1. Directional Sensitivity in Double Chooz
Kathrin A. Hochmuth
Max-Planck-Institut für Physik
LAUNCH Workshop
Heidelberg

2. Outline Neutrino Direction Measurements CHOOZ measurements
Two Reactors
- separation of sources?
- monitoring power output?
analytical estimates and maximum likelihood analysis
- for Double Chooz setup with 30° separation
- for hypothetical setup with 90° separation
in collaboration with M. Lindner and G. Raffelt

3. Neutrino Direction
= average displacement for reactor energies ~ 1.9 cm
Note: uncertainty of locating the positron annihilation and neutron absorption points is large!
Uncertainty of displacement

4. Setup
CHOOZ determined each of the angles with s ~ 12° with 2,500 events
Double Chooz near detector:
160,000 events per year

5. One Reactor
CHOOZ event rate (2,500); true values q f

6. One Reactor CHOOZ event rate (2,500); true values q f
Double Chooz event rate (160,000)

7. Two Reactors ??? 160,000 events Single Reactor Double Chooz
30° separation
Hypothetical setup
90° separation

8. Probability Distribution Function
tilt angle w.r.t x-y plane;
relative strength of the reactors, where (assume for now: )
displacement: 1.9 cm
uncertainty of the displacement: 20 cm
Separation angle
Central angle
For Double Chooz

9. Important Points
y-axis distribution gives information on the angular separation
x-distribution gives only information on the center of the distribution
No distinction from a single Gauss; >10 Mio events needed

10. Important Points
y-axis distribution gives information on the angular separation
x-distribution gives only information on the center of the distribution
No distinction from a single Gauss; >10 Mio events needed

11. Non-Gaussianity Good resolution Bad resolution
No clear distinction because cosf1~1

12. Angular Separation of 2 Sources
160,000 events
Non-Gaussian behavior
No distinction from 0°
Reactor 1
Separation angle
Central angle well determinded
x-distribution behaves like a single Gaussian

13. 7 years Double Chooz 3 s distinction possible after 7 years
Reactor 1
Separation angle
3 s distinction possible after 7 years

14. Hypothetical 90° separation
for 160,000 events:
Clear separation of the angles f1,f2 with s1~3.2°
central angle: sc~2.3°
separation angle: s~4.6°
Note:

15. Reactor Strength Reactor strength 1 year Double Chooz: 160,000 events:
5 years:
f1=45° after 1 year:
True value: b1=b2=0.5
after 1 month

16. Conclusions
Separation of the two Double Chooz reactors challenging, because of small separation angle and
3 s separation of the two Double Chooz reactors after 7 years
Separation Potential increases with increasing angles=> clear distinction for 90° separation after 1 year
Possible to monitor the strength of each individual reactor; for 1 year Double Chooz with

17. References
M. Apollonio et al.(CHOOZ Collaboration), Phys.Rev.D 61 (2000) [hep-ex/ ].
M. Apollonio et al. Eur.Phys.J. C 27 (2003) 331 [hep-ex/ ]
F. Ardellier et al.(Double Chooz Collaboration) hep-ex/ v4 (26 October 2006).
P. Vogel and J. F. Beacom, Phys. Rev. D 60 (1999)
H. O. Back et al. (Borexino Collaboration),physics/
P. H. Frampton and P. Vogel, Phys.Rept. 82 (1982) 339.
K. A. Hochmuth et al, Earth Moon Planets 99: ,2006 ,[hep-ph/ ].
K. A. Hochmuth et al, Astropart.Phys.27:21-29,2007 ,[hep-ph/ ].

18. Thank you! N U L A C H