode read out by a CCD (resolution ~150 mm) for magnetic field tests.
  • Distortions tolerable up to 10 Gauss
  • Flipping of B field shows no change in position residuals (within resolution).

Axial field

Transverse field

III LHC Symposium, Chia, Sardinia, 29 October 2001

mapmt backup
MAPMT (backup)

Multianode Photo Multiplier Tube

  • 8x8 dynode chains, pixel2x2 mm2

(effective size with lenses 3.2x3.2 mm2)

  • Gain: 3.105 at 800 V
  • UV glass window, bialkali photo cathode: QE = 22% at  = 380 nm
  • Test beam data:6.51  0.34 p.e.
  • Expect from simulation:6.21 p.e.
  • MAPMT active area fraction: 38% (includes pixel gap)
  • Increase with quartz lens with one flat and one curved surface to 85%

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich1 engineering
RICH1 Engineering

Photo detectors

Beam-pipe

14% X0

Kapton beam-pipe seal

Mirrors

III LHC Symposium, Chia, Sardinia, 29 October 2001

aerogel

LHCb 1 year

5cm

104 Gy

# photoelectrons vs. thickness

transmission vs. dose

Aerogel
  • Hydroscopic Aerogel provides the best quality
    • clarity:0.0045 m4/cm-1
    • refractive index:1.034
    • radiation hard
    • Thickness:present choice5 cm

III LHC Symposium, Chia, Sardinia, 29 October 2001

slide15

beam pipe

adjuster

spider

prototype

one quadrant of

spherical mirrors

RICH1 Mirrors

  • Baseline:glass mirrors with 3-leg spider

(carbon fiber with screw adjusters)

  • Minimize dead materialwithin acceptance

Alternatives:

glass 6mm : ~ 4.5% X0 , 1.5% l

berillium 5mm : ~ 2% X0 , 1% l

composite : ~ 1% X0 , 0.5% I

very good

repeatability &

stability

beam pipe

330 mrad acceptance

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich2 engineering
RICH2 Engineering

frame

exit window

low mass

12.4% X0

plane

mirrors

magnetic shield box

& backward lid (4 tons)

to shield against magnetic stray field

of ~150 Gauss

spherical mirrors

on supporting planes

photodetectors

with individual magnetic shields

beam pipe envelope

supported by windows

entry window

low mass

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich2 engineering1
RICH2 Engineering
  • Natural frequencies
  • Fundamental frequency ~6Hz

Negligible movement

  • Finite Element Analysis:
    • Deflections under load

(mag. shield 2x11000kg, tracker unit 200kg)

    • max. deflections <5mm achievable

increasing

deflection

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich2 gas enclosure

400Pa

window

RICH2 Gas Enclosure
  • Gas enclosure windows sealed at beam pipe and frame
  • 1mm fibre skins + 48mm PMI foam core: ~30mmat 400Pa
  • Stress on beam pipe sheet:@ 400Pa: ~1 ton
  • Photodetector window

1500x750x5 mm (two plates)

  • Optical transmission:

>90% above 200 nm

Tube

Flange

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich electronics
RICH Electronics
  • Pixel chip
    • encapsulated, binary, 40 MHz, 32:1 MUX
  • Level 0
    • on detector
    • Gbit optical links
    • clocks, triggers - TTC
  • Level 1
    • in counting room
    • buffers data L1 latency, transports to DAQ
    • zero suppression
    • TTC, DCS interface

III LHC Symposium, Chia, Sardinia, 29 October 2001

electronics test bench

JTAG

controller

dTAP

dTAP

Light box

L1

L0

dTAP

X-y

dTAP

HPD assembly

TTCrx

OL

PC

S-link

PCI-FLIC

fpPINT

TTCrx

S-link

HV

HV control

X-y controller

Electronics Test Bench
  • Stand alone system for demonstration and test bench use
  • Nearly final setup (no TTCrx, ECS, DCS) available 01/2002

L1:

stand alone or VME crate

DAQ PC:

DAQ & control

L0:

photo detector test bench

III LHC Symposium, Chia, Sardinia, 29 October 2001

photodetector test facilities
Photodetector Test Facilities
  • ~500 HPD or ~4000 MaPMT to be tested for:
    • functionality within specifications
    • individual characteristics
    • working parameters
    • full automation needed
  • selection of detectors according to test results
    • position in detectors wrt. occupancy
  • to be operational in mid 2002
  • in the case of HPD’s:
    • use the electronics test-bench system
    • estimated time for all measurements & scans

for one tube: 24hrs

(including handling and resting in the dark)

    • 2 test facilities needed for 1 1/2 years

(Edinburgh & Glasgow)

MaPMT test setup

ODE

MaPMT

xy-table

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich gas and monitoring

Ultrasound

Fabry-Perot

RICH Gas and Monitoring
  • by LHC Gas group
  • control & monitor p & T
  • Ultrasound gas monitor:
    • Measure variation of

sound speed

v = (RT/M)1/2

    • monitor gas compositionFabry-Perot monitor:
    • Measure fringes (depend on distance d, , and n)
    • monitor dispersion n()

RICH-2

additional

monitor systems

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich alignment
RICH Alignment
  • Misalignment mirrors: fit photons from data to

Dq = A cos(f) + B sin(f)

  • In RICH2 (two mirrors): can only perform relative alignment
  • Minimise c2for two mirror tilts
  • Photons from ambiguous mirror combinations (20%) degrade performance
  • Seed alignment <1 mrad for no degradation

1 mrad misalignment

III LHC Symposium, Chia, Sardinia, 29 October 2001

rich performance
RICH Performance

3s -K separation

3-80 GeV/c

(2s 1-150 GeV/c)

  • Simulation
    • based on measured test beam HPD data
    • global pattern recognition
    • background photons included
  • # of detected photons
    • 7 Aerogel 33 C4F10 18 CF4
  • Angular resolution[mrad]
    • 2.00 Aerogel 1.45 C4F10 0.58 CF4

III LHC Symposium, Chia, Sardinia, 29 October 2001

slide25
Bd ->  +
  • sensitive to CKM angle 
  •  ~ 20 - 50in 1 year
    • depends on |P/T| and strong phase 
  • Backgrounds also have

Penguin P

Tree T

III LHC Symposium, Chia, Sardinia, 29 October 2001

b s d s k
Bs -> DsK
  • Rate asymmetries measure angleg-2dg
  • Expect 2400 events in 1 year of data taking
  • s(g-2dg) = 60 .. 140

III LHC Symposium, Chia, Sardinia, 29 October 2001

conclusions
Conclusions
  • Physics performance studies show that the RICH is essential for the LHCb physics programme.
  • The RICH design of LHCb with two detectors and three radiators provides 3sp-K separation from 3-80 GeV/c
  • LHCb RICH is progressingsince TDR
    • Pixel HPD chip has incurred a delay but is not in critical path (project under review).
    • Design for subsystems are detailed and advanced
    • Transition from R&D to construction
  • In time to take data when LHC becomes

operational in 2006

III LHC Symposium, Chia, Sardinia, 29 October 2001