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Experimental Summary Talk Physics at the End of the Galactic Spectrum

Experimental Summary Talk Physics at the End of the Galactic Spectrum. Pierre Sokolsky Univ. of Utah. The Hedgehog and the Fox (The Greek poet Archilochus ). “The Fox knows many things, but the the Hedgehog knows one big thing”.

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Experimental Summary Talk Physics at the End of the Galactic Spectrum

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  1. Experimental Summary TalkPhysics at the End of the Galactic Spectrum Pierre Sokolsky Univ. of Utah

  2. The Hedgehog and the Fox(The Greek poet Archilochus) “The Fox knows many things, but the the Hedgehog knows one big thing”

  3. One of the emergent themes of this meeting is the ‘excluded middle’ • HESS results - first sign of CR galactic sources • What is the max energy of the accelerator associated with these sources • What about the knee - propagation vs. acceleration • Kascade results very important - BUT indirect and still model dependent and likely to remain so. • HiRes data shows ankle region is now clearly established, second knee less so but transition to ankle must occur somewhere

  4. ‘Excluded middle’ continued • Transition from galactic to extragalactic • Dip as evidence for extragalactic origin and protonic composition (“more reliable than GZK cutoff” (Berezinsky) • There are “reasonable” pictures of the low and the high energy situation • But - Plan B ( Hillas ) - the missing middle

  5. Hess Results - First evidence (still putative?) of SN CR. • Extended objects • Association with SN remnants • Hard spectra • Detailed comparison with models and X-ray and radio structures

  6. RX J1713 – H.E.S.S & ASCA HESS Preliminary • Gamma-ray and X-ray morphology quite similar ASCA 1 – 3 keV Uchiyama 2002

  7. RX J0852.0-4622 – 'Vela Junior' 2004 - 3hr observation - 4 tels - dN/dE  E-2.2 - 12 sigma from entire SNR (rad < 1 deg) ~ 1 Crab flux 2005 --> further obs. ~15hr expected soon --> high ZA obs! HESS Preliminary ASCA 0.7 – 10 keV Slane 2001

  8. Direct measurements below the knee • Presumably propagation modified reflections of supernova sources • Should reflect max energy of accelerator and (modified) chemistry of the source • Binns talk - evidence for acceleration in superbubbles. • Cannot see turn over in spectra! • Consistency problems at higher energies

  9. CRIS GCR Isotopic Measurements

  10. Two component models • Wolf-Rayet winds from stars with various initial masses, with and without rotation. • Adjust the WR fraction mixed with ISM to match CR 22Ne/20Ne. (Goriely, Arnould & Meynet Modeling) “Combined” data points (red) are mean values of ratios from Ulysses, Voyager, ISEE-3 and HEAO-3-C2

  11. Fraction of WR material mixed with ISM with solar system composition to normalize to 22Ne/20Ne ratio 300 km/s But what about the 14N/16O and N/Ne ratios???

  12. Summary (cont) • We take agreement as evidence that WR star ejecta is likely an important component of cosmic-ray source material. • Since most WR stars & core-collapse SN reside in SBs, then SBs must be the predominant site of injection of WR material and SN ejecta into the GCR source material. • Picture that emerges is that SBs appear to be the site of origin and acceleration of at least a substantial fraction of GCRs.

  13. Balloon borne measurements just below knee

  14. Preliminary Results from ATIC-1 and ATIC-2 • Fill gap between low energy AMS and high energy JACEE with accurate measurements • Preliminary indication that H and He spectral indices are very similar • Measurements of Iron group show flattening of spectrum • Have measured GCR electrons up to about 2 TeV • At the highest energies, the heavy ion spectra show deviations, which might suggest that a modified Leaky Box Model, including a constant residual pathlength (0.13 g/cm2), is needed. Ne Mg Si Fe C O Preliminary charge histograms for E > 50 GeV from the ATIC-2 flight S S Ca

  15. Testing of models with the ATIC-2 spectra of protons and Helium AMS CAPICE98 ATIC-2 Diffusion model (Kolmogorov spectrum of fluctuations) at high energies at low energies (reacceleration process) V. S. Ptuskin et al. astro-ph/0301420

  16. Energy spectra of abundant nuclei Mg C O/10 Si/10 Fe/100 Ne/100 HEAO-3-C2 ATIC-2 CRN

  17. Direct measurements • Some disagreement at the higher energies • Approximately equal power law spectra for different elements • No evidence of turnover to highest energies measured

