michael kachelrieß ntnu, trondheimtaup2009.lngs.infn.it/slides/jul4/kachelriess.pdf ·...

[]

Ultrahigh energy neutrinos: Theoretical aspects

Michael Kachelrieß

NTNU, Trondheim

Introduction

Outline of the talk

1 Introduction

2 Cosmogenic neutrino flux

best estimate

lower and upper limits

3 Astrophysical sources

point sources

Cen A motivated by Auger

diffuse flux

4 Top-down models

5 Summary

Michael Kachelrieß (NTNU Trondheim) Ultrahigh energy neutrinos TAUP 2009 2 / 34

Introduction

The CR–γ–ν connection:

UHE neutrinos and HE photons are unavoidable byproducts of UHECRs

top-down models: large fluxes with Iν ≫ Ip

ratio Iν/Ip fixed by fragmentation


Introduction





astrophysical models, cosmogenic flux: ratio Iν/Ip determined by chemical composition and source evolution


Introduction






astrophysical models, direct flux: strongly model dependent fluxes


Introduction






astrophysical models, direct flux: strongly model dependent fluxes

prizes to win: astronomy above 100 TeV identification of CR sources determine galactic–extragalactic transition of CRs test/discover new particle physics


Cosmogenic neutrinos Best estimate

Estimates for the cosmogenic neutrino flux

choose dip model as most economic description of data

1017 1018 1019 1020 10211023

1024

1025

3

1,2

1 - γg=2.6, m=2.4, z

c=1.2

2 - γg=2.65, m=1.8, z

c=1.2

3 - γg=2.7, m=0

J(E

)E3 , m

-2s-1

sr-1eV

2

E, eV [Berezinsky, Gazizov, Grigorieva ’02 ]





1017 1018 1019 1020 10211023

1024

1025

3

1,2

1 - γg=2.6, m=2.4, z

c=1.2

2 - γg=2.65, m=1.8, z

c=1.2

3 - γg=2.7, m=0

J(E

)E3 , m

-2s-1

sr-1eV

2

E, eV

observed diffuse spectrum does not fix source spectra:e.g. degeneracy of source evolution and spectral index






fix source evolution by observations (AGN evolution/GRB rate)







fix maximal energy







fix maximal energy

E, eV1810 1910 2010 2110

-1st

er-1

sec

-2m2

J(E

) eV

3E

2310

2410

2510=2.7; m=0

gγeV;21=10max=2; Emaxz

HiRes II HiRes I

p

iνΣ

[Berezinsky, Gazizov ’09 ]







fix maximal energy E, eV

E, eV1810 1910 2010 2110 2210 2310

-1st

er-1

sec

-2m2

J(E

) eV

3E

2310

2410

2510=2.47; m=3.2

gγeV;23=10max=5; Emaxz

HiRes II HiRes I

p

iνΣ



Cosmogenic neutrinos Lower and upper limits

Lower limit in the dip model

E, eV1810 1910 2010 2110

-1st

er-1

sec

-2m2

J(E

) eV

3E

2310

2410

2510eV; m=021=10

max=2; Emaxz

HiRes II HiRes I

p

iνΣ

2.7

2.0

2.7

2.0

2.0

2.7




General upper limit

exists a number of “neutrino bounds” a la WB, MPR:derived using special assumptions ⇒ status of best guesses



General upper limit

exists a number of “neutrino bounds” a la WB, MPR:derived using special assumptions ⇒ status of best guesses

cascade limit: [Berezinsky, Smirnov ’75 ]

all energy in γ and e± cascades down to GeV–TeV range, bounded byobservations:

ωcas >4π

c

∫

∞

E0

dE EIν(E) ≥4π

cE0Iν(> E0)

<∼ 2 · 10−6 eV/cm3



Elmag. cascades and EGRET limit:

10-2

1

102

104

106

108 1010 1012 1014 1016 1018 1020 1022 1024

j(E)

E2 [e

V c

m-2

s-1

sr-1

]

E [eV]

MACRO

Baikal

AGASA

Fly’s Eye FORTE

EGRET

GLUE

AMANDA II

RICE

atm ν

γ νi

p

[Semikoz, Sigl ’03 ]


Cosmogenic neutrinos Protons vs. nuclei

Chemical composition via Xmax:

/decade] 18 19

]2>

[g/c

mm

ax<X

650

700

750

800

850

proton

iron

QGSJET01QGSJETIISibyll2.1EPOSv1.99

Auger 2009

HiRes ApJ 2005



Chemical composition via σ(Xmax) from Auger:

E [eV]

1810 1910

E [eV]

1810 1910

]2)

[g/c

mm

axR

MS

(X

10

20

30

40

50

60

70 proton

iron



Mixed composition:

