Ultra High Energy Cosmic-Rays
Recent results from the Pierre Auger Observatory
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
OUTLINE
•  Ultra High Energy Cosmic Rays (UHECRs)
•  The Pierre Auger Observatory
•  Recent (selected) results
•  Upgrading the Observatory
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Centaurus A (aka Cen-A) multi-wavelength
(Credit: X-ray: NASA/CXC/CfA/R.Kraft et al; Radio: NSF/VLA/Univ.Hertfordshire/M.Hardcastle;
Optical: ESO/WFI/M.Rejkuba et al.)
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Centaurus A
13 Millions light years away from Earth
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Multi-messenger astronomy
•  Photons
–  Most of what we know about the Universe comes from photon measurements
•  Neutrinos
–  Sun
–  1987A supernova
–  Ice Cube in Antartica
•  Charged particles?
1018eV
1019eV
1020eV
A charged particle astronomy window
opens up at (ultra) high energy
–  Acceleration process / sites?
–  Galactic magnetic field?
–  Composition?
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
The cosmic-ray energy spectrum
•  Power-law flux over many
orders of magnitude
Knee
•  Direct measurements only
below 1015eV (106GeV)
•  Features: knee, ankle
Ankle
•  End of the spectrum?
–  Flux at 1020eV (1011GeV):
<1particle/km2/century
Ultra-High Energy Cosmic-Rays (UHECRs)
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
The darkest place in the Universe – seen by Hubble
•  Hubble Ultra-Deep Field (HDF)
•  11.3 days total exposure, 800
exposures over 400 orbits
between Sept 24, 2003 and Jan
16, 2004
•  Bottom line: wherever you
look, chances are there is
something!
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
K.Greisen, Phys. Rev. Lett. 16 (1966) 748-750
The end of the cosmic-ray spectrum
•  GZK Cut-off: Interaction of UHECRs with
Cosmic Microwave Background (CMB)
photons.
WMAP
“Rest frame of the Universe”:
UHECR
CMB Photon
Rest frame of the UHECR:
Also Zatsepin and Kuzmin (1966)
CMB Photon
UHECR
p+γcmb→ Δ+ → p + π0
→n+π+
(also photodissociation on heavier nuclei)
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
The GZK horizon / sphere
Solar System
Size of Known Universe
(~5000 Mpc)
Closest Star
(1.3 pc)
10-3
1 pc
Size of
Galaxy
Closest Local
Diameter Galaxy
Supercluster Visible Horizon
~5000 Mpc
(25 kpc) (700 kpc) (50 Mpc)
kpc
Mpc
Gpc
1 parsec (pc) = 3.26 light-years ~3x1013 km
“GZK Sphere”
(∝R3)
3x1020eV
The sources are nearby!
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
20-30Mpc
40-50Mpc
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Accelerator Sites ?
Hillas plot:
PM Bauleo & JR Martino Nature 458, 847-851 (2009)
•  Maximum energy (energy loss not included)
" R %" B %
1018 eV Z $
'
'$
# kpc & # µG &
€
(size of the source)
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Extended Air Shower (EAS)
•  Secondary particles are produced from
a primary interaction with air high in
the atmosphere (20-30km)
•  Subsequent interactions of secondaries
produce an air shower
•  Only a fraction of the particles reaches
the ground
•  The higher the energy of the primary,
the larger the shower
–  For UHECRs, the shower can cover tens
of km2 on the ground
–  A 1020eV primary yields 1011particles at
the maximum development of the EAS.
