Particle ID detectors of other types than RICH

1
Particle ID detectors of other types than RICH

• Introduction
• PID with TOF system
• Scintillation counters
• PPC, Pestov, RPC
• PID with dE/dx measurements
• PID with TR measurement
• PID with threshold-type Cherenkov counters

2
Introduction

• There are some PIDs which are complementary to
  Ring Imaging type Cherenkov detectors
• Use b for PID
• ToF,
• dE/dx (_at_ low p),
• Threshold type Cherenkov
• Use g for PID
• dE/dx(_at_ high p)
• TRD
• Use the Askaryan effect
• Ultra high energy neutrino detection
• 
  

3
PID with TOF system

• Principle of Time of Flight counters
• Obtain mass from p (by radii of track in a
  magnetic field)
• and v by L/t.
• D p/p 10-3, D L/L10-3, t 6.6 ns for L 2
  m, D t 100ps
• D t/t 1.5 dominant error.
• Particle separation capability

4
PID with TOF system (Scintillator)

• Time of Flight counter with scintillation
  counters.
• Well proven technology.
• Mechanism of light emission in the scintillator.
• Primary UV emission
• Secondary emission
• Wavelength shifter
• Transit time spread limits the performance of
  PMT.
• Normal Line-focus type 250 ps for XP2020
• Fine-mesh type 150 ps for R2490-05
• Micro-channel Plate type 55 ps for R2809U

5
PID with TOF system (Scintillator)

• Number of photo-electrons measured by PMTs

Nphoton20,000/cm
6
PID with TOF system (Scintillator)

• Expected timing resolution for long counters

Reference Counter size (cm) Scinti. PMT latt (cm) st(meas) st(exp)
G.D.Agostini 3(t) x 15(W) x 100(L) NE114 XP2020 200? 120 60
T. Tanimori 3 x 20 x 150 SCSN38 R1332 180 140 110
T. Sugitate 4 x 3.5 x 100 SCSN23 R1828 200? 50 53
R.T. Gile 5 x 10 x 280 BC408 XP2020 270 110 137
TOPAZ 4.2 x 13 x 400 BC412 R1828 300 210 240
R. Stroynowski 2 x 3 x 300 SCSN38 XP2020 180 180 420
Belle 4 x 6 x 255 BC408 R6680 250 90 143
7
PID with TOF system (Scintillator)

• NA49
• PbPb collision

TOF-G performance 1x1.5(t)x122(L) cm3 95 ps
expected
TOF-T performance
70 ps
85 ps
8
PID with TOF system (Scintillator)

• Belle

9
PID with TOF system (PPC)

• Time of Flight counter with Parallel Plate
  Chambers.
• Can cover large area (gt 100 m2)
• Operated in avalanche mode.
• Thickness of the gap
• Thick ( 3mm)
• Large signal (10 clusters)
• Worse time resolution due to long drift 1ns.
• Thin ( 1mm)
• Good time resolution lt 200 ps
• Small signal (lt3 clusters)
• Need high gain -gt High sparking rate.
• Double thin gaps (0.6 mm)
• Good time resolution lt 200 ps
• High efficiency .95
• Low spark rate 10-5.

Typical detector size 3x3 to 6x6 cm2.
10
PID with TOF system (PPC)

• Gases
• DME/C2H4F2 80/20
• Having good quenching property.
• 10-5 sparking rate _at_ HV3.4 kV for MIPs
• 100 for slow protons.
• gt 95 efficiency

ALICE prototype PPC
11
PID with TOF system (Pestov)

• Time of Flight counter with Pestov Counters (Ex.
  NA49, FOPI, ALICE ToF).
• 
  Excellent RD work done by the
  PesToF collaboration
  
  
• Idea of a spark counter with a localized (12
  mm2) discharge. (NIM 93(1971)269)
• Operated in streamer/spark mode.
• Use highly resistive anode semi-conductive glass
  (109 1010 Wcm).
• Spark gap 100-2.5 mm.
• HV gt 3 kV for streamer operation.
• Gas Ar/iC4H10/C2H4/C4H676.9/20/2.5/0.6 _at_ 12
  barUV absorptive gas.
• 45 primary electrons for MIPs.
• Rise-time lt 300 ps

Spark
12
PID with TOF system (Pestov)

• Excellent timing resolution 52 ps.
• At higher voltage (2xU0) 25 ps is possible
• Long tail due to delayed spark is
• observed.
• Need time walk correction by double threshold
  discriminator extrapolate to T0 .
• The tail behavior depends on the gas mixture.

Dt(P1-P2)
st (ps)
Dt(P-Scint)
13
PID with TOF system (RPC)

• Time of Flight counter with Resistive Plate
  Counters.
• Operated in avalanche mode at atmospheric
  pressure.
• Use non-flammable gas mixture
• C2H2F4/SF6/iC4H1085/10/5
• Four 0.3 mm gaps Two conductive glass layers
  with electrically floating.
• Need a high precision gap distance 5mm
• Timing resolution 90 ps _at_ 98 efficiency.
• With a new design 50 ps _at_ 99 efficiency.

