The Pierre Auger Observatory Hunting the Highest Energy
The Pierre Auger Observatory Hunting the Highest Energy Cosmic Rays I – High Energy Cosmic Rays and Extensive Air Showers March 2007 E. Menichetti - Villa Gualino, March 2007 1
Discovery of Cosmic Rays Altitude variation of ionisation detected by Hess and Kohlhoster and Pfotzer March 2007 E. Menichetti - Villa Gualino, March 2007 2
The Cosmic Ray Spectrum March 2007 E. Menichetti - Villa Gualino, March 2007 3
Outstanding Issues Acceleration Mechanism GZK Composition Point Sources March 2007 E. Menichetti - Villa Gualino, March 2007 4
The Magnetic Mirror Energy exchange Drift ↔ Revolution Inhomogeneous B field Spiral trajectories around field lines High gradient regions acting like walls March 2007 E. Menichetti - Villa Gualino, March 2007 5
Fermi Mechanism - 2 nd Order Scattering by B-field Stochastic process: DE 2 E Expect: Slow, inefficient March 2007 E. Menichetti - Villa Gualino, March 2007 6
Fermi Mechanism - 1 st Order As before, scattering by B -field irregularities Momentum gain: Speed=U 1 > Speed=U 2 Expect: fast, efficient Shock compression ratio March 2007 E. Menichetti - Villa Gualino, March 2007 7
Maximum Energy Simple estimate of max. energy (Hillas): : plasma speed B: mag field L: source size March 2007 E. Menichetti - Villa Gualino, March 2007 8
Spectral Index, Time Constant Power law spectrum Fermi 2 nd order: Fermi 1 st order: tacc>108 yr! KO tacc~1 month! OK March 2007 E. Menichetti - Villa Gualino, March 2007 9
Compact sources Just meaning: non electromagnetic acceleration Various mechanisms proposed: Black hole accretion disks Gamma ray bursts Topological defects (monopoles, cosmic strings, . . ) UHE n’s from decays of high mass particles March 2007 E. Menichetti - Villa Gualino, March 2007 10
Cosmic Microwave Background Penzias, Wilson & the Antenna March 2007 The CMB spectrum (by FIRAS) E. Menichetti - Villa Gualino, March 2007 11
CMB Photons Peak energy k. BT= 0. 6 me. V Density 400 cm-3 Possible CR interactions: , A March 2007 E. Menichetti - Villa Gualino, March 2007 , A 12
G(reisen), Z(atepsin), K(uz’min) (G, Z&K - 1965) The moral: CR’s above threshold bound to lose energy March 2007 E. Menichetti - Villa Gualino, March 2007 13
The GZK Cutoff So UHECR’s just can’t propagate beyond, say, 50 Mpc! Then we should find a suitable source just ‘round the corner’. But where? March 2007 E. Menichetti - Villa Gualino, March 2007 14
The High End of the CR spectrum ~ x 2 effect ~ 2 -3 s issue. . March 2007 E. Menichetti - Villa Gualino, March 2007 15
Composition Issues Spectrum Galactic? March 2007 Depth of Shower Maximum in Air vs. E Extra-Galactic? E. Menichetti - Villa Gualino, March 2007 16
More on Composition Proton/Iron Discrimination tied to Intra/Extra-Galactic origin March 2007 E. Menichetti - Villa Gualino, March 2007 17
Opening a New Window? Effect of Extra-Galactic Magnetic Field on CR trajectories –Simulation E = 1018 e. V E = 1020 e. V Clearly, around 1020 e. V a new astronomy is feasible… …if Cosmic Rays of that energy are actually observed March 2007 E. Menichetti - Villa Gualino, March 2007 18
The Known Matter (< 21 Mpc) March 2007 E. Menichetti - Villa Gualino, March 2007 19
Anisotropies, Point Sources? AGASA > 6 Clusters observed Controversial results… Issues at stake: Detection Technique Angular Resolution Statistics! HIRES March 2007 No cluster E. Menichetti - Villa Gualino, March 2007 E. Menichetti – SIF 2006 20
Cosmic Rays Detection Direct detection - Up to 1014 e. V Main limitation: Flux Usually performed by balloons, satellites, … Extensive Air Showers – Above 1014 e. V Primary particle interaction in upper atmosphere Developing shower detected by different techniques March 2007 E. Menichetti - Villa Gualino, March 2007 21
EAS Development Primary interaction in the high atmosphere Hadronic Shower ~10 km Charged mesons Muons Neutral mesons Photons Muon component + EM Shower March 2007 E. Menichetti - Villa Gualino, March 2007 22
EAS – Cross Section March 2007 E. Menichetti - Villa Gualino, March 2007 23
EAS – EAS development Next ~6 slides from R. Engel’s simulations See for example: R. Engel EAS Lectures given at ISAPP 2005 Summer School http: //www. isapp 2005. to. infn. it/ March 2007 E. Menichetti - Villa Gualino, March 2007 24
EAS-I March 2007 E. Menichetti - Villa Gualino, March 2007 25
EAS-II March 2007 E. Menichetti - Villa Gualino, March 2007 26
EAS-III March 2007 E. Menichetti - Villa Gualino, March 2007 27
EAS-IV March 2007 E. Menichetti - Villa Gualino, March 2007 28
EAS-V March 2007 E. Menichetti - Villa Gualino, March 2007 29
EAS - Profiles Longitudinal March 2007 Lateral E. Menichetti - Villa Gualino, March 2007 30
EAS - Electron Lateral Distribution March 2007 E. Menichetti - Villa Gualino, March 2007 31
EAS - Muons vs Electrons March 2007 E. Menichetti - Villa Gualino, March 2007 32
EAS- Elongation Rate March 2007 E. Menichetti - Villa Gualino, March 2007 33
EAS Detectors Long history, dating back to the ’ 60 s Volcano Ranch (USA) – Sampling Haverah Park (UK) – Sampling SUGAR (Australia) - Sampling Yakutsk (Russia) - Sampling Fly’s Eye (USA) – Fluorescence AGASA Hi. Res March 2007 E. Menichetti - Villa Gualino, March 2007 34
AGASA Akeno Giant Air Shower Array 111 scintillators + 27 muon det. Akeno, Japan 11 Super-GZK events Small Scale Clustering Constraints on Composition: protons at UHEs. (“Classical” analysis based on Ne vs Nm) March 2007 E. Menichetti - Villa Gualino, March 2007 35
Hi. Res High Resolution Fly’s Eye Pioneers of Fluorescence. Technique Air fluorescence detectors Hi. Res 1 - 21 mirrors Hi. Res 2 - 42 mirrors Dugway, Utah, USA March 2007 No Super-GZK flux No Small Scale Clustering Composition Change E. Menichetti - Villa Gualino, March 2007 36
EAS – The Movie March 2007 E. Menichetti - Villa Gualino, March 2007 37
- Slides: 37