•  Opportunity to study particle physics at
UHE (pA cross-sections…)
–  About 30 times higher c.m. energy than
LHC
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Extended Air Shower (EAS)
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
A (very) large ground array
“We need to think big, VERY big” (circ 1992)
Jim Cronin
Nobel Prize 1980
Alan Watson
Cosmic-Ray Expert
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Surface Detector (SD) Array
1660 detector stations, 1.5 km spacing, 3000 km2
Fluorescence Detectors (FD)
4 telescope buildings, 6 telescopes per enclosure,
3 new HEAT telescopes, 27 telescopes total
+ Atmospheric Monitoring Systems
The Pierre Auger Observatory
500+ PhD scientists
70+ Institutions
19 countries
Calibration facilities
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Surface Detector (SD) Array
1660 detector stations, 1.5 km spacing, 3000 km2
Fluorescence Detectors (FD)
4 telescope buildings, 6 telescopes per enclosure,
3 new HEAT telescopes, 27 telescopes total
+ Atmospheric Monitoring Systems
The Pierre Auger Observatory
400+ PhD scientists
70+ Institutions
19 countries
Calibration facilities
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
EAS measurement
•  Surface detector (SD) array samples the EAS
particle density on the ground. 100% duty cycle.
Robust detectors and good angular resolution.
•  Fluorescence detector (FD) detects UV light from
ionized Nitrogen molecules in the air. 10-15%
duty cycle only. Near calorimetric measurement
and shower development across the atmosphere.
•  Hybrid detector combines SD and FD for more
precise determination of the shower parameters.
The Pierre Auger Observatory
is a hybrid detector
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
The Pierre Auger Observatory
Fluorescence Detector
Surface Detector
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
FD
Longitudinal distribution
(mostly e.m.)
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Measuring the EAS development
SD
Lateral distribution
(µ + e.m.)
Honors Modern Physics, April 2015
Fluorescence Detectors
(~14% duty cycle (moonless nights) - calorimetric method)
440 PMTs / telescope
(Photonis XP 3062)
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
FD event
Duty factor: ~14%
Resolution (after cuts)
•  Cosmic-ray energy: 8% stat + 14% syst
•  Shower direction: < 1°
•  Depth of shower maximum (Xmax): <40 g/cm2
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Surface Detectors
(100% duty cycle - the statistical engine of the Observatory)
PM Bauleo & JR Martino Nature 458, 847-851 (2009)
1.5km
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
The surface detector
dS
S
=
dt
Total
signal:
∫
•
dt
•  Shower direction: (0.5°-3°)
Duty factor: ~100%
Shower size
Air s
how
er pa
rticle
Communication & GPS
antennas
Solar panel
SD electronics and
enclosure
Hatch
PMT, Base
& enclosure
Cherenkov
photons
12m3
Battery
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
of pure water in
a reflective Tyvek liner
Rotomolded
polyethylene tank
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Shower size / energy estimation from SD
SD 1500m θ≤60°
SD 750m θ<55°
SD 1500m 60°>θ>80°
“Vertical” events
Fully efficient: E≥3EeV
Energy estimator: S1000
750m events
Fully efficient: E≥0.3EeV
Energy estimator: S450
“Inclined” events
Fully efficient: E≥4EeV
Energy estimator: N19
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Hybrid events – the “Rosetta stone” of the Observatory
Lateral Distribution Function (LDF)
Hybrid directions cross-check SD directions
S1000:
Etotal
(VEM:
Composition)
(timing:
Composition)
+ arrival direction
Shower profile
Integral:
Etotal
Xmax, ΔXmax: Composition
+ arrival direction
E = A ⋅ Ŝ B
FD calibrates SD energy scale
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent results
Summary
Four-eyes hybrid event
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Atmospheric monitoring
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
CLF / XLF – the “test” beams of the Observatory
Laser
Optical Equivalence:
5 mJ Laser Track~100 EeV EAS track
FD records ~ 500 laser tracks/hour
Applications:
Photometric Calibration
Timing, Pointing, Triggering,
Atmospherics
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Shoot-the-astrophysical sites
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
UHECR spectrum
A.Schulz for the Pierre Auger Collaboration, ICRC 2013
•  SD Data 1500m (Jan’04 - Dec’12, 31645km2 sr yr)
–  Core contained
–  Zenith angle < 60°
–  E > 3.1018eV
Ankle
•  Hybrid Data (Nov’05 - Dec’12)
–  Core contained
–  Zenith angle < 60°
–  E > 1018eV
•  Combined
–  14% systematic uncertainty on the energy scale
GZK-like cutoff
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
(Small scale) anisotropy
Pierre Auger Collaboration, Science 318 (2007) 938
•  Correlation with AGN with redshift < 0.018
(75Mpc)
•  Auger data: E>56 EeV (5.6x1019eV)
•  20 out of 27 events correlate within 3.1°
•  Anisotropy at >99% CL
Pierre Auger Collaboration, Astropart. Phys. 34 (2010) 314
Fraction of events
correlating with
nearby VCV AGNs
38%
Science paper
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
(Small scale) anisotropy
Pierre Auger Collaboration, Science 318 (2007) 938
•  Correlation with AGN with redshift < 0.018
(75Mpc)
•  Auger data: E>56 EeV (5.6x1019eV)
•  20 out of 27 events correlate within 3.1°
•  Anisotropy at >99% CL
A.Letessier-Selvon for the Pierre Auger Collaboration, ICRC 2013
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Cen-A?
