Nuclei As Ultra High Energy Cosmic Rays Oleg Kalashev* UCLA, INR RAS GZK 40: The 3rd International Workshop on THE HIGHEST ENERGY COSMIC RAYS AND THEIR

Nuclei

As Ultra High Energy Cosmic Rays

Oleg Kalashev* UCLA, INR RAS

GZK 40: The 3rd International Workshop on THE HIGHEST ENERGY COSMIC RAYS AND THEIR SOURCES INR RAS, Moscow, 17 May 2006

* e-mail: [email protected]

Overview

Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006

•Motivation

•Propagation of protons and nuclei compared

•Typical propagated spectrum of protons and nuclei

•Fitting AGASA and HiRes spectra

•Conclusion

GZK problem


•All experiments have registered events above 100 EeV•HiRes is claimed to be consistent with GZK cutoff provided that UHECR sources are close enough, however no evident sources has been found yet within GZK sphere

Possible solutions


Possible solutions


Top-Down models:

• Topological defects • Z-burst

Possible models


Top-Down models (disfavored?) :


AGASA muon measurements

γ -ray fraction predicted is close to experimental bounds!Gelmini, Kalashev, Semikoz astro-ph/0506128

Current experimental limitations on Current experimental limitations on γγ ray flux ray flux on 95% CL:on 95% CL:

AGASA, Yakutsk combined (astro-ph/0601449 G.I.Rubtsov et al)

36% above 100EeV

Pierre-Auger(M.Risse, ICRC 2005) 26% above 10EeV




Acceleration (bottom-up) models:

Possible models

Possible models





+ Don’t require new physics

Possible models





+ Don’t require new physics

Hard to achieve energies above 100 EeV (possibly extreme astrophysics needed)

_

Possible models





• protons • nuclei

Possible models





• protons Most natural UHECR candidate as most Most natural UHECR candidate as most abundant element in the universeabundant element in the universe

• nuclei

Possible models





• protons Most natural UHECR candidate as most abundant element in the universe

• nucleiMore efficient acceleration and More efficient acceleration and isotropisationisotropisation


Propagation of Ultra High Energy Cosmic Rays


Propagation of Ultra High Energy Cosmic Rays

A. Uryson – next talk


Main Factors influencing UHECR propagation

Microwave Photon Background (MWB)

Random Extragalactic Random Extragalactic Magnetic Field (EGMF)Magnetic Field (EGMF)

1010-12-12-10-10-9-9 G G

IR/Optic radiation

e, γ

p, n

Nucleiphotodisintegration

Pair production

synchrotronICS, e

+ e- production

& e+e- production

, e+e- , photodisintegration deflection

?Radio background (RB)Radio background (RB)

?


Simulating UHECR propagation

Photodisintegration

e+e- pair production

production

F.Stecker et al. Astrophys.J. 512 (1999) 521-526. E.Khan et al. Astropart.Phys. 23 (2005) 191-201

M.J.Chodorowski et al. Astrophys.J.400,181(1992)

A.Mucke et al.,Comp.Phys.Comm.124,290(2000)

Extragalactic magneticfield

K.Dolag et al., ICRC 2003 proceedings

Infrared background

Sigl et al. astro-ph/0309695

F.Stecker et al. astro-ph/0510449

Energy loss length - Fe


Energy loss length – Fe and p


Phenomenological source model


F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)

Parameter Name Values

Power of the Injection Spectrum, E- 1.0 - 3.0

End point of the Energy Spectrum Σmax 1019 - 1022

Evolution factor: (1+z)3+m m 0 ± 3

Red shift of the nearest source zmin 0 - 0.1

Maximal source redshiftzmax 3

z – red shift, Θ(x)-step function, Emax= Z Σmax, Z- electric charge

Dependence on


F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Protons

Emax= 6 x 1020 eV

m = 0

zmin = 0

Best fit (HiRes)α= 2.6

Dependence on


F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Fe primaries

Σmax= 6 x 1020 eV

m = 0

zmin = 0

Best fit (HiRes)α= 2.4

Dependence on Emax



α = 2

m = 0

zmin = 0

Dependence on Emax



α = 2

m = 0

zmin = 0

Emax=26 x

Dependence on Zmin



α = 2.65

m = 0

Emax= 3 x 1020 eV

Dependence on m


F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)He primaries

α = 2.3

Emax= 5 x 1021 eV

zmin = 0

Composition of the propagated cascade


Nuclei with E > 10-100 EeV are subjected to photodisintegration

Even if primary source composition consisted of single atomic number the propagated spectrum should contain products of photodisintegration

