emilio migneco

E. Migneco Erice ISCRA, July 2-13 2004

Introduction to High energy neutrino astronomy

Erice ISCRA School 2004

Emilio Migneco


Topics

1) Introduction to high energy neutrino astronomy

Motivations for HE neutrino astronomyHE neutrino sourcesNeutrino telescopes operation principlesBackgrounds

2) Future cubic kilometer arrays

Review of existing detectors and projectsFuture detectors:

impact of site parametersarchitectureexperimental challengessimulations and expected performances

1) Introduction to high energy neutrino astronomy

Motivations for HE neutrino astronomyHE neutrino sourcesNeutrino telescopes operation principlesBackgrounds

2) Future cubic kilometer arrays

Review of existing detectors and projectsFuture detectors:

impact of site parametersarchitectureexperimental challengessimulations and expected performances


Neutrino astronomy

Neutrinos are elementary particles with “special” properties:

• light

• neutral

• interact by weak force

Good astrophysical probes:

not deflected point back to the source

not absorbed travel Gpc distances (overcome GZK effect)

But they are difficult to detect

I have done a terrible thing I invented a particle that cannot be detectedW.Pauli


The known cosmic neutrino spectrum

?

SuperKamiokande neutrino image of the Sun

HST image of SN 1987A

The measurements of (low energy) solar, SN and

atmospheric neutrino fluxes is permitting to solve open

questions in astrophysics, nuclear and particle physics... Davis and Koshiba Nobel laureates 2002


High energy astrophysics

The detection of high energy gammas and CR are

milestones in modern astrophysics but there are still open

questions

• Particle acceleration mechanism in astrophysical sources

• Identification of high energy CR sources

• Solution of UHECR puzzle

• Heavy dark matter content in the Universe

The detection of high energy gammas and CR are

milestones in modern astrophysics but there are still open

questions

• Particle acceleration mechanism in astrophysical sources

• Identification of high energy CR sources

• Solution of UHECR puzzle

• Heavy dark matter content in the Universe


The high energy cosmic ray standard paradigm

Ankle

Galactic nuclei

E-3

Sources of high energy protons exists and dominate the CR

spectrum at E> 1018.5 eV

Knee

Gaisser

protons

E-2.7

Galactic protonsE-2.7


To

p D

ow

n

“Top – Down” and “Bottom – Up” processes

MX~102124 eV

CR 1021 eV

decay or annihilation

acceleration

p,e at restgammas and neutrinos

gammas and neutrinos

Bo

tto

m

U

p

CR 1021 eV E-2 spectrum

flat spectrum


Astrophysical sources of UHE particles

•Large cosmic objects

•Intense magnetic field

•High shockwave velocity

18max shockE Z B[ G] L[kpc] 10 eV

HillasFermi acceleration to high energies requires

GRB

GRBL1052 erg/sec

Bright AGNL1047 erg/sec

These values are typical for very bright sources

Emax =1020 eV


Possible extra Galactic sources of CR: AGN

QSO GB1508+5714 Chandra

The term AGNs (Active Galactic Nuclei) gathers a number of astrophysical objects

6 8BHM 10 M • Massive Black Hole

• Accretion disk (UV + lines)

• Collimated jets

QSO 3C273QSO 3C279

EGRET

10

The brightest observed steady sources:

L=1042 1047 erg/s

When the jet is directed towards the Earth luminosity increases ”Blazars”


Possible extra Galactic sources of CR: GRB

GRB (Gamma Ray Bursts) are the most

powerful emissions of gamma rays

ever observed.

Happens at cosmological distances

The observation rate is few/day

GRB have recentely been shown to be

associated with SN, as indicated by the

GRB030329 – SN 2003dh correlation

10MM

s

300

GRB 030329ESO

L = 1051 1053 erg/s

t 1100 s (1/3 <2

sec)

(GRB 030329 z=0.17)


Limits of HE gamma and proton astronomy

The UHE CR and gamma horizon is limited by

interactions with low energy background

radiation

The UHE CR and gamma horizon is limited by

interactions with low energy background

radiation


Absorption of high energy photons and protons

NCMBR N (GZK)

nCMBR ~ 400 cm-3

p~ 100 barn

ECMBR ~ 6.6·10-4 eV Ep ~ 1019.5 eV

pCMBRatt

p CMBR

1<50 Mpc

n

Guaranteed sources of neutrinos

IR,CMBR e+e-

CMBR,IRatt

CMBR,IR

1<10 Mpc

n

ECMBR ~ 6.6·10-4 eV E ~ 1013.5 eV

Lower energy photons interact also with IR backgrond

2 2N

p

m mE E

2

See also T. Stanev,2004 for p-IR interactions


The GZK effect

Closest AGNs

Galactic radius (15 kpc)

5 Gpc


High Energy neutrinos production

Are the astrophysical sources of High Energy

CR also candidate sources of HE neutrinos ?

