Neutrino astronomy

Schule für Astroteilchenphysik Obertrubach-Bärnfels 12.10.2010 – 14.10.2010 9:00-9:45 10:00-10:45Schule für Astroteilchenphysik Obertrubach-Bärnfels 12.10.2010 – 14.10.2010 9:00-9:45 10:00-10:45

Lutz KöpkeJohannes Gutenberg-Universität Mainz

Lutz KöpkeJohannes Gutenberg-Universität Mainz

Subjects covered

• Why neutrino astrophysics? • Some history ….• Sources of neutrinos and their propagation• Neutrino oscillations• Neutrino cross sections • Detection of neutrinos • Angular resolutions• Background processes• Detection principles• The problem with natural media …• IceCube• Antares and Km3Net

Why neutrino astronomy?

• Understanding of fusion processes in the sun

• Understanding of supernova explosions

• Understanding of neutrino properties

(oscillations, mass hierarchy, …)

• Identification and understanding of cosmic ray sources– Universe is transparent to neutrinos!

• Search for the „not yet found“ and unexpected

History of neutrino astronomy

Can one see the sun in O(1-10) MeV neutrinos?Can one see the sun in O(1-10) MeV neutrinos?

Discussions started after 1958 (cross 3He + 4He 7Be+ 1000x expectation)Discussions started after 1958 (cross 3He + 4He 7Be+ 1000x expectation)

Homestead proposal 1964

Clorine Experiment/Super-K

Clorine Experiment (no direction resolution)Observation solar neutrinos …but deficit w.r.t. theory!!!

Clorine Experiment (no direction resolution)Observation solar neutrinos …but deficit w.r.t. theory!!!

Super-Kamiokandeevidence that neutrinos arise from sunSuper-Kamiokandeevidence that neutrinos arise from sun

Supernova 1987A

by chance discovery of 20-23 O(10) MeV neutrinos in 2-3 detectors …by chance discovery of 20-23 O(10) MeV neutrinos in 2-3 detectors …

Kamiokande result Kamiokande result dust ring illuminated by SN-shockdust ring illuminated by SN-shock

High energy neutrino astronomy

Moisei Markov (mid 1950‘s):proposal for deep underground and underwater neutrino observatories

Motivation:

are weak interactions of Fermi-Type or isthere an intermediate boson?

Does the cross section rise with E2 forever?

Could there be 2 different neutrinos?

MACRO, FREJUS, DUMAND

Lake Baikal, AMANDA, …„We propose to install detectors deep in a lake or inthe sea and to determine the direction of charged particles with the help of Cherenkov radiation“Proc. 1960, ICHEP, Rochester, p. 578

„We propose to install detectors deep in a lake or inthe sea and to determine the direction of charged particles with the help of Cherenkov radiation“Proc. 1960, ICHEP, Rochester, p. 578

Moisei Alexandrovich MarkovMarkov warned the soviet leaders in 1947 about „dangerous political-ideological moves that threaten to separate soviet science from thre rest“

This was a brave (almost suicidal) move, as he and other scientists were charged of not sufficiently quoting Russian scientists and „uncritically receiving western physical theories and propagandizing them in our country“

Stalin, however, „chose the atomic bomb over ideology“ which saved their lives …

Later, Markov became active in promoting disarmament

Markov warned the soviet leaders in 1947 about „dangerous political-ideological moves that threaten to separate soviet science from thre rest“

This was a brave (almost suicidal) move, as he and other scientists were charged of not sufficiently quoting Russian scientists and „uncritically receiving western physical theories and propagandizing them in our country“

Stalin, however, „chose the atomic bomb over ideology“ which saved their lives …

Later, Markov became active in promoting disarmament

Dumand

4800 m depth at Hawaii shore4800 m depth at Hawaii shore

Dumand

Prototype string 1987Prototype string 1987

junction box at 4800 m depthsea floorjunction box at 4800 m depthsea floor

1993/94 deployment failed due to leak in penetratororiginal project (256 PMTs) was abandoned1993/94 deployment failed due to leak in penetratororiginal project (256 PMTs) was abandoned

Lake Baikal / AMANDA

1993-20001.5 km deep576 modules

1993-20001.5 km deep576 modules

1993-19981.1 km deep192 modules

1993-19981.1 km deep192 modules

• Direct production of neutrinos– Sun– Supernovae– Geo neutrinos etc

• Acceleration of nucleons

• Neutrinos from „beam dumps“ of accelerated nucleons– nucleon proton and nucleon gamma interactions– Waxman Bahcall bound

Neutrino sources

later

….

later

….

