1. RICH option for PID Fundamentals State of the art in HEP
Future applications
Antonello Di Mauro (CERN, Geneva, Switzerland)
Tau-Charm workshop, La Biodola, Elba, Italy – 28/05/2013

2. PID BY cherenkov ring imaging
Particle Identification:
Cherenkov angle qc
particle velocity b +
momentum p known
Roberts never built a practical device…
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3. PID BY cherenkov ring imaging
Particle Identification:
Cherenkov angle qc
particle velocity b +
momentum p known
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4. Examples of cherenkov angles and Photon yield
L = radiator length
ei = photon detector efficiencies
Np.e. : number of photoelectrons
The figure of merit is a measure of quality of the optical system and detector performance, limited mainly by photon detection efficiency (PDE), which is usually 10-20%
N0 ~ cm-1 typically
Radiator
Refractive
index gt
qmax
Dqc = qc(p)-qc(K)
[mrad]
Nph/(cm eV)
Npe/(cm eV)
(N0=50 & b=1)
Solid Quartz (SiO2)
1.47
1.37
47.1o (823 mrad)
4 GeV/c
199 27
Liquid C6F14
1.3
1.56
39.7o (693 mrad)
4 GeV/c
151 20
Aerogel (SiO2)
1.05
3.3
17.8o (309 mrad)
4 GeV/c
34.4
4.7
C4F10 gas at 1 bar
1.0015
18.3
3.13o (55 mrad)
10 GeV/c
1.1
0.15
He gas at 1 bar
111
0.5o (8.9 mrad)
100 GeV/c
0.03
0.004
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5. Resolution of rich detectors
J. Seguinot and T. Ypsilantis, Nucl. Instr. & Meth. A343(1994), 1-29 and 30-51
E. Nappi and J. Seguinot, Rivista del Nuovo Cimento, Vol 28. N. 8-9 (2005)
Error on particle’s b
sqc (chromatic) : resolution broadening because of radiator dispersion n=n(l)
sqc (pixel) : resolution broadening due to final detector pixel size (spatial resolution)
sqc (imaging) : effect of imaging method (lens, mirrors,…)
goal:
detect the maximum number of photons with the best angular resolution
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6. Ideal particle separation
J. Seguinot and T. Ypsilantis, Nucl. Instr. & Meth. A343(1994), 1-29 and 30-51
E. Nappi and J. Seguinot, Rivista del Nuovo Cimento, Vol 28. N. 8-9 (2005)
b ~ 1
Separation in number of sigmas
In practical counters sqc(tot) is typically between 0.1 and 4 mrad
J. Va’vra, Fermilab
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7. proximity focusing DIRC
Rich counter design
PHYSICS / PID
momentum
range
separation
power
photon detector
radiator
photon detector
configuration
high momenta:
mirror focusing
low momenta:
proximity focusing DIRC
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8. Examples of cherenkov radiators
Material
Refractive
index
@ 600 nm
pthreshold [GeV/c]
cutoff
[nm] p K He
16.68
59.01
112.14
112 Ar
5.87
20.75
39.44
124
CO2
4.66
16.47
21.48
175
C4F10
1.0015
2.5
9.0 17
136
Aerogel
1.03
0.6
2.0
3.8
300
C6F14
1.3
0.174
0.614
1.168
165
H2O
1.33
0.158
0.56
1.065
190
NaF
0.161
0.567
1.079
125
LiF
1.39
0.144
0.509
0.969
105
quartz
1.46
0.132
0.465
0.884
158
solids liquids gases
(limit for total internal reflection ~ 1.41)
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9. Photon detector requirements
Single photon (VUV visible) sensitivity
High photoconverter QE + ese (low noise)
Large packing factor (active area %) egeom
High granularity minimize sq
Depending on experimental conditions:
rate capability and ageing properties
large area coverage (cost)
sensitivity to B
maximize Npe
Gaseous
(UV)
Vacuum based
(UV, visible)
Solid state
(visible)
TEA,TMAE,EF/MWPC, CsI/MWPC,
CsI/THGEM
PMT, MaPMT, MCP-PMT, HPD
G-APD, SiPM
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10. Performance limit
For any combination of radiator and detection bandwidth there is an intrinsic (chromaticity) performance limit
Evolution of RICH technique in last ~15 years:
shift of detector bandwidth from UV to visible (larger N0, higher rate capability,…)
development of CsI-based gaseous UV photo-detectors for large systems to overcome operational issues related to photosensitive vapors used in the past (e.g. DELPHI, SLD)
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11. Some Rich counters in NP and hep experiments
Type
Radiator (n)/L
Photon detector
(photosensitive area)
CERN/LHC
Proximity focusing
C6F14 (1.029)/1.5 cm
CsI-MWPC
(11 m2)
CERN/SPS
Mirror focusing
C4F10 (1.0014)/3 m
CsI-MWPC + MAPMT
(6 m2)
CESR
LiF (1.46) / 1 cm
MWPC (TEA+CH4)
( 16 m2)
RHIC
CF4 (1.0005) / 50 cm
CsI-GEM
(1.5 m2)
CERN/LHC
Aerogel (1.03)/ 5 cm C4F10 (1.0014)/ 80 cm
CF4 (1.0005) / 200 cm
HPD
(3.3 m2)
CERN/SPS
Ne ( ) / 18 m
PMT
( 0.4 m2)
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12. LiF radiator for CLEO III
p/K separation from 470 MeV/c to 2.65 GeV/c with 4σ significance
LiF radiator, photon detector MWPC with TEA/CH4
nLiF (7 eV)= 1.46
total internal reflection
“sawtooth” radiator
track angles < 22 o)
M. Artuso et al., NIMA 554 (2005) 147
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13. Csi: a breakthrough in cherenkov photodetection
multilayer pcb with metalized holes
gold front surface (0.4 mm)
nickel barrier layer (7mm)
(F. Piuz et al., R&D for the development of large area CsI photocathodes, 1992):
CsI processing, QE enhancement (substrate layout and cleaning, slow deposition rate 1 nm/s, thermal treatment at 60 oC for 8 h, in situ encapsulation and dry Ar, in situ measurement of PC response, mounting in glove-box)
Stable operation under gas (read-out electronics with long integration time (1 ms)  low gas gain ~5 x 104)