The interaction of protons with ambient gas or

photon field may produce neutrino fluxes

Are the astrophysical sources of High Energy

CR also candidate sources of HE neutrinos ?

The interaction of protons with ambient gas or

photon field may produce neutrino fluxes


Neutrino production in cosmic accelerators

Halzen

Proton acceleration

• Fermi mechanism

proton spectrum dNp/dE ~E-2

Neutrino production

• Proton interactions

p p (SNR,X-Ray Binaries)

p (AGN, GRB, microQSO)

• decay of pions and muons

Astrophysical jet

Particle accelerator

electrons are responsible for gamma fluxes (synchrotron, IC)


HE proton interaction on ambient p or

Beam dump in SNR environment

0

CANGAROO observationsof RXJ1713.7-3946 fit with TeV gamma ray production by 0 decay (?)

+

-

Muons and muon-neutrinos

Beam dump in astrophysical jet environment (GRB,AGN,microQSO)

p n

Shock waves

Matter shells

HE proton

Target photons

pions

1

muons and neutrinos

2 2

N

N

m mE 0.34 GeV

2m

p0.05

HE proton

SN shells,clouds,..

Shock wave

Target protons


Neutrino fluxes chemical composition

ee

If the muon interaction time (IC) is larger than the muon decay time

electron neutrinos and antineutrinos are also produced

ee

Tau neutrinos are unlikely produced in the sources (M = 1.7 GeV)

They can be detected at the Earth as “oscillated” muon neutrinos:

2 2 2

162 3

3

L kmP sin 1.27 m eV

E GeV

10 L kpc 1P sin 10

10 E TeV 2

e: : 1:1:1


Limits of HE gamma and proton astronomy

High energy protons 50 Mpc

neutrinos

Astrophysicalsource

Low energy protons deflected

High energy gammas 10 Mpc


Motivations of high energy neutrino astronomy

Extend the high energy CR and Horizon (<50 Mpc)

Identify the sources of UHE particles

Explore deep inside the source (where »1 for CR and )

Probe hadronic models in astrophysical sources

Extend the high energy CR and Horizon (<50 Mpc)

Identify the sources of UHE particles

Explore deep inside the source (where »1 for CR and )

Probe hadronic models in astrophysical sources


High energy neutrino fluxes

Astrophysical sources are expected to produce a

diffuse high energy neutrino flux with spectral index 2

The most powerful and/or the closest sources could

give a clear point-like neutrino signal

Time correlations between events and photons will be

clear signatures for transient source detection

Astrophysical sources are expected to produce a

diffuse high energy neutrino flux with spectral index 2

The most powerful and/or the closest sources could

give a clear point-like neutrino signal

Time correlations between events and photons will be

clear signatures for transient source detection


The WB bound

The WB bound is valid for:

• Sources optically thin to UHECR (responsible for the observed spectrum)

• Sources in which CR acceleration takes place (top-down excluded)

“thick sources”

p 1

p 1 “thin sources”

atmo

sph

ericWaxman Mannheim

An upper limit to the diffuse neutrino flux was set by Waxman and Bahcall

assuming that the detected UHECR sources are the only neutrino sources

MPR bound

WB bound

GeV


Possible extragalactic sources and fluxes

Learned Mannheim

AGNGZK

p AGN corespp AGN cores

p blazar

GRB

WB Limit

Diffuse neutrino fluxes

Bright and nearby GRB could produce intense directional fluxes (e.g. GRB

030329) as well as brightest AGNs (3C273, 3C279)

Stecker

Nellen

Mannheim

Bierman

Waxman

Ruled out by

new AMANDA data

(preliminary)


Galactic Sources of HE neutrinos

Galactic sources do not contribute to UHECR fluxes, therefore are not limited

by WB bound. Even if much less intense, their proximity to the Earth may yield

detectable neutrino fluxes

Another important source of TeV neutrinos could be the Galactic centre

(SGR-A*) which is a very active gamma source

SNR, extensively discussed:(see T. Stanev)

