Sergio Petrera L`Aquila IFAE 2005 @ CT 1 Aprile 2005

Sergio Petrera
IFAE 2005 @ CT
1 Aprile 2005
L’Aquila
Neutrini e Raggi Cosmici:
risultati recenti e prospettive
IFAE @ Catania
1-Aprile-2005
S. Petrera
L'Aquila
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Moda ??
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1-Aprile-2005
S. Petrera
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Sergio Petrera
IFAE 2005 @ CT
1 Aprile 2005
L’Aquila
Neutrini e Raggi Cosmici:
risultati recenti e prospettive
•Perché si studiano i Raggi Cosmici
•L’evoluzione dei rivelatori. Gli UHECR
•L’attualità: la controversia AGASA/HiRes
•Il Pierre Auger Observatory
IFAE @ Catania future
•Prospettive
1-Aprile-2005
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CR Energy spectrum
Fermi mechanism accelerates up to
Emax   ZBL
B magnetic field
L size
of shock region
 speed
Z primary charge
(e.g. Gaisser book, 1990)
Why so successful?
• generates a power law spectrum
• below the knee SN explosions can account
for needed CR power
(Ginzburg and Syrovatskii, 1964)  CR I
Extension above the knee
•Other possible Galactic sites with higher
field and/or wider size
(multiple SNR, binary stars, …)  CR II
Consequence:
•At cutoff energy change of chemical
composition
• CR III:
 RLarmor   1   E   B 

     
   
kpc
Z
EeV
  G 

  
p
10 EeV
O
Fe
8kpc
3G
Why are Highest Energies CR’s so puzzling?
•
No convincing acceleration process for explaining
particle energy > 1020 eV: hard to find astrophysical
sites to apply shock acceleration capable to provide
such energies
(Hillas 1984, Drury 1992,…)
• Greisen-Zatsepin-Kuz’min Cut Off
(Greisen 1966, Zatsepin and Kuz’min 1966)
m ( m p  m / 2 )
GZK
p + 2.7K  n + 0
 meV 

Ethr 
 7  10 eV 
2CMB
 CMB 
 Particles >1020 eV should not be there!
p Rachen-Bierman Berezinsky-Grigoreva
But…if they exist then:
Fe Stecker Salomon
•Sources must be < 50 Mpc

Bhattacharjee Sigl
•They should point back to their source allowing astronomy.
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UHECRs, a puzzle
Contemporary astroparticle physics is faced by a
number of acute problems.
One of them concerns dark matter, which one
might (perhaps mischievously) qualify as the
study of particles which should exist...
but until further notice, don’t.
Ultra high energy cosmic rays constitute the
inverse problem: particles which do exist...
but perhaps shouldn’t.
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Difficulties with
Bottom-Up scenario…
then 
Top-Down
Topological Defects
GUT particles
[Vilenkin, Berezinski, Rubakov, Kuzmin,
Schramm, Kolb, Blasi, Sigl, Hill, Kibble...]
• Collapse of cosmic strings
• Unstable although quasi-stable
X-particles decay
• Cosmic necklaces...
No problems but speculative...
Signatures (generic top-down mechanisms):
• Heavy (1024 eV) particle decay spectrum
• Possible anisotropy (if accumulation in the
Galactic Halo)
• No cutoff
• Photons dominant
• Supra GZK  in detectable quantities
 and  strongly connected in TD scenario!
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Other Alternatives
Avoiding the GZK “paradox”:
• Heavy metastable relics in the halo of our own galaxy. [Blasi, Kolb]
• “Z-bursts”
uhe cmb  Z  UHECR [Weiler]
• Magnetic monopoles [Weiler, Biermann]
• SUSY lightest baryonic state [Farrar]
• Strongly interacting neutrinos [Domokos]
• Violation of Lorentz invariance [Gonzalez-Mestres,Coleman,Glashow]
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GZK and relativistic invariance
• GZK process (p + 2.7K  n + 0 ) is well known at
low energy
• Only relativistic invariance needed to relate frames
with relative Lorentz factor L1011
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Relativistic Invariance and Quantum Gravity
[Aloisio, et al.]
•
2
E  p  m2
Normal RI – Invariant
2


