Neutrino Physics Hitoshi Murayama (Berkeley+IPMU) NNN 2007, Hamamatsu Oct 3, 2007

Murayama, NNN Outline Past: Why Neutrinos? Present: Era of Revolution Near Future: Bright Prospect Big Questions: Need Synergies Astrophysical Probe Conclusion

Past Why Neutrinos?

Murayama, NNN Probe to High Energies Effects of physics beyond the SM as effective operators Can be classified systematically (Weinberg)

Murayama, NNN Unique Role of Neutrino Mass Lowest order effect of physics at short distances Tiny effect (m /E ) 2 ~(0.1eV/GeV) 2 =10 –20 ! Inteferometry (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 Not entirely surprising (in retrospect) that neutrino mass was the first evidence for physics beyond standard model

Murayama, NNN Ubiquitous Neutrinos They must have played some important role in the universe!

Murayama, NNN Astrophysical Probe Neutrinos unhindered by the entire star, dusts, CMB, galactic & intergalactic B, even last rescattering surface Possible probe into –Core of stars (Sun, supernovae, GRB) –Near blackholes (AGN) –Dark Matter (Sun, galactic center, subhalo) –Cosmology?

Present Era of Revolution

Murayama, NNN The Data Evidence for oscillation: “Indisputable” –Atmospheric –Solar –Reactor “strong” –Accelerator (K2K) And we shouldn’t forget: “unconfirmed” –Accelerator (LSND) excluded?

Murayama, NNN SuperKamiokande Atmospheric disappear Downwards  ’s don’t 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, NNN SNO Solar transform in flavor 2/3 of e ’s  

Murayama, NNN KamLAND Reactor neutrinos do oscillate!  Proper time  L 0 =180 km TAUP 2007, preliminary

Murayama, NNN 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, NNN 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, NNN Immediate Questions Dirac or Majorana? Absolute mass scale? How small is  13 ? CP Violation? Mass hierarchy? Is  23 maximal?

Future Bright Prospect

Murayama, NNN Immediate Questions Dirac or Majorana? Absolute mass scale? How small is  13 ? CP Violation? Mass hierarchy? Is  23 maximal?

Murayama, NNN Extended Standard Model Massive Neutrinos  Minimal SM incomplete How exactly do we extend it? Abandon either –Minimality: introduce new unobserved light degrees of freedom (right-handed neutrinos) –Lepton number: abandon distinction between neutrinos and anti-neutrinos and hence matter and anti-matter Dirac or Majorana neutrino Without knowing which, we don’t know how to extend the Standard Model KATRIN, 0 , Large Scale Structure

Murayama, NNN Immediate Questions Dirac or Majorana? Absolute mass scale? How small is  13 ? CP Violation? Mass hierarchy? Is  23 maximal?

Murayama, NNN T2K (Tokai to Kamioka)

Murayama, NNN 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, NNN LMA confirmed by KamLAND Dream case for neutrino oscillation physics!  m 2 solar within reach of long-baseline expts Even CP violation may be probable Possible only if: –  m 12 2, s 12 large enough (LMA) –  13 large enough

Murayama, NNN  13 decides the future The value of  13 crucial for the future of neutrino oscillation physics Determines the required facility/parameters/baseline/energy –sin 2 2  13 >0.01  conventional neutrino beam –sin 2 2  13 <0.01   storage ring,  beam Two paths to determine  13 –Long-baseline accelerator: T2K, NO A –Reactor neutrino experiment: 2  CHOOZ, Daya Bay

Murayama, NNN NO A Fermilab to Minnesota 32-plane block Admirer 25kt MINOS NO A L=810km

Murayama, NNN Daya Bay NPP Ling Ao NPP Ling Ao-ll NPP (under const.) Empty detectors: moved to underground halls through access tunnel. Filled detectors: swapped between underground halls via horizontal tunnels. Total tunnel length: ~2700 m 230 m 290 m 730 m 570 m 910 m Daya Bay Near 360 m from Daya Bay Overburden: 97 m Ling Ao Near 500 m from Ling Ao Overburden: 98 m Far site 1600 m from Ling Ao 2000 m from Daya Overburden: 350 m Mid site ~1000 m from Daya Overburden: 208 m Entrance portal Daya Bay

Murayama, NNN  sensitivity on sin 2 2  13

Murayama, NNN T2K vs NO A LBL   e appearance Combination of –sin 2 2  13 –Matter effect –CP phase  95%CL resolution of mass hierarchy

Murayama, NNN Accelerator vs Reactor 90% CL Reactor w 100t (3 yrs) + Nova Nova only (3yr + 3yr) Reactor w 10t (3yrs) + Nova 90% CL McConnel & Shaevitz, hep-ex/ % CL Reactor w 100t (3 yrs) +T2K T2K (5yr, -only) Reactor w 10t (3 yrs) +T2K Reactor experiments can help in Resolving the  23 degeneracy (Example: sin 2 2  23 = 0.95 ± 0.01)

Murayama, NNN My prejudice Let’s not write a complicated theory The only natural measure for mixing angles is the group-theoretical invariant Haar measure Kolmogorov–Smirnov test: 64% sin 2 2  13 >0.04 (2  ) sin 2 2  13 >0.01 (99%CL)  23  12  13

Murayama, NNN T2KK CP-violation may be observed in neutrino oscillation!

Big Questions Need Synergies

Murayama, NNN Immediate Questions Dirac or Majorana? Absolute mass scale? How small is  13 ? CP Violation? Mass hierarchy? Is  23 maximal?

Murayama, NNN 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, NNN 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 15 GeV, but R SM neutral

35 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, Buchmüller, Plümacher)

Murayama, NNN Origin of Universe Maybe an even bigger role Microscopically small Universe at Big Bang got stretched by an exponential expansion (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) Neutrino is mother of the Universe? V()V()  t log R

Murayama, NNN LHC/ILC may help LHC finds SUSY ILC measures masses precisely If both gaugino and sfermion masses unify, there can’t be new particles < GeV except for gauge-singlets

Murayama, NNN 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 or discovered 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)

Neutrinos as Astrophysical Probe

Murayama, NNN

Murayama, NNN Dark Matter Indirect detection of galactic dark matter From the Sun, Galactic Center, Subhalos

Murayama, NNN s &  s EGRET down to   =2  cm -2 sec -1 GLAST down to   ~ cm -2 sec -1 Neutrinos/km 3 :  ~4  cm -2 sec -1 The catch: –GLAST>GeV –Icecube>100GeV? Cross-correlation between s &  s gives us understanding of the source Buckley, Freese, HM, Spolyar, Sourav

Murayama, NNN Dark Energy with Neutrinos? Supernova relic neutrinos come from cosmological distances Its spectrum redshifted and superimposed Depends not only supernova rates and spectra, but also on the geometry of space Count In principle, sensitive to Dark Energy HyperGADZOOKS! Hall, HM, Papucci, Perez 4 Mt years  CDM SCDM

Murayama, NNN Conclusions Neutrino oscillation a unique tool to probe (very) high-energy world Era of revolution sin 2 2  13 decides the future of LBL expts My prejudice:  13 is “large” Reactor & accelerator LBL expts complementary To understand “big questions” we need a diverse set of experiments Neutrinos are also unique astrophysical probes