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Cecilia Lunardini Institute for Nuclear Theory University of Washington http://www.int.washington.edu/users/lunardi/ Slide 2 The subatomic world: particles We are made of atoms Atoms are made of particles Only some particles stay inside atoms There is a whole zoo of free particles Slide 3 We are particle investigators Billions of particles arrive here every day from space! Why are they here? Where do they come from? What are they? We capture them to learn Slide 4 The elusive neutrinos They are invisible! No trace in optical devices (telescopes, etc.) Three species : Electron neutrino Muon neutrinoTau neutrino Slide 5 They are everywhere! about 300 in a teaspoon volume (1 cubic cm) from 1 second after the Big Bang 60 billions every second across your thumbs nail (1 square cm) from the Sun http://www-istp.gsfc.nasa.gov/istp/outreach/sunspotting.html http://hubblesite.org/gallery/album/ Slide 6 How we thought they behaved The old theory of neutrino behavior Slide 7 The mass-less neutrino The mass myself: 50 Kg (110 lb) A particle (proton): Most particles have some mass The neutrino was believed to have no mass proton neutrino 50 Kg 80 billions of billions of billions Slide 8 Mass-less particles have a very ordinary life Born (e.g., in the Sun) Travel at speed of light Get caught (absorbed) by matter (e.g., on Earth) Slide 9 The puzzle of the missing neutrinos Slide 10 The neutrino trap Experimenter Raymond Davis decided to count the neutrinos from the Sun To check the nuclear reactions inside the Sun He made a neutrino trap made of cleaning fluid (containing Chlorine) Slide 11 The trap worked similarly to a colander: Slide 12 The prediction Theorist John Bahcall calculated the number of neutrinos expected in the trap Using knowledge of the Sun He found 9 Solar Units Photo from http://www.sns.ias.edu/~jnb/JohnphotosHtml/ Slide 13 Something was wrong The counted neutrinos were only 2 and Solar Units !! Only about 1/3 of the prediction prediction Slide 14 How they actually do behave The new theory of neutrino behavior Slide 15 Are we catching everyone? The Sun only emits neutrinos of the electron species The trap is unable to catch the muon and tau species!! Slide 16 Are neutrinos mutants? Theorist Bruno Pontecorvo had an idea What if some neutrinos mutate from electron to muon species on the way? Slide 17 A lot of thinking was done Bruno Pontecorvo Alexei Smirnov Lincoln Wolfenstein Stas Mikeyev See http://www.sns.ias.edu/~jnb/ for more photoshttp://www.sns.ias.edu/~jnb/ Slide 18 New theory: neutrinos with mass Maybe the neutrinos have mass.. If so, the electron neutrino and the muon neutrino could be like two sides of the same object Muon neutrino Electron neutrino Slide 19 The oscillations idea The neutrinos could rotate (oscillate) They rotate while the travel Slide 20 Those neutrinos that arrive as muon are missed! Slide 21 You probably know what to do. Slide 22 Lets make a better trap! A colander that catches everyone: Slide 23 The technological challenge Thousands of tons of water (and heavy water) were needed Photo: Kamioka Observatory, ICRR, The University of Tokyo Sudbury Neutrino Observatory, Sudbury, Canada Slide 24 And, finally bingo!! With an all species trap the numbers matched! Neutrinos counted Neutrinos predicted Slide 25 Nobel prize soon came Raymond Davis Masatoshi Koshiba Photo: http://www.yasooo.com/en/people/color2/02.htmlhttp://www.yasooo.com/en/people/color2/02.html December 2002 Slide 26 The fundamental meaning Ok, the neutrinos have mass. But, why is this interesting?? Slide 27 Particles have mass if they can hold hands: Neutrinos are unable to hold hands They are all left-armed Slide 28 Something exotic must happen Probably a new particle helps them! Indication of a new species!! Slide 29 Neutrinos outside the solar system A gallery Slide 30 Exploding stars: supernovae Gravitational energy is converted into neutrinos Huge storm of neutrinos floods the Earth for 10-15 seconds More powerful than all the stars of the universe together Slide 31 In 1987 the star Sanduleak (in the Large Magellanic Cloud) went supernova Kamiokande (Japan) and IMB (USA) captured the neutrinos Slide 32 The gamma ray emitters Exotic supernovae emit powerful flashes of gamma rays Mistaken for new weapon of the Soviet Union. Still mysterious Neutrinos come together with the gamma rays More energetic than any human technology Slide 33 The dark neutrinos The mysterious Dark Matter contains neutrinos Primordial, from the Big Bang http://hubblesite.org/gallery/album/ Slide 34 Slide 35 Slide 36 Slide 37 The question of the mass Speed of light: C= 300000 Km/s ( mph) Human being: m=80 kg (~ 160 lb) E = Slide 38 Mass and neutrino behavior How much do neutrino weigh? Slide 39 Even man-made neutrinos go missing Slide 40 The elusive neutrinos They are invisible! No trace in optical devices (telescopes, etc.) Three flavors