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Fluorescence and Cerenkov photons from air shower 1/9-10/2003 VHENTW-3 Palermo, Italy

Fluorescence and Cerenkov photons from air shower 1/9-10/2003 VHENTW-3 Palermo, Italy. Ming-Huey A. Huang 黃明輝 Department of Physics, National Taiwan University. Contents. Air shower longitudinal profile Fluorescence photon flux simulation Cerenkov photons Arrival time of photons

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Fluorescence and Cerenkov photons from air shower 1/9-10/2003 VHENTW-3 Palermo, Italy

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  1. Fluorescence and Cerenkov photons from air shower1/9-10/2003VHENTW-3Palermo, Italy Ming-Huey A. Huang 黃明輝 Department of Physics, National Taiwan University

  2. Contents • Air shower longitudinal profile • Fluorescence photon flux simulation • Cerenkov photons • Arrival time of photons • Conclusion M.A. Huang

  3. Why need fluorescence and Cerenkov photons ? • Previous simulation require trigger at distance up to 5~7 km from shower core. • Cerenkov photons density decrease exponentially outside Cerenkov ring. • Fluorescence photons distribution is more isotropic • Optical detection can not distinguish fluorescence or Cerenkov photons • Trigger time may different ? • How to use trigger time? M.A. Huang

  4. Longitudinal profile • Tau exit mountain, decay, then initiate air shower • decay length ~ d=50 (E/PeV) m • Assume tau decay to electron • Gaisser-Hillas formula d=5 km d=50 km M.A. Huang

  5. Common environment • Pressure, density of atmosphere taken from typical value at altitude 2.5 km, Hualalai mountain top. • Density is assumed as constant, valid for near horizontal events. M.A. Huang

  6. Parameters of G-H formula • Nmax = E/(1.35 109) • Xmax = 550 + 80log(E/1015) • X0 is insensitive and have large fluctuation, use 5 gm/cm2 M.A. Huang

  7. Simulation • Detection by fluorescence light offers larger solid angle than by Cerenkov lights. • For trial runs: simulate neutrinos from a typical configuration. M.A. Huang

  8. Emission angle  Simulation • Nph=Negf • Mirror size 1m2 • Angular size for each pixel 0.5º • Simplify geometry to 1-D track on shower-detector plane. • 1-D detector, cover  from -80º to +80º • Just to cover whole track, not the finial design =90º M.A. Huang

  9. Fluorescence yield • Y: fluorescence yield • Ne: # of secondary particles • : fluorescence eff. = #/cm/e • q: mean ionization energy 2.2 MeV/(g/cm2) • : density • P: pressure • T: temperature • Ri : Reflectance/transmittance at wavelength I • Ei : intensity • Peff : effective pressure • T0: Temperature at STP M.A. Huang

  10. Fluorescence efficiency • Top : From P. Sokolsky book and many references • Bottom: Data from Bunner’s thesis, used in this simulation. • Quite similar, but small differences M.A. Huang

  11. Geometry factor Rp: distance covered in each pixel : emission angle, between line of sight and shower axis r: distance from detector to shower track in FOV A: mirror/lens area : scattering length ~ 20km M.A. Huang

  12. Photon number per pixel • Threshold = 3 photon per pixel • Even electronics sensitive to single photo-electron, threshold energy is still high ~ 1016.5 eV M.A. Huang

  13. Difficulty in telescope orientation • Different distribution of shower maximum, a small coverage in azimuth angle could only see a fraction of total energy range. M.A. Huang

  14. Difference between results from Giancarlo’s and Alfred’s • Fluorescence efficiency: • G: 4.5 photons/m/e & A: 2.3 photons/m/e • Shower profile: • G: GIL formula • A: Nmax=E/1.35 (E in GeV) • At above 1019 eV, difference ~2% • At 1015 eV, G is 38% higher • Mirror size • G: 2 meter radius, A: 1m2 M.A. Huang

  15. Comparison: • Giancarlo’s results is higher by • Mirror : 12 times larger • Efficiency: 2 times larger • Shower size: 38% larger at 1015 eV • Adapting Giancarlo’s number, the minimum threshold is around 1015 eV • Geometric factor seems OK ! • Questions remains! M.A. Huang

  16. Nighttime airglow Johnston and Broadfoot, 1993, JGR, 98, 21593 • Much complex than previous measurements • Contamination? M.A. Huang

  17. Question: fluorescence efficiency P. Chen’ talk in Workshop of Laboratory Astrophysics, Taipei, 2002. • Wavelength seems O.K. • Absolute intensity is different in Bunner (Alfred’s and Chen’s) and Kakimoton’s M.A. Huang

  18. Cerenkov light simulation • Study photon density and arrival time • Use ground array to sample Cerenkov photons • Cerenkov photons are integrated over whole shower track • Longitudinal profile similar to fluorescence mode. • Shower start at different altitude, 20, 30, and 40 km. • Shower energy 1014, 1016, 1018 eV M.A. Huang

  19. Simulation of photon arrive time • T=0 at injection point, where e • Calculate shower longitudinal profile, produce Cerenkov photons C c/n  • electrons have angular spread according to multiple scattering • Cerenkov photons emit from electrons directions • Calculate photons propagation time and hit positions at ground. M.A. Huang

  20. Fluorescence photon arrival time • Cerenkov photon time + decay time of fluorescence photons (10ns ~ 50ns, depends on wavelength) M.A. Huang

