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New Views on the Problem of CP Violation

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H. Minakata

Tokyo Metropolitan University (TMU)

New Views on the Problem of CP Violation

Neutrino Oscillation in Venice Hisakazu Minakata

- Quantum anomaly tells us that leptons and quarks are related with each other in a deeper level=> we want to know if leptonic KM phase is unsuppressed
“lepton-quark correspondence” in the spirit of Nagoya model (Sakata et al., ‘60th)

Shoichi Sakata

Neutrino Oscillation in Venice Hisakazu Minakata

- Lepton # asymmetry generated by Majorana n converted to baryon # asym. by “spharelon”
- => standard model for baryogenesis?
- Need CP violating phases
- Related with leptonic KM phase d ?

(Buchmuller et al.)

(Fukugita-Yanagida ‘86)

Neutrino Oscillation in Venice Hisakazu Minakata

Neutrino Oscillation in Venice Hisakazu Minakata

P(nm->ne) = P

P(nmbar->nebar)

= CP[P]

DP =P - CP[P] = nonzero

gives you CP violation

N. Cabibbo …

A useful tool for --> representation: Bi-probability plot H.M. & H. Nunokawa (=MN), JHEP 10 (2001) 001

Neutrino Oscillation in Venice Hisakazu Minakata

DP =P - CP[P]

= P(nm->ne;Dm2, d, a) -P(nmbar->nebar; Dm2, d, a)

= P(nm->ne;Dm2, d, a) - P(nm->ne;- Dm2, p-d, a)

If P is insensitive to d =>

= P(nm->ne;Dm2) - P(nm->ne;-Dm2) = Dm2-odd

DP measures sign of Dm2 in d-insensitive region

DP measures d in matter-insensitive region

= P(nm->ne;Dm2, -d, -a)

= P(nm->ne;- Dm2, p-d, a)

(if Dm2solar /Dm2atm << 1)

Low-E superbeam;MN, Sato, Richter, …

Neutrino Oscillation in Venice Hisakazu Minakata

P(nm->ne)=P

P(ne->nm)=T[P]

DPT =P - T[P]

gives you T (=CP under CPT) violation

P = Acosd + Bsind + C

T[P] = Acosd - Bsind + C

DPT =P - T[P] = 2 Bsind

If d = 0 => DPT = 0

Experimentally, it is NOT easy => beta beam!

MN-Parke, hep-ph/0204171

Neutrino Oscillation in Venice Hisakazu Minakata

Neutrino Oscillation in Venice Hisakazu Minakata

Reactor-LBL combination

BNL strategy with several oscillation maxima (neutrino only)

Its low-energy version?

Neutrino Oscillation in Venice Hisakazu Minakata

- Independent of d, matter effect, q23, q12, solar Dm2
=> Pure measurement of q13

ne disappearance probability

(H.M. Sugiyama, Yasuda, Inoue, Suekane, hep-ph/0211111)

Neutrino Oscillation in Venice Hisakazu Minakata

Principle very simple ! => ne appearance at OM + reactor q13 measurement gives you d

- JPARC-HK neutrino mode, 2 years (4 MW & 540 kton, s/bg accounted)
- 50 ton detectors @Kashiwazaki-Kariwa NPP, 1-10 years
- CP violation can be detected by reactor-LBL combination !
(H.M. H.Sugiyama,

hep-ph/0309323 v2 -> PLB)

Neutrino Oscillation in Venice Hisakazu Minakata

Realistic sdb crucial in sensitivity estimate in phase II

Neutrino Oscillation in Venice Hisakazu Minakata

In the case of “C-evaluation” by the HK review committee

- JPARC-SK neutrino mode, 10 years (0.75 MW & 22.5 kton, s/bg accounted)
- 50 ton detectors @Kashiwazaki-Kariwa NPP, 1-10 years
- Though less sensitive, SK can do a job !

the only way to detect CPV without HK?

Neutrino Oscillation in Venice Hisakazu Minakata

This is nothing but Parameter Degeneracy due to sign (Dm2)!

MN, JHEP 10 (2001) 001

Neutrino Oscillation in Venice Hisakazu Minakata

The reason is:

- Large d2 - d1 (= p/2 ~ p) in overlapping region of different-sign Dm2 ==>
- CPC-CPV confusion

Neutrino Oscillation in Venice Hisakazu Minakata

Neutrino Oscillation in Venice Hisakazu Minakata

<=background ?

1 s

- L=295 km/E=0.7 GeV vs. L=2540 km/E=0.5-5GeV
==> 1st oscillation maximum vs. 1st-3rd oscillation max.

- Clean environment for CPV vs. exploring oscillation pattern, sign of Dm213, can prove solar Dm2, can run with only nm

Neutrino Oscillation in Venice Hisakazu Minakata

- JPARC accelerator complex funded =>we will have low-energy neutrino superbeam
- Low-energy beam cannot see 2nd OM because of Fermi motion
- Depend on Dm2 L/2E => p, 3p means the detectors placed at L and 3L =>
- 300 km: Kamioka
- 900 km: Seoul, Korea!

Similar to 2-detector strategy in: MN hep-ph/9706281

Neutrino Oscillation in Venice Hisakazu Minakata

Neutrino Oscillation in Venice Hisakazu Minakata

- Korean detector more important for accurate determination of d (steeper slope)
- It is hard to determine sign(Dm2) from neutrino run only
- Mathematically, there is no degeneracy apart from d -> p - d (similar to KMN)

MN to appear =>

Neutrino Oscillation in Venice Hisakazu Minakata

In the thinnest ellipse limit (KMN)

- There is no degeneracy apart from d -> p - d
- sin22qis the “distance to the origin”

Kajita-MN, hep-ph/0112345

Neutrino Oscillation in Venice Hisakazu Minakata

- Real alternative togood-old n-antin low-E superbeamdoes not appear to show up yet
- Reactor-LBL may work but confidence level less than 2 s even with Hyper-K
- BNL strategy interesting to explore but CP sensitivity less than 1 s=> very long-baseline setting loses statistics
(in conventional beams)

- Need to determine sign Dm2,otherwise CPV-CPC confusion

<= the only way to detect CPV without HK?

Low-E version exists but expensive

Neutrino Oscillation in Venice Hisakazu Minakata

Very simple form !

Very simple form!

JPARC-SK q13 sensitivity; OA2°, 5 years

Neutrino Oscillation in Venice Hisakazu Minakata

- Pure measurement of q13 by reactors help resolve (q23 --> p/2-q23) degeneracy
- If lucky, one may see CP & mass hierarchy

(H.M. Sugiyama, Yasuda, Inoue, Suekane, hep-ph/0211111)

Neutrino Oscillation in Venice Hisakazu Minakata