Reconstruction of the altitude of the shower maximum. …Towards the shower reconstruction Pierre Colin (Petr Sudakov) (LAPP) Dmitry Naumov (LAPP/JINR) 3-5 Febrary

To reconstruct the shower energy Why should we know hmax? To reconstruct the shower energy we need to know the attenuation 2. To do physics transform hmax into xmax and identify neutrinos, protons, iron and all that How can we measure hmax? Using Cherenkov echo information If not… try to use Fluoresence only 3-5 Febrary

Can we do something to save the rest showers?… How often we can use the Cherenkov echo? We do not expect a Cherenkov signal for large  Golden events Fluorescence only Energy, eV , deg. 1020eV Can we do something to save the rest showers?… 3-5 Febrary

A qualitative example: 2 horizontal showers at different altitudes  N =  x yield x attenuation x efficiency x NeL E=1020 eV, proton SLAST N  N  NeL = Ne x/(h) Ntot =   N Nmax/Ntot  (h) 20km 5km t, ms Therefore, Nmax/Ntot is sensitive to the air density for horizontal showers … Look also Eric’s remark on the duration of horizonthal showers 3-5 Febrary

What about inclined showers? Using GIL parametrization we found that hmax can be reconstructed in general case (see details in our memo): tmax = a+b (ln(E/E1) + ln(A)) Hi is the slope in exp(-h/Hi) Unit vector pointing to EUSO from the shower maximum Very weak dependence of the shower energy and nature! 3-5 Febrary

With SLAST we generated 10000 proton initiated Showers with 5.1019 eV < E < 1021 eV 0 <  < 100 0 <  < 360 We tryied to reconstruct that data with Space Telescope Reconstruction Program (STrecon) written within ROOT/C++ (stored under CVS @Lyon CC) applying the following cuts to have «good showers»: N > Threshold = 30 photons Existence of the shower maximum (Nleft > 0 && Nright > 0) Number of hits around maximum > 25 3-5 Febrary

(today we implement and develop the algorithms to reconstruct them) We assumed currently:  That angles are known (today we implement and develop the algorithms to reconstruct them)  Energy is known (it will be reconstructed later in an iterative scheme. We have to implement the atmosphere response (LOWTRAN, etc), Fluorescence Class and some other technical points)  Optics is perfect (important only for angles)  Statistical fluctuations of the number of photons in the shower development are neglected (it is easy to simulate within SLAST but needs a special algorithms to reconstruct). 3-5 Febrary

Results: Hmax(rec)- Hmax(sim) in km 3-5 Febrary

Results: (Hmax(rec)- Hmax(sim))/ Hmax(sim ) 3-5 Febrary

Results: (Hmax(rec)- Hmax(sim))/ Hmax(sim ) vs  3-5 Febrary

We can reconstruct Hmax relying on the Fluorescent light only. A Short summary: We can reconstruct Hmax relying on the Fluorescent light only.  Our procedure is weakly dependent on the shower Energy and its Nature  Effect of clouds have to be studied, however we expect it to be small  A good check is to work with other generators as well Technical details: STrecon is a self-documented system (ROOT “trucs”) CVS allows interested people to:  write/test the code (author login)  to be systematically and automatically informed who and what has been commited (euso guest login) 3-5 Febrary

 Internal Note explaing all the details We are working on: Reconstruction of:  angles, energy, Hmax  particle type  Internal Note explaing all the details Optional Future Implement all that inside ESAF to have the whole chain:  simulation of the shower, optics, electronics  analysis 3-5 Febrary