If  13 is large, then what ? Hisakazu Minakata Tokyo Metropolitan University

Title too timely? Yes, but meant to be a speculative one when proposed August 1-6,

Apparently  13 is large 6 events at T2K ! August 1-6, Released in June

T2K appearance event distribution August 1-6,

MINOS also saw excess August 1-6,

Global analysis All experiments coherently support  13 ~ 8 degree August 1-6, Fogli et al. June 29

We will soon hear more about this from reactors! August 1-6,

August 1-6, There are two issues (at least)

Two issues of large  13 What is the influence of large  13 on strategies of future oscillation experiments ? What the large  13 means? Physics behind the large  13 August 1-6, Smirnov’s talk Mohapatra’s talk …

Wide possibilities are now open for CP Conventional  superbeam can do a much better job for CP (and possibly for mass hierarchy) than it was thought This means that we should reconsider about strategy for CP I believe megaton-scale water Cherenkov / 100 kt liquid Ar is still needed for robust discovery of CPV Yet, the paths to go there could have more variety “guerrilla type” approaches possible August 1-6,

August 1-6, Various options become possible for CP

Reactor accelerator combination August 1-6, HM-Sugiyama 04 Huber et al. 09

+ -bar combination in NO A / T2K August 1-6, June17

Reactor-accelerator & + -bar methods Apparently the methods works, but unlikely to cover all the  space Quantitative estimation of CP sensitivity required very interesting !! Results of CP sensitivity studies indicate the importance of mass hierarchy resolution August 1-6,

Various options possible… August 1-6, MEMPHYS: Dashed line = combining SPL + beta Campagne et al. 07

August 1-6, What do you propose?

Opening the possibility of “all in one” With large  13 ~ Chooz limit a megaton scale water Cherenkov can do many With intense and -bar beam it can measure  With gigantic atmospheric events it could determine mass hierarchy in situ measurement of everything in a single detector It can do proton decay It can do many astrophysics too August 1-6, water Cherenkov vs. liquid Ar vs. TASD debatable Kakuno-san’s talk

August 1-6, Issues in precision measurement of CP

megaton class detectors (examples) August 1-6, T2K II MEMPHYS

CP sensitivity is not maximal at sin 2  13 =0.1 August 1-6, MEMPHYS

August 1-6, T2KK vs. T2K II Comparison Total mass of the detectors = 0.54 Mton fid. mass 4 years neutrino beam + 4 years anti-neutrino beam Total mass of the detectors = 0.54 Mton fid. mass 4 years neutrino beam + 4 years anti-neutrino beam 3  (thick) 2  (thin) Mass hierarchy CP violation (sin  ≠0) hep-ph/ T2K T2KK 4MW!

Precision CP requires … T2K-T2KK comparison seems to indicate necessity of mass hierarchy resolution importance of lifting sign  m 2 degeneracy Comparison of different error treatments in -bar shows the relative cross section error affects CP sensitivity August 1-6, cross section measurement crucially important Supported by analysis in Kakuno-san’s talk

August 1-6, Does large  13 require new oscillation formula?

Large  13 corrections to Cervera et al. formula August 1-6, Cervera et al. 00 Good perturbative formula for small  13 with s 13 ~  m 2 21 /  m 2 31 =  2 nd order formula But, for large  13 ~ 10 deg. s 13 ~ \sqrt{  higher order corrections needed P NC ~ s 13 4, or ~ s 13 2  Computed: K. Asano-H.M. JHEPJune7, 2011

Some features of the new formula August 1-6, All the  dependence is in half- integer power of  General theorems! r  =  m 2 21 /  m 2 31 r  = a /  m 2 31  =  m 2 31 / 2E

Correction terms are small August 1-6, All the correction terms are of order ~  2 General theorems! r  =  m 2 21 /  m 2 31 r  = a /  m 2 31  =  m 2 31 / 2E

August 1-6, Is parameter degeneracy affected by large  13 ?

P degeneracy well understood August 1-6, Cervera et al. formula HM-Uchinami JHEP10

Is P degeneracy unchanged for large  13 ? One can show on general ground that P NC must be order (  m 2 21 /  m 2 31 ) 2 ~ Difference between Cervera sol. and our solutions is tiny (apart from a particular region) August 1-6, P NC ~ s 13 4, or ~s 13 2  m 2 21 /  m 2 31 Cervera et al. formula Asano-HM JHEP11

August 1-6, What large  13 means?

Large  13 is natural because in U=V l + V two angles are large, and hence extremely small  13 is not expected, Anarchy ? The above argument assumes no symmetry is hidden symmetries which enforce  13 =0 somewhat discouraged (?) unless you have good reasons August 1-6,

Large  13 in QLC context August 1-6, Bimaximal mixing from charged leptons Bimaximal mixing from neutrinos Large  13 prefers bimaximal mixing from Raidal 04, HM-A.Smirnov 04 QLC based on observation:  12 +  C =  /4

August 1-6, Conclusion large  13 opens up wide range of possibilities for hunting CP & mass hierarchy While guerrilla type approach is possible, a charming case would be to determine all at once by a megaton-scale detector (+proton decay) Hyper-K Yet, precision measurement would require resolution of sign-  m 2 degeneracy Physical meaning of the large  13 has to be understood