•  Cen-A is the closest AGN from our galaxy
•  Weak anisotropy signal
–
–
–
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
E > 55EeV
Δθ < 20°
P ~ 1% (including penalty for scan)
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Composition study with FD
From: M.Unger, Snowpac and Snowcluster 2010
PHOTON
PROTON
Depth of shower maximum (Xmax)
IRON
Shower-to-shower fluctuation (σXmax)
Number of muons (Nµ)
•  Xmax and σXmax reflect the properties of the first interaction
•  The first interaction for heavier particle happens at shallower depth with less fluctuation
•  The interpretation relies on hadronic models
–  Opportunity to study particle physics
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Composition
A.Letessier-Selvon for the Pierre Auger Collaboration, ICRC 2013
•  Apparent transition towards heavier composition
•  Break in <Xmax> behavior seems to occur around the Ankle energy
•  Break in RMS(Xmax) at roughly the same energy
•  Appears to be confirmed by SD composition analysis as well
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Two very different scenarii!
A.Schulz for the Pierre Auger Collaboration, ICRC 2013
e+e-
Proton sources
Photo-pion production
Iron sources
Photo-disintegration
Fe-scenario: sources running out of steam before GZK effect
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Mixed composition
The Pierre Auger Collaboration, Phys Rev D (2014)
?
1018
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
1019
Energy (eV)
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
More results!
Hadronic cross section: Pierre Auger Collaboration, PRL 109 (2012) 062002
Photons: M.Settimo for the Pierre Auger Collaboration, ICRC 2011
Neutrinos: P.Pieroni for the Pierre Auger Collaboration, ICRC 2013
•  Hadronic cross-sections, well above LHC energies!
•  Existence of UHE (GZK) photons and neutrinos?
+
Neutrinos (5%): p + γ CMB → Δ(1232) → n + π
0
Photons (10%): p + γ CMB → Δ(1232) → p + π
↓
γ +γ
↓
µ+ + νµ
↓
e+ + ν µ + ν e
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
The big picture in one plot
Ankle
“GZK-like”
Isotropic
Anisotropic
Light
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Becoming
heavier
End of FD
composition data
End of SD
composition data
PUZZLING… BUT EXCITING!!!!
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent (selected) results
Upgrading the Observatory
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Nµ and Xmax: more discrimination
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent results
JEM-EUSO
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
NASA grant: 1.7M$ out of 4.4M$ for Mines!
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent results
JEM-EUSO
Space… the final frontier
The Extreme Universe Space Observatory (EUSO)
A cosmic-ray telescope on board of the ISS
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Honors Modern Physics, April 2015
Ultra High Energy Cosmic Rays (UHECRs)
The Pierre Auger Observatory
Recent results
JEM-EUSO
Fred Sarazin (fsarazin@mines.edu)
Physics Department, Colorado School of Mines
Exposure is key!
Honors Modern Physics, April 2015