tom gaisser, leeds, july 23, 2004 in honor of alan watson the next 10 years in particle astrophysics...
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Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
The next 10 years in Particle Astrophysics
Workshop summary
Some personal observations
Tribute to Alan
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Solar flare shock acceleration
Coronal mass ejectionCoronal mass ejection 09 Mar 200009 Mar 2000
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
SOHO/LASCO
CME of 06-Nov 1997
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
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
R.A. Mewaldt et al., A.I.P. Conf. Proc. 598 (2001) 165
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
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. 598 (2001) 165
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Knee
AnkleAnkle
Highest energy cosmic rays• Emax ~ shock Ze x B x Rshock for SNR
Emax ~ Z x 100 TeV– Many potential sources
• Knee region:– Differential spectral index changes at
~ 3 x 1015eV, – Some SNR can accelerate protons to
~1015 eV (Berezhko & Völk)– 1016 to 1018 eV: a few special
sources? Reacceleration?• Ankle at ~ 3 x 1018 eV:
– Flatter spectrum– Suggestion of change in composition– New population of particles, possibly
extragalactic?• Look for composition signatures of
“knee” and “ankle”
Extragalactic?Extragalactic?
galacticgalactic
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
30
Rigidity-dependence• Acceleration, propagation
– depend on B: rgyro = R/B
– Rigidity, R = E/Ze
– Ec(Z) ~ Z Rc
• rSNR ~ parsec Emax ~ Z * 1015 eV
– 1 < Z < 30 (p to Fe)
• Slope change should occur within factor of 30 in energy
• Characteristic pattern of increasing A with energy
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Direct measurements to 100 TeV:No major composition change
RUNJOB: thanks to T. ShibataATIC (preliminary): thanks to E-S Seo & J. Wefel
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Recent Kascade data show increasing fraction of heavy nuclei 1015-3x1016 eV
Note anomalous He / proton ratio in recent Kascade analyses
K-H Kampert et al., astro-ph/0204205 ICRC 2001 (Hamburg)
M. Roth et al., Proc ICRC 2003 (Tsukuba) vol 1, p 139
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Völk & Zirakashvili, 28th ICRC p. 2031
Galactic models of knee & beyond: conspiracy or accident?
• Axford: – continuity of spectrum over factor
300 of energy implies relation between acceleration mechanisms
– reacceleration by multiple SNR
• Völk:– reacceleration by shocks in
galactic wind (analogous to CIRs in heliosphere)
• Erlykin & Wolfendale:– Local source at knee on top of
smooth galactic spectrum– (bending of “background” could
reflect change in diffusion @ ~1 pc)
• What happens for E > 3x1016 eV?
Erlykin & Wolfendale, J Phys G27 (2001) 1005
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Chem. Composition
AMANDA
1 km
2 km
SPASE-AMANDAAstropart. Phys. (2004)
AM
AN
DA
(nu
mbe
r o
f m
uons
)
Spase (number of electrons)
Iron
Proton
log(E/PeV)
SPASE(Bartol-Leeds)
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Rates of contained, coincident events in IceCube
Area--solid-angle ~ 1/3 km2sr (including angular dependence of EAS trigger)3000 x aperture of SPASE-AMANDA
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Two DOMs: 10” PMTOne high-gain; one low-gain in each tank
To DAQ
IceCubeDrill Hole
~10-20 m
HG HG LGLG
IceTop station• Two Ice Tanks 3 m2 x 0.9 m deep (scaled down from Haverah, Auger)• Integrated with IceCube: same hardware, software• Coincidence between tanks = potential air shower• Signal in single tank = potential muon• Significant area for horizontal muons• Low Gain/High Gain operation to achieve dynamic range• Two DOMs/tank gives redundancy against failure of any single DOM
because only 1 low-gain detector is needed per station
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
PY03:4
PY04:12PY05:16
PY06:18
PY07:18
PY08:12
IIceCube Layout
100 m
Grid north
South Pole
Large showers with E ~ 100-1000 PeV will clarify transition from galactic to
extra-galactic cosmic rays.
