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) radiation discovered First eV CR detected 1966 Proposal of GZK cutoff Relic from Big Bang 1 eV: Energy acquired by an electron in 1 V p +  CMB -> N  cutoff=5x10 19 eV Interaction of CR proton with CMB radiation eV 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 3x10 20 eV CR 1994 AGASA detected 2x10 20 eV CR Probably CRs hit their heads? CR 1996 SK started to take data 1998 Discovery of atmospheric neutrino oscillation by SK 2002 Confirmation of solar neutrino oscillation by SNO Ray Davis Masatoshi Koshiba 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 nucleus quarks proton What is the world made of?

Particle Physics 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  + : ud - Particles made of quarks are called 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 GUTs hard 19 th c. 20 th c. 21 st 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  = neutrinos with definite mass Probability  1-Probability   Probability Neutrino pathlength (km) It depends on neutrino energy, masses and  What is neutrino oscillation? (flavors) ~Earth’s diameter 12,000 km 

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 to avoid most of cosmic rays Ray Davis experiment detected the first solar neutrinos using Chlorine Cl at Homestake Kamiokande detected the first neutrinos from a supernova using water (3,000 tons).

Atmospheric Neutrinos Super-Kamiokande: The successor of highly successful Kamiokande 50,000 tons of pure water equipped with 12, cm photomultipliers and 2, cm photomultipliers (PMTs). 40 m diameter 40 m height 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 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 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 e-e- Major interactions: Most of time invisible

An event produced by an atmospheric muon neutrino

Atmospheric Neutrinos How do we see neutrino oscillation in atmospheric neutrinos? Probability (     Neutrino pathlength cos (zenith angle) downward-going upward-going Actual probability for measured zenith angle due to measurement errors  a b cos  = a/b

Atmospheric Neutrinos Evidence of neutrino oscillation/mass low energy  e high energy  e 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 = 1x10 6 eV Kamiokande

Solar Neutrinos How do we detect solar neutrinos? Ray Davis Homestake Experiment: 615 tons Counts the number of 37 Ar using 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 : Kamiokande : Super-Kamiokande : Flux: measured/expected Neutrino deficit!!!  is not visible to all experiments above

Solar Neutrinos How can we prove it’s neutrino oscillation? Neutral current SNO experiment uses heavy water D 2 O instead of normal water H 2 O

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 SNO But not to Homestake, Kamiokande or Super- Kamiokande. Even if solar neutrino  e changes its flavour to  or  total flux of solar neutrino can be measured by SNO Solar flux measured: x 10 6 cm -2 s -1 Solar flux predicted : x 10 6 cm -2 s -1 Solar neutrinos oscillate!!!!

Supernova

SN 1987A, Feb.23, 1987 in Large Magellanic Cloud At about 170,000 light years away Before After Neutrinos from this SN were observed by Kamiokande and IMB 12 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 Number of photomultipliers fired A 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 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 DavisMasatoshi KoshibaRiccardo Giocconi

Nobel Prize for Physics in 2002 At Kamioka with Prof.KoshibaAt 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?