2 112

ergE 10

cm s

CRAB, Protheroe

2 9 112

ergE 10 10

cm s

microquasarMost powerful GX339-4 SS433

Distefano


High energy neutrino detection

Detection of HE astrophysical neutrinos is achieved

through CC neutrino interaction with matter with

charged lepton production

Neutrino astronomy requires reconstruction of

direction and energy of the reaction products

(charged leptons)

Detection of HE astrophysical neutrinos is achieved

through CC neutrino interaction with matter with

charged lepton production

Neutrino astronomy requires reconstruction of

direction and energy of the reaction products

(charged leptons)


Neutrino cross section

N X

Neutrinos are detected indirectly,

following a DIS on a target

nucleus N:

1 TeV 1 PeV

1.5

E TeV

X

N

At >TeV energies the muon and the neutrino are co-linear

Reconstruction of the trajectory allows the identification of the direction

N0.4

E E 5TeV

E E 5TeV

Gandhi

10-33 cm2

10-35cm2


Muon Range

E(GeV)R

ang

e (m

)

Muons have long tracks in water

2

24

dEa b E

dx

GeVcma 0.2

g

cmb 4

1R ln a bE

b

10g

Due to its larger mass (m/ me~200) radiative losses of muons are

strongly suppressed with respect to electrons

R E 300GeV 1 km

Gaisser

1 TeV 1 PeV

2·103

2·104

In w

ater


Muon vs electron range

Spiering Wiebush

Electron

Muon 100 TeV

1 TeV

100 GeV 10 GeVGeant 3.21


Neutrino detection probabilty

6 2.2 3

6 0.8 3 6

1.3 10 E 1 10 GeV

1.3 10 E 10 10 GeV

,min

CC 'E Nmin ' min '

A eff'E

d E ,EP E ,E N dE R E ,E

dE

Instrumented detector D<R

Due to the long muon range the target volume is much bigger than the

detector instrumented volume

Probabilty to produce a detectable (E>Emin) muon


P

·10-3

LogE(GeV)

,minE 1TeV

E,min=1GeV

• Probabilty to produce a detectable (E>Emin) muon

tot A

,min

E,min E N Z

,minE

N E ,dE E , P E ,E e

AT

Neutrino-induced muon fluxes

deg

PE

arth

100 TeV

10 TeV

1 TeV

• Earth transparency to HE neutrinos >PeV neutrinos search for “horizontal” tracks

The number of muon events in units of detection area A and observation time T is:

• Neutrino flux spectrum


Detection area for astrophysical UHE neutrino fluxes

2 82

GeV4.5 10

cm s sr

The observation of TeV

neutrino fluxes

requires km2 scale

detectors

2

84 10 7

y5 kmE 100TeV

2

E 100TeV

4.5 10N 10 10 A 3 10 T 2

10

N 70 AT km y

The expected number of events for WB sources is roughly:


Expected astrophysical neutrino induced muons in 1 km2

DiffuseGuaranteed (GZK): few / year ?

Diffuse GRB: 20 / year

Diffuse AGN (thin): few / year

(thick): >100 / year

Point-likeGRB (030329): 110 / burst

AGN (3C279): few / year

Galactic SNR (Crab): few / year ?

Galactic microquasars: 1 100 / year

Waxman

Waxman

Dermer

Distefano

Mannheim

Protheroe


km3 scale neutrino detectors

The requirement of large neutrino interaction target

induced Markov and Zheleznykh to propose the use

of natural targets.

Deep seawater and polar ice offers:

• huge (and inexpensive) target for neutrino interaction;

• good optical characteristics as Cherenkov radiators;

• shielding from cosmic background.

The requirement of large neutrino interaction target

induced Markov and Zheleznykh to propose the use

of natural targets.

Deep seawater and polar ice offers:

• huge (and inexpensive) target for neutrino interaction;

• good optical characteristics as Cherenkov radiators;

• shielding from cosmic background.


Underwater Cherenkov detectors: detection principles

neutrino

muon

Cherenkov light

~5000 PMT

Connection to the shore

neutrino

atmospheric muon

depth>3000m


The km3 telescope: a downward looking detector

Neutrino telescopes search for muon tracks induced by neutrino interactions

The downgoing atmospheric flux overcomes by several orders of

magnitude the expected fluxes induced by interactions.