Showers triggering 4 stations give ~300 TeV threshold for EAS array
Small showers (2-10 TeV) associated with the dominant background in the deep detector are detected as 2-tank coincidences at a station.Detection efficiency ~ 5% provides large sample to study this background
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Test station deployed at South Pole November, 2003
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Filling 03/04 test tanks
• Tank10 (1 m deep)– Filled Nov 22, 2003
• 20 minutes to fill
• < 10 RPSC man hours for transport and filling
• Tank09 ( 0.9 m )– Filled Nov 26, 2003
• Freeze time 60+ days– 40 days planned– Plan revised to finish freeze
after closing tank
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Tanks closed Jan 23-26
a) Dec 6 during freeze (cover used as extra sun shade)
b) Jan 23 after closing, tent used as outer cover over
black vinyl sheeting
Tank10 during freeze and after closing
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Feb 10/11, 2004
Tank 9 with telescope Tank 10
Remote operation since February • pre-pre-production DAQ and main board• monitoring temperatures during austral winter• limited muon data
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Primary composition with IceCube
• N from deep IceCube; Ne from IceTop
• High altitude allows good energy resolution
• Good mass separation from N/Ne
• 1/3 km2 sr (2000 x SPASE-AMANDA)
• Covers sub-PeV to EeV energies
Simulations of R. Engel
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Transition from Galactic to Extra-galactic origin?
• Where is the transition? (Hillas’ talk)
• Composition signature:– From mostly heavy primaries at end of
galactic origin to large fraction of protons
• Continuous coverage over a large energy range would be helpful (G Thomson’s talk)
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
<ln(A)> = 0, E > 3 1016 eV
Protons
<ln(A)> = 4 ±2, E ~ 1015 eV
Elongation rate, Xmax & composition(Linsley & Watson 1981)
Xmax = ln(E0/A) + B
Analysis of fluctuations in rise-time, 1973:“…departure of individual showers from the mean behaviour … most readily understood if some of the primary particles of energy E ~ 1018 eV are light, probably protons…”---A.A. Watson & J.G. Wilson, 1974
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Change of composition at the ankle?
Original Fly’s Eye (1993): transition coincides with ankle
G. Archbold, P. Sokolsky, et al.,Proc. 28th ICRC, Tsukuba, 2003
HiRes new composition result: transition occurs before ankle
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Exposure of giant arrays (as of ICRC-2003, thanks to M.Teshima)
1018-1019 eV threshold regime
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
More questions about UHECR
• What are the sources: – GRB? (Waxman), AGN? (Berezinsky), Top-down? (Sigl)
• Does spectrum continue past GZK limit?• What is the distribution of sources? – Medina-
Tanco, Olinto, Sommers– Clustering? – How many sources?– Point sources?– Galactic halo distribution?– Importance of magnetic fields?
• Need all-sky coverage for full picture
Energy content of extra-galactic component depends on location of transition
• Normalize @ 1019 eV:CR = 2 x 10-19 erg/cm3
Power ~ CR / 1010 yrs
~ 1045 erg/Mpc3/yr
Uncertainties:• Normalization point:
1018 to 1019.5 usedFactor 10 / decade
• Spectral slope =2.3 for rel. shock = 2.0 non-rel.
• Emin ~ mp (shock)2
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
GRB model
• Assume E-2 spectrum at source, normalize @ 1019.5
• 1045 erg/Mpc3/yr• ~ 1053 erg/GRB• Evolution like star-formation
rate• GZK losses included• Galactic extragalactic
transition ~ 1019 eV
Bahcall & Waxman, hep-ph/0206217Waxman, astro-ph/0210638
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Berezinsky et al. AGN
• Assuming a cosmological distribution of sources with:– dN/dE ~ E-2, E < 1018 eV– dN/dE ~ E, 1018< E < 1021
– = 2.7 (no evolution)– = 2.5 (with evolution)
• Need L0 ~ 3 ×1046 erg/Mpc3 yr
• They interpret dip at 1019 as– p + 2.7p + e+ + e-
Berezinsky, Gazizov, Grigorieva astro-ph/0210095
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Plot from HiRes, astro-ph/0208301Plot from HiRes, astro-ph/0208301
Does spectrum exceed GZK?
