LBL neutrinos; looking forward to the future Hisakazu Minakata Tokyo Metropolitan University

LBL neutrinos; looking forward to the future

Hisakazu Minakata

Tokyo Metropolitan University

September 14, 2009 Ustron09

n oscillation has been clearly seen!

K2K

SK

MINOS 07KamLAND 08

September 14, 2009 Ustron09

Exploring the unknowns; 1-3 sector and mass hierarchy na=Uai

ni

SK-atm+K2K+MINOS

solar+KamLAND

Atm + accel n=>

<= solar + reactor n

September 14, 2009 Ustron09

Next generation experiments

260m high Mt.

88m high Mt.

Ustron09September 14, 2009

Foreseeing the next

step

Next step?

• Proof of validity of lepton KM mechanism in n mass embedded SM

• Indicate quark-lepton unity/correspondence

• vacuum environment cleaner, but doable in matter

• Conventional vs. unconventional mass pattern of neutrinos

• Probe physics of neutrino mass

• matter effect required to resolve the mass hierarchy

September 14, 2009 Ustron09

CP violation Mass hierarchy

Ustron09September 14, 2009

Terminology; degeneracy & bi-P plot

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A machinery in my talk

Oscillation probability draw ellipse if plotted in bi-P plane

Role played by CP phase and the matter clearly distinguished

Art work by Adam Para

Two solutions of S232 x

HM-Nunokawa JHEP01

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Cause of the degeneracy; easy to understand

• You can draw two ellipses from a point in P-Pbar space

• Intrinsic degeneracy

• Doubled by the unknown sign of m2

• 4-fold degeneracy

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Origin of sign-Dm2 degeneracy

• Pme in vacuum has an approximate invariance under the transformation

• It ensures the degree of freedom of sign-Dm2 flipped solution

• Continuity in change in matter effect guarantees its existence generically in matterSeptember 14, 2009

MN JHEP01

September 14, 2009 Ustron09

Various options/possibilit

ies

September 14, 2009

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Strategy for both CP and MH• Neutrino oscillation probability is a function

of L/E in vacuum• In matter, matter effect comes in via a

different way, aL =\sqrt{2}GFNeL

• There are two ways to explore structure of oscillation => mixing parameters

• used by BNL-type multi-OM approach (also used in off-axis beam)

• 2 detector approach

Vary E

Vary L

September 14, 2009 Ustron09

BNL strategy (hep-ex/0211001)

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Project X: Off-axis NOVA --> VLBL multi-OM type approach

September 14, 2009

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Perspectives

(mainly) in the

North East Asia

T2K (Tokai-to-Kamioka) 2nd phase and CERN-MEMPHYS

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CP violation measurement at low E and short L=best place for looking for CP violation (low E superbeam, HM-Nunokawa 00)

4 MW + 1 megaton water Cherenkov

Mass hierarchy difficult to resolve

September 14, 2009 Ustron09

Lepton CP sensitivity at T2K

thick: 3, thin: 2

• Sensitivity to CPV at T2K is roughly comparable to T2KK, a more aggressive setting

T2KK T2K

September 14, 2009 Ustron09

More ambitiou

s approach

es

J-PARC beam at Tokai

September 14, 2009 Ustron09

2.5 degrees off-axis beam @ Kamioka

L=1000 km

OA1.5

OA1.0

L=1100 km

Rubbia@T2KK WS

September 14, 2009 Ustron09

658km0.8deg. Off-axis

シナリオ２

δ=0°

νeSpectrum

Beam νe

Background

CP Measurement Potential

NP08, arXiv:0804.2111

δ=90°

δ=180° δ=270°

sin22θ13=0.03,Normal Hierarchy

3s

• 100kton Lq. Ar TPC @ 658km• n beam only. 1.66 MW

sin22q13

d

A.Rubbia et al. presented by T. Nakaya, June09

Okinoshima

A J-PARC version of BNL strategy

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What’s good in T2KK?

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T2KK=Tokai-to-Kamioka-Korea

Why don’t you bring one of the 2 tanks to Korea? (@EPP2010)

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Original idea: sensitive because dynamism in 2nd oscillation maximum

Ishitsuka-Kajita-HM-Nunokawa 05

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Two detector method is powerful

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Spectral information solves intrinsic degeneracy

from 1000 page Ishitsuka file

SK momentum resolution ~30 MeV at 1 GeV

T2K T2KK

2 detector method powerful!

Ishitsuka-Kajita-HM-Nunokawa 05

Ustron09September 14, 2009

Two-detector setting is powerful

• With the same input parameter and Korean detector of 0.54 Mt the sign-m2 degeneracy is NOT completely resolved

T2KK Korea only

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Latest development

September 14, 2009

F. Dufour, T. Kajita, E. Kearns, K. Okumura, to appear

Another realization of BNL strategy (see also Hagiwara et al.)

Sensitivity to CP and MH

September 14, 2009 Ustron09

5 + 5 years neutrino anti-neutrino running with 1.66 MW beam (10 2.59×10 21 POT) with 40GeV protons, 2 x 0.27Mton(FV) detector.∗

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CP fraction plot

September 14, 2009

F. Dufour, T. Kajita, E. Kearns, K. Okumura, to appear

September 14, 2009 Ustron09

Robustness matters

September 14, 2009

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Relative cross section error does matter

• Identical 2 detector setting robust to larger systematic error • It gives conservative lower bounds on sensitivity estimate

of mass hierarchy and CP

Barger et al. 07

T2K II

T2KK

September 14, 2009 Ustron09

Another issue; matter density profile

Large q13 perturbation theory of n oscillation

• Only known small parameter is e=Dm2

solar/Dm2atm ~ 0.03 various

possibilities

September 14, 2009 Ustron09

We take the last one, large q13 just below Chooz limit

Large q13 perturbation theory (continued)

September 14, 2009 Ustron09

~ e1/2 ~ e1

~ e2~ e3/2

Matter density variation

September 14, 2009 Ustron09

asymmetric baseline

T violation

September 14, 2009 Ustron09

50% correction to the main term if Im(rn) ~ r0 for L=1000 km, E=2 GeV, r=2.8 g/cm3, s13=0.17, etc. => confuse T violation

See also Akhmedov et al.01

September 14, 2009 Ustron09

Conclusion

• Some perspectives of future LBL experiments for CP and mass hierarchy are reviewed with an emphasize of North-East Asian perspective

• Emphasis placed on “principle” than numerical results

• Robustness issues addressed• Large q13 perturbation theory is

formulated to address uncertainty in matter density profile

• issue of asymmetric profile