Speaker
Dr
Frederick Kuehn
(Fermilab)
Description
We present preliminary results from the most recent data on the absolute
yield of fluorescence photons in atmospheric gases by the AIRFLY
collaboration. Currently, the uncertainty in the yield forms the dominant contribution to
the systematic uncertainty in the Pierre Auger Observatory's energy
spectrum, and are at the level of 10%. Data were taken in 2009 and 2010 at
the test beam facility, M-Test, at Fermilab using protons, electrons and
pions, in nitrogen, air, and in non fluorescing gases like argon, and
helium. The instrument is operated in two main modes. In the first, fluorescence
photons are observed, whereas in the second, both Cherenkov as well as
fluorescence are observed. Comparisons of the ratio of these measurements,
combined with the known Cherenkov spectrum allows for the absolute yield to
be determined with reduced systematic uncertainties. In addition, the
absolute yield is found by comparing the fluorescence yield to the
observed photon yield of a NIST calibrated laser source directed into the
apparatus. The consistency of these independent calibrations indicates
that a systematic uncertainty of 5% or better is within reach.
Primary author
Dr
Frederick Kuehn
(Fermilab)