Experimental Summary TalkPhysics 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”

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

‘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

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

RX J1713 – H.E.S.S & ASCA• Gamma-ray and X-ray morphology quite similar

ASCA1 – 3 keVUchiyama 2002

HESS Preliminary

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!

ASCA0.7 – 10 keVSlane 2001

HESS Preliminary

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

CRIS GCR Isotopic Measurements

•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 & MeynetModeling)

“Combined” data points (red) are mean values of ratios from Ulysses, Voyager, ISEE-3 and HEAO-3-C2

Model WR Fraction

M60-no rot 0.20

M85-no rot 0.12

M120-no rot 0.16

M40-rot 0.22

M60-rot 0.16

M85-rot 0.41

M120-rot 0.35

Fraction of WR materialmixed with ISM with solarsystem composition tonormalize to 22Ne/20Ne ratio

300 km/s

But what about the 14N/16O and N/Ne ratios???

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.

Balloon borne measurements just below knee

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.

Preliminary charge histograms for E > 50 GeV from the ATIC-2 flight

Preliminary Results from ATIC-1 and ATIC-2

C O Ne Mg Si

S

Fe

S Ca

Testing of models with the ATIC-2 spectra of protons and HeliumAMS

CAPICE98

ATIC-2

Diffusion model (Kolmogorov spectrum offluctuations)

at high energies

V. S. Ptuskin et al.astro-ph/0301420

at low energies(reacceleration process)

Energy spectra of abundant nuclei

C

O/10

Ne/100

Mg

Si/10

Fe/100

HEAO-3-C2

CRN

ATIC-2

Direct measurements

• Some disagreement at the higher energies

• Approximately equal power law spectra for different elements

• No evidence of turnover to highest energies measured

All particle spectrum: ATIC, emulsion, and EAS data

RUNJOB

JACEE

CASA-BLANCA

TibetKASKADETUNKA

ATIC-2

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

Fit to the all-particle spectrum with rigidity dependent cut-off

common c

0.1162/dof

1.87 +- 0.18c

-4.68 +- 0.23c

4.51 +- 0.52Ep [PeV]

c

Zc

c

Z

å

ããå

p

0ã0

0Z0

0

Z

EZ

E1EÖ)(E

dE

dÖ

−

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡

⎟⎟⎠

⎞⎜⎜⎝

⎛

⋅+=

0.1132/dof

1.90 +- 0.19c

2.10 +- 0.24

4.49 +- 0.51Ep [PeV]

common

cc

Z

å

Äãå

p

0ã0

0Z0

0

Z

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⋅+=

Two dimensional shower size spectrum lg Ne vs. lg N

M Roth et al, 28th ICRC, Tsukuba 1 (2003) 139

KASCADE

derive E0 and A from Ne and N data

∫∞

=0

)()|lg,(lg)lg,(lg dEEpENNtNNg ieiei μμ

Fredholm integral equations of 1st kind:

E0

A

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

QGSJET

KASCADE: Energy spectra for individual elemental groups

distribution

!

distribution

!

SIBYLL

H. Ulrich et al., Int. J. Mod. Phys. A (in press)

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’

Now for the High Energy end

• Evidence for second knee

• Evidence for ankle

• Composition change

• Models based on transition from Galactic to Extragalactic flux

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!

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.

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.

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 .

rectilinear propagation diffusive propagationLemoine 2004, Aloisio, V.B. 2004

DIP as SIGNATURE of PROTONS INTERACTING with CMB

(model independent analysis in terms of modification factor)Definition:

(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.

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)

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.

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 ).

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.

knee 2nd kneeankle

?

x 92

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

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.

A POSSIBLE (?) ALTERNATIVE TO MEASURE THEENERGY 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 interactionlengths. Then 0.67% of protons will survive (factor 400 morethan at sea level). If the hadron calorimeter has the same sensitivity as that of Kascade (320 m2 sr) its effective geometricfactor would be 2.14 m2 sr. The ACCESS goal for protons would be achieved within 0.5 years of observation!

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?

Basics of the Technique

• Light near the core are emitted deeper in the atmosphere

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.