  18. All particle spectrum: ATIC, emulsion, and EAS data RUNJOB JACEE CASA-BLANCA Tibet KASKADE TUNKA ATIC-2

  19. The knee • Change of slope appears in all particle spectrum in indirect experiments. • Structure MUST appear in elemental spectra • But many possible combinations can produce same overall spectrum • Indirect experiment mass resolution is poor

  20. Fit to the all-particle spectrum with rigidity dependent cut-off common Dg Ep [PeV] 4.49 +- 0.51 Ep [PeV] 4.51 +- 0.52 Dg 2.10 +- 0.24 gc -4.68 +- 0.23 ec 1.90 +- 0.19 ec 1.87 +- 0.18 c2/dof 0.113 c2/dof 0.116 common gc

  21. Two dimensional shower size spectrum lg Ne vs. lg Nm A E0 derive E0 and A from Ne and Nm data Fredholm integral equations of 1st kind: KASCADE M Roth et al, 28th ICRC, Tsukuba 1 (2003) 139

  22. All-particle energy spectrum two hadronic interaction models: CORSIKA 6.018/GHEISHA 2002 - QGSJET 01 - SIBYLL 2.1 T. Antoni et al., Astropart. Phys. in press

  23. KASCADE: Energy spectra for individual elemental groups c2 distribution c2 distribution ! ! QGSJET SIBYLL H. Ulrich et al., Int. J. Mod. Phys. A (in press)

  24. Kascade Results • Careful measurement of Ne and Nmu + hadronic model can yield a remarkable amount of information • However, significant model dependence remains • Rather indirect, complex analysis • That being said, results are ‘sensible’

  25. Now for the High Energy end • Evidence for second knee • Evidence for ankle • Composition change • Models based on transition from Galactic to Extragalactic flux

  26. Best Evidence (cont’d)Second Knee at 1017.6 eV • Yakutsk, Akeno, Fly’s Eye Stereo, HiRes Prototype/MIA all saw flat spectrum followed by a steepening in the power law. The break is called the second knee. • Correct for varying energy scales: all agree on location of the second knee. • There are THREE spectral features in the UHE regime. • But location of second knee is unknown. • The ULTIMATE experiment is one which would see the three UHE cosmic ray features with good statistics!

  27. Physics in the UHECR Regime: Best Evidence so far… HiRes observes the ankle; Has evidence for GZK suppression; Can not claim the second knee. Galactic/Extragalactic Transition: HiRes/MIA hybrid experiment, and HiRes Stereo results.

  28. Fitting the Spectrum • It is important to fit the spectrum to a model that incorporates known-physics. • Position of the ankle is important for determining the distance to sources. • Regions of poor fit quality indicate where the model may break down. • Problem near 1019.5 eV? Six points with chi squared 10. • Problem at 1017.5 eV? The second knee is too weak.

  29. SECOND KNEE and EXTRAGALACTIC PROTONS Second knee automatically appears in the total spectrum (galactic +extragalactic) due to low-energy flattening of extragalactic spectrum, which appears at Ec~ 1×1018 eV.This energy is universal for all propagation modes (rectilinear or diffusive) and it is determined by transition from adiabatic to e+e- -energy losses . g diffusive propagationLemoine 2004, Aloisio, V.B. 2004 rectilinear propagation

  30. DIP as SIGNATURE of PROTONS INTERACTING with CMB (model independent analysis in terms of modification factor)Definition: h(E) = Jp(E)/Jpunm (E) (3) Jp(E) is calculated with all energy losses included. Jpunm (E) - only adiabatic energy losses included. • Dip is stable: • to propagation modes (rectilinear or diffusive), • to variation of source separation (d=1-60 Mpc), • to inhomogeneities in source distribution, • to fluctuations in interaction.

  31. DIP and DISCREPANCY between AGASA and HiRes DATA(energy calibration by dip) We have shifted the energies to obtain the best fit to the dip: AGASA : E→kAE (best fit kA=0.90)HiRes : E→kHiRE (best fit kHiR=1.25)

  32. Aside on energy adjustments • While it is not unreasonable to assume a fixed energy scale systematic - this may not be the source of the problem • Differences in energy resolution and tails in energy resolution may also be important • Systematic errors in calculating the detector aperture can induce apparent slope changes. • This can be important for ground array experiments at energies below full efficiency as well as fluorescence experiments near threshold.