  21. Cerenkov longitudinal profile Nph=Neexp(-r/  ) •  is Cerenkov efficiency • Depend on mean energy and index of refraction • ~ 203 photons/(g/cm2)/e •  length in FOV • : scattering length ~ 20km 1018 eV M.A. Huang

  22. Fast simulation Arrival time CORSIKA 500ns • Similar to simulation by Corsika 500ns M.A. Huang

  23. Mean arrival time • Depends mainly on shower position M.A. Huang

  24. Cerenkov photons Arrival time Photon wave front Rp • T=0 when first photon hit detector • Time gate for coincidence between two detectors • in the order of sec. • depends on distance between detectors and Rp • important tools to reconstruct event arrival direction and Rp M.A. Huang

  25. RMS of arrival time • Depend mainly on shower position M.A. Huang

  26. c c/n RMS of arrival time If electronics can measure the spread of arrival time, pulse width, it can be correlated to Rp! • Photons from different part of showers arrive same detector at different time. • Time gate for individual detector • Depend on Rp • Could be as large as 200 ns (Rp<5km). M.A. Huang

  27. Conclusion on arrival time • Arrival time is critical for : • requirement for electronics design • event reconstruction • Still need more works in reconstruction programs • For two detectors separated by 1km • Gate time for one detector: RMS of arrival time ~ 200ns at Rp = 3km • Coincidence time between detectors: ~ 1 s M.A. Huang

  28. Fluorescence + Cerenkov • For events near shower core, small Rp, detected photons are combination of Cerenkov photons and fluorescence photons • Need to combined two simulation • Need to separate two photons in reconstruction. • For events with large Rp and large energy, fluorescence photons is as important as Cerenkov photons. M.A. Huang

  29. Conclusion • Photons are photons, no need to exclude fluorescence or Cerenkov photons. • Near PeV, Cerenkov photons flux is higher • Near EeV, both signals are strong, fluorescence mode have larger acceptance. • Dream detector: • Detect both Cerenkov and fluorescence photons • Best way to take advantage of all signals. • Difficult to design electronics and trigger. M.A. Huang

  30. On-going and future projects • Simulation: • Fluorescence + Cerenkov photons • Reconstruction • Parameters form stereo observation by two detectors • Theoretical side: • e &  via W resonance • Energy resolution M.A. Huang

  31. Detector Design Concept 1/10/2003 Ming-Huey A. Huang 黃明輝 Department of Physics, National Taiwan University

  32. Contents • Sensitivity and Event rate • Requirements on detector design • Multi-mirrors approach • Site issues M.A. Huang

  33. Expected performance Target volume: better than the design goal of IceCube ~ 1 km3 at E > 1015 eV M.A. Huang

  34. New flux sensitivity • 0.3event/year/half decade of energy • Similar to single event sensitivity (SES) • Great chance to see AGN and TD M.A. Huang

  35. Sensitivity and Event Rate • Sensitivity : 1 event/yr/half decade of energy • A=R  R2=(2 /1 )R1 • Total Rate in 1014 ~ 1018 = 12.2 events/yr (include 10% duty time) • Assuming detection efficiency 0.3-0.7, R~ 4-8 events/year M.A. Huang

  36. Requirements on detector • Field of view 12º135º • 30 photons in 1 m2 mirror/lens • pixel size ~ 0.5º • Trigger condition • 2 pixels triggered with 2 photo-electrons • combined efficiency (reflectance/transmission/quantum efficiency) ~ 4/30 ~ 0.13 M.A. Huang

  37. Lateral profile of Cerenkov photons 1018 eV 1016 eV 1014 eV • Similar profile for showers produced by e– and  • Cerenkov ring distance ~ (L-Rmax)Tan c • Outside ring, photon density ~ exponential decay • Detector can trigger far away from Cerenkov ring M.A. Huang

  38. Optical system • Technical difficulty: • Odd shape field of view 12º135º, difficult to covered by a single mirror or lens • F value! • Constraints: • Palermo: 290 8x8 MAPMT • Budget • Construction time/complexity M.A. Huang

  39. Connecting several small telescopes to cover full FOV Each unit can be modified from existing models and available technologies. Options: 4 Fresnel lens telescopes, each cover 12º36º Similar to Shimizu’s EUSO prototype 11 Reflective telescopes, each cover 12º12º Similar to HiRes (16º16º) Solution: multiple telescopes Divide and Conquer M.A. Huang

  40. The good All technologies available! Modularized design easy construction schedule operation start from first module, early start! Chance to learn from first module, easy to modify. The bad Complexities in calibration and installation Can not be avoid and can be done! The Ugly Environmental impact larger building Advantages and Disadvantages M.A. Huang

  41. Example: 11 modules Top view Side view M.A. Huang

  42. F problem Lens/Mirror • Large FOV and small pixel size  F < 1 • Very difficult in optical design • loss effective collection area at large off axis angle. • Can be manipulated by light guide • Also kill the dead-space problem • Light guide can match curved focal surface. Light guide MAPMT array M.A. Huang

  43. Site requirements • Detector housing • Two 48 feet container for 11 reflective mirrors • one for telescopes and one for electronics and others • One 48 feet container for 3-4 Fresnel lens • Power • Solar and wind • Communication M.A. Huang

  44. Some issues related to site • Is Hawaii the only site available? • Worry about inversion layer of Hualalai site • Site survey of White mountain, CA? • Need long term weather information • Pressure, temperature, wind speed, humidity, ... • Cloud height, visibility (aerosol contents …) • On-site background measurement M.A. Huang

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