On the other hand, muons cannot

travel in rock or water more than

50 km at any energy

Upgoing and horizontal muon

tracks are neutrino signatures


Cherenkov light emission and propagation

2n 1

700nm

300nm

dN 2 1 1 1 -

dx c n

dN photons300

dx cm

The Cherenkov light is efficiently emitted by relativistic particles in water

at UV-blue wavelengths under the condition: n() > 1

Superkamiokande muon event

C ~ 42°

n (300700nm) ~ 1.35


Cherenkov track reconstruction

pseudo vertex

j 0 j j cc(t - t ) = l + d ctg( )

De Jong

Cherenkov photons emitted by the

muon track are correlated by the

causality relation:

The track can be reconstructed

during offline analysis of space-

time correlated PMT signals (hits).


Detector granularity

a

D0

a

I I e

L blue 70m

Spacing of optical sensors inside the instrumented volume must be of the order of the light absorption lenght in water (70 m for blue light)

About 5000 optical sensors are needed to fill up one km3

Visible light


Backgrounds

Neutrino detectors must identify few astrophysical

events on top of diffuse atmospheric backgrounds

Neutrino detectors must identify few astrophysical

events on top of diffuse atmospheric backgrounds


Backgrounds: atmospheric muons and neutrinos

Atmospheric neutrinos:

• upward tracks are good neutrino candidates; • event direction and energy criteria can be used to discriminate background from astrophysical signals.

Atmospheric muons:

• downgoing events background is due to mis-reconstructed (fake) tracks;

• improve analysis filters for atmospheric muon background rejection.

ANTARES


Atmospheric muon background vs depth

Downgoing muon background is

strongly reduced as a function of

detector installation depth.

Depth >3000 m (1 km rock) is

suggested for detector installation

NEMO

NESTOR

ANTARESAMANDA

Bugaev

BAIKAL


First detection of HE neutrino events

Proof of the underwater (and underice) Cherenkov

detection technique has been achieved by AMANDA

(South Pole) and BAIKAL-NT (Lake Baikal) detectors

Proof of the underwater (and underice) Cherenkov

detection technique has been achieved by AMANDA

(South Pole) and BAIKAL-NT (Lake Baikal) detectors


The AMANDA neutrino sky

AMANDA and BAIKAL have demontrated the viability of neutrino detection with underwater and underice Cherenkov detectors at TeV energy scale

AMANDA PRELIMINARY

(neutrino 2004 conference)

The atmospheric neutrino spectrum has been measured by AMANDA and BAIKAL

See Silvestri’s talk


The future neutrino telescopes

The quest to reach the km2 effective area is open !

Southern Hemisphere ICECUBE

Northern HemisphereMediterranean km3

1400 m

2400 m

IceTop

>3000 m


Summary

• High energy astrophysical neutrino fluxes are expected on the

base of CR and observations

• Neutrino detection will provide unique informations on

astrophysical sources:

overcomes the limitations of and CR astronomy due to

absorption on CMBR at cosmological distances;

evidence on the role of hadronic processeses in

astrophysics

• Neutrino events correlated in space and time with point-like

(transient) sources will be probably the first evidence of detection

of astrophysical neutrinos

• The expected fluxes from sources implies >1km2 effective area to

detect TeV-PeV neutrinos

• High energy astrophysical neutrino fluxes are expected on the

base of CR and observations

• Neutrino detection will provide unique informations on

astrophysical sources:

overcomes the limitations of and CR astronomy due to

absorption on CMBR at cosmological distances;

evidence on the role of hadronic processeses in

astrophysics

• Neutrino events correlated in space and time with point-like

(transient) sources will be probably the first evidence of detection

of astrophysical neutrinos

• The expected fluxes from sources implies >1km2 effective area to

detect TeV-PeV neutrinos


Other scientific goals

Galactic SN:

search for intense fluxes of electron anti-neutrinos

need low optical background task for AMANDA-ICECUBE

Dark Matter:

search for neutrinos ( 10 GeV) originated by the

annihilation of neutralinos in the Sun, Earth, Galactic Centre

low energy threshold, good event direction reconstruction

Galactic SN:

search for intense fluxes of electron anti-neutrinos

need low optical background task for AMANDA-ICECUBE

Dark Matter:

search for neutrinos ( 10 GeV) originated by the

annihilation of neutralinos in the Sun, Earth, Galactic Centre

low energy threshold, good event direction reconstruction

emilio migneco

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