Astrophysical neutrino flux

1.9 K cosmic background neutrinos 6 x 60/cm3

σ@ 1.7x10-4 eV ~10-55 cm2

Solar O(1 MeV) neutrinos

Supernova O(10 MeV) neutrinos

Atmospheric O(1-1000 GeV) μ-neutrinos

AGN O(10 TeV) neutrinos

20 decades in energies30 decades in fluxes20 decades in cross sections

20 decades in energies30 decades in fluxes20 decades in cross sections

How does the acceleration work?

• Supernova explosion emits fast matter streams O(106…7m/s)

• Shock fronts from when matter stream hits interstellar matter

• some “lucky” particles pass shock fronts frequently and obtain accelerating “kicks”

A. Reimer

example: acceleration in supernova remnant shock frontsexample: acceleration in supernova remnant shock fronts

Dynamics of a shock front

Each time a particle crosses front, it enters “an approaching medium”

the shock front as such

the upstream rest system

the downstream rest system

the shock front rest system

Charles Jui

Acceleration in a shock front• Assume relativistic particle, p~E, at one side of shock• If particle crosses shock, its energy in the rest frame on the other side

for vertical crossing is given by:

• Multiple crossings yield increasing energy; require “turn-around” of particle in magnetic fields

• Escape probability per cycle ~u/c

The Hillas plot

• Which object accelerates to what energies?

• Difficult to explain energies >~1021 eV for protons

• Easier for heavy nuclei

ZqBRcE

ZqBRp

R

ZqB

pRgyro

2

2

2)(

protonsprotons

c: velocity of scattering centers, transforms R< 2Rgyro R< 2Rgyro/

• Neutrinos from „beam dumps“– Proton proton and proton gamma interactions– Waxman Bahcall bound

High energy neutrinos

p, Np, N

, N, N

, K, Kμμ

μμ

ee

eeμμ

00

expect:

μ : e : = 2 : 1 : 1

however, energydistributions different!

expect:

μ : e : = 2 : 1 : 1

however, energydistributions different!isospin!isospin!

Nucleons interact with ambient photons around source and baryonic matter …Nucleons interact with ambient photons around source and baryonic matter …

Proton proton cross sections

Proton gamma cross sectionCross section ~ 400 times smaller than for pp

Transparency of the UniverseE

nerg

y

„seeing“ range

excluded due tomessenger interactionwith photon background

photons of all energies aboundin universe (3K visible)

interactions with p and γ:

p + γ(3K) (1232) p + π

γ + γ(IR + 3K) e+ e-

limits „seeing“ range …

…transparency of the Universe

• Only ’s can “see” beyond local Universe above 100 TeV

• Only ’s can escape from dense environments

• Only ’s can unambiguously prove hadronic acceleration

useful range for point searches:

99%

of u

nive

rse

99.9

9999

9%

3x105 3x107 3x109 Ly

Our vicinity

us

105 Ly

25 x 10 5 Ly

1.5 x 105 Ly

60 MiILLION LIGHTYEARS

Local groupNot to scale !

Our vicinity

us

105 Ly

25 x 10 5 Ly

1.5 x 105 Ly

60 MiILLION LIGHT YEARS

1020 eV p, 100 TeV : seeing range 60 million light years

Galaxies and stars within 60 million Ly

… our vicinity

us

105 Ly

25 x 10 5 Ly

1.5 x 105 Ly

400 MiILLION LIGHT YEARS

100 GeV : 500 million light years

• average path length LA for a particle A travelling through medium of particles B with number density B

LA = 1 / (B)

Order of magnitude for 1 TeV neutrinos in open space:

TeV) = 10-39 m2, = 0.4/cm3 L = 2.5 x 1022 Ly

larger than size of universe …

• Blessing and curse of neutrino astronomy:

– neutrinos pass through almost everything … also through the detector

Absorption length for neutrinos

Waxman-Bahcall limit

Idea: constrain possible neutrino flux from extragalactic cosmic ray intensityIdea: constrain possible neutrino flux from extragalactic cosmic ray intensity

power required over 1010 years to producecosmic ray flux: power required over 1010 years to producecosmic ray flux:

yearMpc

erg3

4410

conservatively assume that energy generation rate increases with redshift at maximal rate astronomically observed …conservatively assume that energy generation rate increases with redshift at maximal rate astronomically observed …

Assume „optically thin sources“: I=I0exp(-p) with p<1Assume „optically thin sources“: I=I0exp(-p) with p<1

Assume that nucleons interacting in surroundingmaterial by p (and pp, pn) interaction pions and kaons neutrinos

Assume that nucleons interacting in surroundingmaterial by p (and pp, pn) interaction pions and kaons neutrinos

Extrapolate to lower energy assuming E-2 fluxExtrapolate to lower energy assuming E-2 flux

…. Waxman Bahcall bound

1122

8

srscm

GeV109.1

E

p

1122

8

srscm

GeV109

E

pp

for pΔ++nfor pΔ++n

for ppNN+pionsfor ppNN+pions

limit mostly quoted as 5x10-8

Note that oscillations give factor 0.5limit mostly quoted as 5x10-8

Note that oscillations give factor 0.5

Note that this is a (conservative) upper limit for „thin“ sources!

Waxman-Bahcall: expected flux factor 5/p smaller !

Note that this is a (conservative) upper limit for „thin“ sources!

Waxman-Bahcall: expected flux factor 5/p smaller !

Optical thick sources (like AGN cores) absorb cosmic rays (p~100) limit not applicable

Optical thick sources (like AGN cores) absorb cosmic rays (p~100) limit not applicable

… Waxman-Bahcall bound

Include oscillations: Waxman-Bahcall limit x 3/2 for sum of all neutrino flavorsInclude oscillations: Waxman-Bahcall limit x 3/2 for sum of all neutrino flavors

Neutrino Oscillations

• Oscillation phenomenons

• MSW effects in Sun, Earth and Supernovae

• Collective Oscillations

Bruno Pontecorvo 1913-1993Bruno Pontecorvo 1913-1993

Bruno PontecorvoBruno Pontecorvo (born 22.8.1913, Pisa, died 24. 9. 1993, Dubna)

an Italian-born physicist who was a pioneer in the study of the elusive subatomic particles called neutrinos and who defected to the Soviet Union in 1950, died in Dubna, outside Moscow. He was 80. Mr. Pontecorvo was one of a group of talented young physicists who worked with Enrico Fermi in Rome in the early 1930's on experiments that proved radioactive isotopes of a number of elements can be produced by exposing the elements to neutrons that have been slowed down.

After Mussolini passed laws that discriminated against Jews, Mr. Pontecorvo moved to Paris and left for the United States in 1940 after the Nazi invasion.

He worked briefly for an American oil company and then moved to Canada, where he applied to become a British citizen. In 1948, after he completed his naturalization, he moved to England to join the Atomic Energy Research Laboratory at Harwell, near Oxford.

But in the late summer of 1950, Mr. Pontecorvo and his family disappeared during a vacation in Rome. They were last seen in Helsinki on Sept. 2, 1950, and were believed to have taken a ship to the Soviet Union with the help of Soviet diplomats in the Finnish capital. It was not until 1955, whenMr. Pontecorvo published articles in Pravda and Izvestia, that officials were certain he was working in the Soviet Union.

His defection, which came the same year that one of his colleagues, Klaus Fuchs, was convicted of espionage in Britain, raised fears that the Italian scientist had fled with secrets that could be used to help build a hydrogen bomb. Another colleague, Alan Nunn May, was convicted of espionage charges in Canada in 1946.

But in frequent statements to the press in the Soviet Union, and during his first trip back to Italy in 1978, he maintained that his research in Canada and England had no military applications. He said he had defected to pursue nuclear research for peaceful purposes because investigations into scientific espionage had made it too difficult for him to work.