Mean 744.8RMS 62.02

]2 [g/cmmaxX600 650 700 750 800 850 900 9500

0.02

0.04

0.06

0.08

0.1

0.12

Mean 744.8RMS 62.02

70% proton

30% iron

sum

σ2 =∑

i

fiσ2i +

∑

i<j

fifj(Xmax,i − Xmax,j)2



Cosmogenic neutrino flux: p versus Fe

[Anchordoqui et al. ’07 ]


Astrophysical sources

What is the bonus of UHE neutrino astronomy?

astronomy with VHE photons restricted to few Mpc:

10

12

14

16

18

20

22

Gpc100Mpc10MpcMpc100kpc10kpckpc

log1

0(E

/eV

)

photon horizon γγ → e+e− CMB

IR

radio




astronomy with VHE photons restricted to few Mpc:

10

12

14

16

18

20

22


log1

0(E

/eV

)


IR

radio

ambiguity: leptonic/hadronic origin



UHE neutrino astronomy vs UHECRs?

10

12

14

16

18

20

22


log1

0(E

/eV

)

proton horizon


IR

Virgo ⇓



UHE neutrino astronomy vs UHECRs?

10

12

14

16

18

20

22


log1

0(E

/eV

)

proton horizon


IR

Virgo ⇓

large statistics of UHECRs, well-suited horizon scale

but no conclusive evidence that qB is small enough




Neutrino astronomy:

large λν but also large uncertainty 〈δϑ〉 >∼ 0.1 − 1




Neutrino astronomy:


small event numbers: <∼ 1/yr for PAO or ICECUBE

103

102

10

1

10-1

1022102110201019101810171016

j(E)

E2 [e

V c

m-2

s-1

sr-1

]

E [eV]

WB

max

0.2

CR flux

⇒ identification of steady sources challenging




Neutrino astronomy:


small event numbers: <∼ 1/yr for PAO or ICECUBE

103

102

10

1

10-1

1022102110201019101810171016

j(E)

E2 [e

V c

m-2

s-1

sr-1

]

E [eV]

WB

max

0.2

CR flux

⇒ identification of steady sources challenging

correlation with AGN flares, GRBs

which AGNs? GeV/TeV photon sources?


Astrophysical sources Point sources

HESS observations of M87:

Date12/1998 12/2000 12/2002 12/2004 12/2006

)-1

s-2

(E>7

30G

eV)

(cm

Φ

0.0

0.5

1.0

1.5

-1210×

)-1

s-2

f(0.

2-6

keV

) (e

rg c

m

0

20

40

-1210×

2003

2004

2005

2006

H.E.S.S.

average

HEGRA

Chandra (HST-1)

Chandra (nucleus)

B

09/Feb 16/Feb

)-1

s-2

(E>7

30G

eV)

(cm

Φ

0

2

4

6

-1210×Feb. 2005

A

09/Mar 16/Mar

March 2005

30/Mar 06/Apr

April 2005

Date04/May 11/May

May 2005



HESS observations of M87:

Date12/1998 12/2000 12/2002 12/2004 12/2006

)-1

s-2

(E>7

30G

eV)

(cm

Φ

0.0

0.5

1.0

1.5

-1210×

)-1

s-2

f(0.

2-6

keV

) (e

rg c

m

0

20

40

-1210×

2003

2004

2005

2006

H.E.S.S.

average

HEGRA

Chandra (HST-1)

Chandra (nucleus)

B

09/Feb 16/Feb

)-1

s-2

(E>7

30G

eV)

(cm

Φ

0

2

4

6

-1210×Feb. 2005

A

09/Mar 16/Mar

March 2005

30/Mar 06/Apr

April 2005

Date04/May 11/May

May 2005

fast variability excludes acceleration along kpc jet

acceleration in hot spots marginally okay

favors acceleration close to SMBH



HESS observations of Cen A

no variability




no variability

consistent withpoint source




no variability

consistent withpoint source

HE emission fromcentral region(1’≃ 1.1 kpc)


Astrophysical sources Centaurus A

Multi-messenger astronomy with Cen A?

+ 2 events correlated with Cen A within 3.1

+ more events close-by [Gorbunov et al. ’07, Fargione ’08, Rachen ’08 ]

+ general correlation with AGN







− confusion with LSS?− no confirmation by HiRes− tension to PAO chemical composition− Emax for most AGN (incl. Cen A) high enough?







− confusion with LSS?− no confirmation by HiRes− tension to PAO chemical composition− Emax for most AGN (incl. Cen A) high enough?

correlations with AGN:independent/additional evidence?

Cen A closest AGN

⇒ good test case for multi-messenger astronomy: accompanying γ-rayand neutrino fluxes?



