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New Views on the Problem of CP ViolationPowerPoint Presentation

New Views on the Problem of CP Violation

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Why do we look for leptonic CP violation?

Neutrino Oscillation in Venice Hisakazu Minakata

Lepton-quark correspondence

- 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

Leptogenesis

- 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

Good old way

Neutrino Oscillation in Venice Hisakazu Minakata

Good-old way of measuring CPV

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

DP =P - CP[P]; sign of Dm2 or CPV?= 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

TV; Cleanest way of measuring CPV

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

New ways

Neutrino Oscillation in Venice Hisakazu Minakata

New ways of measuring CPV?

Reactor-LBL combination

BNL strategy with several oscillation maxima (neutrino only)

Its low-energy version?

Neutrino Oscillation in Venice Hisakazu Minakata

Reactor measurement of q13

- 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

Reactor-LBL combination

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

Detecting CPV by reactor-LBL combination; details

Realistic sdb crucial in sensitivity estimate in phase II

Neutrino Oscillation in Venice Hisakazu Minakata

Can Super-K Do the Job?

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

We must know sign of Dm2 in advance, otherwise …

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

MN, JHEP 10 (2001) 001

Neutrino Oscillation in Venice Hisakazu Minakata

Why so much ambiguity by sign-Dm2 degeneracy?

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

BNL strategy (hep-ex/0211001)

Neutrino Oscillation in Venice Hisakazu Minakata

JPARC-HK vs. BNL proposal

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

Low-energy version of BNL strategy?

- 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

Shooting Korea

Neutrino Oscillation in Venice Hisakazu Minakata

Bi-probability plot for JPARC-Korea

- 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

n-antin run at the oscillation maximum (reminder)

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

Conclusion

- 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

LBL measurement of q13

Very simple form !

Very simple form!

JPARC-SK q13 sensitivity; OA2°, 5 years

Neutrino Oscillation in Venice Hisakazu Minakata

Reactor-LBL complementarity I

- 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

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