1. 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.

2. 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

3. III LHC Symposium, Chia, Sardinia, 29 October 2001
LHCb Experiment
LHCb Detector: forward single arm spectrometer
Acceptance:
mrad bending
mrad non-bending
RICH1
RICH2
III LHC Symposium, Chia, Sardinia, 29 October 2001

4. Particle Identification
Momentum vs polar angle
Momentum
RICH system divided into 2 detectors and 3 radiators: aerogel, C4F10, CF4
Excellent Particle Identification (p-K separation) required from GeV/c
III LHC Symposium, Chia, Sardinia, 29 October 2001

5. III LHC Symposium, Chia, Sardinia, 29 October 2001
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 cm n
qc mrad
p GeV
K GeV
III LHC Symposium, Chia, Sardinia, 29 October 2001

6. III LHC Symposium, Chia, Sardinia, 29 October 2001
Photo Detectors
C4F10
small rings
Aerogel
large rings
Photo detector area: 2.6 m2
Single photon sensitivity: nm, quantum efficiency > 20%
Good granularity: ~ 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

7. Hybrid Photo Diodes (HPD)
Quartz window, thin S20 photo cathode 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)
Pixel HPD (baseline)
-20 kV
61 pixel HPD
Existing prototype external read-out
 = 80 mm
III LHC Symposium, Chia, Sardinia, 29 October 2001

8. III LHC Symposium, Chia, Sardinia, 29 October 2001
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

9. III LHC Symposium, Chia, Sardinia, 29 October 2001
HPD Electronics
Pixel chip
Occupancy
Max Mean
RICH % 1.2%
RICH % 0.4%
ALICE / LHCb development
(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
50 mm
III LHC Symposium, Chia, Sardinia, 29 October 2001

10. Pixel HPD Chip Status
Chips received: 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 bonding to ceramic carrier: Edgetek (Paris), good quality
LHCb chip redesign to achieve 40 MHz: submission IBM November
All current and voltage DACs redesigned and correctly layed-out
Improved uniformity of pulser
Clock skew 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

11. III LHC Symposium, Chia, Sardinia, 29 October 2001
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

12. III LHC Symposium, Chia, Sardinia, 29 October 2001
MAPMT (backup)
Multianode Photo Multiplier Tube
8x8 dynode chains, pixel 2x2 mm2
(effective size with lenses 3.2x3.2 mm2)
Gain: 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: 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

13. III LHC Symposium, Chia, Sardinia, 29 October 2001
RICH1 Engineering
Photo detectors
Beam-pipe
14% X0
Kapton beam-pipe seal
Mirrors
III LHC Symposium, Chia, Sardinia, 29 October 2001

14. Aerogel Hydroscopic Aerogel provides the best quality
clarity: m4/cm-1
refractive index: 1.034
radiation hard
Thickness: present choice 5 cm
transmission vs. dose
LHCb 1 year
104 Gy
# photoelectrons vs. thickness
5cm
III LHC Symposium, Chia, Sardinia, 29 October 2001

15. III LHC Symposium, Chia, Sardinia, 29 October 2001
RICH1 Mirrors
one quadrant of
spherical mirrors
beam pipe
Baseline: glass mirrors with 3-leg spider
(carbon fiber with screw adjusters)
Minimize dead material within acceptance
Alternatives:
glass 6mm : ~ 4.5% X0 , 1.5% l
berillium 5mm : ~ 2% X0 , 1% l
composite : ~ 1% X0 , 0.5% I
spider
prototype
adjuster
very good
repeatability &
stability
beam pipe
330 mrad acceptance
III LHC Symposium, Chia, Sardinia, 29 October 2001

16. RICH2 Engineering frame exit window plane mirrors magnetic shield box
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

17. III LHC Symposium, Chia, Sardinia, 29 October 2001
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

18. III LHC Symposium, Chia, Sardinia, 29 October 2001
RICH2 Gas Enclosure
Gas enclosure windows sealed at beam pipe and frame
1mm fibre skins + 48mm PMI foam core: ~30mm at 400Pa
Stress on beam pipe 400Pa: ~1 ton
window
400Pa
Tube
Flange
Photodetector window
1500x750x5 mm (two plates)
Optical transmission:
>90% above 200 nm
III LHC Symposium, Chia, Sardinia, 29 October 2001

19. III LHC Symposium, Chia, Sardinia, 29 October 2001
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

20. Electronics Test Bench
Stand alone system for demonstration and test bench use
Nearly final setup (no TTCrx, ECS, DCS) available 01/2002
Light box
X-y L1 PC
JTAG
controller
PCI-FLIC
S-link OL
HPD assembly L0 HV
HV control
X-y controller
dTAP
TTCrx
fpPINT
L0:
photo detector test bench
L1:
stand alone or VME crate
DAQ PC:
DAQ & control
III LHC Symposium, Chia, Sardinia, 29 October 2001

21. 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

22. RICH Gas and Monitoring
by LHC Gas group
control & monitor p & T
Ultrasound
Ultrasound gas monitor:
Measure variation of
sound speed
v = (RT/M)1/2
monitor gas composition Fabry-Perot monitor:
Measure fringes (depend on distance d, , and n)
monitor dispersion n()
RICH-2
Fabry-Perot
additional
monitor systems
III LHC Symposium, Chia, Sardinia, 29 October 2001

23. III LHC Symposium, Chia, Sardinia, 29 October 2001
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 c2 for 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

24. III LHC Symposium, Chia, Sardinia, 29 October 2001
RICH Performance
3s -K separation
3-80 GeV/c
(2s GeV/c)
Simulation
based on measured test beam HPD data
global pattern recognition
background photons included
# of detected photons
7 Aerogel C4F CF4
Angular resolution [mrad]
2.00 Aerogel C4F CF4
III LHC Symposium, Chia, Sardinia, 29 October 2001

25. III LHC Symposium, Chia, Sardinia, 29 October 2001
Bd ->  +
sensitive to CKM angle 
 ~ in 1 year
depends on |P/T| and strong phase 
Backgrounds also have
Penguin P
Tree T
III LHC Symposium, Chia, Sardinia, 29 October 2001

26. III LHC Symposium, Chia, Sardinia, 29 October 2001
Bs -> DsK
Rate asymmetries measure angle g-2dg
Expect 2400 events in 1 year of data taking
s(g-2dg) =
III LHC Symposium, Chia, Sardinia, 29 October 2001

27. III LHC Symposium, Chia, Sardinia, 29 October 2001
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 3s p-K separation from GeV/c
LHCb RICH is progressing since 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