1. Toward realistic evaluation of the T2KK physics potential
What’s that ?
Preliminary
KEK
Dec.12, 2007
N.Okamura (KEK)

2. What’s the T2KK ??
There are 6 parameters in the “neutrino oscillation”
Unknown parameters
The sign of the larger mass-squared difference
Value of the CP phase (MNS)
Value of the 13  Reactor exp. will measure
The correct value of 23 (larger or smaller than 45o)
T2KK = Tokai-to-Kamioka exp. (T2K, will start 2009)
+ far detector in Korea (L~1000km)
T2K neutrino beam
will reach Korea,
automatically.

3. Digest of our previous work
5x1021POT exposure
include the “reactor exp.”
Volume 22.5 kton/100Kton (SK/Kr)
OAB : 3.0/0.5 (SK/Kr)
essence of T2KK
2 detectors, 300km km
matter effect helps to determine
2 of 3 (1acc.,2detector) exist
sin22RCT=0.1, MNS=0.0
2 = 22 (input : normal)
mass hierarchy
CP phase
1 ~ 30o
w/o anti-neutrino
Detail of T2KK
K.Hagiwara,
K.Senda, NO,
PLB (2006)
PRD (2007)
K.Hagiwara, NO,
hep-ph/
and ref. there in

4. motivation We study the robustness of the results,
previous work
this work CC
CCQE only
CCQE + -Res. NC no
0 background
binning energy
Neutrino
Reconstructed
 (SK/Kr)
2.8/3.0 (g/cm3)
2.6/3.0 (g/cm3)
error of  3% 6%
miss ID (e)
1%(1%)
efficiency (e)
100%
90%(5%)
efficiency ()
100%(-1%)
resolution
include
We study the robustness of the results,
best combination, hierarchy (2), CP phase (MNS).

5. CC
Reconstruction
Resolution
Fit functions

6. event selection (106):mono. energy only one  (e)
CCQE
Res.
20000
15000
10000
5000
25000
E = 1GeV
(106):mono. energy
400MeV
Erec
total (CC) :
CCQE :
resonance :
only one  (e)
|p| > 200MeV
no high energy +/-
|p| < 200MeV
no high energy 
|p| < 30MeV
no 0/Ks/K+/K-
nuance Ver (Apr/25,2006)
D. Casper (UC.Irvine)

7. resolution -like e-like p %  1.8o 3.0o Detector has the resolution
for momentum and the angle.
Dilute the reconstruction energy
obtained from the momentum of e,
and scatter angle.
e :E=2GeV
-like
e-like p % 
1.8o
3.0o
(from SK)

8. fit functions For E  Erec conversion : fit function CCQE Res.
Sum of the 3 gauss functions for CCQE, 3 or 4 gauss functions for resonance mode.
Cover region : Erec > 0.4GeV for E=0.3 ~ 6.0GeV
Erec < 0.4GeV
rapid oscillation, small , etc. not include
E > 6.0GeV  no beam flux

9. NC
0 event
(for e-like background)

10. event selection only one 0 no- / e no high energy +/-
|p| < 200MeV
no high energy 
|p| < 30MeV
no Ks/K+/K-
0.5 OAB
480 event at GeV
300 event at GeV
0 distribution after event selection

11. 0 event cut 0 () sometimes seems an “e-like” events.
energy ratio (E1>E2)
E2 /(E1+E2) < 0.2 : 100% missed
opening angle (cos)
cos > cos17o = 0.956

12. Pe/(|p|)
Pe/
|p|(GeV)

13. Event Numbers

14. events at Korea e  e 0 dominates at low energy (Erec<1GeV)
CCQE event is larger than the others
Erec= GeV 
Almost CCQE
Resonant mode is comparable at low energy
Erec= GeV 
sin22RCT=0.1, MNS=0.0

15. events at SK e  e CCQE event is dominant Erec=0.4-1.2GeV
Event from resonance is smaller.
Erec= GeV 
sin22RCT=0.1, MNS=0.0

16. 2 Best combination Effect mass hierarchy CP phase (MNS)
0, resonance mode

17. input and systematic Solar Atmospheric matter density (uncertainty 6%)
sin22 = 0.83 0.07, m2 = (8.2  0.6) 10-5 eV2
Atmospheric
sin22 = 1.000.96, m2 = 2.5 10-3 eV2
matter density (uncertainty 6%)
 = 2.6 / 3.0 (g/cm3) (SK/Korea)
Systematic
flux normalization (3%) (each flavor to SK/Korea)
fiducial volume (3%) (SK / Korea)
CCQE  (3%) ( / )
Resonance (10%) ( / )
 (30%) ( = )
efficiency (100-1%/905%) ( /e)
miss PID (11%)
#total:26

18. 2 -rule of the game- statistics systematic input expected error
of reactor exp.
Reactor experiments helps T2KK to solve the degeneracy.

19. Condition fiducial volume exposure base-line and off-axis
SK : 22.5 kton Korea : 100 kton
exposure
5 x 1021 POT
no anti-neutrino phase
base-line and off-axis
SK: L=295km with =2.5o or 3.0o
KR: L= km with =(0.5o ~ 3.0o) / 0.5o step
Previous results for mass hierarchy
and (L=1000km) is the best combination
2 = 22, input : normal, sin22rct = 0.10, MNS=0.0
2 = 21, input : inverted, sin22rct = 0.10, MNS=0.0

20. Results Best combination is still SK(3.0) and Kr(0.5) L=1000
2=13 (input : normal)
2=11 (input : inverted)
contribution to 2 (normal)
Previous Setup 22.9
matter density (SK) 0.5
resonance
density error -0.6
miss ID (-e) -1.0
reconstruction -2.3
efficiency (e) -2.3
0 background -6.5
total
normal
normal
positive
negative
inverted
inverted
sin22RCT=0.1, MNS=0.0

21. Contour (input : normal)25 9
sin22rct ~ 0.05
MNS~ 30o
sin22rct ~ 0.09
MNS~ 45o 9 25

22. summary hierarchy CP phase CC ( res.) positive negative NC(0)
The others, reconstruction, matter profile, and so on, do not change the results drastically.
“3.0 at SK and 0.5 at 1000km” is still the best.
  (input : normal)
21  (input : inverted)
MNS 30o  45o (3 2)

23. Thank you for your attention