THE NEUTRINO PARTICLE: HOW TO LEARN A GREAT DEAL BY OBSERVING NOTHING A DRAMA in Four Acts and a Dozen Scenes Haim Harari THE NEUTRINO PARTICLE: HOW TO LEARN A GREAT DEAL BY OBSERVING NOTHING A DRAMA in Four Acts and a Dozen Scenes Haim Harari

Act I BEFORE PRE-HISTORY Act I BEFORE PRE-HISTORY

Looking Back in Time The detector must observe the desired radiation, not the undesired one. SCENE 1 The edge of the universe Studying the beginning of the universe The beginning of the universe Distant observations "Conventional" astronomy: Visible light and other kinds of radiation "Obstacles": Clouds, the atmosphere Avoiding "background": A Dark night, no background radiation = 

Darkness The universe is "flat" and its total mass is known 70% - Dark energy 25% - Dark matter, mostly unknown 4% - Free Hydrogen and Helium 0.5% - Stars SCENE 2 The beginning of the universeComplete darkness Outer SpaceComplete darkness Most matter in every galaxyInvisible and dark Most matter in the universeInvisible and dark Most energy in the universeInvisible and dark Understanding the universe and its creation requires an intensive study of the invisible dark matter and energy

Light and other radiation, come to us from the surface of a star What happens inside the sun? What happens inside a star, when it is born? When it develops? When it explodes? The Inside story The temperature on the surface of the sun: thousands of degrees. The temperature inside the sun: millions of degrees. Understanding the secrets of the suns requires looking inside the sun Understanding the secrets of a star requires an "inside photograph" SCENE 3

Act II A “TERRIBLE” TALE ABOUT AN INVISIBLE PARTICLE Act II A “TERRIBLE” TALE ABOUT AN INVISIBLE PARTICLE

A 1  A 2 + e - e-e-  decay Dear Radioactive Ladies and Gentlemen SCENE 1

N 1  N 2 + e - e-e- e-e- e-e- e-e- The electron energy: Always the same? Dear Radioactive Ladies and Gentlemen SCENE 1  decay

Dear Radioactive Ladies and Gentlemen SCENE 1 The electron energy: Always the same? Experiment: Not at all. Every time a different energy Some energy is always missing Someone is "stealing" energy The Neutrino: Dark, invisible, penetrating, elusive, massless (?) Neutrino

N 1  N 2 + e - + e-e- e-e- e-e- e-e- Dear Radioactive Ladies and Gentlemen SCENE 1  decay

n  p + e - + n p n p e-e- e-e- e-e- e-e- e-e-  decay Dear Radioactive Ladies and Gentlemen SCENE 1

WE NEED A PROCESS, WHICH IS A MILLION TIMES "STRONGER“ ! WE NEED A PROCESS, WHICH IS A MILLION TIMES "STRONGER“ ! What is the source of energy of the sun? Burning conventional fuel? The mass is sufficient for thousands of years. But the sun exists billions of years. SCENE 2 The Secret of the Sun

A nuclear "fire" inside the sun All nuclear processes in the sun emit neutrinos the life story of every star is related to similar processes Creating the heavy chemical elements p n e, Hans Bethe We must: Look into the center of the sun Look into the center of the star SCENE 2 The Secret of the Sun

Nevertheless: +n  e - + p When 10 neutrinos pass through Earth, only one hits something. SCENE 3 Catching the thief Pauli:"I did a terrible thing. I postulated a particle, which cannot be discovered" 16

Reines-Cowan 1956 THE THIEF HAS BEEN CAUGHT! SCENE 3 Catching the Thief DetectorReactor

Act III "WHO ORDERED THAT?" Act III "WHO ORDERED THAT?"

p, n, e -, 1935: The Elementary Particles SCENE 1 And what would you like for dessert?

A comedy of errors Yukawa predicted 1935 Anderson-Nedermayer discovered 1937 The celebration started … and ended 1945 Powel discovered the Yukawa particle Anderson-Nedermayer remained with a shocking discovery p, n, e -, 1935: The elementary particles SCENE 1 And what would you like for dessert?  – 200 times heavier than the electron, but identical to it in all other properties

Meanwhile: Dozens of new particles All are made out of quarks Ordinary matter Heavy matter s  -  u d e - e e   The first neutrino beam in an accelerator A proof that there are two distinct kinds of neutrinos Schwarz Lederman Steinberge SCENE 1 And what would you like for dessert? And the neutrino?The electron comes with a neutrino  is also created with a neutrino Are these neutrinos identical?

11/11/1974 An indirect observation of an additional quark c Completing the "second generation" of building blocks SCENE 2 The November Revolution u d e e c s   t b   First generation Second generation Third generation No more! The standard model  tb  Within a year Discovery of the third "brother" of the electron Predicting the third neutrino Predicting the "third generation" of quarks

Does the neutrino have a mass? If so, it is tiny Theory: There is a good reason for a tiny mass, no explanation for a zero mass.    e   No reason for an identity between the two classifications Mixing and oscillations are expected A three-way schizophrenia SCENE 3 Reincarnation

Example: e Emitted from the sun. On its way to us, converts into   Emitted from an accelerator. On its way to detector converts into  Conclusion: Neutrino oscillations non-vanishing neutrino masses First experiments in accelerators and nuclear reactors – negative results! SCENE 3 Reincarnation

Act IV WE SEE NOTHING Therefore EVERYTHING IS CLEAR Act IV WE SEE NOTHING Therefore EVERYTHING IS CLEAR

What is happening inside the sun? Who can escape from the center of the sun and reach us on earth? Where can we "catch" a neutrino" Everywhere ! Where is the minimal "background"? Deep underground How do you catch neutrinos? SCENE 1 Underground Astronomy

 Ga     e + Ge 71 Gallex 30 tons 400 tons of cleaning fluid  Cl     e + A 37 Homestake SCENE 1 Underground Astronomy

e  + n  e + p Kamiokande 5000 tons water SCENE 1 Underground Astronomy Super-luminary "Boom"

Koshiba et al: The ratio between the types of neutrinos in cosmic radiation is also different from the expected ratio. SCENE 2 What did the fourth guest get for dessert? Davis et al: Number of neutrinos arriving from the sun is only one third of the expected number Kirsten, Dostrovsky et al: About half of the expected number Koshiba et al: About half of the expected number

Conclusion: Neutrino mixing and neutrino oscillations!!! The neutrinos have tiny masses!   e And the fourth guest also received something he did not order! SCENE 2 What did the fourth guest get for dessert? - 50 meV - 8 meV - Lighter

The challenge: Understanding the dark matter and the dark energy The birth of a neutrino astronomy, performed underground 1.Understanding processes inside the sun 2.Understanding star explosions (Supernova) 3.Studying neutrino properties Neutrinos are approximately 0.5% of the universe mass. In every cubic centimeter of the universe there are 400 photons and 110 neutrinos of each of the three kinds. SCENE 3 A voyage into the darkness

"Neutrino physics is largely the art of learning a great deal by observing nothing" The tiniest and most elusive particle plays a crucial role in creating the universe We observe the inside of a star and study the darkness of the universe, by going underground ! Epilog