The Troublesome Kid An introductory course on neutrino

The Troublesome Kid An introductory course on neutrino physics (III) J. J. Gómez-Cadenas IFIC-Valencia Summer Student School CERN, July, 2006

A man sits in a deep mine baby sitting a tank of cleaning fluid He says he can count solar neutrinos…

Solar neutrinos

The chlorine experiment Cl 37 25% of all natural chlorine Inverse beta decay (0. 86 Mev threshold) Cl 37+n Ar 37+e. Ar is chemically very different from Chlorine. An inert gas that can be eventually removed from chlorine. It is radioactive and reverts to Cl 37 emitting an Auger electron

The hero in the mine Concept: Count the atoms of Ar 37 produced by neutrinos Only a few atoms of Ar 37 per run! 380 000 liters of C 2 Cl 4 (a cleaning fluid) deep inside Homestake mine to shield from natural radiation (a Olympic swimming pool) Let Argon-37 accumulate from 1 to 3 months. Flush with He gas to remove Ar from fluid. Let the Ar condensate in a 77 K charcoal trap. Collect and purify Ar. Count the number of Auger electrons from Ar 37

Chlorine by numbers 37 Cl(n 37 Ar (E = 813 ke. V) , e) e thr Kshell EC t = 50. 5 d 37 Cl + 2. 82 ke. V (Auger e-, X) Expects 8. 2 SNU 1. 8 Observs 2. 56 SNU 0. 23

The solar neutrino problem • Also called “paradox”, “dilemma”, “puzzle” and other nice words that showed that every body (secretly) believed that: • Davis (Chlorine experiment) was wrong • Bahcall (The solar model) was wrong Or, more likely: Both were wrong!

Gallium experiments 71 Ga(n e, e) 71 Ge K, L shell EC (Ethr = 233 ke. V) t = 16. 5 d 71 Ga + 10 ke. V, 1 ke. V (Auger e-, X) Expects 127 SNU 12 Observs 68. 1 SNU 3. 75

What does a neutrino in water?

Water detectors: Concept

Water detectors: Concept

Super Kamiokande

The eyes of Super-Kamiokande

Super-Kamiokande solar results

A neutrino picture of the sun Super-K observation Neutrinos come from the sun indeed!

Super-Kamiokande by numbers

The solar neutrino problem after Super Kamiokande So Davis was not wrong after all!

SNO

SNO detector

Signals in SNO

SNO observations CC ES NC

The solar neutrino problem So the sun is shining the expected number of neutrinos but many of them are nm and/or nt! Not only Davis, but also Bahcall was right!

Atmospheric neutrinos

Atmospheric flux prediction Ingredientes: • Primary proton flux • Hadronic production models • Hadron propagation (geomagnetic effects)

Zenith angle measures n path lengt Notice: Three decades of path length from O(104) to O(10) km.

Super-K sees also atmospheric neutrinos

The atmospheric neutrino problem

Energy dependence Effect depends no only on the path length but also on the energy

Solar & Atmospheric neutrino problems • The combination of all solar neutrino experiments (before SNO) implied that solar neutrinos were disappearing between production (in the sun core) and detection in the earth. • SNO shows that the sun is shining the expected n flux but most of them are nm and/or nt • The zenith dependence observed by Super-Kamiokande experiment showed that nm (but not ne) produced in the atmosphere were also disappearing. The effect depends on the zenith angle, that is on the neutrino path length, between production and detection and on the energy