14
PID with TOF system (RPC)

• Multigap Resistive Plate Counters.
• 5 gas gaps with 220 mm 6 glass layers.
• Induced signal on the electrode is sum of all the
  activity of all gaps.

15
PID with TOF system (RPC)

• Timing resolution 70 ps _at_12kV
• -gt 50 ps from MRPC
• Tail contribution is only 0.16
• Time walk 25ps/kV
• Rate vs Timing even at 200Hz/cm2
• 70 ps with gt 95
  eff.

16
PID with dE/dx measurements (1)

• Measurements of Energy loss.
• Modified Bethe-Bloch equation include the
  Fermi effect
• At low b -1/b2
• Minimum at bg 3 4
• At high bg lng2
• Saturates due to density function d(bg)
• Saturates at gsat. 154 for He
• 230 Ar
• 68.4 CH4
• 55.3 C2H6
• 42.4 C4H10
• 
  5.6 Si

17
PID with dE/dx measurements (2)

• Ecut depends on gases and tracking method etc.
• 10 to 100 kev
• For a thin layer of gases, better energy loss
• calculation is obtained by a PAI method
• as Allison and Cobbs approach. (by H. Bichsel)
• Use photo-absorption cross-sections.
• At a thickness of xgt15 mm, it gives the same
• results by the Landau-Valilov

Ecut dependence.
18
PID with dE/dx measurements (3)

• Particle Separation
• Expression of dE/dx resolution (A.H. Walenta et
  al. NIM 161(1979)45)
• n number of sampling layers,
• t thickness of the sampling layer
  (cm)
• p pressure of the gas (atm)
• It doesnt depend on n-0.5 due to the Landau
  flactuation.
• If the total lever arm (nt) is fixed, it is
  better to increase n
• so long as the number of produced ion-pairs
  are enough in each layer.

19
PID with dE/dx measurements (4)

• Data from M. Hauschild (MIN A 379(1996) 436)

Type n X (cm) P (bar) Gas Calc.() Meas.()
Belle Drift ch. 52 1.5 1 He/C2H650/50 6.6 5.1
Babar Drift ch. 40 1.4 1 He/C4H1080/20 7.5 7.2
CLEOII Drift ch. 51 1.4 1 Ar/C2H650/50 6.4 5.7
ALEPH TPC 338 0.4 1 Ar/CH491/ 9 4.6 4.5
TPC/PEP TPC 183 0.4 8.5 Ar/CH480/ 20 2.8 3.0
OPAL Jet ch. 159 1.0 4 Ar/CH4 /iC4H10 88.2/9.8/2 3.0 2.8
MKII/SLC Drift ch. 72 0.83 1 Ar/CO2 /CH4 89/10/1 6.9 7.0
Higher pressure gives better resolution, however,
the relativistic rise saturate at lower bg.
4 5 bar maybe an optimum
pressure. Higher composition of hydro-carbons
gives better resolution. Belle and CLEOII.
Landau distribution (FWMH) 60 for noble
gas, 45 for CH4,33 for C3H6
20
PID with dE/dx measurements (5)

• Example of the Belle PID by dE/dx (80 truncated
  mean)

21
Chrenkov and Transition radiations
Cherenkov radiation n(w)b gt 1. Emits
inside a medium. Transition radiation n(w)b lt
1. Only at the boundary btw two media.
Mostly x-ray region.
22
PID with TRD

• Principle of Transition Radiation. (Frank and
  GinzburgJ. Phys.9(1945)353)
• Radiation at the boundary btw two media having
  different e.
• A kind of dipole radiation (charged particle
  and its mirror image).
• Spectrum of TR
• 
  
• w1 and w2 are Plasma frequencies of
  two media.
• 
  
• 
  20eV for styrene.
• Energy loss by the TR increases with g linearly.

23
PID with TRD

• Direction of TR
• Number of TR photons
• 0.59 z 2 for
  2keV (g1000)
• Needs lots of thin material with low z
• (transparent for X-rays absorption Z5
• 
  Lithium, polypropylene foils).
• Need careful optimization for the foil
  thickness and the spacing .
  

f 1/g
24
PID with TRD

• Pulse height spectrum by ATLAS TRT
• Detector
• Straw tubes 4 mmf, 40-150 cm (L)
• Gas mixture
• Xe/CF4/CO2/
• 70/20/10

With radiator
5
10
0
Energy (keV)
Without radiator
25

• ATLAS-TRT
• Radiators

26
PID with TRD

• Analysis methods
• Needs to separate dE/dx signals and TR x-ray
  signals.
• Total energy method
• Maximum Likelihood
• Truncated mean cut at 30-40 of maximum (reduce
  Landau tail)
• Q-method
• Cluster counting method
• N-method set threshold at a few keV and
  count TR hits.
• Fine-grain structure a lot of thin
  radiator-layers and
• x-ray detectors.
• (Q,N) method
• 2dimensional information of Q and N.