"In 1950, the atmosphere was such that I could no longer breathe," he wrote in the 1955 article in Pravda. In the article, he also said that he had signed a petition along with several other nuclear scientists calling for a worldwide ban on nuclear weapons.

His British citizenship was revoked because it was believed he defected with military secrets, but he was never charged with espionage. He is known in his field for being one of the first physicists to suggest using a solution containing chlorine to detect neutrinos.

Bruno Pontecorvo (born 22.8.1913, Pisa, died 24. 9. 1993, Dubna)

an Italian-born physicist who was a pioneer in the study of the elusive subatomic particles called neutrinos and who defected to the Soviet Union in 1950, died in Dubna, outside Moscow. He was 80. Mr. Pontecorvo was one of a group of talented young physicists who worked with Enrico Fermi in Rome in the early 1930's on experiments that proved radioactive isotopes of a number of elements can be produced by exposing the elements to neutrons that have been slowed down.

After Mussolini passed laws that discriminated against Jews, Mr. Pontecorvo moved to Paris and left for the United States in 1940 after the Nazi invasion.

He worked briefly for an American oil company and then moved to Canada, where he applied to become a British citizen. In 1948, after he completed his naturalization, he moved to England to join the Atomic Energy Research Laboratory at Harwell, near Oxford.

But in the late summer of 1950, Mr. Pontecorvo and his family disappeared during a vacation in Rome. They were last seen in Helsinki on Sept. 2, 1950, and were believed to have taken a ship to the Soviet Union with the help of Soviet diplomats in the Finnish capital. It was not until 1955, whenMr. Pontecorvo published articles in Pravda and Izvestia, that officials were certain he was working in the Soviet Union.

His defection, which came the same year that one of his colleagues, Klaus Fuchs, was convicted of espionage in Britain, raised fears that the Italian scientist had fled with secrets that could be used to help build a hydrogen bomb. Another colleague, Alan Nunn May, was convicted of espionage charges in Canada in 1946.

But in frequent statements to the press in the Soviet Union, and during his first trip back to Italy in 1978, he maintained that his research in Canada and England had no military applications. He said he had defected to pursue nuclear research for peaceful purposes because investigations into scientific espionage had made it too difficult for him to work.

"In 1950, the atmosphere was such that I could no longer breathe," he wrote in the 1955 article in Pravda. In the article, he also said that he had signed a petition along with several other nuclear scientists calling for a worldwide ban on nuclear weapons.

His British citizenship was revoked because it was believed he defected with military secrets, but he was never charged with espionage. He is known in his field for being one of the first physicists to suggest using a solution containing chlorine to detect neutrinos.

IntroductionBasic idea (Pontecorvo, 1957):

If neutrinos have small and different masses:

flavour eigenstate = e, μ , of weak interactions propagation mass eigenstate i = 1, 2 ,3

Basic idea (Pontecorvo, 1957):

If neutrinos have small and different masses:

flavour eigenstate = e, μ , of weak interactions propagation mass eigenstate i = 1, 2 ,3

… nothing special, typical quantum mechanical effect relating orthonormal vectors… nothing special, typical quantum mechanical effect relating orthonormal vectors

Eigenstates connected by unitäry 3 x 3 matrix UiEigenstates connected by unitäry 3 x 3 matrix Ui

111

111

331

UUU

UUU

UUU

U

ii

i

ii

i

U

U

Neutrino Oscillation (3 flavors)

…this formula assumes that all components of U are real, there is no CP-violation, and neutrinos are of Dirac type…this formula assumes that all components of U are real, there is no CP-violation, and neutrinos are of Dirac type

Assume you produce a at t = 0:

Simple case: 2 neutrino flavors

LoscLosc

3-Flavor neutrino oscillationssin22θ13 = 0.08

sin22θ13 = 0.08

Red:

blue:

black: e

Status of neutrino oscillation parameters

Mixing angles:Mixing angles: Mass differences:Mass differences:

CP-violation parameter , Majorana parameters 1, 2 and sign of m232 unknown CP-violation parameter , Majorana parameters 1, 2 and sign of m232 unknown

if m1=0: m20.009 eV 5x 10-7 me; m30.05 eVif m1=0: m20.009 eV 5x 10-7 me; m30.05 eV

Cosmological relevanceContribution to energy budget of the Universe:

stretching cosmology < 0.2 eV?