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

IceTop

• Concept– Surface array is unique

opportunity for -telescope in deep ice

• Purpose– To detect cosmic-ray showers

related to events deep in IceCube

• Calibration of IceCube– Pointing– E/E (energy resolution)

• Tagging background for study and rejection

• Related cosmic-ray physics from “knee” to “ankle”

1400 m

2400 m

AMANDA

South Pole

IceTop

• 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

IceCube

•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

IceTop Tank

2 m

0.9 m ice

Diffusely reflecting liner

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 : 1.3 kHz / tank• flux measured at SP with telescope

• Tank rate inferred from geometry

• Soft Component (>30 MeV): 1.2 kHz

Using TeV Gamma Ray detectors ?

• HESS/Veritas and extensions have ~ 1 km^2 collecting areas and ~ 5-10 deg acceptance.

• Background hadrons could in principle be analyzed a-la DICE ( stereo reconstruction of shower centroid to get Xmax ).

What about the second knee and ankle?

• Present fluorescence experiments have difficulty going below 10^17 eV - short lever arm for second knee.

• Composition measurement is crucial. Xmax composition requires careful control of resolution function - stereo important

• Detectors should have smoothly and slowly changing acceptance over the structures they are trying to measure

Cont.

• Smooth acceptance for Fe and p implies higher elevation angles for mirrors near 10^17 eV ( Tower of Power)

• Smooth acceptance as function of energy implies HiRes type of stereo separation (12km) is too large.

Observe the Ankle in Stereo Mode

• HiRes stereo (12.6 km separation) has rapidly-changing aperture below 1018.5 eV (Auger and STA stereo and hybrid are not better).

• Flatten the aperture by having the two stereo detectors be closer: STA and HiRes fluorescence detectors 6 km apart.

• Perform composition-correlated measurement of spectrum.

Lower-energy Limitations

• HiRes observes elongation above 1018.0 eV clearly.

• HiRes looks up to 31o, can’t see Xmax for close-by (low energy) events.

• Makes spectrum measurements difficult below 1017.5 eV.

• Composition bias for E < 1018.0 eV.

Before bracketing and Cerenkov cuts

Observe the Second Knee in Hybrid Mode with a Tower Detector

• Two methods of lowering the minimum energy:– Use bigger mirrors.– Look higher up.

• Tower detector with 3x larger mirrors:– 750 cm radius of curvature.– Cluster box at 97% of focal

length.– Use HiRes-type phototubes

with Winston cones.– Collect 2.88 times as much

light.

Tower Detector

• Simulate a five-ring detector.

• Rings 1 and 2 have standard HiRes mirrors.

• Rings 3-5 have 3x larger mirrors and Winston cones.

• Compare with HiRes2 (data set 2).

• Compare with a tower detector with standard HiRes mirrors throughout.

Lower Emin by order of magnitude.

• Test tower detector design: MC ~ 2 mo running. – cover 90o azimuthally.

– 15 mirrors in rings 3-5.

– HiRes-size mirrors reach down ½ order of magnitude.

– 3x larger mirrors reach down full order of magnitude.

How would this be realized?TA/TALE version

• Use TA fluorescence detectors as pair partners with reconfigured HiRes detectors to provide Stereo aperture for ankle region

• Add a Tower of Power with larger mirrors to extend low energy response to 10^16.5.

• Add an infill array to TA array to have hybrid detection for Tower of Power.

• Addition of Auger water tanks would be ideal for muon detection ( co-siting of N. Auger would be great)

TA Design• SA: 576 scintillation counters,

each 3 m2 area, 1.2 km spacing.• 3 fluorescence stations, each

covering 108o in azimuth, looking inward.

• Central laser facility.• Millard County, Utah, flat

valley floor for SA, hills for fluorescence, low aerosols.

• A 1020 eV event (on a night when the moon is down) will be seen by SA and all three fluorescence detectors.

• A powerful detector for hybrid and stereo cross correlation with SA.

TA Progress (FD)

Increase the High Energy Fluorescence Aperture of TA by Factor of 3.6

• Two HiRes detectors, moved to Millard Co.

• One is a TA fluorescence detector (360o azimuth).

• 6 km stereo with Black Rock Mesa TA fluorescence detector.

