Transcript Gaisser-aspen-intro - Aspen Workshop on Cosmic Ray Physics

What’s new and what questions
remain since our previous
meeting?
Workshop on
Physics at the End of the
Galactic Cosmic-ray Spectrum
April 26-30, 2005
Aspen, April 16, 2007
Tom Gaisser
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Outline
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Below the knee
Knee region
Sources & acceleration mechanisms
End of galactic cosmic-ray population?
Where is transition to extra-galactic?
What is the nature of the ankle?
Extra-galactic cosmic rays and GZK
Lessons from the heliosphere (2nd edition)
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Final Results of RUNJOB and Related Topics
Makoto Hareyama, Toru Shibata and the Runjob collaboration
(Aspen, 2005)
Observed spectrum
~ E(-2.7) to 100 TeV
JACEE and results of other
balloon experiments ~100 TeV
reported by M. Cherry, Aspen 2005
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All particle spectrum
Note difference
between JACEE
and RUNJOB for
~100 TeV helium
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ATIC, John Wefel, Tokyo ’07 (also discussed in Cherry’s talk, Aspen 2005)
Helium more like JACEE ?
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Hard all-nucleon spectrum?
Tom Gaisser
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TRACER
(heavy nuclei only)
= sum of TRACER: O + Ne + Mg + Si + S + Ar + Ca + Fe
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HESS Direct Cherenkov
measurement of Fe spectrum
F. Aharonian et al.
PR D75 042004 (2007)
Method proposed by Kieda,
Swordy & Wakely, 2001:
Use ACT on ground.
Previously attempted
from balloons, Sood, 1983;
Clem, Evenson, Seckel, 2002
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H.E.S.S. Direct Cherenkov
Fe spectrum measurement
Consistent with RUNJOB
Inferred spectrum
with QGSjet
Inferred spectrum
with SIBYLL
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Standard model of cosmic-rays to ~100 TeV
• Diffusive shock acceleration in galactic SNR
– 15 % of energy goes into accelerated p & nuclei
– dN / dE ~ E(-2.1) (source spectrum)
– secondary / primary nuclei  tesc ~ E(-0.6) to make
dN / dE (observed) ~ E(-2.7)
• Problems: (e.g. Ptuskin et al., Jokipii)
– strong energy dependence of tesc violates observed
isotropy when extrapolated to PeV
– observed turbulence prefers tesc ~ E(-0.3)
– high efficiency  non-linear acceleration  event
flatter source spectrum
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Rigidity-dependence
• Acceleration, propagation
•
– depend on B: rgyro = R/B
– Rigidity, R = E/Ze
– Ec(Z) ~ Z Rc
Peters cycle: systematic increase of < A >
approaching Emax
rSNR ~ parsec
–  Emax ~ Z * 1015 eV
–
1 < Z < 30 (p to Fe)
• Slope change should occur
within factor of 30 in energy
• With characteristic pattern
of increasing A
• Problem: continuation of
smooth spectrum to EeV
B. Peters, Nuovo Cimento 22 (1961) 800
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Composition in the knee region
EASTOP, M. Aglietta et al., Astropart. Phys.
20 (2004) 641
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SPASE-AMANDAB10, superimposed on
data summary of Swordy et al.,
Astropart. Phys. 18 (2002) 129.
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KASCADE: Energy spectra for individual elemental groups
Andreas Haungs Aspen, 2005 SIBYLL
QGSJET
c2 distribution
!
H. Ulrich et al., Int. J. Mod. Phys. A (in press)
c2 distribution
!
What interaction model to use?
• In KASCADE data, both QGSjet01 and
SIBYLL have problem areas
• The greater energy reach of KASCADEGrande may help unscramble this
– Xmax deeper in atmosphere, fluctuations less
severe
– Gives a longer range of energy over which to
test the models
– Hope to hear KASCADE-Grande results here
at Aspen 2007
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Maximum energy for acceleration
by SNR shocks
• Magnetic field amplification (Bell et al.)
much discussed at Aspen 2005
– See paper of Hillas, for example.
– Emax > PeV for protons no problem
• Non-linear diffusive shock acceleration
– H. Völk et al. (also Blasi et al.)
– Most of energy content may be near Emax
• Do we need a galactic “component B”
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Cosmic-ray energy spectrum (Aspen, 2005)
J Hörandel
?
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according to Astropart. Phys. 19 (2003) 193
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HILLAS (Aspen, 2005)
Atoyan (Aspen, 2005)
Model: GRB origin of CRs at and above the knee
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Cosmic Rays below
≈ 1014 eV from SNe
that collapse to
neutron stars
–
Cosmic Rays above
≈ 1014 eV from SNe
that collapse to black
holes
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CRs between knee
and ankle/second
knee from GRBs in
Galaxy
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CRs at higher
energy from
extragalactic/
cosmological origin
(Wick et al. 2004)
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BEREZINSKY
TRANSITION
The galactic component at E ≥ 1×1017 eV is assumed to be iron nuclei. The
spectrum is found as difference of the total (observed) spectrum and
extragalactic proton spectrum (model).
