Neutrino Oscillation - Stony Brook NN Group

Download Report

Transcript Neutrino Oscillation - Stony Brook NN Group

Seeing the Sky Underground
The Birth of Neutrino Astronomy
Chiaki Yanagisawa
Stony Brook University
October 13, 2007
Custer 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) Relic from Big Bang
radiation discovered
1 eV: Energy acquired
by an electron in 1 V
First 1020 eV CR detected
1966 Proposal of GZK cutoff
p + gCMB -> Np : Ecutoff=5x1019 eV
Interaction of CR proton with
CMB radiation
1019 eV
1020 eV
History of Cosmic Rays/Neutrino Astronomy Researches
1967 Ray Davis detected first solar neutrinos Birth of neutrino astronomy
1979 Masatoshi Koshiba got a new idea
using water for proton decays
1981 Kamiokande started
1987 Neutrinos from Supernova SN1987A
observed by Kamiokande/IMB
Ray Davis
1991 Super-Kamiokande (SK) construction started
Fly’s Eye detected
Probably CRs
hit their heads?
1994 AGASA detected 2x1020 eV CR
1996 SK started to take data
1998 Discovery of atmospheric neutrino oscillation by SK
2002 Confirmation of solar neutrino oscillation by SNO
Nobel Prize to Davis,Koshiba,&Giacconi
Particle Physics
What is the world made of?
Model of Atoms
Old view
electrons e-
Modern view
Semi-modern view
Particle Physics
What is matter made of?
Building Blocks of Matter
Discoveries of too many “elementary” particles lead to more
fundamental model the Standard Model.
Proton p
: uud
Neutron n : udd
Pion p
: ud
Particles made of quarks are
called hadrons
Particle Physics How many kinds of forces are there?
Fundamental Forces
There are four know fundamental forces:
An example:
Free neutron decay
Particle Physics
Fundamental Forces
An example of weak interaction
Free neutron decay: n p + e- + ne
Particle Physics
What is our dream?
Unification of Forces
Grand Unified Theories (GUTs)
20th c.
19th c.
21st c.?
GUTs predict:
Nucleon decays
Neutrino mass/oscillation
Particle Physics
What is neutrino oscillation?
Neutrino Oscillation
There are three kinds of neutrinos: ne
If neutrinos have mass, they can change their identities (flavors)
A simple example:
nm =
cos q n1 - sin q n
nt =
sin q n1 + cos q n2
neutrinos with definite mass
Neutrino pathlength (km)
~Earth’s diameter 12,000 km
It depends on
neutrino energy,
masses and q
Atmospheric Neutrinos
Source of atmospheric neutrinos
Earth’s atmosphere is constantly
bombarded by cosmic rays.
Energetic cosmic rays (mostly
protons) interact with atoms in
the air.
These interactions produce many
particles-air showers.
Neutrinos are produced in decays
of pions and muons.
Atmospheric Neutrinos
Underground Experiments
Ray Davis experiment detected
the first solar neutrinos using
Chlorine Cl at Homestake
to avoid most of cosmic rays
Kamiokande detected the first
neutrinos from a supernova using
water (3,000 tons).
Atmospheric Neutrinos
Super-Kamiokande: The successor of highly successful Kamiokande
40 m height
50,000 tons of pure water equipped with 12,000 50 cm photomultipliers
and 2,800 20 cm photomultipliers (PMTs).
1,000 m deep
40 m diameter
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 How does a water Cherenkov detector work?
Water Cherenkov Detector: Kamiokande,IMB,Super-Kamiokande,SNO
Water is cheap and easy to handle!
When the speed of a charged
particle exceeds that of light
IN WATER, electric shock
waves in form of light are
generated similar to sonic boom
sound by super-sonic jet plane .
These light waves form a cone
and are detected as a ring by
a plane equipped by photosensors.
Atmospheric Neutrinos
How do we detect atmospheric muon and electron neutrinos ?
muon-like ring
Major interactions:
ne + n -> p + enm + n -> p + mMost of time invisible
electron-like ring
An event produced by an atmospheric
muon neutrino
Atmospheric Neutrinos
Neutrino pathlength
How do we see neutrino oscillation in atmospheric neutrinos?
q cos q
= a/b
Probability (nm->nm)
cos (zenith angle)
Actual probability for measured zenith angle
due to measurement errors
Atmospheric Neutrinos
Evidence of neutrino oscillation/mass
with oscillation
without oscillation
low energy ne
low energy nm
high energy ne
high energy nm
First crack in the Standard Model!!!
Solar Neutrinos
How does the Sun shine?
Nuclear fusions generate:
- energy/heat/light
- neutrinos
1 MeV = 1x106 eV
Solar Neutrinos How do we detect solar neutrinos?
Ray Davis Homestake Experiment:
615 tons
3,000 tons , 50,000 tons
- Detect the recoil electron which is kicked by
a solar neutrino out of a water molecule.
Counts the number of 37Ar
using a chemical methods
- Can measure the energy and direction of the
recoil electron.
Solar Neutrinos How do we see the Sun?
Image of Sun by Super-Kamiokande
Solar neutrinos
Seeing the Sun undergraound
Solar Neutrinos
Seeing the Earth’s Orbit Underground!
Distance Earth-Sun
Summer: 4 Jul. 156 million km
Winter : 3 Jan. 146 million km
Solar neutrino flux ~ (1/distance)2
Note: Flux less than half of
expected (deficit)!!!
Solar Neutrinos How do we see neutrino oscillation with solar neutrinos?
Flux: measured/expected
: 0.27+- 0.06
: 0.44+- 0.06
Super-Kamiokande : 0.465+-0.005+0.016-0.015
nm is not visible to all
experiments above
Neutrino deficit!!!
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
-This reaction is available only for n e .
-Available for both water and heavy
Neutral current interaction
-This reaction is flavour blind and is
available for all kinds of neutrinos.
- Available only for heavy water.
Solar Neutrinos
Confirmation of solar neutrino oscillation by SNO
nm is visible only to SNO
But not to Homestake,
Kamiokande or SuperKamiokande.
Even if solar neutrino ne
changes its flavour to nm
or nt total flux of solar
neutrino can be measured
by 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!!!!
SN 1987A, Feb.23, 1987 in Large Magellanic Cloud
At about 170,000 light years away
12 events
8 events
Neutrinos from this SN were observed by Kamiokande and IMB 10 sec
Supernova How do we know detected neutrinos are from a supernova?
Birth of a supernova witnessed with neutrinos
Number of photomultipliers fired
A few hours before optical observation
Background level
Taken by Hubble Telescope
( 1990)
Why is detection of supernova neutrinos important?
We learn:
- Properties of neutrinos: its mass (or limit of it), magnetic moment,electric
charge, etc.
- Details of supernova explosion: how a star dies
- 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 chlorine
experiment, and the subsequent confirmation by Kamiokande
using real-time directional information and the first detection
of supernova neutrinos opened up a new exciting field of
neutrino astronomy. For these great achievements Ray Davis
and Masatoshi Koshiba shared a Nobel Prize with Riccardo
Giaconni 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?
-Where is all the missing
- Are there any other neutrino
point sources?
- Origin of ultra high energy
cosmic rays around and
beyond cutoff
GZK cutoff
Auger Project