27
PID with TRD

• Time over threshold method (V. Bashikirov NIM
  A433(1999)560
• 
  B. Dolgoshein
  NIM A433(1999)533)
• Can be used for trigger.

p
e
TM
p
e
ToT
28
PID with TRD

• Time over threshold method vs. N-method (ATLAS
  TRT)
• 
  NIM A
  474(2001) 172
• For 5 GeV/c pseudo-tracks estimated by a
  single straw beam test result.

ToT
Nclust
29
PID with TRD

• E715 (TRD 30cmx12 modules3.6 m)
• e/p separation1500/1 (hegt99.5)

Number of detected X-rays/module
p
Egt6.5 keV
e
Lorentz factor (g)
No. of clusters
30
PID with TRD

• TRD performance vs detector length

31
PID with TRD

• Si-pixel TRD
• Proposed for TESLA experiment
• Operated in 3T magnetic field
• Separate the TR and the track with
• a fine spatial and energy resolution.

32
PID with Threshold type Cherenkov counters

• Threshold type Cherenkov counter.
• Much simpler than RICH only ON/OFF (Npe)
  information.
• Needs highly transparent and low refractive index
  materials for a radiator to separate p/K at a few
  GeV/c range necessary for heavy
• flavor physics.

Material Refractive index
Solid Glass 1.47
Silica Aerogel 1.006 1.08
Liquid Water 1.33
Liq. Hydrogen 1.112
Gas CO2 (1 atm) 1.000410_at_STP
Air (1 atm) 1.000293_at_STP
For a p/K separation at a few GeV/c region, only
the silica-aerogel is the candidate.
33
PID with Threshold type Cherenkov counters

• Aerogel radiator
• Hydrophobic silica aerogels by a surface
  modification.

34
PID with Threshold type Cherenkov counters

• Number of photo-electrons.
• More than 99 efficiency with Npe 5, however,
  if we set threshold
• at 1 pe, then 97 .
• Provide N0 90/cm, L 10 cm and n 1.01, then
  17 pes are expected for b 1, however, in
  reality life is not so easy, especially in a high
  magnetic field.
• Further reduction of pes is observed in 1.5
  Tesla for FMPMT
• about ½.
• Light yield saturates at around 14 cm in depth
• (PMT acceptance) /(Aerogel surface area)
  decreases.

35
PID with Threshold type Cherenkov counters

• ACC
• K/p in 1.5ltplt3.5 GeV/c
• Barrel 960 modules
• in 60 f-segments
• n 1.010 1.028
• FWD endcap 228 modules
• in 5 layers
• n 1.030

36
PID with Threshold type Cherenkov counters

• p/K separation capability by
• the Belle Aerogel Cherenkov
• Counter (ACC)
• The performance is very stable
• for 4 years operation.

37
Radio pulse Cherenkov Radiation

• Detection of a radio pulse Cherenkov radiation
  for an ultra-high energy neutrino detection
  (GeV-TeV region can be covered by NESTOR).
• Askaryan effect. (Zh. Eksp. Teor. Fiz
  41(1961)616)
• In an electromagnetic shower there is an
  asymmetry between e and e-, which results in a
  negative net charge. An emission of coherent
  radio pulses is expected for a wavelength
  comparable with the shower size.
• The power of radio pulse is proportional to
  quadratic of E not to linear.
• Total power W 5x10-14E(TeV)2nmax/IGHz2.
• Possible radiators
• Antarctic Ice Transparent to radio and micro
  waves.
• RICE (Radio Ice Cherenkov Experiment)
• Rock salt latt gt 400m _at_ 100 MHz. Salt dome(1-2
  km f) x (gt10km)
• Higher density than ice -gt small shower size -gt
  may coherent even at 10 GHz.
• Limestone
• Moon Use a few meters of the surface regolith as
  the radiator and radio
• telescopes as the detector.

38
Radio pulse Cherenkov Radiation

• Observation of the Askaryan effect
  
• 
  Phys.Rev.Lett.86(2001) 2802
• Use silica sand as a radaiator.
• Power profile (1.7-2.6 GHz). is consistent with
  the shower theory

39
Summary

• ToF
• Timing resolution of 50 ps is obtained by small
  scintillators.
• Almost the same or better performance is
  demonstrated with Pestov counters and the newly
  developed RPC.
• dE/dx
• dE/dx resolution can be improved by a selection
  of gas mixture.
• TRD
• Have excellent performance for lepton (e/p)
  identifications.
• Threshold Cherenkov
• The transparent silica-aerogels covers the index
  gap between
• gases and liquids. The hydrophobic aerogels show
  no degradation after 6 years operation.
• The Askrayan effect is observed.
• Now people are using radio-pulse Cherenkov
  radiation.

40
Summary
Belle PID performance
Quote from the Prof. Dolgosheins talk at the
last RICH Workshop.
41
Summary
Quote from the Prof. Dolgosheins talk at the
last RICH Workshop.