the auger project
DESCRIPTION
The Auger Project. Seeking the Source of Ultra High Energy Cosmic Rays. A New Window on Astronomy. Generic Colloquium Slides Prepared December 11, 1997. David F. Nitz University of Michigan. Outline. Introduction Historical Perspective CR Spectrum Extensive Air Showers Array layout - PowerPoint PPT PresentationTRANSCRIPT
The Auger Project
Seeking the Source of Ultra High Energy Cosmic Rays
A New Window on Astronomy
Generic Colloquium SlidesPrepared December 11, 1997
David F. NitzUniversity of Michigan
Outline
• Introduction– Historical Perspective– CR Spectrum– Extensive Air Showers– Array layout– EeV data
• Possible Sources of Cosmic Rays– “Standard” Acceleration– Propagation and GZK– Top down (topological defects)– Monopoles– Gamma Ray Bursts
• Observations and Physics Issues– Magnetic fields– Point Sources– AGASA pairs– Sky Coverage
• Auger Detectors & Techniques– Fluorescence detectors– Tanks– Hybrid Operation– Timing– Trigger– Front-end electronics– Communications network– Energy, Direction, Composition resolution
The Beginning
Ever since Victor Hess discovered
cosmic rays in 1912, a primary question has been "Where do they come from?". After more than 80 years of research
this question remains largely unanswered. The origin of the
highest energy cosmic rays remains one of the great unsolved
mysteries of physics.
The Observed Cosmic Ray Spectrum
Layman’s Terms?
Energy Scales
The Highest Energy Particle Ever Observed
E = 3 x 1020eV 50 J!50 J!
Flux of EeV Particles
The Question
The International Collaboration
A 1019 eV Extensive Air Shower
Auger Array Layout
Two Hemispheres
Anu Talvari is an artist of Estonian origin, born in Sweden and living in Buenos Aires -- a
background not unlike the world-wide composition of the Auger Collaboration. She describes the
painting thusly: “Earth. The Blue Planet. The known space is enclosed in the
lower left corner. The unknown space opens in the upper right
corner. Two Auger Observatories installed in both hemispheres.
Two eyes looking for information from the unknown space.”
The Auger Project is named after the late French physicist Pierre Auger, who discovered extensive air showers. He received a Nobel Prize for his work on “Auger electrons” and was influential in the founding of CERN.
Auger Observatory Sites
#S
#S
Northern Hemisphere Site
Southern Hemisphere SiteArgentinaArgentina
Site Photos
Astrophysical Miscellanea
Possible SourcesPossible Sources
• Diffusive shock acceleration (Fermi) in extended objects– Lobes of radio galaxies (Biermann)
– Galaxy cluster accretion shocks (Kang, et. al)
– Collisions of galaxies (Cesarsky)
– Motion of galaxies in ISM
• Acceleration in strong fields associated with accretion disks and compact rotating galaxies (Colgate)
Astrophysical Acceleration Mechanisms
Black Hole(Artist’s Conception)
NGC4151
Caveats?
Limits to Acceleration
cZeBLE max
Attenuation of Cosmic Rays
All known particles except neutrinos undergointeractions with the CMBR:
This is the GZK cutoff
Distance Scales
The GZK Cutoff
Possible SourcesPossible Sources
• Top down models – Decay of topological defects (Kibble, Bhattacharjee,
Hill, ..)– Window to Post-Inflationary Reheating Epoch?
(Kuzmin & Rubakov) – Decaying Vortons (Masperi & Solva)– Relic monopoles (Kephart & Weiler) (Escobar &
Vazquez : “No”)
• Acceleration in catastrophic events – In association with gamma ray bursts (Waxman, Vietri,
Milgrom)
• Other New Physics – Supersymmetric particles (Chung, Farrar, & Kolb) – Strongly interacting neutrinos (Bordes)– Needs to be at few Gev or cross section too low => not
likely - ruled out by accelerator data (Halzen)– Decay of energetic new long lived progenator
(Frampton, Keszthelyi, & Ng)
Exotic Mechanisms
Topological Defect Model
CASA/MIA
Auger Neutrino Detection
(A recent analysis by Ralstan et al. suggests the cross section is likely to be closer to MRS)
Neutrino rates for 2 extreme extrapolations of the cross section
00.20.40.60.8
11.21.41.61.8
2
17 18 19 20 21
Log10 Electron Neutrino Energy
Log
10 k
m**
3 sr
wat
er
equi
vale
nt
Magnetic Magnetic MonopolesMonopoles
• Consideration of relic monopoles motivated by 2 interesting facts:– Observed CR flux >1020 eV similar to Parker Bound
• Higher flux would have violated bound• Lower flux would not have been observed
– Dirac monopoles can be accelerated to >1020 eV with typical galactic magnetic field strengths and field coherence lengths
• Must be relativistic to initiate observed air showers==> masses <1019 eV
• Observational consequences:– Energetic monopoles may be distributed preferentially in the direction of local
galactic magnetic field– Air showers produced by monopoles may have distinctive characteristics
• Detailed modeling of interactions of monopoles in upper atmosphere not yet been carried out.
