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Particle ID detectors of other types than RICH

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. Introduction.

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Particle ID detectors of other types than RICH

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  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 PID’s which are complementary to Ring Imaging type Cherenkov detectors: • Use b for PID • ToF, • dE/dx (@ low p), • Threshold type Cherenkov • Use g for PID • dE/dx(@ 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 fromp (by radii of track in a magnetic field) and v by L/t. D p/p= 10-3, D L/L=10-3, 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 emissionin 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 PMT’s Nphoton~20,000/cm

  6. PID with TOF system (Scintillator) • Expected timing resolution for long counters

  7. PID with TOF system (Scintillator) • NA49 • Pb+Pb 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 (> 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; < 200 ps • Small signal (<3 clusters) Need high gain -> High sparking rate. • Double thin gaps (0.6 mm) • Good time resolution; < 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 @ HV=3.4 kV for MIPs 100 % for slow protons. • > 95 % efficiency ALICE prototype PPC

  11. Gap (100 mm) Strip Line Resistive anode Pressure Vessel Cathode PID with TOF system (Pestov) • Time of Flight counter with Pestov Counters (Ex. NA49, FOPI, ALICE ToF). Excellent R&D work done by the PesToF collaboration • Idea of a spark counter with a localized (1~2 mm2) discharge. (NIM 93(1971)269) • Operated in streamer/spark mode. • Use highly resistive anode: semi-conductive glass (109 ~ 1010Wcm). • Spark gap: 100+-2.5 mm. • HV > 3 kV for streamer operation. • Gas: Ar/iC4H10/C2H4/C4H6=76.9/20/2.5/0.6 @ 12 bar：UV absorptive gas. • 4~5 primary electrons for MIPs. • Rise-time: < 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/iC4H10=85/10/5 • Four 0.3 mm gaps: Two conductive glass layers with electrically floating. • Need a high precision gap distance: 5mm • Timing resolution: 90 ps @ 98 % efficiency. • With a new design: 50 ps @ 99 % efficiency.

  14. Schott 8540 (2mmt) (1010Wcm) Anode (3x3 cm2) Schott A14 (0.5 mmt) (1.5x1012Wcm) Schott A2 (0.5 mmt) (8x1012Wcm) Cathode (3x3 cm2) 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 @12kV -> 50 ps from MRPC • Tail contribution is only 0.16% • Time walk: 25ps/kV • Rate vs Timing: even at 200Hz/cm2 70 ps with > 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 Cobb’s approach. (by H. Bichsel) • Use photo-absorption cross-sections. • At a thickness of x>15 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 doesn’t 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) 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. Dispersion Cherenkov radiation X-ray region 1/b Refractive index (n(w)) 1 Frequency of photon (w) Chrenkov and Transition radiations Cherenkov radiation: n(w)b > 1. Emits inside a medium. Transition radiation : n(w)b < 1. Only at the boundary btw two media. Mostly x-ray region.

  22. PID with TRD • Principle of Transition Radiation. (Frank and Ginzburg:J. 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. 0V HV TR dE/dx PID with TRD • Direction of TR • Number of TR photons; 0.59% z 2 for ~ 2keV (g=1000) 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 0 5 10 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 modules=3.6 m) e/p separation:1500/1(he>99.5%) Number of detected X-rays/module p E>6.5 keV e Lorentz factor (g) No. of clusters

  30. p-rejection factor Detector length (cm) 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. For a p/K separation at a few GeV/c region, only the silica-aerogel is the candidate.

  33. O O Si(CH3)3 O O H Si Si O O O Si O Si Si Si 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 pe`s are expected for b = 1, however, in reality life is not so easy, especially in a high magnetic field. • Further reduction of pe’s 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 1.5<p<3.5 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~ 5x10-14[E(TeV)]2[nmax/IGHz]2. • Possible radiators • Antarctic Ice: Transparent to radio and micro waves. RICE (Radio Ice Cherenkov Experiment) • Rock salt: latt > 400m @ 100 MHz. Salt dome:(1-2 km f) x (>10km) • Higher density than ice -> small shower size -> 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. 3s separation for p/K 10 ToF (100ps@FWHM) TR+dE/dx RICH Gases dE/dx 1 Aerogel Detector length (m) Liquid-Solid 10-1 ACC 10-2 10-1 1 101 102 103 Momentum (GeV/c) Summary Belle PID performance Quote from the Prof. Dolgoshein’s talk at the last RICH Workshop.

  41. 3s separation for e/p 10 ToF (100ps@FWHM) RICH dE/dx Gases 1 Aerogel TR+dE/dx Detector length (m) Liquid-Solid 10-1 10-2 10-1 1 101 102 103 Momentum (GeV/c) Summary Quote from the Prof. Dolgoshein’s talk at the last RICH Workshop.

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