Cherenkov detector R&D for super B factory - Introduction - Prototype development - Performance test - Summary K. Inami (Nagoya university)
Current Belle detector � PID of π ± /Κ ± � Aerogel Cherenkov counter (Threshold type) � TOF counter � dE/dx in drift chamber � Contribute to flavor discrimination � Physics analysis � B � ππ /K π , ργ , K νν etc. � Flavor tag, Full reconstruction � Current performance � Efficiency; 90~ 80% � Fake rate; 5~ 10% Want less fake rate for precise measurements � 2009/3/9-10 2
Belle PID upgrade - PID ( Κ/π ) detectors - Barrel PID and Aerogel RICH counters are both Cherenkov ring imaging detectors. - dE/dx in drift chamber Aerogel RICH Focusing DIRC / TOP counter / iTOP 1.2m 2.6m e + e - 3.5GeV 8.0GeV 2009/3/9-10 3
TOP counter � Cherenkov ring in quartz bar � Reconstruct ring image using ~ 20 photons on the screen reflected inside the quartz radiator as a DIRC. � Photons are detected with photon detectors. Different ring image for the pion and kaon of the same momentum K π y x θ c = cos (1/n β ) Need large screen... Φ Quartz : n = 1.471 (@ λ =390nm) 2009/3/9-10 4
TOP counter � 2D position information � Position+ Time � Compact detector! Simulation y 30000 TDC (ps) 2GeV/c, θ =90 deg. ~400mm Linear array PMT (~ 5mm) Quartz radiator Linear-array type Time resolution σ ~ 40ps z 28000 x photon detector 20mm 26000 L ~ 2m X 24000 θ = β cos 1 / n 22000 c 20000 ~ 200ps K 18000 π 16000 Different opening angle for the same momentum 14000 � Different propagation length(= propagation time) 12000 -20 -10 0 10 20 X (cm) + TOF from IP works additively. 2009/3/9-10 5
TOP counter � Quartz: 255cm L x 40cm W x 2cm T � Focus mirror at 47.8deg. to reduce chromatic dispersion � Multi-anode MCP-PMT � Linear array (5mm pitch), Good time resolution (< ~ 40ps) � � Measure Cherenkov ring image with timing information Focus mirror (sphere, r=5000) z=1830 z=1070 z=-780 R=1180 Forward Backward MCP-PMT o 5mm 47.8 2cm o ~123.5 o 32.8 IP 40cm 2009/3/9-10 6
Expected performance � K/ π separation power Current Belle � GaAsP photo-cathode + Focusing mirror 16 100 Separation power ( σ ) Efficiency (%) 2.0GeV/c 98 14 2GeV/c 3.0GeV/c 96 3GeV/c 4GeV/c 12 94 4.0GeV/c 92 10 90 40 50 60 70 80 90 8 θ (deg.) 10 Fake rate (%) 4.0GeV/c 6 8 6 4 4 2 3.0GeV/c 2 2.0GeV/c 0 0 40 60 80 100 120 40 50 60 70 80 90 polar angle (deg.) θ (deg.) > 4 σ K/ π upto 4 GeV/c, θ< 90 ﾟ , < 2% fake rate 2009/3/9-10 7
Prototype development � Demonstration of the performance Glued Glued 915mm 915mm PMT 400mm 400mm 400mm quartz quartz 20mm 20mm 20mm Prototype overview Filter ( λ >400nm) Photon detector Quartz radiator (Fused silica) ・ ・ Flatness:<1.2 µ m/m ・ Time resolution Suppression of chromatic ・ ・ Efficiency Roughness:0.5nm dispersion 2009/3/9-10 8
Photon detector Square-shape multi-anode MCP-PMT � Single photon detection � 1ch 2ch 3ch 4ch Fast raise time: ~ 400ps � Gain= 1.5x10 6 @B= 1.5T � T.T.S.(single photon): ~ 35ps @B= 1.5T � 22(effective area) 27.5mm Position resoltion: < 5mm � Semi-mass-production (14 PMTs) � QE [%] σ =34.2 ± 0.4ps QE ： 24% @400nm TDC [1count/25ps] Wavelength [nm] TTS ＜ 40ps for all channels Ave. QE ： 17% @400nm 2009/3/9-10 9
