Fluorescence from Air in Showers(FLASH)

J. Belz1, Z. Cao2, P. Chen3*, C. Field3, P. Huentemeyer2, W-Y. P. Hwang4, R. Iverson3, C.C.H. Jui2, T. Kamae3, G.-L. Lin4, E.C. Loh2, K. Martens2, J.N. Matthews2, W.R. Nelson3, J.S.T. Ng3,

A. Odian3, K. Reil3, J.D. Smith2, P. Sokolsky2*, R.W. Springer2, S.B. Thomas2, G.B. Thomson5, D. Walz3

1University of Montana, Missoula, Montana2University of Utah, Salt Lake City, Utah

3Stanford Linear Accelerator Center, Stanford University, CA4Center for Cosmology and Particle Astrophysics (CosPA), Taiwan

5Rutgers University, Piscataway, New Jersey

* Collaboration Spokespersons

Proposal E-165

• Cosmic Rays have been observed with energies at up to ~1020 eV:

• The flux (events per unit area per unit time) follows roughly a power law

~E-3

• Changes of power-law index at “knee” and “ankle”.

Onset of different origins/compositions?

Where does the spectrum stop?

Discrepancy Between Two UHECR Experiments

AGASA

HiRes

HiResAGASA

UHECR From Source to DetectorUHECR From Source to Detector

CMB γ

Greisen-Kuzmin-Zatsepin (GZK) Cut-off

(protons)

3×1020 eV

50 Mpc ~Size of local

cluster

•Protons above 6×1019 eV will loose sizable energy through CMB

•Super-GZK events have been found with no identifiable local sources

Extensive Air ShowersExtensive Air Showers

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Extensive Air Shower DevelopmentExtensive Air Shower Development

Hadronic shower initiated by primaryHadronic shower initiated by primaryElectromagnetic Shower produced by Electromagnetic Shower produced by γ’sγ’s from from 00 decays… decays…

Observation of Cosmic Ray with Fluorescence Technique

• The two detector sites are located 12 km apart

• Geometry of an air shower is determined by triangulation.

• Energy of primary cosmic ray calculated from amount of light collected.

Previous Fluorescence MeasurementsPrevious Fluorescence Measurements

• (1967) A.N. Bunner PhD thesis at Cornell– Compiled a spectrum from many sources.

– Unknown systematic errors.

• (1996) Kakimoto et al. NIM paper.– Measured 3 narrow band lines not a spectrum.

• (Present) Nagano unpublished.

Other Proposed Fluorescence ExperimentsOther Proposed Fluorescence Experiments

•Carlos Escobar (Campinas, Italy)

•Andrea Santangelo (Palermo, Italy)

- Lab. measurements induced by hard-x-ray photons

•Paolo Privitera (Rome, Italy)

- similar approach to Kakimoto and Nagano

•Hans Klages (Karlsruhe, Germany)

- Karlsruhe activities on Air Shower Light

•Pierre Colin (LAPP, France)

- MacFLY Photons

•Philippe Gorodetzky (College de France)

- Measurements planned at CERN

UNIQUE LABORATORY ASTROPHYSICS OPPORTUNITY

•High intensity e-/e+ beams ultra-fast (< 50 fsec), high energy (~30GeV/e)

ultra-high intensity (~ 1022 W/cm2)

very high repetition rate (10 Hz)

•High fluence photon beams

1. X-ray from undulator (~ 109 γ/pulse at 1.5 Å)

2. Terawatt laser (at ~ 1 μm)

3. Gamma-ray (up to ~ 15 GeV) through laser-particle beam Compton- backscattering

* Experiments can be performed with different combinations of these beams

MEASURING FLUORESCENCE AT SLAC

• Extensive Air Showers (EAS) are predominantly a superposition of EM sub-showers.

• Important N2 transition (2P) not accessible by proton excitation; only e-beam can do it.

• FFTB beam-line provides energy equivalent showers from ~1015 to ~1020 eV.– 108-1010 electrons/pulse at 28.5 GeV.– 2% of electron pulse bremsstrahlung option.

FLASH useful for future UHECR Experiments Ground-Based: The Pierre Auger Observatory

• Hybrid detection

• 1600 Cherenkov detectors 1.5 km gridin 3000 km2

• 4 fluorescence eyes – Comparable to HiRes

65 km

Space-Based: EUSO, OWL/AirWatch