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 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 - 2nd Order Scattering by B-field Stochastic process: E β 2 E Expect: Slow, inefficient EE1 cos E 4 ' E2E21 cos2 E 1, 3 2 ' 1 1 1 2 March 2007 E.Menichetti - Villa Gualino, March 2007 6
Fermi Mechanism - 1st Order Speed=U 1 > Speed=U 2 E 4 R1 E 3 R angles As before, scattering by B -field irregularities Momentum gain: p p2 U c head-on acceleration Expect: fast, efficient 1 p p2 U c tail-on deceleration 2 p p 2 UU c >0 net gain 1 2 Shock compression ratio March 2007 E.Menichetti - Villa Gualino, March 2007 7
Maximum Energy Simple estimate of max. energy (Hillas): Emax ZeBL β: plasma speed B: mag field L: source size March 2007 E.Menichetti - Villa Gualino, March 2007 8
Spectral Index, Time Constant Power law spectrum NE E x Fermi 2nd order: x1 1 acc esc τ acc >10 8 yr! KO Fermi 1st order: R 2 x 2 R 1 τ acc ~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 ν s from decays of high mass particles March 2007 E.Menichetti - Villa Gualino, March 2007 10
Cosmic Microwave Background Penzias, Wilson & the Antenna The CMB spectrum (by FIRAS) March 2007 E.Menichetti - Villa Gualino, March 2007 11
CMB Photons Peak energy k B T= 0.6 mev Density 400 cm -3 Possible CR interactions:,a,a March 2007 E.Menichetti - Villa Gualino, March 2007 12
G(reisen),Z(atepsin),K(uz min) p2.7k n 0 p2.7k p 19 E thresh 6 10 ev En.loss 20% /int 2.7 p K p e e 18 E thresh 1 10 ev En.loss 0.1% /int (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 σ issue.. March 2007 E.Menichetti - Villa Gualino, March 2007 15
Composition Issues Spectrum Depth of Shower Maximum in Air vs. E Galactic? Extra-Galactic? March 2007 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 = 10 18 ev E = 10 20 ev Clearly, around 10 20 ev 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 HIRES Controversial results Issues at stake: Detection Technique Angular Resolution Statistics! No cluster March 2007 E.Menichetti - Villa Gualino, March 2007 20 E.Menichetti SIF 2006
Cosmic Rays Detection Direct detection - Up to 10 14 ev Main limitation: Flux Usually performed by balloons, satellites, Extensive Air Showers Above 10 14 ev Primary particle interaction in upper atmosphere Developing shower detected by different techniques March 2007 E.Menichetti - Villa Gualino, March 2007 21
EAS Development ~10 km Primary interaction in the high atmosphere Hadronic Shower 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.isapp2005.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 Lateral March 2007 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 60s Volcano Ranch (USA) Sampling Haverah Park (UK) Sampling SUGAR (Australia) - Sampling Yakutsk (Russia) - Sampling Fly s Eye (USA) Fluorescence AGASA HiRes 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 N e vs N µ ) March 2007 E.Menichetti - Villa Gualino, March 2007 35
HiRes High Resolution Fly s Eye Pioneers of FluorescenceTechnique Air fluorescence detectors HiRes 1-21 mirrors HiRes 2-42 mirrors Dugway, Utah, USA No Super-GZK flux No Small Scale Clustering Composition Change March 2007 E.Menichetti - Villa Gualino, March 2007 36
EAS The Movie March 2007 E.Menichetti - Villa Gualino, March 2007 37