PMT module HV divider + AMP + Discriminator � Small size (28mm W ) � Prototype � � Fast AMP (MMIC, 1GHz, x20) � Fast comparator (180ps propagation) AMP+ CFD � CFD with pattern delay Performance � � Test pulse � ~ 5ps resolution � MCP-PMT amp comparator � σ < 40ps to TDC � Working well to ADC input low voltage supply 2009/3/9-10 10
Quartz radiator MCP ‐ PMT � Check the quality for time resolution � Single photon pulse laser � λ = 407nm � MCP-PMT � Several incident position MCP ‐ PMT 47.2 deg. � � No degradation of time Quartz resolution � Enough quartz quality Line 1 Time resolution [ps] Line 2 σ <40ps Line 3 2009/3/9-10 Propagation length [mm] 11
Chromatic dispersion effect Variation of propagation velocity depending on the wavelength of Cherenkov photons QE [%] Group velocity (m/ns) 0.21 Light propagation velocity inside quartz 0.2 0.19 300 400 500 600 700 Wave length (nm) Wavelength [nm] � Range of detectable wavelength of Cherenkov photons � Time fluctuation of the Cherenkov ring image � Time resolution depends on the propagation length. 2009/3/9-10 12
Beam test � At Fuji beam line in June and Dec. � Using real size quartz and MCP-PMT � MCP-PMT: Multi-alkali p.c., C.E.= 60% Quartz + support jig TOP counter Timing counter Quartz bar (1850 × 400 × 20mm) 10mm φ quartz + MCP-PMT σ t0 < 15ps MWPC 1 MWPC 2 Trigger counter � Check MCP-PMT (56ch) Lead glass + � Ring image Finemesh PMT � Number of photons � Time resolution 2009/3/9-10 13
Ring image Data Simulation (4) TDC [1count/25ps] TDC [1count/25ps] (3) (2) (1) ch ch quartz (4) � Proper ring image Beam 915mm � Same time interval with simulation (2) (1) 358mm 2009/3/9-10 14
Number of detected photons Ave. num. of photons:15.7 Num. of photons � Normal incidence (90 deg.) � Obtained number of photons as expected � � We can expect ~ 22 photons/event, if we use 14 PMTs. � Normalized by active area (10 � 14 PMTs) 2009/3/9-10 15
Time resolution � TDC distribution of ch.29 � Compare with the distribution expected by a simulation including PMT resolution and chromatic dispersion effect Simulation ch29 Data 1 st 3 rd 3 rd 1 st Focus 2 nd 2 nd mirror quartz Beam Beam 1850mm (875mm) (875mm) 3 rd [1count/25ps] [1count/25ps] 2 nd 875mm 1 st Resolution(1 st peak) 76.0 ± 2.0 [ps] Data MCP ‐ PMT(ch29) 77.7 ± 2.3 [ps] Simulation 2009/3/9-10 16
Time resolution vs. propagation length � Check time resolution � For several incidence condition and channel Time resolution [ps] Simulation Propagation length [mm] � Data agrees well with simulation expectation. � Confirmed the level of chromatic dispersion effect 2009/3/9-10 17
Summary � R&Ds of Cherenkov detectors are in progress! � TOP counter for barrel PID upgrade at super B factory � Cherenkov ring imaging with precise timing information ( σ < 40ps) � Prototype development � Multi-anode MCP-PMT � 14 prototype PMTs show enough performance � TTS < 40ps for single photon for all channels � Integrated module with amplifier and CFD � Quartz radiator � Enough quartz quality for single photon detection � Performance test with beam � Proper ring image, number of detected photons (15.7 photons) � Time resolution as expected by simulation � Confirmed chromatic dispersion effect 2009/3/9-10 18
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