Exploring Laser Light

1. Exploring Laser Light Ruben Conceição

2. Pierre Auger Observatory • Ultra High Energy Cosmic Rays • Pierre Auger Observatory • Fluorescence Detector • Longitudinal Profile • Fluorescence light • Surface Detector • Ground charged lateral distribution Sesimbra, IDPASC 2010

3. Following the light Multiple Scattering FD Point Spread Function  Sesimbra, IDPASC 2010

4. Measuring the differential light profiles • Angular distance to spot center: • Zeta () • Evaluate By using • Measured in each pixel i • Average many profiles to reduce statistical fluctuations • Need to control • Event similarity • Clouds • Undershooting CLF shot seen at LL with full camera aquisition Zeta Applicable in full camera acquisition or in a band! Sesimbra, IDPASC 2010

5. CLF @ Coihueco • Light lateral profile vs. angular distance to spot center (zeta) Direct light  Detector PSF Multiple Scattering

6. CLF @ Coihueco Total light vs. elevation angle a (several millions CLF shots) Rayleigh Mie The shape of the light profile is sensitive to VAOD

7. Geant4 Laser Simulation • Photon tracking in the atmosphere done with Geant4: • Rayleigh scattering • Mie scattering • Layers with constant depth (20 g/cm2) • Different atmospheric profiles • Detectors implemented as cone sections, 2 m height to simulate camera aperture and inclination. • Can suffer any number of Mie or Rayleigh scatterings • Comparison between data and simulation Sesimbra, IDPASC 2010

8. Conclusions • Powerful tools for understanding the multiscattered light • Further studies to check the dependency with altitude, time of arrival and distance can be done • First data/MC comparison results are encouraging • Reasonable agreement • The detector PSF can be acquired up to 10-4 of maximum signal

9. BACKUP Sesimbra, IDPASC 2010

10. CLF @ Los Leones Sesimbra, IDPASC 2010