40 cm
60 cm
H. Hoedlmoser et al., NIM A 574 (2007) 28.
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14. Csi deposition plant at CERN
Mass production of ALICE
RICH CsI photocathodes
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H. Hoedlmoser et al., NIM A 566 (2006) 338.

15. High Momentum Particle Identification Detector
alice hmpid at LHC
High Momentum Particle Identification Detector
p/K: 1-3 GeV/c
K/p: GeV/c
1.3m
1.4m
Pb-Pb collisions
7 proximity focusing RICH modules, ~ 11 m2 of CsI photosensitive area, 5 m from IP
6 CsI photocathodes of 0.64m x 0.40m per module
Charged particles multiplicity ~10000/evt, trigger rates ~ 5kHz
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16. alice hmpid at LHC Radiator: 15 mm C6F14 – n=1.3 @ 170 nm
Photon detector:
MWPC, CH4 at atm. P, 8x8.4 mm2 pad segmented cathode coated with 300 nm CsI layer
multiplexed analogue pad readout, ~ channels
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17. High rates: the case of compass at cern/sps
Hadron PID from 3 to 60 GeV/c
Photosensitive area ~ 6 m2
Trigger rates: up to ~30 kHz, beam rates up to ~40 MHz
RICH in operation since 2002, upgraded in 2006 with Hamamatsu R M16 MaPMTs on 25% of active area
5 m
6 m
3 m
MWPC’s + CsI
UV mirror
wall
Al vessel
radiator gas: C4F10
PMT’s
MWPC+CsI operation at large rates induces PC ageing due to ion bombardment and/or instability owing to space charge build up
1.6 mC/cm2
6.3 mC/cm2
6.8 mC/cm2
H. Hoedlmoser et al., NIM A 574 (2007) 28.
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18. CsI + GEMs • fast signals [1-10 ns] • high gain [>105]
R. Chechik and A. Breskin
NIM A 595 (2008) 116
Micro-hole + Flipped reverse-bias strip plates:
ions are trapped by negatively biased cathode strips
semi-transparent
photocathode
• fast signals [1-10 ns]
• high gain [>105]
• operation in noble gases(mixtures)
• high 2D precision
• largely reduced photon feedback compared to “open” geometry
• no ion feedback
• high rate capability
(> 106 particles/mm2)
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19. Phenix HBD at Rhic B≈0 0.65 m qpair mesh El. Field e- e+ 1.21 m
Cherenkov
blobs e+ e-
qpair
opening angle
B≈0
1.21 m
mesh
El. Field
primary ionization from dE/dx
photo
electron
CsI (350 nm)
GEMs
pads
Hadron Blind Detector, 50 cm CF4 gas radiator, proximity focusing, photon blobs imaging by CsI/3-GEM operated with same CF4 (windowless detector, record N0 ~ 300 cm-1)
Reverse bias in drift region for “hadron blindness”, detect only e+/e-
NIMA (2011) doi: /j.nima
QM2011
Distinguish open Dalitz (2 singles) from close conversion (one double) e+e- pair
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20. THGEM & RETGEM
THGEM
Standard GEM
1mm
105 gain in single-TGEM
Thick-GEMs (TGEMs) were introduced later in the last decade as evolution of GEMs towards a simpler and more robust detector (holes are drilled in standard PCB, Cu etching of hole’s rims)
gain in single GEM
V. Peskov et al., Nucl. Instrum. Methods A576(2007), 362
Resistive TGEMs (RETGEM) have resistive instead of metallic electrodes, providing additional protection against sparks
100 mm
V. Peskov et al., Nucl. Instrum. Methods A478(2002), 377
Hole diameter d = mm
Pitch a = mm
Thickness t = mm
IBF <10%
time resolution of 8 ns RMS
Thick GEM and RETGEM are robust and cost effective solution for large area RICH applications
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21. ALICE & COMPASS R&D on CsI-Thgem counters
ALICE VHMPID
Effective gain:
0.91 · 106
Ar/CH4: 50/50
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22. ALICE VHMPID upgrade VHMPID DCAL
Integration RICH+EMCAL to address jet physics → limited space, reduce radiator L
Lower PID range (p/K: 5-16 GeV/c, K thresh. 1 bar ~ 9 GeV/c)
A. Di Mauro et al, VCI 2013 proceedings
C4F8O radiator gas pressurization: tune refractive index + increase photon yield to compensate shorter L
CERN PS/T10, 3.5 bar
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23. Aerogel as cherenkov radiator
Silica SiO2 colloid, the lightest “solid”, : mg/cc
