Directional Sensitivity in Double Chooz
Kathrin A. HochmuthMax-Planck-Institut für Physik
LAUNCH Workshop
Heidelberg
23.3.2007
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
Neutrino Direction
nepe
= average displacement for reactor energies ~ 1.9 cm
Note: uncertainty of locating the positron annihilation and neutron absorption points is large!
Uncertainty of displacement cmL 20~
Setup
CHOOZ determined each of the angles with ~ 12° with 2,500 events
Double Chooz near detector:
160,000 events per year
2
222
32/3 2
)coscos()sincos()sin(exp
)2(
1)(
L
yxz
Lrf
N
iirf
1
)(Likelihood
One ReactorCHOOZ event rate (2,500); true values
0,0
One ReactorCHOOZ event rate (2,500); true values
Double Chooz event rate (160,000)
0,0
Two Reactors ???
Single Reactor
Double Chooz
30° separation
Hypothetical setup
90° separation
160,000 events
Probability Distribution Function
2
12
22
2
2
32/3 2
)coscos()sincos(exp
2
)sin(exp
)2(
1)(
i
iii L
yxb
L
z
Lrf
21,bb
L
tilt angle w.r.t x-y plane;
displacement: 1.9 cm ne
121 bbrelative strength of the reactors, where (assume for now: )
uncertainty of the displacement: 20 cm
1521
0
Separation angle 21
Central angle 2211 bbc
For Double Chooz
21 bb
Important Points
N
L
1cos
L
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
122222 sin Lxx
2
2)(2
2)(
L
x
L
x
ee
Important Points
N
L
1cos
L
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
122222 sin Lxx
2
2)(2
2)(
L
x
L
x
ee
Non-Gaussianity
No clear distinction because cos
Good resolution
Bad resolution
Angular Separation of 2 Sources
58.1c
x-distribution behaves like a single Gaussian
Central angle well determinded
c
160,000 events
Non-Gaussian behavior
No distinction from 0°
Reactor 1 Separation angle
7 years Double Chooz
3 distinction possible after 7 years
Reactor 1 Separation angle
Hypothetical 90° separation4521
for 160,000 events:
Clear separation of the angles 1,2 with ~3.2°
central angle: c~2.3°
separation angle: ~4.6°
Note: 12
Reactor Strength
05.0~b
N
Lb
1sin2
1
022.0~b
1 year Double Chooz: 160,000 events:
5 years:
02.0~b=45° after 1 year:
07.0~bafter 1 month
Reactor strength21,bb
True value: b1=b2=0.5
Conclusions• Separation of the two Double Chooz reactors
challenging, because of small separation angle and • 3 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
L
05.0~b
ReferencesM. Apollonio et al.(CHOOZ Collaboration), Phys.Rev.D 61 (2000) 012001 [hep-ex/9906011].
M. Apollonio et al. Eur.Phys.J. C 27 (2003) 331 [hep-ex/0301017]
F. Ardellier et al.(Double Chooz Collaboration) hep-ex/0606025v4 (26 October 2006).
P. Vogel and J. F. Beacom, Phys. Rev. D 60 (1999) 053003
H. O. Back et al. (Borexino Collaboration),physics/0408032.
P. H. Frampton and P. Vogel, Phys.Rept. 82 (1982) 339.
K. A. Hochmuth et al, Earth Moon Planets 99:253-264,2006 ,[hep-ph/0610048]. K. A. Hochmuth et al, Astropart.Phys.27:21-29,2007 ,[hep-ph/0509136].
Thank you!
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