Naotoshi Okamura (YITP) 2005/06/22 @ NuFact05 Solving the neutrino parameter　degeneracies by measuring the T2K off-axis beam in Korea Naotoshi Okamura (YITP) 2005/06/22 @ NuFact05 K.Hagiwara and K.Senda hep-ph/0504061 e-mail:okamura@yukawa.kyoto-u.ac.jp

content short review (8-fold ambiguities) Tokaimura-to-Kamioka (T2K) experiment off-axis beam JapanKorea solve the ambiguities mass hierarchy CP phase Summary

Parameters neutrino physics 7/9 parameters neutrino oscillation neutrino masses m1 m2 m3 flavor mixing angles 12 23 13 CP phase  Majorana phases 1 2 squared-differences m212 m213 (m23-m21) flavor mixing angles 12 23 13 CP phase  Majorana phases nothing

8 fold ambiguities exist sign of m213 2 fold ambiguity difficult !! unknown parameters 2 fold ambiguity will measure value of 23 2 fold ambiguity best fit is 45 8 fold ambiguities exist

today’s topic “mass hierarchy” and “CP phase”

Tokaimura-to-Kamioka (T2K) J-PARC (under construction) Place : Tokaimura (NE-60km from KEK) 50 GeV Proton Synchrotron (1021 POT/year) neutrino intensity is O(2) higher than that of K2K Super-K (exist) Distance : L=295 km Place : Kamioka 50Kton water Cherenkov detector (fiducial 22.5Kton) good e/ identification cannot measure the charge Plan to use the off-axis beam (OAB)

off-axis beam (OAB) E(GeV) 2.0 0.0 2.5 3.0 OAB will go to Korea     Conventional Super Beam ( from  decay) From the conservation low E(GeV) features of OAB upper limit of the neutrino energy reduce the high energy tail reduce the BG peak energy --- off-axis angle tune the peak easily 2.0 0.0 2.5 3.0 OAB will go to Korea E(GeV)

Neutrinos will go to Korea OAB : cone, umbrella Super-K L=295km,  =2.0-3.0 J-PARC on-axis L=1000-1200km,  =1.0-4.0 S-Korea 2.5@SK

angle in Korea depends on that at SK which combination ?? angle in Korea depends on that at SK 2.5@SK 3.0@SK Optimization :where in Korea which angle in Korea/SK ??

Condition fiducial volume exposure time base-line and off-axis SK : 22.5 kton Korea : 100 kton exposure time 5 years with 1021 POT/year T2K running time base-line and off-axis SK: L=295km with =2.5o / 3.0o KR: L=1000-1200 km with =(0.5o - 3.0o) / 0.5o Angle in Korea depends on the distance and angle at SK

Parameters Solar sin22 = 0.84 0.07, m2 = (8.3  0.6) 10-5 eV2 Atmospheric sin22 = 1.0 0.04, m2 = (2.5  0.5) 10-3 eV2 matter density (uncertainty : 3%)  = 2.8 / 3.0 (g/cm3) (SK/Korea) others (uncertainty : 3%) flux normalization (each species) CCQE cross section ( / anti-) fiducial volume (SK / Korea)

event number (1) CCQE event easy reconstruct the neutrino energy easy distinguish, e-like, -like binning bin width : 200MeV summation region (#event > 10) 0.4 – 5.0 GeV for -like (SK/Korea) 0.4 – 1.2 GeV for e-like (SK) 0.4 – 2.8 GeV for e-like (Korea) BG beam contamination Not include NC background

event number (2) event number (  ) true : fit :  E:200MeV depends on the matter density: f (L) true : fit :

2 - rule of the game - event numbers systematic errors parameter

Best Place in Korea true : “normal” fit : “inverted” true : sin2213= 0.1  free : fit  = 0.0  free Best Place : L=1000km with 0.5o and 3.0o@SK

Q : Where is the best ?? A : east coast of Korea = 0.5o L = 1000 km with  = 3.0o@SK A : east coast of Korea

hierarchy We can distinguish the mass hierarchy with 1OAB – 2Detectors exp., if we are lucky. (true : sin2213 > 0.06) Optimized combination L=1000km with 0.5o (vicinity of here) L=295km with 3.0o 2  16 (4) (true : sin2213 =0.1, =0.0o)

CP phase distinguish

KJ experiment summary 3 type ambiguities “mass hierarchy”, “CP phase + 13”, “sin23” T2K + Korea (1.OAB - 2.Detectors) L=295km OA:3.0 and L=1000km OA:0.5 with reactor experiment we get them mass hierarchy : 2 > 9 (sin2213  0.06) CP phase : 0180 (sin2213  0.06) KJ experiment

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