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, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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

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

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

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

90Sr spectrum 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

Electron ADC (1st threshold) 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

Electron ADC (2nd threshold) 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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

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

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

Why a spectrometer? Filter properties vary with incident angle Here, we respect the Numerical Aperture 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

PMT window ===> Silica 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

Gas Very clean No argon ∆P/P ~ 0.1% Flow = 1 l/h 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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

Photon spectrum (single pe) 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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

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

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

How many Photoelectrons ? Analysis Fluo yield ε = Nphotons / Lelectrons How many Photoelectrons ? How many Photons ? Electrons travel? 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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

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, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

Pressure and temperature Discriminator cut PMT-2020 : + 3.76 % PMT-JY : + 3.85 % 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, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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 = 46.11 ± 0.2 mm ePMT :absolute efficiency of PMT = 0.178 ± 0.004 Tquartz: transmission of silica window = 0.992 ± 0.003 Egeo: geometrical efficiency (3.689 ± 0.02)10-4 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

Results With our temp and pressure: 3.86 ± 0.09 ph / m for Ee = 1.19 MeV P = 753.8 mm Hg, T = 295.95 K 3.87 ± 0.09 ph / m for Ee = 1.54 MeV P= 751.8 mm Hg, T = 296.05 K to normalize to 0.85 MeV, we use dE/dx 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

Theoretical normalization b) To normalize to US standard P and T 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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

Normalized results [300-430 nm] Our results, normalized to 0.85 MeV, and US standard conditions 3.945 ± 0.120 photons / meter 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

Spectrometer resolution With a He-Ne laser 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

Spectrometer calibration Not better than 20% 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

The lines Ulrich Our work with 6 nm FWHM Intensity (arb. units) 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris

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/0206217 v5 27 Feb 2003) 4th air fluo workshop Prague, 17-20 / 05 2006 P. Gorodetzky APC - Collège de France Paris