Proximity focusing RICH with flat pannel PMTs as photon detector

Transcription

1 Proximity focusing RICH with flat pannel PMTs as photon detector Peter Križan University of Ljubljana and J. Stefan Institute For Belle Aerogel RICH R&D group

2 Contents Motivation and requirements Beam test results Optimisation of counter parameters Summary

3 PID upgrade in the forward direction improve π/k separation in the forward (high momentum) region for few-body B decays good p/k separation for b -> d γ, b -> s γ improve purity in fully reconstructed B decays ('full recon. tag') low momentum (<1GeV/c) e/µ/π separation (B ->Kll) keep high the efficiency for tagging kaons talk by Toru Iijima on Belle PID upgrade (Friday)

4 PID upgrade in the forward direction n=1.28 I CDC 854 (BACC) n=1.2 n=1.15 H G F E D C B (1.5Tesla) 195(EACC/outside) 167(EACC/inside) 1622(BACC) n=1.13 n=1.1 A 3" FMPMT 2.5" FMPMT 2" FMPMT K/π separation at 4 GeV/c 3.m 2.5m 2.m 1.5m 1.m.5m.m B 34.2 AEROGEL RICH θ c (π) ~ 38 mrad ( n = 1.5 ) θ c (π) θ c (K) ~ 23 mrad 17. R 885 (BACC/inner) R 1145 (EACC/outer) R 1165 (BACC/outer) aerogel Proximity focusing RICH with aerogel as radiator Cherenkov photons photon detector charged particle δθ c (meas.) ~ 12 mrad With 2mm thick aerogel and 6mm PMT pad size 6σ separation with N pe ~1 2 cm 2 cm

5 Beam tests Beam Test Nov MAPMTs 3mm pitch, 36% eff. area, 192 readout channels single photon Cherenkov angle resolution better than 1mrad number of photons consistent with expectations, but clearly too low Beam tests Nov new aerogel samples new photon detector Hamamatsu H85 (flat pannel PMT) new readout electronics (124 channels)

6 Aerogel production improvement R&D in cooperation with Matsushita aim: better optical quality for n~1.5 hydrophobic aerogel a new solvent (Di-Methyl- Formamide instead of Methylalcohol) precursor (Methyl-silicate-51) from a different supplier -> considerable improvement Transmission length(mm) Matsushita (DMF) Matsushita (MtOH) Chiba-U. (MtOH) Novosibirsk (PrOH) 21 year (MtOH) Refractive index Ichiro Adachi s talk on aerogel R+D

7 Hamamatsu H85 (flat panel PMT) as photon detector 8x8 multi-anode PMT (64ch) by HPK Effective area=89% ( 49mm for 51.7mm package ) 4x4 array used in beam tests (124 ch in total ) channels) Not suitable for operation in magnetic field, but still good for the understanding of the detector behavior intermediate step in our R+D talks by Takayuki Sumiyoshi and Andrej Gorišek

8 Read-out electronics IC s with analog memory 2 analog memory chips for 1 PMT (each for 32ch) 8 step pipe-line ( 1µs x 8 ) Serial signal sent to VME ADC (1µs period x 256ch) Use 4 VME ADC channels for 124 ch readout Assembled flat panel PMT with read-out Analog memory board

9 Beam test set-up π - beam RICH1 RICH2.5 to 4. GeV/c RICH1: Flat panel PMTs and aerogel radiator MWPCs for tracking RICH2: as a reference (with R59-M16 PMTs) CO 2 threshold Gas Cherenkov counter for electron veto

10 Beam test results y (mm) x (mm) RICH1 ring Accumulated hits Clear rings, little background

11 Cherenkov angle resolution and number of photons Entries 35 3 (a) Cherenkov angle θ C σ =.314 rad = 14.1 mrad Entries (b) Number of hits N all = 6.84 N sig = θ C (rad) 1 2 N

12 Resolution for single photons Typically around 13 mrad (for 2 cm thick aerogel) Shown as a function of thickness, momentum σ θ (mrad) σ θ (mrad) n= 1.56 n= 1.51 n= thickness (mm) 5 n=1.56 n= Momentum (GeV/c)