Study two base models [MK, Ostapchenko, Tomas ’08 ]

neglect details of acceleration

fix 2 basic scenarios: “core” and “jet”

acceleration close to the core

acceleration in accretion shock/regular fields

pγ interactions

τγγ ≫ 1, synchrotron losses for e±

acceleration in jet

shock acceleration

pp interactions

τγγ ≪ 1, synchrotron losses for e±



Results for acceleration close to the core: α = 1.2

initialprotons

final protons

totalneutrinos

γ

γ

HESSCGRO

FERMI

PAO

8 10 12 14 16 18 2013

14

15

16

17

18

log10 (E/eV)

log 10

(E

2 Φ/e

V k

m-2

yr-1

)



Results for acceleration close to the core: α = 2

initial protons

final protons

totalneutrinos

γ

γ

HESS

CGRO

FERMI

PAO

8 10 12 14 16 18 2014

15

16

17

18

19

log10(E/eV)

log 10

(E

2 Φ/e

V k

m-2

yr-1

)

promising test case for HESS / FERMI

γ-ray spectrum rather insensitive to α



Comparison to recent HESS and FERMI observations

initial protons

final protons

totalneutrinos

γ

γ

HESS

FERMI

PAO

8 10 12 14 16 18 2014

15

16

17

18

19

log10(E/eV)

log 10

(E

2 Φ/e

V k

m-2

yr-1

)



Comparison to recent HESS and FERMI observations

initial protons

final protons

totalneutrinos

γ

γ

HESS

FERMI

PAO

8 10 12 14 16 18 2014

15

16

17

18

19

log10(E/eV)

log 10

(E

2 Φ/e

V k

m-2

yr-1

)

shape and normalization okay

TeV γ-ray and neutrino source



Regenerating TeV photons: a) in the source

injection spectrum Fγ(E) ∝ 1/E2

10 12 14 16 18 20

E2 F

(E)

log10(E/eV)Michael Kachelrieß (NTNU Trondheim) Ultrahigh energy neutrinos TAUP 2009 21 / 34


Regenerating TeV photons: a) in the source

: thin above 1016eV, ultra-rel. regime

10 12 14 16 18 20

E2 F

(E)

log10(E/eV)

⇓

Eγεγ

m2e

ultra-rel. regime



Regenerating TeV photons: b) on CMB

photons above 1016eV cascade on CMB

10 12 14 16 18 20

E2 F

(E)

log10(E/eV)




photons above 1016eV cascade on CMB : fill up TeV range

10 12 14 16 18 20

E2 F

(E)

log10(E/eV)




photons above 1016eV cascade on CMB : fill up TeV range

10 12 14 16 18 20

E2 F

(E)

log10(E/eV)

main criteria: LUHE, not shape

evidence for acceleration to UHECRs?however: anisotropic UV field complicates picture already in source



Neutrino event rates per km3 per year

acceleration in the jet (α = 2 or broken power-law)

spectral break Eb/eV - 1018 1017

contained ν-events 0.02 0.4 2.0

muon events 0.01 0.2 0.7

acceleration near the core (α = 2 or broken power-law)



muon events 7 × 10−3 0.1 0.5



Neutrino event rates per km3 per year

acceleration in the jet (α = 2 or broken power-law)



muon events 0.01 0.2 0.7

acceleration near the core (α = 2 or broken power-law)



muon events 7 × 10−3 0.1 0.5

“good” neutrino cases excluded by HESS/Fermi

diffuse flux more promising


Astrophysical sources Diffuse flux

Diffuse flux from AGN - normalized to Cen A

assume Cen A is a “typical source” with injection spectrum j(E)

diffuse flux from all Cen A-like sources

ϕdiff(E) =cn0

4π

∫

∞

0

dz

∣

∣

∣

∣

dt

dz

∣

∣

∣

∣

dE0(E, z)

dEε(z)j0(E0) ,

enhancement between O(10) (no evolution) and O(100) (strongevolution) [Koers, Tinyakov (’08) ]

Halzen, O’Murchadha (’08): all FR-I radio galaxies: 5 events/yr


UHE neutrinos from top-down models

Top-Down Models

UHECR primaries are produced by decays of supermassive particle X withMX >∼ 1012 GeV.

topological defects: monopoles, strings, super-strings. . . .[Hill ’83; Ostriker, Thompson, Witten ’86 ]

superheavy metastable particles[Berezinsky, MK, Vilenkin ’97; Kuzmin, Rubakov ’97 ]

Main properties:

theoretically well-motivated; testable predictions

no acceleration problem

no visible sources

if X ∈ CDM, no GZK-cutoff



Raison d’etre for top-down models

AGASA excess as original motivation for top-down models is gone

Photon and anisotropy limit allow only subdominant contribution toUHECRs

allows still search for inflationary/GUT/string scale physics

can still give largest neutrino fluxes, especially at UHE



Gravitational creation of superheavy matter

Small fluctuations of field Φ obey

ϕk +[

k2 + m2eff(τ)

]

ϕk = 0





ϕk +[

k2 + m2eff(τ)

]

ϕk = 0

If meff is time dependent, vacuum fluctuations will be transformedinto real particles.





