Nuclei As Ultra High Energy Cosmic Rays Oleg Kalashev* UCLA, INR RAS GZK 40: The 3rd International...
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Transcript of Nuclei As Ultra High Energy Cosmic Rays Oleg Kalashev* UCLA, INR RAS GZK 40: The 3rd International...
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
•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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Possible solutions
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Top-Down models:
• Topological defects • Z-burst
Possible models
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Top-Down models (disfavored?) :
• Topological defects • Z-burst
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Top-Down models (disfavored?) :
• Topological defects • Z-burst
Acceleration (bottom-up) models:
Possible models
Possible models
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Top-Down models (disfavored?) :
• Topological defects • Z-burst
Acceleration (bottom-up) models:
+ Don’t require new physics
Possible models
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Top-Down models (disfavored?) :
• Topological defects • Z-burst
Acceleration (bottom-up) models:
+ Don’t require new physics
Hard to achieve energies above 100 EeV (possibly extreme astrophysics needed)
_
Possible models
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Top-Down models (disfavored?) :
• Topological defects • Z-burst
Acceleration (bottom-up) models:
• protons • nuclei
Possible models
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Top-Down models (disfavored?) :
• Topological defects • Z-burst
Acceleration (bottom-up) 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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Top-Down models (disfavored?) :
• Topological defects • Z-burst
Acceleration (bottom-up) models:
• protons Most natural UHECR candidate as most abundant element in the universe
• nucleiMore efficient acceleration and More efficient acceleration and isotropisationisotropisation
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Propagation of Ultra High Energy Cosmic Rays
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Propagation of Ultra High Energy Cosmic Rays
A. Uryson – next talk
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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)
?
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Energy loss length – Fe and p
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Phenomenological source model
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Protons
α = 2
m = 0
zmin = 0
Dependence on Emax
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Fe primaries
α = 2
m = 0
zmin = 0
Emax=26 x
Dependence on Zmin
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Protons
α = 2.65
m = 0
Emax= 3 x 1020 eV
Dependence on m
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
F(E, z) = f E-α(1+z)3+mΘ(Emax- E) Θ(z-zmin) Θ(zmax-z)Fe primaries
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
Composition dependence on Emax
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
<A> ≡ Σ Ai Fi / Ftot
Fi – flux of Ai
Σmax
Composition dependence on Emax
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
<A> ≡ Σ Ai Fi / Ftot
Fi – flux of Ai
Σmax
Fitting experimental spectra*
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
α = 2.6 ; Emax= 1022eV; m=0; zmin=0
Proton source + LECProton source + LEC
HiRes stereo and mono combined fit
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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)
HiRes stereo and mono combined fit
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
)
HiRes stereo and mono combined fit
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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)
HiRes stereo and mono combined fit
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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)
More heavy elements
HiRes stereo and mono combined fit
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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)
More protons
Conclusions
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
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
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
Protons versus nuclei
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
AGASA, ICRC 2005, K.Shinozaki at al
Experimental limitations
Appendix
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
AGASA fitting attempts
Oleg Kalashev GZK 40, INR RAS, Moscow, 17 May 2006
IronIron Emax= 2.6x1020eV; m=0; zmin=0ProtonsProtons Emax= 1022eV; m=0; zmin=0