1. Precise measurement of air fluo yield
TITLE
Precise measurement of air fluo yield
How?
Control everything
b) Work with Gwenaelle
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

2. The bench
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

3. 4th air fluo workshop Prague, 17-20 / 05 2006. P
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

4. The cross
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

5. Electron beam
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

6. 90Sr spectrum
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

7. Electron ADC (1st threshold)
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

8. Electron ADC (2nd threshold)
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

9. “Integral” PMT
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

10. The spectrometer
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

11. Entrance slit alignment
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

12. Why a spectrometer? Filter properties vary with incident angle
Here, we respect the Numerical Aperture
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

13. PMT window ===> Silica
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

14. Gas Very clean No argon ∆P/P ~ 0.1% Flow = 1 l/h
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

15. Daq
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

16. Photon spectrum (single pe)
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

17. TDC spectrum Atmospheric pressure
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

18. Discriminators dead-time
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

19. dE/dx
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

20. How many Photoelectrons ?
Analysis
Fluo yield ε = Nphotons / Lelectrons
How many Photoelectrons ?
How many Photons ?
Electrons travel?
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

21. dE/dx
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

22. How many Photoelectrons ?
a) Région C : N(S+B)
b) NB on the same interval
c) NS = N(S+B) - NB
d) Ns / Nhisto = Npe / Ncoïnc
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

23. Pressure and temperature
Discriminator cut
PMT-2020 : %
PMT-JY : %
Pressure and temperature
Measured inside and outside the chamber.
Values sent to a slow 2048 channels ADC
Around 760 mm Hg and 22°, channels # around 1000
Variations in a run: typically 1 channel
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

24. Analysis P: number of counts in TDC peak T: integral of TDC spectrum
C: number of coinc (scaler)
D: discri cut
Ne: :Electrons that reached the scintillator (scaler)
TM: dead time of scaler
Lmoy :travel of electrons = ± 0.2 mm
ePMT :absolute efficiency of PMT = ± 0.004
Tquartz: transmission of silica window = ± 0.003
Egeo: geometrical efficiency (3.689 ± 0.02)10-4
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

25. Results
With our temp and pressure:
3.86 ± 0.09 ph / m for Ee = 1.19 MeV P = mm Hg, T = K
3.87 ± 0.09 ph / m for Ee = 1.54 MeV P= mm Hg, T = K
to normalize to 0.85 MeV,
we use dE/dx
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

26. Theoretical normalization
b) To normalize to
US standard P and T
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

27. Bianca
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

28. Normalized results [300-430 nm]
Our results, normalized to 0.85 MeV,
and US standard conditions
3.945 ± photons / meter
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

29. Nitrogen to air ratio
4.90 ± 0.01
OK with Nagano (thanks to his error bars)
Excludes Davidson & O’Neil
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

30. Spectrometer resolution
With a He-Ne laser
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

31. Spectrometer calibration
Not better
than 20%
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

32. The lines Ulrich Our work with 6 nm FWHM Intensity (arb. units)
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris

33. Conclusion (preliminary)
If HiRes took Kakimoto 1.4 MeV
==> their showers are now~ 20% lower in energy than published
It does not go along Bahcall and Waxman explanation
J.N. Bahcall and E. Waxman (hep-ph/ v5 27 Feb 2003)
4th air fluo workshop Prague, / P. Gorodetzky APC - Collège de France Paris