2
E p
2
• E  p  m 1   (  2 )  ...
M m


Modified RI, Invariant?
• Natural candidate M=Planck Mass
• For massive particles, important effects are expected
when p3m2M
i.e. (protons) p21015eV
• ...Planck scale phenomenology accessible
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1-Aprile-2005
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La rivelazione di Air Showers
Area  Energia
 Rivelatori sparsi
EM shower
• Direzione dai tempi
Shower front
• Misura delle densita’ di particelle nei
rivelatori sparsi
• Asse dello sciame
• Size totale
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Shower core
hard muons
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Dalla Size all’energia
•
•
Calorimetro (HEP) ad aria ad un solo sampling !
Pero’ si puo’ risalire a Nmax sfruttando le proprieta’ del
“fascio”
 Constant intensity cuts :
1. Il flusso e’ isotropo e costante nel tempo
2. Uguale rate = Uguale energia
Shower Max
•Variando  si costruisce N(X)
1011 Particles
at surface
N
•Da N(X) su ricava Nmax
 Nmax
E
Sea level
IFAE @
Catania
Depth
in the Atmosphere
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UHECR (>1017eV)
AGASA
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A new technique: the Air Fluorescence
(see e.g. http://www.cosmic-ray.org/learn.html
•The term “fluorescence” refers to the process by which atoms absorb photons of
one wavelength and emits photons at longer wavelength. e.g. in fluorescent lamps
with mercury gas: collision excited atoms emit UV photons (this emission is
properly “luminescence” or “scintillation” ). These photons are absorbed by
phosphor coating of the bulbs, which re-emit in the visible.
•The passage of charged particles in an EAS through
the atmosphere ionizes and excites N molecules. This
excitations produces isotropical UV emission
(properly luminescence)
•Air fluorescence studied (early 60’s) by Los Alamos
Sc. Lab. as a method for detecting the yield on nuclear
explosions in atmospheric tests.
•Emission spectrum studied by A. Bunner (PhD thesis,
1967) , a student of Rossi and Greisen (formerly in
Manhattan Project).
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Early Fluorescence in air
Excitation of the nitrogen molecules
and their radiative dexcitation .
Collisional quenching
1967 First full-scale
experiment by
Greisen’s group at
Cornell
337 nm
~ 300 - 400 nm
357 nm
313 nm
391 nm
1976 Fluorescence Detector realized by Utah
University and installed at Volcano Ranch,
New Mexico
1967 Bunner, Ph.D
Thesis Cornell Univ.
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Fly’s Eye Air Fluorescence Detector
1981 The University of Utah Cosmic Ray group
(G.Cassiday and coworkers) constructed Fly’s Eye, a
full-scale observatory based on the Volcano Ranch
prototype basic design.
The experiment was located in the West Desert of
Utah, within the US Armi Dugway Proving Ground
(DPG), 160 km southwest of Salt Lake City.
(Baltrusaitis et al., 1985)
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Air Shower parameters from Fluorescence
Detection I: Geometry (single eye)
1. Determination of the Shower-Detector
plane (SDP)
2. Time fit: t(χi) = t0 + Rp*tan [(χ0 - χi)/2]
Caveat: 3D reconstruction relies on curvature (i.e. the
tangent term). For “flat” dependence space reconstruction is
inaccurate.
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χi
Rp
t0
χ0 20
Air Shower parameters from Fluorescence
Detection II: Shower Energy
)  ( T)  (  
A
 )  ( N   .e.p N

iR4
Emitted Geometry Atmosphere
Photons
Detector
At each time: Cherenkov (direct, Raleigh and
Mie scattered) subtracted.
 X  xam X 