Photodisintegration kinematics

EA` = EA A`/A

mA, m A’, mp >> k ~ 10 MeV k – background photon energy in the nucleus rest frame

γ = constkth =f(γ, A)

γ = const-photodisintegration chaincontinues

Composition dependence on Emax



α = 2

m = 0

zmin = 0

Mea

n at

omic

num

ber

<A

> in

the

cas

cade

Fe

<A> ≡ Σ Ai Fi / Ftot

Fi – flux of Ai

Σmax



F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Fe and O primaries

α = 2

m = 0

zmin = 0Fe

O

Fe

Mea

n at

omic

num

ber

<A

> in

the

cas

cade


Fi – flux of Ai

Σmax



F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Fe and O primaries

α = 2

m = 0

zmin = 0Fe

O

Fe

Mea

n at

omic

num

ber

<A

> in

the

cas

cade


Fi – flux of Ai

Σmax

Fitting experimental spectra*


F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Source model

Lower energy component (LEC) if needed

FLEC(E) = fo (E/Eo)-β exp(-E/Eo)whereβ = 2.7, Eo = 10 EeV,fo – free normalization parameter

Here we assume that LEC has galactic origin and so we neglect propagation effects, however one can show that spectrum of the form close to (2) can be obtained as a result of propagation of extragalactic protons or nuclei from the source like (1).

+(2)

(1)

* O. Kalashev, J. Lee, K. Arisaka, G. Gelmini work in preparation

The fit is done above 3 EeV

HiRes stereo and mono combined fit


α = 2.6 ; Emax= 1022eV; m=0; zmin=0

Proton source + LECProton source + LEC



α = 2.6 ; Emax= 1022eV; m=0; zmin=0

Proton source + LECProton source + LEC

α = 2.1÷2.7(α = 2.5÷2.7 if no LEC assumed)

Emax≥ 1020.2eV

m ≤ 0

Zmin<0.01 (50Mpc)



He source + LECHe source + LEC

α = 2.3 ; Emax= 5x1021eV; m=0; zmin=0

α = 2.2÷2.3

Emax> 1020.5eV

Zmin<0.02 (100Mpc)

-2≤ m ≤ 2

lg(Σ

ma

x/eV

)



α = 1.4 ; Emax= 2.6x1020eV; m=0; zmin=0

Fe source + LECFe source + LEC

lg(Σ

ma

x/eV

)

α = 1.0÷2.0

Emax =1019.8-1020.5eV

-3≤ m ≤ 3 works fine

Zmin<0.05 (250Mpc)



α = 1.4 ; Emax= 2.6x1020eV; m=0; zmin=0


lg(Σ

ma

x/eV

)

α = 1.0÷2.0

Emax =1019.8-1020.5eV


Zmin<0.05 (250Mpc)

More heavy elements



α = 1.4 ; Emax= 2.6x1020eV; m=0; zmin=0


lg(Σ

ma

x/eV

)

α = 1.0÷2.0

Emax =1019.8-1020.5eV


Zmin<0.05 (250Mpc)

More protons

Conclusions


Nuclei-reach sources may explain UHECR spectrum as well as pure proton sources.

+ Nuclei sources models with low enough Emax may be less limited in terms of distance to the closest source (250 Mpc compared to 50 Mpc for HiRes)

+/- Lot of parameters to play with

_ LEC is normally required

_ Composition study made so far by AGASA and HiRes does not support

heavy nuclei as primaries for the showersMore accurate composition study will clear the picture


Protons versus nuclei


AGASA, ICRC 2005, K.Shinozaki at al

Experimental limitations

Appendix


AGASA fitting attempts


IronIron Emax= 2.6x1020eV; m=0; zmin=0ProtonsProtons Emax= 1022eV; m=0; zmin=0

Documents

Nuclei As Ultra High Energy Cosmic Rays Oleg Kalashev* UCLA, INR RAS GZK 40: The 3rd International Workshop on THE HIGHEST ENERGY COSMIC RAYS AND THEIR