The Little Neutral One (The neutrino and it’s detection) Presented by: André M. Gagnier For: Questions contemporaines en physiques (PHY3903)

Plan Brief history of the neutrino Physical properties of the neutrino Detection of neutrinos Sudbury Neutrino Observatory (SNO) AMANDA observatory The future and beyond!

Brief History of the Neutrino In 1930, Wolfgang Pauli proposed the existence of a particle that was “not detectable”, later named ‘neutrino’ by Enrico Fermi. This was bizzare in the fact that the particle was proposed theoretically without any experimental proof. W Pauli ( )

What lead to the “Neutrino Theory” β-decay: M(A, Z +1) D(A, Z) + e - * Missing energy Non-conservation of the angular momentum (spin) n p + e - + ν e *The neutron was not discovered by James Chadwick ( ) until 1932.

Tricksy neutrinos (some properties) The neutrino is a product of nuclear reactions (see the Sun’s core, for example) Chargeless and nearly or completely massless (mass still debated) Three different flavours of neutrino: ν e (see previous slide) ν μ : π + μ + + ν μ ν τ : τ e + + ν e + ν τ

Comparative analysis Mass m (eV/c 2 ) Cross-section σ (cm 2 ) Mean-free-path (stellar atmoshpere: ρ ~ (g/cm 3 )) (cm) Hydrogen Atom H 1.67 x x x Neutrino υ< * Photon γ x 10 7 * 1 au = 1,4960 x (cm)

Detection of the neutrino It took 26 years to prove the existance of the neutrino. In 1956 Clyde Cowan and Frederick Reines were the first to discover Pauli’s “undetectable particle”. They based themselves on the reaction: υ e + p e + + n

Two scientists and some distant relatives Clyde Cowan ( ) and Fred Reines ( ) My mom and maternal grand- parents (25 years ago): Brenda Gagnier and Miles and Margaret Cowan.

The Cowan-Reines Detector 511 keV photon from e - - e + annihilation Followed μs later by a neutron capture reaction. Savannah River Nuclear Reactor, Georgia 4200 (L) of liquid scintillator υ e + p e + + n

Modern Neutrino Detectors There are currently neutrino detectors all over the world (many of them underground). Most of them are very massive (irony?...) Neutrino detectors have been set up on every continent. A couple examples...

Sudbury Neutrino Observatory (SNO) Uses 1000 tonnes of heavy water (D 2 O). Located in a mine, 6800 ft below ground. Shielded against background radiation Photomultiplier tubes capture photons emitted by Cherenkov radiation.

The Detector and one reaction Photos courtesy of SNO

SNO pictures (part 2) Photo courtesy of Ernest Orlando Lawrence Berkeley National Laboratory Photo courtesy of Ernest Orlando Lawrence Berkeley National Laboratory

Antarctic Muon and Neutrino Detection Array (AMANDA) Under ice, instead of under-ground. Detects Cherenkov radiation from the creation of muons. Points downwards, instead of upwards like reguliar telescopes.

Pictures of AMANDA

The Future and beyond... There are still many un-answered questions concerning the neutrino (mass or massless, for example). They act as messengers from the sky and continue to confirm/negate astrophysical theories. Start planning the 50 th Anniversary Party for next year!!!!! (Dr. Joós will cover the costs).

Sources The following websites: astr.gsu.edu/hbase/particles/neutrondis.html

Sources (continued)... And the following books: K Zuber, NEUTRINO PHYSICS, Institute of Physics Publishing, Philadelphia, 2004 H V Klapdor, NEUTRINOS, Springer-Verlag, New York, 1988 D Ostlie, MODERN STELLAR ASTROPHYSICS, Addison- Wesley

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LA FIN