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HiRes Usage

HiRes Usage. Outline. Shower energy ( Size, dE/dx ) Atmospheric profile ( stdz76, radiosonde) Rayleigh Scattering Aerosols Model ( density, variability ) Aerosols Scattering Detector Optical Efficiency. Old HR1 Mono Shower Energy. E tot = E em + E miss E em = Profile Integral x const.

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HiRes Usage

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  1. HiRes Usage

  2. Outline • Shower energy ( Size, dE/dx ) • Atmospheric profile ( stdz76, radiosonde) • Rayleigh Scattering • Aerosols Model ( density, variability ) • Aerosols Scattering • Detector Optical Efficiency.

  3. Old HR1 Mono Shower Energy • Etot = Eem + Emiss • Eem = Profile Integral x const. • Profile Integral <== Nmax, x0, xmax • const = 2.18 ( Average dE/dx ) • Nmax = Etot / 1.3e9 • Emiss ~ 5-15 % ( Linsley )

  4. New HR1 Mono Shower Energy • Etot, Nmax,xmax, x0 ( Based on Corsika ) • Nmax/Etot=a0+a1*x+a2*x*x • x== xmax - x0 • Nmax/ Etot ~ 0.65 or Nmax ~ Etot / 1.5e9 • But ~ 11% shower particles below tracking threshold in Corsika, so put them back in: • Nmax/Etot ~ 0.73 or Nmax ~ Etot / 1.4e9 • No explicit missing energy correction

  5. Proper Accounting ?! • Old vs. New HR1 mono: • Old Nmax > New Nmax by ~10% • Old dE/dx < New dE/dx by ~ 10% • A shower with a given energy will produce the roughly the same amount of light at the detector in old/new analysis • An observed event will be reconstructed to the same nominal energy in old/new analysis. • BUT for real showers, reconstructed Nmax will be 10% too high

  6. Energy Reconstruction • We use an “inverse Monte Carlo” technique for energy reconstruction. • Calculate tube signals for a shower with “unit energy”, compare to measured tube signals and do fit to best match observed tube signals. • The fit energy = scaling factor x “unit energy” • So, the ratio of Nmax to Etot factors out and does not affect energy estimate.

  7. Scintillation Yield • dE/dx: • Old: Based on Hillas Calculations • New: Based on Corsika simulations • Yield: • Old/New use Kakimoto et al. total yield • Wavelength Dependence: • Old/New use Bunner Spectrum • New Analysis may be updated to use newer measurements

  8. Atmospheric Profile • Old Analysis uses the 1976 U.S. Standard Atmosphere Model. • New Analysis uses Radiosonde measured profiles IF available, reverts to standard atmosphere otherwise. • Atmospheric ceiling at 70 km for old analysis, Radiosonde data available up to 30 km. • We use linear interpolation of measured points, maybe can improve?

  9. Rayleigh Scattering • Depends on atmospheric density, so altitude. • Well known physics ... but • Wavelength dependence of scattering length changed from 1/lambda4 to 1/lambda4.22 in MC and reconstruction codes!

  10. Aerosols Scattering • Mostly in the forward peak ( Longtin Phase function ) • Weak wavelength dependence ( Etterman ) • At Dugway Average attenuation length 25 km, average scale height 1 km. ( No mixing layer ) • Data Base: fit for attenuation length and scale height; No mixing layer ( 2 parameter fit )

  11. Detector Optical Efficiency • Mirror Reflectivity • Nominal Value / Measured • Time Variability • Wavelength Dependence • UV Filter Transmission • PMT QE • PMT Response profile

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