13 Number of photons As a function of momentum, thickness, transmission length N pe n= 1.56, Λ = 3. mm n= 1.51, Λ = 18.3 mm thickness (mm) N pe n= n= Momentum (GeV/c) N pe (corrected) n 1.5 n Transmission length (mm) In good agreement with expectations. Can we increase the number of photons by keeping the good single photon resolution resolution? talk by Samo Korpar

14 PID capability on test beam data Entries Pseudo K from π (1.1 GeV/c) π (4. GeV/c) θ (rad) From typical values (single photon resolution 13mrad and 6 detected photons) we can estimate the Cherenkov resolution per track: 5.3mrad -> 4.3 sigma π/k separation at 4GeV/c. Illustration of PID performance: Cherenkov angle distribution for pions at 4GeV/c and 'kaons' (pions at 1.1GeV/c with the same Cherenkov angle as kaons at 4GeV/c). Details on the beam test: NIM A521 (24) 367 (physics/3932)

15 Resolution studies Cherenkov angle distribution. σ θ is obtained by fitting the θ distribution Gaussian + background σ θ (data)=14.3mrad 2 emp σ θ ( calc) = σ + σ 2 pix σ(calc) σ pix σ emp 11.8 mrad 7.8 mrad 8.8 mrad Radiator: thickness 2.5mm 2 emp 2 pix σ θ = σ + σ + σ What is rest? 2 rest

16 Resolution studies 2 σ θ (data) : Data(n=1.46) Cherenkov angle resolution σ calc : Calculated value (σ pix2 + σ emp2 ) 1/2 σ rest : (σ data2 - σ calc2 ) 1/2 Rest component σ rest =7~8 mrad doen not depend on radiator thickness Refractive index n(λ) Chromatic error? 2-3 mrad (depends on the sample)

17 Resolution studies 3 Non-uniformity of the radiator? Group tracks according to the impact position in 5mmx5mm regions, plot Cherenkov angle distribution for each of them: Cherenkov angle variation due to non-uniformity of aerogel: 1 mrad

18 Resolution studies 4 Does it depend on the orientation of the sample? Measure the Cherenkov angle and sigma for both orientations of the aerogel tile some samples have large difference in sigma for AB and BA cases AB sigma side BA (mrad) BA sigma side AB (mrad) still under study

19 Optimisation of counter parameters How to design radiator tiles: at the tile boundary photons get lost. Relative response aerogel beam direction aerogel x track(mm) 2 mm Scan with the beam across the tile boundary. As expected, the yield is affected over a few mm in the vicinity of the boundary. A simple model (all photons hitting the boundary get lost) accounts for most of the dependence Reduce the fraction of tracks close to tile boundaries and corners

20 Tiling of the radiator Two aerogel radiator tiling schemes for two max. tile size cases Ichiro Adachi s talk on aerogel R+D

21 Summary Proximity focusing RICH with aerogel as radiator looks as a very promissing option for the PID system upgrade of the endcap part of the Belle detector Flat panel PMT is an excellent single photon detector, suitable for RICH counters in absence of magnetic field Efficiently used to test design options of the Belle endcap PID upgrade, understanding of the system, improved aerogel samples and configirations, read-out systems under development. R&D issues for Belle endcap upgrade: development and testing of a multichannel photon detector for high mag. fields Mass production of large aerogel tiles Readout electronics

22 Back-up slides

23 Surface uniformity Study uniformity of the sensitivity over the surface - source: LED in the eyepiece of a microscope on a 2d stage - spot size 5 µm y(mm) x(mm) Single channel response of the H85 PMT

24 Read-out electronics RC Analog Memory Driver filter HV(11V) N ch Ext. power (5V) PMT 64ch (H85) AM(32ch) AM(32ch) Analog out AM control +5V Power PMT 64ch (H85) PMT 64ch (H85) AM(32ch) AM(32ch) AM(32ch) AM(32ch) GND Analog out AM control +5V GND Analog out AM control +5V GND AM control ADC Control pulse F I/O delay 1.5µs Analog Memory Controller Ext. Trigger Busy Trigger Gate from all system PMT 64ch (H85) AM(32ch) AM(32ch) Ditto Analog out AM control +5V GND Output Input Gate Input Software veto VME I/O Register VME ADC VME Bus Ditto Ditto Ethernet cable Sparc board Ext. Hard disk * System developed by Meisei Co.