ϕk +[

k2 + m2eff(τ)

]

ϕk = 0


⇒ expansion of Universe,

m2eff = M2a2 + (6ξ − 1)

a′′

a

leads to particle production





ϕk +[

k2 + m2eff(τ)

]

ϕk = 0


⇒ expansion of Universe,

m2eff = M2a2 + (6ξ − 1)

a′′

a

leads to particle production

In inflationary cosmology

ΩXh2 ∼

(

MX

1012GeV

)2 TRH

109GeV

dependent only on cosmology, for MX <∼ HI

[Kuzmin, Tkachev ’98; Chung, Kolb, Riotto ’98 ]



Topological defect models

+ “generic” in SUSY-GUTs+ produced during reheating

- typical density: one per horizon/correlation length- main energy loss low-energy radiation?



Topological defect models [Allen, Shellard ’06 ]

box 2ct

matterepoch

scalingregime




+ “generic” in SUSY-GUTs

+ produced during reheating

- typical density: one per horizon/correlation length

- main energy loss low-energy radiation?

favourable models for UHECRs:

monopole-antimonopole pairs

hybrid defects: cosmic necklaces




+ “generic” in SUSY-GUTs

+ produced during reheating

- typical density: one per horizon/correlation length

- main energy loss low-energy radiation?

favourable models for UHECRs:

monopole-antimonopole pairs

hybrid defects: cosmic necklaces G → H ⊗ U(1) → H ⊗ Z2

monopoles M ∼ ηm/e connected by strings µs ∼ η2

s

parameter r = M/(µd): r ≪ 1 normal string dynamics r ≫ 1 non-rel. string network



Fragmentation of heavy particles

XqL qL

g

g

g

qL

qL

1 TeV(SUSY

+ SU(2) ⊗ U(1)

breaking)

qq

gq

q

χ02

qL

χ01q

1 GeV(hadronization)

qL

B

qR

qR

qW

τ

a−

1

ρ−

π−νµ

µ− νµ

νe

e−

π0 γ

γ

π0

γ

γντ

ντ

qq

g

gq

q

gq

q

n

p

e−

νe

π0

γ

γ



Neutrino fluxes from necklaces:

E3J(E

)/m

−2s−

1eV

2

E/eV [Aloisio, Berezinsky, MK, ’03 ]

ν

p γ

p+γ

1e+22

1e+23

1e+24

1e+25

1e+26

1e+27

1e+18 1e+19 1e+20 1e+21 1e+22



EGRET versus ντ limit:

104

103

100

10

1

0.11022102010181016101410121010108

E2 j(

E)

[eV

cm

-2 s

-1 s

r-1]

E [eV]

EGRET

RICE

PAO ν

PAO ν

[Semikoz, Sigl ’03 ]



Summary

1 astrophysical origin of main component of UHECRs is established

⇒ exists cosmogenic neutrino flux

2 size and energy range uncertain, mainly because of unknown chemicalcomposition

3 ICECUBE is coming close to predicted levels of (“direct”) diffuseneutrino flux

4 detection of point sources requires correlations

5 top-down models may still be dominant neutrino source at UHE


Which sources?

Use the auto-correlation function,

w(ϑ) =DD(ϑ)

RR(ϑ)− 1 ,

where DD: number of pairs in catalogue RR: number of pairs in random sets

for most popular sources of UHECRs:


Which sources?


w(ϑ) =DD(ϑ)

RR(ϑ)− 1 ,

for most popular sources of UHECRs: AGN


Which sources?


w(ϑ) =DD(ϑ)

RR(ϑ)− 1 ,

for most popular sources of UHECRs: AGN and GRB

[ ]Michael Kachelrieß (NTNU Trondheim) Ultrahigh energy neutrinos TAUP 2009 35 / 34

Clustering signal of PAO for N = 40 [A. Cuoco et al. ’07 ]


Pion-nucleon ratio:

f(x

)

x

pions

nucleons

0.001

0.01

0.1

1

1e-05 0.0001 0.001 0.01 0.1 1

[Aloisio, Berezinsky, MK, ’03 ]


Photon-nucleon ratio:

f(x

)

x

pions

nucleons

0.1

1

10

1e-05 0.0001 0.001 0.01 0.1 1

[Aloisio, Berezinsky, MK, ’03 ]


Summary

AGASA excess as main motivation for top-down models is gone

no positive evidence for superheavy dark matter from its two keysignatures:

photons galactic anisotropy

SHDM remains an interesting DM candidate

topological defects are generic prediction of (SUSY-) GUTs

should be searched for as subdominant sources of UHECR


michael kachelrieß ntnu, trondheimtaup2009.lngs.infn.it/slides/jul4/kachelriess.pdf ·...

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