KTH ROYAL INSTITUTE OF TECHNOLOGY Panel Discussion on the Nobel Prize in Physics 2015 Tommy Ohlsson Motivation for the Nobel Prize in Physics 2015 The Nobel Prize in Physics 2015 was awarded jointly to Takaaki Kajita and Arthur B. McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass" Takaaki Kajita Arthur B. McDonald (Super-Kamiokande) (SNO) Motivation for the Nobel Prize in Physics 2015 The Nobel Prize in Physics 2015 was awarded jointly to Takaaki Kajita and Arthur B. McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass" Ed Kearns Takaaki Kajita Arthur B. McDonald Dave Wark (Super-Kamiokande) (Super-Kamiokande) (SNO) (SNO) Super-Kamiokande (in Japan) In June 1998, the Super-Kamiokande collaboration presented its first results of measurements of atmospheric neutrinos that give evidence for neutrino oscillations (i.e. quantum mechanical effects over distances of thousands of kilometers). This result is the first solid evidence for physics beyond the Standard Model of particle physics. The atmospheric neutrino analysis of the Super-Kamiokande collaboration was led by Takaaki Kajita. SNO (in Canada) In April 2002, the SNO collaboration presented the first direct measurement of the total flux of all active boron-8 neutrinos arriving from the Sun, which provided additional evidence for neutrino flavor transitions. The SNO collaboration was led by Art McDonald. ) -1 8 SNO SNO s q q -2 7 ES CC cm 6 6 (10 o 5 µ q SNO 4 qNC 3 qSSM 2 1 0 0123456 6 -2 -1 qe (10 cm s ) Other neutrino oscillation experiments • KamLAND • first results on anti-electron neutrino flux from distant nuclear reactors • demonstrated disappearance of anti-electron neutrinos and showed that the LMA solution is the only remaining solar neu. osc. solution • K2K/T2K & MINOS • confirm and improve atmospheric results of Super-Kamiokande • MiniBooNE • disfavor existence of sterile neutrinos (however, some overlap with LSND) • Daya Bay (& Double Chooz & RENO) • initial finding of the third and last unknown leptonic mixing angle • IceCube • reported 37 detected neutrinos which are likely to originate outside our solar system (May 2014) • obtained results of fundamental neutrino parameters that are comparable with results of dedicated neu. osc. experiments Parameter values from global fits ) ) !"#"$%&%#' !()' !(*' !)*' "' #! )(' #! *(' +",-%' **./0'±'1.20' 2./0'±'1.*0' 3).*0'±'*.10' -454674' 89./'±'1.):'$'(1;/'%+)' ±'8)./'±'1.(:'$'(1;*'%+)' ' Open questions • Are neutrinos their own anitparticles? Are neutrinos Dirac or Majorana particles? • What is the value of the leptonic CP-violating phase? • What is the absolute neutrino mass scale? • How are the neutrino masses ordered? (Normal hierarchy?, Inverted hierarchy? Degenerate?) • What mechanism gives rise to neutrino masses? BACKUP SLIDES Neutrino oscillations – two flavors ! " Neutrino oscillations – three flavors Series expansion formulas for three-flavor neutrino oscillation probabilities in matter of constant density up to second order in small parameters: E.K. Akhmedov, R. Johansson, M. Lindner, T. Ohlsson, and T. Schwetz, JHEP 04, 078 (2004), arXiv:hep-ph/0402175. Neutrino oscillations – three flavors II An example: The electron-muon neutrino oscillation probability .