1. E.A.Kravchenko Budker INP, Novosibirsk, Russia
Status of FARICH
E.A.Kravchenko
Budker INP, Novosibirsk, Russia

2. Outline FARICH |Vub| from charmless B decays
MCP PMT aging (Peter Krizan aging results)
Status of FARICH FastSIM
|Vub| from charmless B decays
FARICH prototype and test beam line, status

3. FARICH with short DC Expansion gap 200 mm
Burle MCP PMT with 3.2x3.2 mm pixels (16x16 matrix), photoelectron collection efficiency 70%, geometrical factor 85%
3-layer focusing aerogel, nmax=1.07, total thickness 30 mm
Number of PMTs ~ 450
Number of channels ~
Amount of material, (X0) = 3.5%(aerogel)+ 2.5%(water)+ 14%(MCP PMT)+8% (support, electronics, cables) ~ 28%

4. FARICH expected performance
Excellent PID → π/K separation from 0.6 to 8 GeV/c, μ/π separation from 0.15 to 1.4 GeV/c
Very good overlap with dE/dx PID (even in the case of ‘shorter’ DC)
Additional momentum measurement
4 times smaller number of channels comparing with previous 100 mm expansion gap option

5. FARICH momentum resolution
σP/P=γ2∙σβ/β K π

6. Burle MCP PMT aging (Ljubljiana group results)
10% drop in PDE after 400 mC/cm2 => no problem with MCP PMTs for the endcap device (Peter Krizan)
Burle expect to improve the ageing by a factor > 5 (use a different scrubbbing technique, deep UV → electrons)
SuperB expected dose mC/cm2 (?)

7. Status of FARICH FastSim
The following packages are written:
PacEnv/MaterialsList.data  - material description PacForwardPid/ForwardPid_aerogel.xml     - xml description PacForwardPid/PacForwardPidMeasurement.* - hit data interface PacForwardPid/PacForwardPidReco.*        - hit generation PacForwardPid/PacForwardPidResponse.*    - hit PacPid/PacPidAerogelTruthSelector.*      - selector
Next step is the incorporation into the FastSim code
I apologize for communication problems from our side which cause significant delay in this work.

8. |Vub| measurement from inclusive spectrum of charmless semileptonic B decays
|Vub| plays a critical role in testing of SM
Currently one of the most promising procedure for |Vub| measurement is to extract it from inclusive B →Xulν decays where theoretical uncertainties are significantly reduced:
needs full reconstruction of tagging B-meson =>
Breco procedure (used at BaBar) is based on identification of single kaon and assumes that all other particles are pions
With this procedure the profit from Forward PID is proportional to the increase in PID solid angle coverage. Is this procedure optimal for SuperB?
Kaon veto is used to suppress the background from charm semileptonic decays =>

9. Use of kaon veto for charm B decays suppresion
K+ theta distribution for background events, coming from B->Xclν
Kaon veto efficiency is proportional to 1- Ω·ε, Ω - solid angle coverage, ε - detection efficiency.
Example: if ε=1, Barrel PID Ω = 85% , Barrel+Forward PID Ω = 90% => 33% less background
For |Vub| with forward PID S/N ratio will be better by ~15% (5% better tagging efficiency + 10% less background)
(I express my gratitude to Concenzio Bozzi and Marcello Rotondo for fruitful discussions and prepared plots)
No veto
kaon veto

10. Test beam at VEPP-4M, Novosibirsk
Emaxbeam = 5.5 GeV
We insert the converter in the beam halo to obtain bremstrahlung gammas or use the bremstrahlung gammas from the residual gas
We convert gamma-quanta to electron-positron pairs in the target.
To select electrons (positrons) with the required energy we use the magnet

11. Test beam apparatus Magnet Coordinate chambers
Veto and trigger counters
NaI calorimeter
FARICH prototype

12. What we have for the test beam and prototype

13. FARICH prototype status
Aerogel test samples parameters are measured
SiPM tests are in progress
Boards with discriminators were received in November
All components are available, assembly are in progress
Tests with pulsed laser in January-February

14. Conclusion
The Focusing Aerogel RICH system is suggested for SuperB forward particle identification.
Burle MCP PMT aging is acceptable for SuperB conditions
FARICH FastSim was delayed, but it looks it will be ready for use in the nearest future.
|Vub| S/N ratio with forward PID will be better by ~15%
Kaon veto procedure is very sensitive to PID coverage.
Tests with FARICH prototype equipped with MRS APD photon detectors are scheduled in January-February 2010.

15. |Vub| measurement from inclusive spectrum of semileptonic B decays
Particles momentum spectrums
for 50% of pions P > 400 MeV
for 50% of kaons P> 800 MeV π K p n

16. |Vub| measurement from inclusive spectrum of semileptonic B decays
The first step is the geometry efficiency study.

17. no decays K± , π± , μ± in flight
|Vub| measurement from inclusive spectrum of charmless semileptonic B decays
PID system
100% reco γ in calorimeter
no magnetic field
100% reco Kl and n(.n) in calorimeter
no decays K± , π± , μ± in flight
barrel
0.82
3.23
7.03
12.88
barrel +forward
1.32
4.73
10.03
19.32
barrel +backward
1.23
4.23
9.00
16.95
barrel +forward +backward
2.0
6.25
13.00
25.84
Forward gives at least 30% increase in efficiency
the loss of the detection efficiency due to decays is very large
What about backward PID?

18. FARICH with MRS APD
Noise increase by a factor of 2 after 1010 neutrons (1-2 MeV) per cm2 :
BaBar rates - ~ 5 · 1011 in a year at the EMC endcap (at 7 · 1033 cm-2 sec-1) (J. Va’vra)
Belle rates - 4 · 1011 in a year at the EMC endcap (P. Krizhan)
Currently SiPM can not be used at SuperB FARICH unless some serious efforts will be done:
Cooling up to -50 Co
Annealing at 250 Co
Progress in initial radiation hardness (move from p type to n type)

19. Optimizing FARICH momentum resolution
σP/P=γ2∙σβ/β
Change of the momentum focus for aerogel from βopt= 1 to βγopt= 1

20. Aerogel photos These 4 large and many of small multylaer aerogel
2 layers
These 4 large and many of small multylaer aerogel
blocks are ready for testing with the beam
4 layers

21. MRS APD parameters
Producer - Center of Perspective Technology and Apparatus – CPTA, Moscow
Genuine name - MRS APD (other names: silicon photomultiplier, PPD,MPPC…)
2.1x2.1 mm sensor
4x4 mm case size
600 nm
Gain ~ 4·105
Time resolution ~100 ps
Dark counts ~10 MHz (0.5pe threshold)