Solving the Mystery of the Highest Energy Cosmic

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 1 st cosmic ray ~ 1020 e. V

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 Hi. Res AGASA Auger ~1998 -2006 1992 -2004 - area km 2 exposure 1016 (m 2 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 e. V 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/ km 2/ century 3000 km 2 -> 30 events / year Simon Swordy University of Chicago

proton + cmb -> + nucleon 3

4

5

Portugal Netherlands

1438 deployed 1400 filled 1364 taking data 090707 ~ 85% All 4 fluorescence buildings complete, each with 6 telescopes 1 st 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. 2 m 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 (= 90 o- Ψ) Get T 0 from SD tank! Geometry uncertainties shrink!

A “perfect” hybrid event: few are as beautiful as this one ! Miguel Mostafa New Mexico/Utah

S 1000 is Energy parameter 8

S 38 (1000) vs. E(FD) 4 x 1019 e. V 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.

6 sigma deficit from power-law assumption

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.