Seeing the Sky Underground

The Birth of Neutrino Astronomy

Chiaki Yanagisawa

Stony Brook University

October 13, 2007Custer Institute

History of Cosmic Rays/Neutrino Astronomy Researches

1921 Hess discovered cosmic rays (CRs)

1932 Anderson found the first antimatter : anti-electron (positron)

1937 Discovery of muon by Anderson

Birth of elementary particle physics

1949 Fermi’s theory of CR acceleration

1962 Cosmic Microwave Background (CMB) radiation discovered

First 1020 eV CR detected

1966 Proposal of GZK cutoff

Relic from Big Bang1 eV: Energy acquired by an electron in 1 V

p + CMB -> Ncutoff=5x1019 eV

Interaction of CR proton with

CMB radiation

1019 eV

1020 eV

1967 Ray Davis detected first solar neutrinos

1979 Masatoshi Koshiba got a new idea using water for proton decays

1981 Kamiokande started

Birth of neutrino astronomy

1987 Neutrinos from Supernova SN1987A

1991 Super-Kamiokande (SK) construction started

observed by Kamiokande/IMB

Fly’s Eye detected 3x1020 eV CR

1994 AGASA detected 2x1020 eV CR

Probably CRs hit their heads?

CR

1996 SK started to take data

1998 Discovery of atmospheric neutrino oscillation by SK2002 Confirmation of solar neutrino oscillation by SNO

Ray Davis

MasatoshiKoshiba

Nobel Prize to Davis,Koshiba,&Giacconi

History of Cosmic Rays/Neutrino Astronomy Researches

CR

Particle Physics

Model of Atoms

electrons e-

nucleus

Old view

Semi-modern view

Modern view

nucleusquarks

prot

on

What is the world made of?

Particle Physics

Building Blocks of Matter

Discoveries of too many “elementary” particles lead to morefundamental model the Standard Model.

Proton p : uud

Neutron n : udd

Pion + : ud-

Particles made of quarks arecalled hadrons

What is matter made of?

Particle Physics

Fundamental Forces

There are four know fundamental forces:

An example:Free neutron decay

How many kinds of forces are there?

Particle Physics

Fundamental Forces

An example of weak interaction

Free neutron decay: n p + e-e

-

Particle Physics

Unification of Forces

Grand Unified Theories (GUTs)

Strong

Electric

Magnetic

Electromagnetic

Weak

Electroweak

Gravitational

GU

Ts

hard

19th c.

20th c.

21st c.?

GUTs predict:

Nucleon decays

Neutrino mass/oscillation

What is our dream?

Particle Physics

Neutrino Oscillation

There are three kinds of neutrinos: e

If neutrinos have mass, they can change their identities (flavors)

e

A simple example:

=

2

cos

+ cos

- sin

sin =

1

1

2

neutrinos with definite mass

Probability 1-Probability

Pro

babi

lity

Neutrino pathlength (km)

It depends onneutrino energy,masses and

What is neutrino oscillation?

(flavors)

~Earth’s diameter 12,000 km

Atmospheric Neutrinos

Source of atmospheric neutrinos

Earth’s atmosphere is constantlybombarded by cosmic rays.

Energetic cosmic rays (mostlyprotons) interact with atoms inthe air.

These interactions produce manyparticles-air showers.

Neutrinos are produced in decaysof pions and muons.

Atmospheric Neutrinos

Underground Experiments to avoid most of cosmic rays

Ray Davis experiment detectedthe first solar neutrinos usingChlorine Cl at Homestake

Kamiokande detected the firstneutrinos from a supernova usingwater (3,000 tons).

Atmospheric Neutrinos

Super-Kamiokande: The successor of highly successful Kamiokande

50,000 tons of pure water equipped with 12,000 50 cm photomultipliersand 2,800 20 cm photomultipliers (PMTs).

40 m diameter

40 m

he

ight

1,000 m deep

Physicists are having fun on a boat in Super-Kamiokande

A physicist is checking installed photomultipliers

Physicists are preparing photomultipliers: See how big they are!

Atmospheric Neutrinos

Water Cherenkov Detector: Kamiokande,IMB,Super-Kamiokande,SNO

Water is cheap and easy to handle!

When the speed of a chargedparticle exceeds that of lightIN WATER, electric shockwaves in form of light are generated similar to sonic boomsound by super-sonic jet plane .

These light waves form a coneand are detected as a ring bya plane equipped by photo-sensors.

How does a water Cherenkov detector work?

