Takaaki Kajita, ICRR, Univ. of Tokyo

◆Introduction

◆T2KK @TAUP05

◆Updating T2KK

- L dependence, - Higher energy option, - Octant of 23,

◆Summary

TAUP07, Sep.2007, Sendai

13

13

Sign of m232Sign of m232

CP ?CP ?

3

21

e

If 23 ≠/4, is it >/4 or </4 ?

If 23 ≠/4, is it >/4 or </4 ?

3

oror

e

3

How much will Kamioka-Korea 2 detector setup (T2KK) contribute to these measurements?

sin212, sin2223, m122, =m23

2| ・・・・ Already measured.

Let’s assume that non-zero 13 will be observed by the next generation oscillation experiments.

Possible experimental setup Possible experimental setup

JPARC0754MW

Off-axis angle

2.5deg.off-axis beam @Kamioka

Distance from the target (km)

2.5 deg. off axis2.5 deg. off axis

2.5 deg. off axis(or smaller off-axisAngle)

2.5 deg. off axis(or smaller off-axisAngle)

Fig. from Senda NP04

0.27Mton0.27Mton

Osc. probability Osc. probability in in KamiokaKamioka and and KoreaKoreasin2213=0.05sin2213=0.05

BG & efficiency: almost identical both 2.5 deg. off axis beam

Expected sensitivity Expected sensitivity Total mass of the detectors = 0.54 Mton fid. mass4 years neutrino beam + 4 years anti-neutrino beam

Total mass of the detectors = 0.54 Mton fid. mass4 years neutrino beam + 4 years anti-neutrino beam

3 (thick)3 (thick) 2 (thin)2 (thin)

Mass hierarchyMass hierarchy CP violation (sin≠0)CP violation (sin≠0)

hep-ph/0504026

Update (1)Update (1)- 1050km: a special baseline ? - - 1050km: a special baseline ? -

2.5 degree off-axis beam with L between1000km and 1250km is available.

Checked if the sensitivity depends strongly on the baseline length.

2.5 degree off-axis beam with L between1000km and 1250km is available.

Checked if the sensitivity depends strongly on the baseline length.

Sensitivity to mass hierarchy(True = normal hierarchy)

sin

22 1

3

The sensitivity does not depend strongly on L !

K.Okumura, 2nd T2KK workshop, Seoul 2006

Update (2): higher energy optionUpdate (2): higher energy option

T2KK ‘s sensitivity on mass hierarchy is still limited compared with the US studies… Higher energy better ? T2KK ‘s sensitivity on mass hierarchy is still limited compared with the US studies… Higher energy better ?

Mass hierarchyMass hierarchy

3(black)

3(black)

3 (thick)3 (thick)

arXiv:0705.4396

Motivation:

Higher energy beam Higher energy beam

1.0 to 2.5 degree off axis beam available in Korea.

E (GeV)

Flu

x (a

rb.

unit)

P(

e

)

Energy Dependent Maximum Likelihood

Analysis

Energy Dependent Maximum Likelihood

Analysis

Signal and BG for various off-axis beams Signal and BG for various off-axis beams

KamiokaKamioka KoreaKorea

2.5 degree 1.0 degree 1.5 degree

2.0 degree 2.5 degree

signal

BG

sin2(213)=0.1 =1/24 year neutrino run4MW beam

Smaller off-axis angle:

Low E BG more serious.

(2nd osc. Max. difficult to see.)

But larger matter effect at the 1st osc. Max..

signal

BG

33 sensitivities for various OA angles sensitivities for various OA angles

Mass hierarchyMass hierarchy CP violationCP violation

F.Dufour, 2nd T2KK workshop, July 2006, Seoul

(Updated)

Preliminary

Mass hierarchy: OA1.0 @Korea gives the best sensitivity

CP violation: Sensitivity depends weekly on the beam option

Could be slightly too optimistic for OA angle less than 2.5 degrees (The syst errors are assumed to be fully correlated between 2 detectors)

Kam only (OA2.5)Kam + Korea OA1.0Kam + Korea OA1.5Kam + Korea OA2.0Kam + Korea OA2.5

33

Update (3):Update (3): Octant ambiguity of Octant ambiguity of 2323

In the previous study, maximal 23 mixing (23=/4) was assumed. However, 23 might not be /4. In this case, there should be additional ambiguity in the parameter measurements (especially in that of sin213) due to the ambiguity in the octant of 23 (i.e., 23 >45 or <45 deg.).

It will be very nice if the same setup can solve the octant ambiguity of 23.

Oscillation probabilities and the signal Oscillation probabilities and the signal P(e) by the solar m2 is proportional to

sin2212 ・ cos223

Solar oscillation effect visible in a very long baseline (or very large L/E) experiment.

P(e) by the solar m2 is proportional to

sin2212 ・ cos223

Solar oscillation effect visible in a very long baseline (or very large L/E) experiment. Solar term

Atm. + CP terms

BG eventssin2212 ・ cos223

effect visible

○sin2 23 = 0.4, sin2 213 = 0.01●sin2 23 = 0.6, sin2 213 = 0.0067(sin223 ・ sin2213 is equal in the two cases.)

m2: positive, =3/4

○sin2 23 = 0.4, sin2 213 = 0.01●sin2 23 = 0.6, sin2 213 = 0.0067(sin223 ・ sin2213 is equal in the two cases.)

m2: positive, =3/4

Sensitivity to octant of Sensitivity to octant of 2323

22

33

sin2 2

13

sin2223=0.96sin2223=0.99

Octant ambiguity of 23 can be resolved at 2 if sin2223 < ~0.97 (almost independent of the value of sin2213 and mass hierarchy).

Octant ambiguity of 23 can be resolved at 2 if sin2223 < ~0.97 (almost independent of the value of sin2213 and mass hierarchy).

Could resolve the 8 hold degeneracy of the oscillation parameters.

OA 2.5 degree for both Kamioka and KoreaOA 2.5 degree for both Kamioka and Korea

hep-ph/0609286

Discussing T2KK more Discussing T2KK more

Sep.30 and Oct. 1Univ. of Tokyo

Your participation and contribution are most welcome!

http://www-rccn.icrr.u-tokyo.ac.jp/workshop/T2KK07/

If non-zero 13 is observed….

• We hope to proceed to the next phase of experiment with higher power beam and larger detector(s).

• Goals: discovery of leptonic CP violation, and determination of mass hierarchy and octant of 23. (+ Various non-LBL physics).

• T2KK is one of the serious possibilities.• We will continue the studies.

If non-zero 13 is observed….

• We hope to proceed to the next phase of experiment with higher power beam and larger detector(s).

• Goals: discovery of leptonic CP violation, and determination of mass hierarchy and octant of 23. (+ Various non-LBL physics).

• T2KK is one of the serious possibilities.• We will continue the studies.

End