High Energy Cosmic Rays

Eli WaxmanWeizmann Institute, ISRAEL

Cosmic ray flux and Composition

E [GeV]

log [dJ/dE]

1 106 1010

E-2.7

E-3

Heavy Nuclei

Protons

Ucr(1GeV)=1 eV/cm3

Galactic plane enhancement

Isotropy

Galactic

X-Galactic)?(

[Blandford & Eichler, Phys. Rep. 87; Axford, ApJS 94; Bird et al. 94; Nagano & Watson, Rev. Mod. Phys. 00; Abu-Zayyad et al. 01]

Lighter

Composition

HiRes/MIAFly’s Eye [Abu-Zayyad et al. 01]

[Bird et al. 94]

Acceleration Problem

]K. Arisaka 02[

X-Galactic Ultra High Energy p

• High energy, XG sources existp (pN) ’s e’s, ’s

• UHE p flux Handle on flux, detector size

• Prime telescope motivation: Identify UHE p source(s)

The Data

Data- Calibrated at 1019eV

Model• Fly’s Eye fit for Galactic heavy (<1019eV): JG~E-3.50

• X-Galactic protons: Generation spectrum (shock acceleration):

Generation rate (GRB motivated):

Redshift evolution ~ SFR (GRB motivated).

;2,/ nddn nppp

[EW 95]

;yrMpc

erg103

344

0

eV10

eV10

21

19

zp

ppp d

ndd

R

Model vs. DataX-G Model: 2n yr;erg/Mpc105.3 344 R

]Bahcall & EW 02[

Ruled out 7

Data/Model consistency

• Define:

• 1019eV to 1020eV:

Data (YK,AG,FE,HR) and model consistent with

XG protons, + GZKyrMpc

erg108.0

3442

p

pp d

nd

ji Modelij

ModelijijModel

ji HRij

HRijijHR n

nnNs

n

nnNs

, ,

2,12

, ,

2,12 ~

;

36~

,20.1;26,06.1 22 NsNs ModelHR

Conclusions are Robust 2.1n yr;erg/Mpc100.3 344 R

A note on GRBs• Energy generation rate:

• Proton acceleration: Ep,max ~ 1021 eV

Claims for Ep,max << 1021 eV - irrelevant for the

model (May be valid for “external shocks” only)

• For more: See talk by P. Meszaros and Lec. Notes Phys. review (astro-ph/0103186)

yrMpc

erg103.1erg105.2

yrGpc

5.0

energy photon x MeV rate GRB

34453

3

2

e

ee d

nd

[Frail et al. 01; Schmidt 01]

Summary• Yakutsk, Fly’s Eye, HiRes: Consistent with

XG protons: + GZK

(Robust; Consistent with GRB model predictions [see talk by P. Meszaros])• AGASA (25% of total exposure): Consistent below 1020eV Excess above 1020eV: 2.2+/-0.8 8

observed New source/ New physics/ 25% energy Local inhomogeneity over-estimate

• Need: Hybrid 1018eV to 1020eV observations

yrMpc

erg108.0

3442

p

pp d

nd

??

Implications for telescopes

• X-Galactic sources of high energy ’s are out there

• UHE p flux constrains expected flux ~ 1 km3 scale required at 1 to 103 TeV

energies >> 1 km3 required at >>103 TeV (see J. Bahcall’s talk)