Transcript Solving the Mystery of the Highest Energy Cosmic Rays : 1938 to 2007 cosmic rays: James W.

Solving the Mystery of the Highest
Energy Cosmic Rays : 1938 to 2007
cosmic rays:
James W. Cronin
Inaugural Conference:
Institute for Gravitation
and the Cosmos
Aug 9, 2007
Penn State University
On the way to
Solving the Mystery of the Highest
Energy Cosmic Rays : 1938 to 2007
cosmic rays:
James W. Cronin
Inaugural Conference:
Institute for Gravitation
and the Cosmos
Aug 9, 2007
Penn State University
Victor Hess 1911-12
 = 5  sec
Decoherence curve at the Jungfraujoch
Auger and collaborators
Pierre Auger at the University of Chicago 1940
Following World War II cosmic ray research
resumed with arrays of Geiger counters
Professor Zatsepin in the Pamir mountains
B. Rossi
Volcano Ranch
J. Linsley
1963 1st cosmic ray ~ 1020 eV
Two techniques:
• detect shower particles
on the ground
• detect air fluorescence
produced by shower
particles
Cassiday, Bergeson, Loh, Sokolsky et al.
Utah Fly’s Eye 1981-1993
Instruments for the study of the highest energy cosmic rays
operation
period
Volcano Ranch 1960-1980
Haverah Park
1967-1987
SUGAR
~1968-1980
Yakutsk
1974-1995
Fly’s Eye
1981-1992
HiRes
AGASA
Auger
~1998-2006
1992-2004
2004-
area
km2
exposure
1016 (m2 sec sr)
8
12
60
18
0.2 (?)
2.6
~2.6
1.4
2.6 (mono)
100
3000
~10 (mono)
~6.0
16 (~0.8 yr opr.)
1020 eV proton
16 joules energy
Kinetic energy of Andy
Roddick’s second serve
But momentum of a snail
Macroscopic energy in
a microscopic particle
No known astrophysical
sources “seem” able to
produce such enormous
energies
1/ km2/ century
3000 km2 -> 30
events / year
Simon Swordy
University of Chicago
proton + cmb ->  + nucleon
3
4
5
Portugal
Netherlands
Argentina
Australia
Bolivia*
Brasil
Czech Republic
France
Germany
Italy
Poland
Mexico
Slovenia
Spain
United Kingdom
USA
Vietnam*
The Pierre Auger Observatory
38° South, Argentina, Mendoza,
Malargue 1.4 km altitude, 850
g/cm 2
1438 deployed
1400 filled
1364 taking data
090707
~ 85%
All 4 fluorescence
buildings complete,
each with 6 telescopes
1st 4-fold on 20 May 2007
AIM: 1600 tanks
HYBRID DETECTOR
Surface Detector
GPS timing precision
7
Cosmic Muon Calibration
The Fluorescence Detector
3.4 metre diameter segmented mirror
24 telescopes in 4 eyes
2.2m diameter aperture stop, corrector lens and
optical filter. 440 pixel camera.
HYBRID → PRECISE SHOWER GEOMETRY
first step towards precise energy, depth of maximum
Arrival time at ground provided by the
SD, removes degeneracy in the FD
geometry fit
Can be ~ straight line,
but 3 parameters in fit
HYBRID → PRECISE SHOWER GEOMETRY
first step towards precise energy, depth of maximum
Arrival time at ground provided by the
SD, removes degeneracy in the FD
geometry fit
(= 90o- Ψ)
Get T0 from SD tank!
Geometry uncertainties shrink!
A “perfect” hybrid event: few are as beautiful as this one !
Miguel Mostafa
New Mexico/Utah

S1000 is
Energy parameter
8
S38 (1000) vs. E(FD)
4 x 1019 eV
Nagano et al, FY used
387 hybrid events
Auger Spectrum 2007
Three spectra combined
weighting statistical
error in each energy bin.
Low energy from Hybrid
observation, High
energy from SD.
JS  E-2.6
‘ankle’ and ‘steepening’
seen in
(nearly) model and
mass-independent
measurement .
  3.30  0.06
Eankle  10
18.65
eV
  2.62  0.03
Esteepen  10
19.55
eV
  4.1  0.4
6 sigma deficit from
power-law assumption
1E-27
1E-28
Auger Combined
HiResI
HiResII
1E-29
1E-31
1E-32
1E-33
2
J (m sr s eV)
-1
1E-30
1E-34
1E-35
1E-36
1E-37
1E-38
17.0
17.5
18.0
18.5
19.0
log E (eV)
19.5
20.0
20.5
How we try to infer the variation of mass with energy
photons
Xmax
protons
Data
Fe
Energy
Elongation Rate measured over two decades of energy
Fluctuations in Xmax to be exploited
326
111 69
25
12
426
Large number of events allows good control
and understanding of systematics
Photon limit
Conclusions
We are at the point where we have some
confidence that the angles and energies
of the highest energy cosmic rays can be
measured accurately.
Good progress is being made for statistical
determination of the composition.
It remains to make a connection with the
cosmic accelerators. This requires patience
and the benevolence of Nature.