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!

L AU N

C

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