1. Peggy Norris, Black Hills State Univ/Sanford Underground Laboratory at Homestake

2.  At 15 million degrees Celsius in the center of the star, fusion ignites !  4 ( 1 H) --> 4 He + 2 e + + 2 neutrinos + energy  Where does the energy come from ?  Mass of four 1 H > Mass of one 4 He E = mc 2

3.  4 ( 1 H) --> 4 He + 2 e + + 2 neutrinos + energy  Energy released = 25 MeV  = 4 x 10 -12 Joules  = 1 x 10 -15 Calories  But the sun does this 10 38 times a second !  Sun has 10 56 H atoms to burn !

4.  M p = 1.0078  M He = 4.0026  = 0.025 amu 

5. 10 17 photons/cm 2 /sec Based on solar models, John Bahcall predicted that our Sun puts out 10 11 /cm 2 /sec

9. to measure the neutrinos coming to Earth from the Sun and prove John Bahcall’s prediction But how to detect such an elusive particle? Go very deep and very large!

10. High energy protons and other particles from the Sun and from outside the solar system are constantly bombarding the top of the atmosphere, making cascades of muons, electrons, their neutrinos and other particles. Electrons, their two heavier cousins, and neutrinos make up the lepton family of particles

11. to Homestake Mine Ray Davis and John Bahcall at 4850’ 110,000 gallons of dry cleaning fluid

13. Ray Davis was a chemist so he looked to nuclear chemistry for the answers:  -decay: 37 Ar  37 Cl +  - + e Davis looked for the inverse reaction: 37 Cl + e  37 Ar (t 1/2 =35 d) +  - Davis ran He gas through the tank to purge out any gases and collected Ar in a charcoal filter. Then he looked for

14.  After years of collecting data, he found conclusively that the number of neutrinos was 1/3 that expected  No one believed him! Scientists everywhere thought they understood how the Sun worked and so the experiment had to be wrong  Davis stood by his data!

15. Did scientists really understand neutrinos?  They assumed that the neutrinos from the Sun weren’t changed by the journey  The family of leptons is part of the Standard Model of particle physics, and that model predicted neutrinos had zero mass In the 1980s, Bruno Pontocorvo and others suggested that if neutrinos did have mass, they could ‘oscillate’ from one flavor to another. This might explain Davis’ results because his experiment was only sensitive to electron neutrinos. e  

16. In Canada SNO In Japan superKamiokanda 50,000 tons H 2 0

17.  Neutrinos really do oscillate from one flavor to another  John Bahcall was right in how the Sun works but 2/3 of the electron neutrinos made in the Sun have changed flavor by time they get to Earth  Neutrinos do have mass and the Standard Model is wrong! The Nobel Prize in Physics 2002 "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos" And Homestake Mine had its first scientific gold!

18. In order to fix the standard model, scientists need to understand more about neutrinos 1. What is the mass ‘hierarchy’ of neutrinos, that is which is the heaviest and which the lightest (actually measuring their absolute mass is probably impossible) 2. Are neutrinos their own antiparticles? Experiments are planned for the DUSEL Laboratory at Homestake to answer both questions

19. 19 “Long Baseline” studies  Make a beam at an accelerator lab  Steer it to a distant site  Install biggest detector you can

20. 20 Fermilab

21. 21 Fermilab

22. 22 Homestake 900 miles Fermilab

23. 23 50,000 tons…

24. 24 1,000,000 tons…

25. 25 Neutrinoless double-beta decay:

28. 28