Neutrinos from far away sources

ad 1: Neutrinos are created as flavor eigenstates (e, μ , ) identified by energy, momentum, spin direction and neutrino flavor

ad 2: • Neutrino oscillation length much shorter than travel distance• Source extension larger than oscillation length• Broad energy spectrum leads to varying oscillation lengths• Wave packets separate so that oscillations are no longer possible

What remains is an averaged effect:

ad 1: Neutrinos are created as flavor eigenstates (e, μ , ) identified by energy, momentum, spin direction and neutrino flavor

ad 2: • Neutrino oscillation length much shorter than travel distance• Source extension larger than oscillation length• Broad energy spectrum leads to varying oscillation lengths• Wave packets separate so that oscillations are no longer possible

What remains is an averaged effect:

1. Which information does a neutrino carry when it is created?2. What happens on the way to detector?3. What can be measured in the detector?

1. Which information does a neutrino carry when it is created?2. What happens on the way to detector?3. What can be measured in the detector?

22

ii

i UUP

…neutrinos from far away sources

bcsUUUUUUP

bcsUUUUUUP

bascUUUUP

eeii

eie

eeii

eie

eeeii

eiee

212

212

2

2

2

2

2

1

2

1

22

212

212

2

2

2

2

2

1

2

1

22

412

412

4

2

4

1

2221

assume that Ue3 = 13 = 0, 23=450 …assume that Ue3 = 13 = 0, 23=450 …

first assume only e production at source: e : μ : = 1 : 0 : 0first assume only e production at source: e : μ : = 1 : 0 : 0

2

1

2

1122

112

2

1

2

1122

112

1212 0

cs

cs

sc

U i

fluxes at Earth: e : μ : = 1-2b : b : bfluxes at Earth: e : μ : = 1-2b : b : b

…neutrinos from far away sources

flux at source: e : μ : = 1 : 0 : 0 flux at Earth: e : μ : = 1-2b : b : bflux at source: e : μ : = 1 : 0 : 0 flux at Earth: e : μ : = 1-2b : b : b

flux at source: e : μ : = 0 : 1 : 0 flux at Earth: e : μ : = b : c : c (*)flux at source: e : μ : = 0 : 1 : 0 flux at Earth: e : μ : = b : c : c (*)

flux at source: e : μ : = 0 : 0 : 1 flux at Earth: e : μ : = b : c : cflux at source: e : μ : = 0 : 0 : 1 flux at Earth: e : μ : = b : c : c

from pion decay with subsequent muon decay at source expect: e : μ : = 1 : 2 : 0

from pion decay with subsequent muon decay at source expect: e : μ : = 1 : 2 : 0

flux at Earth: e : μ : = 1-2b+2b : b+1-b : b+1-b = 1 : 1 : 1

flux at Earth: e : μ : = 1-2b+2b : b+1-b : b+1-b = 1 : 1 : 1

(*) 2 sin2cos2=1-sin4-cos4 2c=1/2(a+1)=1-b(*) 2 sin2cos2=1-sin4-cos4 2c=1/2(a+1)=1-b

for pion decay expect equal fluxes of neutrino species at Earth, independent on value for 12 !!however, energy distribution of e and μ and thus detection thresholds are different …

for pion decay expect equal fluxes of neutrino species at Earth, independent on value for 12 !!however, energy distribution of e and μ and thus detection thresholds are different …

…neutrinos from far away sources

ad 3: What is measured at the detector?

Before reaching the detector several additional effects happen:•the neutrino undergoes oscillations in Earth (not relevant for high energies)•the neutrino may get absorbed

ad 3: What is measured at the detector?

Before reaching the detector several additional effects happen:•the neutrino undergoes oscillations in Earth (not relevant for high energies)•the neutrino may get absorbed

(E/TeV)

_105.3

(E/TeV)

105.4

105.5(E/TeV) m106.7

1066.1 714

33240-

27 diameterEarthm

mkg

kgud

mean free path length in the Earth:mean free path length in the Earth: