Neutrino Oscillation Hitoshi Murayama (Berkeley) PRC-US IHEP June 12, 2006 Murayama, IHEP, June 12, Outline Past: Why Neutrinos? Present: Era of Revolution Future Conclusion Past Why Neutrinos? Murayama, IHEP, June 12, Interest in Neutrino Mass So much activity on neutrino mass already. Why am I interested in this? Window to (way) high energy scales beyond the Standard Model! Two ways: Go to high energies Study rare, tiny effects Murayama, IHEP, June 12, Rare Effects from High-Energies Effects of physics beyond the SM as effective operators Can be classified systematically (Weinberg) Murayama, IHEP, June 12, Unique Role of Neutrino Mass Lowest order effect of physics at short distances Tiny effect (m /E ) 2 ~(0.1eV/GeV) 2 =10 20 ! Interferometry (i.e., Michaelson-Morley) Need coherent source Need interference (i.e., large mixing angles) Need long baseline Nature was kind to provide all of them! neutrino interferometry (a.k.a. neutrino oscillation) a unique tool to study physics at very high scales Murayama, IHEP, June 12, Ubiquitous Neutrinos They must have played some important role in the universe! Present Era of Revolution Murayama, IHEP, June 12, The Data Evidence for oscillation: Indisputable Atmospheric Solar Reactor strong Accelerator (K2K) And we shouldnt forget: unconfirmed Accelerator (LSND) Murayama, IHEP, June 12, SuperKamiokande Atmospheric disappear Downwards s dont disappear 1/2 of upwards s do disappear 2 /dof=839.7/755 (18%) m 2 =2.5 eV 2 sin 2 2 =1 Murayama, IHEP, June 12, SNO Solar transform in flavor 2/3 of e s Murayama, IHEP, June 12, KamLAND Reactor neutrinos do oscillate! Proper time L 0 =180 km Murayama, IHEP, June 12, What we learned Lepton Flavor is not conserved Neutrinos have tiny mass, not very hierarchical Neutrinos mix a lot the first evidence for demise of the Minimal Standard Model Very different from quarks Murayama, IHEP, June 12, Typical Theorists View ca Solar neutrino solution must be small angle MSW solution because its cute Natural scale for m 2 23 ~ 10100 eV 2 because it is cosmologically interesting Angle 23 must be 23 ~ V cb =0.04 Atmospheric neutrino anomaly must go away because it needs a large angle Wrong! Murayama, IHEP, June 12, The Big Questions What is the origin of neutrino mass? Did neutrinos play a role in our existence? Did neutrinos play a role in forming galaxies? Did neutrinos play a role in birth of the universe? Are neutrinos telling us something about unification of matter and/or forces? Will neutrinos give us more surprises? Big questions tough questions to answer Murayama, IHEP, June 12, Immediate Questions Dirac or Majorana? Absolute mass scale? How small is 13 ? CP Violation? Mass hierarchy? Is 23 maximal? LSND? Sterile neutrino(s)? CPT violation? Future Murayama, IHEP, June 12, Immediate Questions Dirac or Majorana? Absolute mass scale? How small is 13 ? CP Violation? Mass hierarchy? Is 23 maximal? LSND? Sterile neutrino(s)? CPT violation? Murayama, IHEP, June 12, Immediate Questions Dirac or Majorana? Absolute mass scale? How small is 13 ? CP Violation? Mass hierarchy? Is 23 maximal? LSND? Sterile neutrino(s)? CPT violation? Murayama, IHEP, June 12, LSND doesnt fit into the picture Sterile neutrino (3+1) barely consistent with short-baseline data Sterile neutrinos are strongly constrained by WMAP+SDSS: m0.01 conventional neutrino beam sin 2 2 13 0.04 (2 ) sin 2 2 13 >0.01 (99%CL) 23 12 13 Murayama, IHEP, June 12, Immediate Questions Dirac or Majorana? Absolute mass scale? How small is 13 ? CP Violation? Mass hierarchy? Is 23 maximal? LSND? Sterile neutrino(s)? CPT violation? Murayama, IHEP, June 12, What about the Big Questions? What is the origin of neutrino mass? Did neutrinos play a role in our existence? Did neutrinos play a role in forming galaxies? Did neutrinos play a role in birth of the universe? Are neutrinos telling us something about unification of matter and/or forces? Will neutrinos give us more surprises? Big questions tough questions to answer Murayama, IHEP, June 12, Seesaw Mechanism Why is neutrino mass so small? Need right-handed neutrinos to generate neutrino mass To obtain m 3 ~( m 2 atm ) 1/2, m D ~m t, M 3 ~10 14 10 14 GeV, but R SM neutral 37 Leptogenesis You generate Lepton Asymmetry first. (Fukugita, Yanagida) Generate L from the direct CP violation in right-handed neutrino decay L gets converted to B via EW anomaly More matter than anti-matter We have survived The Great Annihilation Despite detailed information on neutrino masses, it still works (e.g., Bari, Buchmller, Plmacher) Murayama, IHEP, June 12, Origin of Universe Maybe an even bigger role: inflation Need a spinless field that slowly rolls down the potential oscillates around it minimum decays to produce a thermal bath The superpartner of right-handed neutrino fits the bill When it decays, it produces the lepton asymmetry at the same time (HM, Suzuki, Yanagida, Yokoyama) Decay products: supersymmetry and hence dark matter Neutrino is mother of the Universe? ~ amplitude size of the universe R Murayama, IHEP, June 12, LHC/ILC may help LHC finds SUSY ILC measures masses precisely If both gaugino and sfermion masses unify, there cant be new particles < GeV except for gauge-singlets Murayama, IHEP, June 12, Plausible scenario 0 found LHC discovers SUSY ILC shows unification of gaugino and scalar masses Dark matter concordance between collider, cosmology, direct detection CP in -oscillation found Lepton flavor violation limits ( e , e conversion, etc) improve Tevatron and EDM (e and n) exclude Electroweak Baryogenesis CMB B-mode polarization gives tensor mode r=0.16 If this happens, we will be led to believe seesaw+leptogenesis (Buckley, HM) Murayama, IHEP, June 12, Conclusions Neutrino oscillation a unique tool to probe (very) high-energy world Era of revolution sin 2 2 13 decides the future My prejudice: 13 is large Reactor & accelerator LBL expts complementary To understand big questions we need a diverse set of experiments Murayama, IHEP, June 12, The I visibles Murayama, IHEP, June 12,