1. Testing the HiRes Detector Simulation against UHECR Data Andreas Zech ( Rutgers University) for the HiRes - Fly´s Eye Collaboration ICRC 2003 in Tsukuba

2. HiRes Collaboration J.A. Bellido, R.W. Clay, B.R. Dawson, K.M. Simpson University of Adelaide J. Boyer, S. Benzvi, B. Connolly, C. Finley, B. Knapp, E.J. Mannel, A. O’Neil, M. Seman, S. Westerhoff Columbia University J. Belz, M. Munro, M. Schindel Montana State University G. Martin, J.A.J. Matthews, M. Roberts University of New Mexico D. Bergman, L. Perera, S. Schnetzer, G.B. Thomson, A. Zech Rutgers University N. Manago, M. Sasaki University of Tokyo T. Abu-Zayyad, J. Albretson, G. Archbold, J. Balling, K. Belov, Z. Cao, M. Dalton, A. Everett, J. Girard, R. Gray, W. Hanlon, P. Hüntemeyer, C.C.H. Jui, D. Kieda, K. Kim, E.C. Loh, K. Martens, J.N. Matthews, A. McAllister, J. Meyer, S.A. Moore, P. Morrison, J.R. Mumford, K. Reil,R. Riehle, P. Shen, J. Smith, P. Sokolsky, R.W. Springer, J. Steck, B.T. Stokes, S.B. Thomas, T.D. Vanderveen, L. Wiencke University of Utah J. Amann, C. Hoffman, M. Holzscheiter, L. Marek, C. Painter, J. Sarracino, G. Sinnis, N. Thompson, D. Tupa Los Alamos National Laboratory

3. The HiRes FADC Detector (HiRes-2) n The newer one of the 2 HiRes air fluorescence detectors n 2 rings with 21 mirrors each n Located on Camel’s Back Ridge in Dugway (Utah) n Started taking data in fall 1999

4. The HiRes FADC Detector (HiRes-2) n 256 photomultiplier tubes per mirror. n Flash ADC electronics record at a frequency of 10 MHz.

5. The Role of Monte Carlo Simulations in the HiRes Experiment We need M.C. to calculate the acceptance of our detectors for the flux measurement: M.C. is also a powerful tool for resolution studies and for tests of our reconstruction programs. è This requires a simulation program that describes the shower development and detector response as realistically as possible. è We want our code to simulate events under the exact data-taking conditions.

7. M.C. Input Energy & Composition The composition is chosen from our HiRes Stereo and HiRes/MIA measurement. The Fly’s Eye Stereo spectrum is used as an input for the M.C.

8. CORSIKA Shower Library (proton & iron) Gaisser-Hillas fit to the shower profile: Fit parameters scale with primary energy:

9. Adding Noise to the M.C. Ambient light level (low amplitude) can be measured from the width of the FADC pedestals. Additional sky noise (high amplitude) is added to the M.C. to get agreement with data of a certain period. FADC counts in all trigger channels black: data red: M.C. total noise tubes distribution black: data red: M.C.

10. A few Data / Monte Carlo Comparisons or: Testing how well we understand our experiment... n HiRes-2 data shown from 12/99 until 09/01. n ~ 556 Hours of good weather data. n average atmosphere used for consistency with HiRes-1. n Statistics: – rec. geometry: 6309 events – after all cuts: 2274 events n M.C. : ~ 4 x data statistics

11. Signal tubes / χ of linear time fit 2

12. Light per Track Length / Čerenkov Fraction

13. Rp / Rp Resolution

14. Energy / Energy Resolution

15. HiRes-2 Exposure Flux:

16. HiRes-2 Energy Spectrum n HiRes-2 data from 12/’99 until 09/’01

17. HiRes Mono Energy Spectra n HiRes-1 data from 06/’97 until 02/’03 n HiRes-2 data from 12/’99 until 09/’01

18. Conclusions n Our data analysis relies on a realistic M.C. simulation for the aperture calculation and for resolution studies. n We have generated air showers and detector response for the HiRes FADC detector under the exact data-taking conditions. n We have tested our simulation successfully against data taken by HiRes-2. è Our M.C. simulation provides a realistic and detailed model of our experiment.

19. HiRes and Fly’s Eye Stereo n HiRes-1 n HiRes-2 n Fly’s Eye Stereo

20. HiRes and Fly’s Eye Stereo n HiRes-1 n HiRes-2 n Fly’s Eye Stereo Energy rescaled by - 6 %

21. HiRes and HiRes / MIA n HiRes-1 n HiRes-2 n HiRes Prototype & MIA muon array ( hybrid )

22. HiRes and AGASA n HiRes-1 n HiRes-2 n AGASA

23. Cuts n Track length n Number of signal tubes n Zenith angle n Track angle n Psi angle n Error in Psi angle n Pseudodistance n Good weather conditions n Time tangent fit Chi Squared n Profile fit Chi Squared n Čerenkov light fraction n ‘Bracketing’ cut

24. Čerenkov Light Simulation The Longitudinal Profile calculated in the M.C. is in good agreement with results from CORSIKA. Lateral Profile: - we fit CORSIKA density profiles to the sum of 3 exponentials. - fits are parametrized with zenith angle and distance between detector and X max. black: CORSIKA long. Čerenkov profile vs. atmospheric depth red: our M.C. simulation red: CORSIKA lateral Čerenkov density vs. radial distance in meter black: our fit using the sum of 3 exp.

25. Shower Geometry

26. Pseudodistance / Angle of shower axis in shower-detector plane