• AGASA now finished– No sign of cutoff– Clusters10-5 sources/Mpc3
• HiRes– Consistent with GZK cutoff– No clustering observed
• Auger South– Should answer the question
within a year or so
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
UHECR Spectrum
Haverah Park Edge et al., 1973
1 event per km2
per century withE > 1020 eV
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Connection to -rays and
• Talks of Völk, Hinton, Weekes, Mirzoyan
• Is there more than electron acceleration in GRB and AGN ?
• Zas: p/ as a probe of top-down vs acceleration models of UHECR – Also probes evolution of sources
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
New experiments
• Telescope array• Auger North• EUSO• Neutrino telescopes
– AMANDA, Baikal continue in short term– ANTARES (& Nestor) in 2005, 2006?– IceCube– Km3 in Mediterranean– Radio detection for UHE
Matter Distribution 7 Mpc < D < 21 Mpc
Cronin astro-ph/0402487 [Kravtsov]
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Closing remarks
• Thanks to – Johannes, Jeremy and colleagues– to Carol Ward and Maria– to Mansukh Patel
• Thanks to Auger Collaboration for a great experiment
• Best wishes to Alan for future science
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Power needed for extragalactic cosmic rays assuming transition at 1019 eV
• Energy density in UHECR, CR ~ 2 x 10 erg/cm3
– Such an estimate requires extrapolation of UHECR to low energy CR = (4/c) E(E) dE = (4/c){E2(E)}E=1019eV x ln{Emax/Emin}
– This gives CR ~ 2 x 10 erg/cm3 for differential index = 2, (E) ~ E-2
• Power required ~ CR/1010 yr ~ 1045 erg/Mpc3/yr– Estimates depend on cosmology and extragalactic magnetic fields:
– 3 x 10-3 galaxies/Mpc3 5 x 1039 erg/s/Galaxy
– 3 x 10-6 clusters/Mpc3 4 x 1042 erg/s/Galaxy Cluster
– 10-7 AGN/Mpc3 1044 erg/s/AGN
– ~1000 GRB/yr 3 x 1052 erg/GRB
• Assume E-2 spectrum. Then signal ~ 10 to 100/km2yr
– ~20% have E>50 TeV (greater than atmospheric background)
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Remote operation of DOMs
• Pre-production main boards; pre-production DAQ– Use SPASE GPS
clock for time stamp– Slow readout (large
dead-time)
• No local coincidence• Study main board
temperatures during austral winter
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Remote operation of DOMs
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Energy-dependence of secondary/primary cosmic-ray
nuclei • B/C ~ E-0.6
• Observed spectrum:– (E) = dN/dE ~ K E-2.7
• Interpretation:– Propagation depends on E– (E) ~ E-0.6
– (E) ~ Q(E) x (E) x (c/4)
• Implication:– Source spectrum Q(E) ~ E-
2.1
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Problems of simplest SNR shock model
• Expected shape of spectrum:– Differential index ~ 2.1 for
diffusive shock acceleration• observed ~ 2.7source ~2.1;
~ 0.6 esc(E) ~ E-0.6
• c esc Tdisk ~100 TeV
Isotropy problem
• Emax ~ shock Ze x B x Rshock
Emax ~ Z x 100 TeV with exponential cutoff of each component
– But spectrum continues to higher energy:
Emax problem
• Expect p + gas (TeV) for certain SNR– Need nearby target as shown
in picture from Nature (April 02)
– Interpretation uncertain; see• Enomoto et al., Aharonian (Nature);
Reimer et al., astro-ph/0205256
Problem of elusive 0 -rays
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
Speculation on the knee
K-H Kampert et al., astro-ph/0204205
3 components
Total
protonshelium
CNOMg…
Fe
Tom Gaisser, Leeds, July 23, 2004
in honor of Alan Watson
UHECR spectrum
Haverah Park, Edge et al., 1973