Fills the gap between gaseous and liquid radiators, n:
Production of hydrophobic aerogel of outstanding quality driven by BELLE
n=1+0.26*
most of the
photons experience
Rayleigh scattering
T=A*exp(-Ct/4)
visible light detection
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24. LHCb RICHs Two RICHs for p/K separation from 1 to 100 GeV/c
Photon detectors: 484 HPDs developed in collaboration with industry (Photonis:)
quartz window with S20 photocathode;
cross-focusing optics;
- space resolution 2.5 x 2.5 mm2;
- low noise (dark count rate < 5 kHz/cm2);
- 0.5 Mchannels
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25. LHCb RICHs - huge yields of charmed hadrons 10 x B-factories
C4F10
(small rings)
Aerogel (large rings)
CF4
RICH1
RICH2
- huge yields of charmed hadrons 10 x B-factories
very low background
first evidence for charm CP-violation
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26. LHCb RICHs UPGRADE
HPD issues: constantly increasing rate of ion feedback (residual gas ionization) + 1 MHz readout of encapsulated FEE not compatible with future high luminosity (2x1033 cm-2 s-1) replace photodetectors (MaPMT, MCP- PMT under consideration)
RICH1 aerogel radiator, compromised p/K separation at high luminosity (low photon yield wrt background) DIRC type TOF detector called TORCH (Time Of internally Reflected Cherenkov light) with MCP-PMT behind RICH2
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27. FDIRC, TOP, TORCH
Focusing-DIRC: add focusing mirror to correct emission point uncertainty+ arrival time of photons to correct chromatic error
p/K separation > 2.5 s up to 4.2 GeV/c
Needs ~ 200 ps time resolution (Photonis MCP)
Time Of BELLE II
Measure D(TOF+TOP) to identify p/K < 4 GeV/c
Needs ~ 40 ps time resolution (Hamamatsu MCP)
NIMA 639 (2011), 282
K. Matsuoka, proceedings of VCI 2013
In PANDA FDIRC: chromaticity corrected by LiF block
TORCH
Measure D(TOF+TOP) to identify p/K < 10 GeV/c
L~ 10 m, DTOF (p-K) = 35 ps at 10 GeV → aim for ~15 ps resolution per track
Need ~ 40 ps time resolution (Photonis MCP)
NIMA 639 (2011), 173
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28. MCP-PMT
MCP-PMTs (1960s) are based on the concept of continuous dynode electron multiplier (Farnsworth, 1930)
concern: limited photocathode
life-time due to ion feedback, Al layer blocks almost all ions
Commercial devices (Photonis, Hamamtsu, …) still very expensive due to Pb-glass processing.
LAPPD (Large Area Picosecond Photon Detectors) collaboration at Argonne and Chicago uses atomic layer deposition on Incom glass, aim at cheap large area MCP production.
8” x 8” plate
A. Elagin, VCI 2013 Proceedings
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29. FARICH
Proximity focusing RICH with aerogel and NaF radiator+ MCPPMT, proposed for SuperB and Tau-Charm factory at Novosibirsk.
NaF radiator has the lowest n among solids 600 nm), no internal reflection down to ~ 170 nm
p/K separation > 3 s up to ~ 7 GeV/c
X0 ~ 26% :
Aerogel, 3 layers, 40 mm in total ~ 4%
Naf, 5 mm ~ 4%
MCP-PMT ~ 8%
Cables, mechanics ~ 10 %
NIM A 639(2011), 290
NIM A 595(2008), 100
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30. Summary Reach of present PID techniques
J. Va’vra, Fermilab
TOF& dE/dx cover the lowest momentum range, “the RICH technique is clearly superior to all other methods” (J. Va’vra)
For a given Cherenkov radiator several options exist for the photon detector and the choice will depend mainly from experimental conditions (and cost…)
Availability of commercial devices with time resolution of a few10 ps is pushing the mixing of TOF and RICH techniques (FDIRC, TOP, TORCH,…) for all high luminosity future systems
Interesting developments are ongoing in the field of micropattern gaseous photon counters (CsI+GEM, TGEM, …) which represent still the most cost-effective solution for large photosensitive surface (> 1 m2)
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31. backup
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32. BABAR dirc
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33. A. Di Mauro - CERN