p xe



2
Gaisser-Hillas fit
0 X  x am X
 
IFAE @ Catania
1-Aprile-2005
X X 
 0
 xam N  ) X ( N
 0 X  xam X 
S. Petrera
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E ~ 1019 eV
Xmax ~ 780 g/cm2
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A true air calorimeter !
the “Fly’s Eye Methodology”
Primary Energy: a calorimetric measurement
1.
2.
3.
EM shower energy is ~90% of Eprim
Compensate for atmospheric attenuation and Cherenkov
contribution.
PMT light yield after corrections  Ne  EEM  Eprim.
FD only  E / E  10% for hadronic showers
Composition: direct view of shower development
allows direct measurement of Xmax
Stereo Analysis: FE 2 operated >1986 (with
36/67 mirrors, 3.4 Km away).
Stereo reconstruction technique much more
accurate than time fit  more reliable
energy measurement.
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AGASA / HiRes
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AGASA / HiRes
HIRES Coll. astro-ph/0208301
SD
FD
Berezinsky, Gazizov,
Grigorieva hep-ph/0204357
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AGASA / HiRes
AGASA data renormalized by 20 % (Energy scale)
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Where do they come from?
Above 4  1019eV:
• No convincing evidence for anisotropy, nor galactic neither super-galactic.
• No obvious association with known astrophysical candidates.
• Abnormal rate of angular coincidences:
5 “doublet” and 1 “triplet” events. Angular coincidences within 2.5°. Chance
coincidence prob. is ~1-2 %
AGASA
E > 4  1019eV
Clearly:
more statistics
and
4 sky coverage
required
IFAE @ Catania
1-Aprile-2005
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The Auger hybrid concept
300-400 nm light from deexcitation of atmospheric nitrogen
(fluorescence light)
Fluorescence Detector
• E + longitudinal
development
• Time ≈ direction
Surface Detector
• Shower size ≈ E
• Time ≈ direction
IFAE @ Catania
1-Aprile-2005
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IFAE @ Catania
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IFAE @ Catania
1-Aprile-2005
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The FD buildings
Fully operating
Los Leones
Coihueco
Los Morados
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The FD telescopeSchmidt optics:
Spherical mirror, 3.4 m
radius of curvature
2.2 m diameter diaphragm,
corrector ring
30ox30o FOV, 15 mm
diameter spot
Spherical focal surface:
 20x22 hexagonal PMTs
(Photonis XP3062)
 light collectors to recover
cracks; pixel size = 45 mm
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The Auger Zoo
Hybrid
Stereo
…Future entries!
Stereo-Hybrid
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Time (100 ns)
Stereo
COIHUECO
IFAE @ Catania
1-Aprile-2005
Telescopes
relative timing
and alignment
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A tour through event
673411.
A hybrid event and a
stereo event (nearly).
Here is what one finds
on the SD event
display.
Stereo-Hybrid
From Coihueco->
From Los Leones->
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Event 673411
Fluorescence Display
Coihueco (6 pixels)
Los Leones (29 pixels)
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Event 673411
Hybrid Reconstruction
Mono fit
Hybrid fit
<- SD times
<- SD times
<- FD times
Hybrid (Los Leones)
Easting
Northing
Theta
Phi
IFAE @ Catania
1-Aprile-2005
465960 ± 80
6090234 ± 20
36.7 deg
185.8 deg
S. Petrera
<- FD times
Surface
Difference
465830
6090308
35.9 deg
186.7 deg
130 m
-74 m
0.8 deg
-0.9 deg
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Event 673411
Ne maximum = 1.4x1010
Ne maximum ~ 7x1010  energy = 1020 eV
FD energy ~ 2x1019 eV
SD energy = 2.1x1019 eV
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Present Status of Auger
as of March 15, 2005
FD :
• two Eyes (Los Leones and Coihueco) fully operational
• Los Morados: building ready, commissioning 3
PRESENT STATUS OF THE ARRAY
telescopes, operational by summer 2005
SD :
• 749 detectors in the field
• 716 detectors filled with water
• 683 detectors with E-kit
• 663 detectors operational
• 10 assembled detectors ready in AB yard
• 130 tanks available in AB yard
~1/2 Auger South
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Present Status of the Array
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Forthcoming Science Results (ICRC 2005)
 VES
 λ

E[10EeV]   1000 exp  0 secθ   1
X

S
•Energy scale from hybrids
 Energy spectrum
•Photon flux limit
•Anisotropy studies (Galactic Center, Large Scale, Small Scale)
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α
UHE Neutrinos: Horizontal Showers
Atmosphere:
1000g/cm2 thick vertically
36000g/cm2 thick horizontally
 Look for interactions at deep column densities
i.e. large zenith angles: 75°<  < 90°
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UHE Neutrinos: Horizontal Showers
 : “new” showers
3000 g/cm2
EM shower
hadrons: “old” showers
1000 g/cm2
Shower front
EM shower
Signal is:
Few events per year
EM rich, curved and thick front
Broad signals
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S. Petrera
3000 g/cm2
Shower front
Shower core
hard muons
Background is:
Thousands events per year
EM poor, muon rich, flat and thin front
Prompt signal
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Sciame vecchio (71°)
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Sciame giovane (verticale)
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Expected sensitivity from AUGER
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Outlook
• UHECR, a field of interest for both theory and
detection techniques
• The Auger Experiment is in advanced installation
and commissioning phase:
~1/2 now in operation, completed mid 2006
• Data taking in parallel with installation: very
important
• First evaluation of detector performances fully
satisfactory: shower reconstruction, hybrid
technique
• Going towards physics results!
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Hybrid Geometry
reconstruction
tGND = t0 + RGND· S /c
IFAE @ Catania
1-Aprile-2005
t(χi) = t0 + Rp· tan [(χ0 - χi)/2] /c
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SD data
FD only fit
SD data
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Hybrid fit
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Tau neutrino detection
X.Bertou, P.Billoir, O.Deligny,
A.Letessier-Selvon
• Principle:
– Interaction length in the earth ~ 300 km at
– Tau path of flight ~ 50 km at 1018 eV
– 1° below horizon  200 km of rock
– Shower maximum ~10 km after decay
In practice 85 < z < 95
AUGER window: 1017 to 1020 eV
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1018 eV
astro-ph/0104452v4
Accepted in Astropart. Phys.
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Preliminary Gamma Flux Limits
@ Catania
D.IFAE
Barnhill
et. al. GAP 2005-024
1-Aprile-2005
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Distribuzione in energia degli
eventi
ibridi
Preliminare
Gennaio 2004 – Marzo 2005
Solo SD
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Neutrino detection in AUGER
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