  33. TRANSITION from GALACTIC to EXTRAGALACTIC CR in DIFFUSIVE PROPAGATION Assumptions: • power-law Qgen(E) ~ E-2.7 generation spectrum for extragalactic protons • Lp = 3.0×1048 erg/s for source separation d=30 Mpc • Lp = 1.5×1048 erg/s for source separation d=50 Mpc • magnetic field with Kolmogorov spectrum B0 =1 nG on the basic scale lc=1 Mpc • several different regimes in low-energy region (Kolmogorov, Bohm and D(E) ~ E2 ).

  34. In principle, the observed dip can be explained by the galactic component. In the absence of the detailed theory of propagation in galactic magnetic fields, the precise description of the dip shape in this case looks like a formal fitting exercise with many free parameters.

  35. knee 2nd knee ? ankle x 92

  36. The Fox - how do we improve the low and high energy data? • Low energy - how far up can direct measurements go? • Working group answer ~ 2 x 10^14 eV • High altitude proton detector • Transition radiation balloon flights for high Z spectra • Subtract high Z from all- particle spectra

  37. Conclusion: If we use balloon observations we need larger instruments than currently exist. (We also may have to be concerned about nuclear interactions in the residual atmosphere). For calorimeters, a significant increase is not be possible because of weight constraints. For TRD’s, an increase to a detector area of about 5x5 m2 (as opposed to the current 2x2 m2) may be possible. This would reduce the number of required TRD flights from 60 to 10. • For protons and helium, balloon measurements cannot reach the ACCESS goal. For the heavier nuclei, the gap between balloon flights and ACCESS is considerably smaller.

  38. A POSSIBLE (?) ALTERNATIVE TO MEASURE THE ENERGY SPECTRUM OF PROTONS 1011 TO 1016 eV: Hadron Calorimeter (such as the one of Kascade), at high mountain altitude; detect surviving single protons. Some numbers: assume residual atmosphere to have 5 proton interaction lengths. Then 0.67% of protons will survive (factor 400 more than at sea level). If the hadron calorimeter has the same sensitivity as that of Kascade (320 m2 sr) its effective geometric factor would be 2.14 m2 sr. The ACCESS goal for protons would be achieved within 0.5 years of observation!

  39. How to improve indirect data around the knee • Kascade type detector enhanced by Cherenkov array that is sensitive to Xmax • Overlap with direct measurements near 10^14 eV. • Xmax measurement reduces reliance on hadronic models, reduces shower fluctuations in Ne and Nmu • Detector with improved logA resolution and improved systematics • Kascov or Cherenkade?

  40. Basics of the Technique • Light near the core are emitted deeper in the atmosphere

  41. Proposed Cherenkade Detector • Combination fluorescence + Cerenkov + muon array • 3km  3km • Can probably sparsify the Cerenkov spacing from BLANCA • May need larger light collectors to reach down to 1014 eV • Infill scintillator array needed for lowest energies.

  42. Another approach • Snow-top detector has unique ability to study multi-hundred GeV muon content of shower. • Important check on hadronic models • Very good energy resolution • This would be even better with a Cherenkov detector to determine Xmax! • Snow-kov

  43. IceTop • Concept • Surface array is unique opportunity for n-telescope in deep ice • Purpose • To detect cosmic-ray showers related to events deep in IceCube • Calibration of IceCube • Pointing • DE/E (energy resolution) • Tagging background for study and rejection • Related cosmic-ray physics from “knee” to “ankle”

  44. IceTop AMANDA • 1 station on top of each IceCube string • 2 ice tanks per station • 2 DOMs in each tank • IceTop will detect Air Showers • of energies 3x1014 eV to 1018 eV South Pole • 4800 PMT • Instrumented volume: 1 km3 (1Gt) • 80 Strings • IceCube is designed to detect neutrinos of all flavors at energies from 107 eV to 1020 eV 1400 m IceCube 2400 m

  45. 2 m IceTop Tank 0.9 m ice Diffusely reflecting liner

  46. The IceTop km2 array • Array consists of 160 tanks at 80 stations • each station near top of string • each tank connected to surface cable at junction with down-hole cable • Single low-energy m: 1.3 kHz / tank • m-flux measured at SP with m telescope • Tank rate inferred from geometry • Soft Component (>30 MeV): 1.2 kHz

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