lbl neutrinos; looking forward to the future hisakazu minakata tokyo metropolitan university
TRANSCRIPT
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
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Exploring the unknowns; 1-3 sector and mass hierarchy na=Uai
ni
SK-atm+K2K+MINOS
solar+KamLAND
Atm + accel n=>
<= solar + reactor n
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Next generation experiments
260m high Mt.
88m high Mt.
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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
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CP violation Mass hierarchy
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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
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Various options/possibilit
ies
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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
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BNL strategy (hep-ex/0211001)
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Project X: Off-axis NOVA --> VLBL multi-OM type approach
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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
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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
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More ambitiou
s approach
es
J-PARC beam at Tokai
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2.5 degrees off-axis beam @ Kamioka
L=1000 km
OA1.5
OA1.0
L=1100 km
Rubbia@T2KK WS
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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
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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
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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
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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
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F. Dufour, T. Kajita, E. Kearns, K. Okumura, to appear
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Robustness matters
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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
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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
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We take the last one, large q13 just below Chooz limit
Large q13 perturbation theory (continued)
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~ e1/2 ~ e1
~ e2~ e3/2
Matter density variation
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asymmetric baseline
T violation
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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
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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