• Each detector has two rings.• High enegy instantaneous

aperture of 18000 km2 ster.• Increase high energy

fluorescence aperture by factor of 3.6

• Total high energy aperture of 3200 km2 ster.

TA FD, Tower, Infill Array

• 15 mirrors, 3xHiRes area, in rings 3,4,5.

• 111 AGASA counters, spacing of 400m, shown in red. Can see events hitting outside also.

• 10 x HiRes/MIA hybrid aperture.

TA/TALE Apertures

How would this be realized/ S. Auger version

• Build additional Auger fluorescence mirrors to reach higher elevation angles and improve acceptance to lower energy Fe showers.

• Infill array of Auger water tanks to provide hybrid reconstruction.

FD telescopes: vertical field of view vs. minimal distance

600 viewing angle 300

Height a.s.l. [km]

distance from eye[km] 5 10

5.0

2.5

7.5

X ~ 430 g/cm² vertical ~ 500 g/cm² at 300 zenith angle

~ 3 km ~ 9 km

summer

atm.winter

~ eye level1400 m

Possible FD upgrade proposal(for 2006/2007, after Auger South experiment is fully commissioned)

• 3 additional FD telescopes at Loma Amarilla increasing vertical f.o.v. to 600 for ~ 900 in azimuthstandard or new telescope design for R&D ?

• Additional infill SD array with (50-100) tanks at R = 3 – 9 kmwith an area ~ 50 - 100 km²

• Hybrid detection and engineering array for Auger North

threshold for high quality data : < 2 x 1017 eV

statistics for LE hybrid data ~ 10.000 / year

1,5 km1,5 km

866 m866 m

A simple layout for an infill array

What about the Hedgehog?

• How do we connect the low energy and the high energy measurements?

• Push fluorescence measurement as low as possible ( 10^16.5 eV?)

• Build Cherenkade as big as possible - reach 10^17 eV

• Direct cross calibration of Xmax techniques is then possible - event by event

• Overlap in physics reach with direct measurements at 10^14 eV

The CR Grand Staircase V1.0

• Isotopic measurements (balloon flights)• TR type detector (balloon flights)• High mountain proton flux measurement• Cherenkade *• TALE TOP detector *• TALE Stereo detector *• TA *• TA (+) N. Auger *(?) * = co-sited

The CR Grand Staircase ( V1.1)

• As before

• S. Cherenkade *

• S. Auger low energy hybrid extension *

• S. Auger *

• EUSO

• OWL

The Hedgehog and the Fox, cont.

• If we are like the Fox, by 2010 we will have:

- Continuing balloon flights

- Snow-top + (Tunka?)

- S. Auger low energy extension

- TALE (?) not guaranteed

- TA

Fox, cont.

• This leaves very unpleasant gaps between direct measurements and snow-top

• Snow-top has no Xmax measurement

• No event by event correlation is possible with fluorescence

How expensive is the Hedgehog?

• Can we afford all of this?• S. Auger extension money is identified• TA is fully funded.• HiRes equipment can be moved from Dugway for

TALE.• Major expense is TR balloon flight program, high

altitude proton detector (re-use existing calorimeter?), TALE tower of power and Cherenkade detector(s)

Contra Mike Turner

• Competition is good

• Some duplication is essential

• Planning is just the beginning!

• Government exists by the consent of the governed (Thomas Jefferson)

• This applies to funding agencies too!

Importance of other particles

• Gamma rays and neutrinos are also cosmic rays.

• Some breakthroughs relating to charged particle CR come from neutrals (HESS)

• Example: Anita-light may have ruled out Z-burst model in two day balloon flight.

• The picture will always remain incomplete if we don’t put all the information together.

Importance of Connections to Other Disciplines

• The “Vapor pressure of Copper” problem• Implications and integration with

- Astronomy/Astophysics

Magnetic fields

SN modeling

Galactic structure

Is clustering scale relevant?

Galactic evolution

Integration, cont.

• Particle Physics– GZK resolution may bring in new physics– String theoretical predictions - modifications of

cross sections ( strong neutrinos )- Framgmentation physics

- Total cross-sections

Let’s Get Busy!