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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?