Ec is considered as a free parameter in a range (0.3 - 2)×1018 eV
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(de) constructing the extra-galatic
spectrum
dip
GZK feature
(due to pair production)
End of
Galactic population
(not shown)
Distant sources
Contribution
depends on
evolution and
propagation in
Bextra-galactic
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recovery
(depends on
source density)
Nearby sources
clustering,
anisotropy?
Doug Bergman et al. (HiRes), Proc 29th ICRC, 7 (2005) 315
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BERGMAN
Best USM Fit to HiRes
• Fit USM varying
m and g
– g = 2.38
– m = 2.55
– Galactic
spectrum falls
steeply above
100 PeV
Extragalactic
Galactic
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Bahcall & Waxman (GRB)
Physics Letters B556 (2003) 1
• Galactic extragalactic
transition ~ 1019 eV
• Assume E-2 spectrum at
source, normalize @ 1019.5
• 1045 erg/Mpc3/yr
• ~ 1053 erg/GRB
• Evolution ~ star-formation
• GZK losses included
Bahcall & Waxman hep-ph/0206217
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Transition < 1018 eV
N Busca, WG-4, Aug 29
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Transition at 1019 eV
Allard et al. astro-ph/0605327
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Where is transition to extragalactic CR?
Original Fly’s Eye (1993):
transition coincides with ankle
HiRes new composition result:
transition occurs before ankle
0.3 EeV
3 EeV
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G. Archbold, P. Sokolsky, et al.,23
Proc. 28th ICRC, Tsukuba, 2003
Muon / electron ratio reflects
nuclear composition of primaries
KASCADE-Grande
Calculations of Ralph Engel,
presented at Aspen, April, 2005
IceCube
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Simulations: Em at 2 km in IceCube
vs Energy deposited in tanks
Projection on
mass axis
0.64, 0.8, 1.0, 5.0, 6.25, 10, 12.5 PeV
Projection on
energy axis
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AGASA, HiRes, Auger
Auger spectrum, from
Paul Sommers’ talk at Pune
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HiRes GZK cutoff
(astro-ph/0703099)
E3 x differential spectrum
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Integral spectrum / E-1.81
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Lessons from the heliosphere
• ACE energetic particle fluences:
• Smooth spectrum
– composed of several distinct
components:
• Most shock accelerated
• Many events with different shapes
contribute at low energy (< 1 MeV)
• Few events produce ~10 MeV
– Knee ~ Emax of a few events
– Ankle at transition from heliospheric
to galactic cosmic rays
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R.A. Mewaldt et al., A.I.P. Conf. Proc. 598 (2001) 165
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Solar flare shock acceleration
Coronal mass ejection
09 Mar 2000
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SOHO/
LASCO
CME of
06-Nov
1997
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LASCO event of 23 Nov 97
http://lasco-www.nrl.navy.mil/best_of_lasco_apr98/index.htm
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Heliospheric
cosmic rays
• ACE--Integrated fluences:
– Many events contribute to
low-energy heliospheric
cosmic rays;
– fewer as energy increases.
– Highest energy (75 MeV/nuc)
is dominated by low-energy
galactic cosmic rays, and this
component is again smooth
• Beginning of a pattern?
R.A. Mewaldt et al., A.I.P. Conf. Proc.
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598 (2001) 165
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Examples of power-law distributions
(M.E.J. Newman, cond-mat/0412004)
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More examples from M.E.J. Newman, cond-mat/0412004
Casualties per attack in Iraq
(Neil F. Johnson, et al., from APS News, 8 Nov 2006)
Differential
a ~ 2.5
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Three classes of sources
Presenter
at this
conference
A
Extra- galactic
B
Power
(Rc,PV)
Atoyan
Galactic GRB
Berezinsky
None if
Ec = 0.3 PeV
2.5
Bergman
-
Biermann
-
Hillas
3
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Hörandel
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g+1
m
required
?
?
?
3.5 x 1046
erg/Mpc3/yr,
for Ec = 1 PeV
2.7
0
2.4
2.5
?
Wolf-Rayet SNR
?
?
?
SNII into slow
wind
2.3
3
?
-
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UH nuclei
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Outstanding issues
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Direct measurements for calibration
Isotropy / propagation problem
Non-linear acceleration  hard spectrum
How many sources?
What interaction model to use?
Is there a component “B”?
Where is transition to extra-galactic
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