– Not known whether monopole can produce showers like those observed by AGASA and Fly’s Eye
Auger is designed to be sensitive to air shower structure
N.A. Porter, Nuov. Cim. 16 958 (1960)T.W. Kephart and T.J. Weiler, Astropart. Phys. 4, 271 (1996)
k M
G pc
M
kpc
E q BL N
B
B
L
L
R
R
~/ /
6 1020
300
1 2
30
1 2
eV
F M lM H c
~ .0 2 1025 3 3
eV / cm / sec / sr2F
M
PL 10 15 / cm / sec / sr2
M lc H
1020 eV
RM
M M
M
PL
E F
F~ 10
108
20
eV
Horizon size Phase transition correlation length
Monotonic relationship betweenmonopole flux & mass
(Parker bound)
(Doesn’t overclose Universe)
==>
AssociationAssociation with Gamma Ray with Gamma Ray BurstsBursts
• If cosmological, power needed to account for flux of highest energy cosmic rays is comporable to average power in gamma rays
• Observed spectrum consistent with Fermi acceleration in region and cosmological distribution
• Observed rate– 2 CR events above 2 x 1020 eV observed in 26 months– ~1 GRB per 50 years within field of view of experiments and within 100 Mpc
(GZK cutoff)==> Requires 1020 eV protons produced in distant GRB burst are dispersed in time
>50 years==> Inter-Galactic Magnetic Field >10-12 G
• Each of 2 highest energy CR within ~5o of a strong BATSE GRB (but not statistically compelling)
• If highest energy CRs associated with distant GRBs– GZK cutoff– If GRB sources associated with luminous matter, expect CR anisotropy related to
large scale structure of local (<100 Mpc) universe– Energy dependent delays in arrival times induced by IGMF
• Brightest sources may be different at different energies
• If highest energy CRs associated with local GRBs– No GZK cutoff– New >1020 eV events should be correlated with GRBs– Isotropic CR distribution due to observed isotropy of GRBs
E. Waxman, Phys. Rev. Lett. 75, 386 (1995)M. Vietri, Astrophys. J. 453, 883 (1995)E. Waxman, Astrophys. J. 444, L1 (1995)E. Waxman & P. Coppi, astro-ph/9603144M. Milgrom & V. Usov, Astrophys. J. 448, L37 (1995)M. Vietri, Mon. Not. R. Astron. Soc. 278, L1 (1996)J. Miralda-Escude & E. Waxman, astro-ph/9601012
Possible Source Conclusions
No really satisfactory model has emerged
Magnetic Field Deflection
AGASA pairs
• 2-3 cases of 2 cosmic rays coming from the same direction within 1.6 deg. angular resolution
– 1% random chance if isotropic distribution– 2% if use >4 x 1019 eV
• One pair includes highest energy event observed by AGASA
– Assume same species & source– Trace back 30-50 Mpc to source
Need more data, more sky coverageWe expect >50 events in Auger from this sourcein same length of time (5 years)
20 events eV 5 1019
36 events > 4 10 eV19
B h B e h( ) ( ) . 0 0 8 2
(Parker)
Auger Philosophy
• Large aperture (>10X previous generation)
• Uniform sky coverage
• Hybrid operation
• Good energy & direction measurement
• Composition sensitivity
Northern Observatory Exposure
AGASA Events(E > 5x1019eV)
Havarah Park Events (E > 5x1019eV)
Southern Observatory Exposure
Auger Observatory Exposure
AGN Catalog of Huchra (< 100 Mpc)
D ~ cz/H (for small z)
Hybrid Operation
Fluorescence Detector
Surface Detector Station
GPS Timing
Tandar Test Tank
White top: 55 ns
Black top: 21 ns
Data Simulation (Pryke)
Trigger Hierarchy
Auger Communications System Functional
Overview
Control Center
Concentrator
Remote Station1600/site
Fluorescence Eye
~0.5 Mbits/s each
~1.1Mbits/s aggregate 1600 stations
Level 2 Triggers~20 Hz @24 bits each Poisson distributed
Event Data ~15 Kbits/s @ ~2600 interval Poisson distributed
Monitoring Data ~200 bits/s mean program controlled
Software Download ~2 Mbits/hr infrequently
Control 100 bits/s?
+ ACK, NAK as required
Level 3 Trig. 0.2 hz
Test Tank at AGASA
1020 eV event
1.7 km from core
30o zenith angle
Ground Array Energy Reconstruction
Can probably remove offset
Primary Composition Sensitivity
Performance Summary
Conclusions