Atmospheric Neutrinos

How do we detect atmospheric muon and electron neutrinos ?

electron-like ring

muon-like ring

+ n -> p +

e

+ n -> p +

e-

Major interactions:

Most of time invisible

An event produced by an atmosphericmuon neutrino

Atmospheric Neutrinos

How do we see neutrino oscillation in atmospheric neutrinos?

Pro

babi

lity

(

N

eutr

ino

path

leng

th

cos (zenith angle)

downward-goingupward-going

Actual probability for measured zenith angledue to measurement errors

a

b

cos = a/b

Atmospheric NeutrinosEvidence of neutrino oscillation/mass

low energye

high energye

low energy

high energy

with oscillation

without oscillation

First crack in the Standard Model!!!

Solar Neutrinos How does the Sun shine?

Nuclear fusions generate: - energy/heat/light - neutrinos

1 MeV = 1x106 eV

Kamiokande

Solar Neutrinos How do we detect solar neutrinos?

Ray Davis Homestake Experiment: 615 tons

Counts the number of 37Arusing a chemical methods

Kamiokande,Super-Kamiokande:3,000 tons , 50,000 tons

- Detect the recoil electron which is kicked by a solar neutrino out of a water molecule.

- Can measure the energy and direction of the recoil electron.

Solar Neutrinos

Solar neutrinos

background

Seeing the Sun undergraound

Image of Sun by Super-Kamiokande

How do we see the Sun?

e

e

Solar Neutrinos

Summer: 4 Jul. 156 million km

Winter : 3 Jan. 146 million km

Distance Earth-Sun

Solar neutrino flux ~ (1/distance)2

Seeing the Earth’s Orbit Underground!

Note: Flux less than half of expected (deficit)!!!

Solar Neutrinos How do we see neutrino oscillation with solar neutrinos?

Homestake : 0.27+- 0.06

Kamiokande : 0.44+- 0.06Super-Kamiokande : 0.465+-0.005+0.016-0.015

Flux: measured/expected

Neutrino deficit!!!

is not visible to allexperiments above

Solar Neutrinos How can we prove it’s neutrino oscillation?

Neutral current

SNO experiment uses heavy water D2O instead of normal water H2O

Solar Neutrinos How does the neutral current confirm neutrino oscillation?

Elastic scattering Neutral current interaction

-This reaction is available only for e . -This reaction is flavour blind and is available for all kinds of neutrinos.

-Available for both water and heavy water. - Available only for heavy water.

Solar Neutrinos Confirmation of solar neutrino oscillation by SNO

is visible only to SNOBut not to Homestake, Kamiokande or Super-Kamiokande.

Even if solar neutrinoe

changes its flavour to

or total flux of solarneutrino can be measuredby SNO

Solar flux measured: 6.4+-1.6 x 106 cm-2 s-1

Solar flux predicted : 5.1+-1.0 x 106 cm-2 s-1

Solar neutrinos oscillate!!!!

Supernova

Supernova

Supernova

SN 1987A, Feb.23, 1987 in Large Magellanic CloudAt about 170,000 light years away

Before After

Neutrinos from this SN were observed by Kamiokande and IMB12 events 8 events

10 sec

Supernova

Background level

Birth of a supernova witnessed with neutrinos

How do we know detected neutrinos are from a supernova?

Kamiokande

Num

ber

of p

hoto

mul

tipl

iers

fir

edA few hours before optical observation

Taken by Hubble Telescope ( 1990)

Supernova Why is detection of supernova neutrinos important?

- Properties of neutrinos: its mass (or limit of it), magnetic moment,electric charge, etc.

- Details of supernova explosion: how a star dies

We learn:

- How a neutron star or a black hole is formed if it happens

Nobel Prize for Physics in 2002

The first detection of solar neutrinos by Ray Davis’s chlorineexperiment, and the subsequent confirmation by Kamiokande using real-time directional information and the first detectionof supernova neutrinos opened up a new exciting field ofneutrino astronomy. For these great achievements Ray Davisand Masatoshi Koshiba shared a Nobel Prize with RiccardoGiaconni who is the founding father of x-ray astronomy.

Ray Davis Masatoshi Koshiba Riccardo Giocconi

Nobel Prize for Physics in 2002

At Kamioka with Prof.Koshiba At Stony Brook with Dr.Davis

What’s Next? Are all the mysteries solved?

ANTARES

Auger Project

GZK cutoff

?

- Origin of ultra high energy cosmic rays around and beyond cutoff

- Are there any other neutrino point sources?

-Where is all the missing mass?