CS-IN2P3 20-21 Mars 2006 Thierry Lasserre (CEA/Saclay & APC) Pour la collaboration Double Chooz

CS-IN2P320-21 Mars 2006

Thierry Lasserre (CEA/Saclay & APC)Pour la collaboration Double Chooz

http://cdfinfo.in2p3.fr/Store/APCP7/logo-apc-web.gif

Th. Lasserre CSIN2P3 20/03/06

Collaboration

+ SpainCIEMAT


Limit on 13 from Chooz

@m2atm = 2 10-3 eV2

sin2(2θ13) 0.2 (90% C.L)M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374

e e (disappearance experiment)

Pth= 8.4 GWth, L = 1.050 km, M = 5 t

overburden: 300 mwe

R = 1.01 2.8%(stat)2.7%(syst)

3

2

1

1212

1212

1313

1313

2323

2323

100

0

0

0

010

0

0

0

001

cs

sc

ces

esc

cs

sci

ie

sol13, atm


13 & beam experiments

Appearance probability :

dependences in sin(223), sin(23), sign(m231), -CP phase in [0,2]

13 & reactor experiments• <E> ~ a few MeV only disappearance experiments

sin2(213) measurement independent of -CP

• 1-P(e e) = sin2(213)sin2(m231L/4E) + O(m2

21/m231)

weak dependence in m221

• a few MeV e + short baselines negligible matter effects (O[10-4] ) sin2(213) measurement independent of sign(m2

13)


Near

dete

ctor

Far

dete

ctor

Concept of the experiment


Oscillation signal & Baseline

Rate + shape information

@1,05 km

Far/

Near

energ

y b

in r

ati

o

Nuclear reactor2 cores: 4.27 GWth

Near detector10.3 m3

Far detector10.3 m3

D~280 m D = 1050 m

e e,,

Isotropic e flux (uranium 235,238 & plutonium 239, 241 fission fragments)

Detection tag : e + p e+ + n, <E>~ 3 MeV, Threshold ~1.8 MeV

Disappearance experiment: Rate modification Energy spectrum shape distortion


Site in Ardennes, France


Site in Ardennes, France

Chooz-near

Chooz-far


Far site Near site

1.05 m300 m.w.e

70 events/day

~250 m~70-80 m.w.e

1000 events/day(preliminary)

DA

PN

IA

~30 m

Start of integration 2006

Available end of 2008 ?

0 50 100 150 200 250 300m.w.e

1

5

10

50

100

Intensity Total

flux x ~10

Flat to

polo

gy a

pp

roxim

atio

n

mwe) (300φ(depth)φ μμ


Detector Systematics


Accidental backgrounds

1-

delayed

1-

prompt1-accidental h 83

R

s 1

R0.2~)(d R

Material radiopurityCHOOZ measured n rate

Not reproduced by simulationRdelayed~45 n/h

Double Chooz n rateConservative esimation

Rdelayed~83 n/hConservative estimationRprompt < 10Hz

Raccidental < 2/dCan be measured with 10% precision


Fast Neutrons & Capture

Fast Neutrons

Full simulation Geant + Fluka

CHOOZ Dominant bkg

Simulated: 0.8/d Measured: ~ 1/d

Simulation is reliable

Double Chooz (simulation)Far : 0.15/d Near : 1.4/d

Measure in-situError ~100%

Spallation fast neutron

μ capture

Recoil p n capture on Gd

Gd

Gd

Recoil p n from capture

μμ Capture

Estimation

Double-Chooz Dead materials

Target+GCBuffer Vessel

Buffer OilSteel shield

Chimney

Far : 0.06/d Near : 0.42/d

Inner+Outer VetoError ~50%


9Li spallation background crossing the detector

Likely to be seen by the Veto

β decayed followed by n emission, =178 ms

μ interacti

onon 12C

CHOOZTotal Chooz rate: fast neutrons + 9Li

<0.6/d from CHOOZ data fit(non official analysis of CHOOZ data)

Double ChoozScaling from ChoozFar: 1/d & Near: 7/d

Inner/Outer Veto + Reactor Off?

9Li Fast neutron

Chooz data

MeV

even

ts


Background Summary

Fast neutron 9Li Accidentals

4.1


Computation of the Sensitivity

Systematics

σabs = 2.0 %σrel = 0.6 %σshp = 2.0 %

σΔm2 =

10.0 %

σE = 7 %@1 MeV

Backgrounds

1% subtraction error Uncorrelated between Near/Far Uncorrelated between Energy bins

Or

Background shape + rate Rate + Shape error

FN,A

N

1i

K

1k

2

Ak

Aki,

2

Ai

K

1k

Aki,

Aki,

Ai

Ai

2bins

σ

α

U

SαTOχ

OiA : event number in the i-th bin at the A detector

TiA : theoretical event number in the i-th bin at the A detector (with oscillation

parameter)Ti

A : systematic and background terms


Sensitivity & luminosity (GW.ton.year)

Background subtraction error - Included as a bin-2-bin error

- Impact depends on luminosity• Double Chooz < 5 years 0.5%-2% difference

Modest impact on sensitivity

• Double Chooz > 10 year 0.5%-2% différenceCrucial for 2nd génération of reactor experiments


Sensitivity & m2atm (90% C.L.)

Systematics included

σabs = 2.0 %

σrel = 0.6 %

σshp = 2.0 %

σΔm2

= 10.0 %

σE = 7 %@1 MeV

3 years of data with both detectors


Discovery potential & m2atm (3)


σabs = 2.0 %

σrel = 0.6 %

σshp = 2.0 %

σΔm2

= 10.0 %

σE = 7 %@1 MeV



Near Detector Location• Uncorrelated fluctuations included• Relative Error : 0.6%• Spectral shape uncertainty 2%• m2 known at 20%• Power flucutation of each core: 3%

Suitable area

3 years data taking

~277 m

~277 m


@1,05 km

@1,05 km

Optimum Baseline & m2atm

Near detector distance: 280 m

Systematics included:

– σabs = 2.0 %– σrel = 0.6 %– σshp = 2.0 %– σΔm

2 = 10.0 %

Resolution : σE = 7 %@1 MeV

Dn Df

Oscillation parameters chosen:

– Δm231 = 2.0-3.5 10-3 eV2

– sin2(2θ13)=0

Double Chooz optimized for m2atm>2.5 10-3 eV2

But @m2atm=2.0 eV2, sensitivity decreased to 25% with respect to optimium




σabs = 2.0 %

σshp = 2.0 %

σΔm2

= 10.0 %

σE = 7 %@1 MeVm2=2.5 10-3 eV2

Sensitivity & Relative Error


A Realistic Scenario

90% C.L. contour if sin2(2)=0m2

atm = 2.5 10-3 eV2 is supposed to be known at 20% by MINOS

Far detector only

Far & Near detectorstogether

sys=2.5% sys=0.6%

• Efficiencies included

• 1% background subtr.

• Systematics: - σabs = 2.0% - σrel = 0.6% - σscl = 0.5% - σshp = 2.0%

- σΔm2= 20%

•rate info only: no-osc excluded @ 2.66σ•Rate+shape info: no-esc excluded @ 5.98σExemple: sin2(213)=0.10


Complementarity with Superbeams

3 discovery potential 3 sensitivity (no signal)


Towards CP- experiments


Relative Systematic Error Goal: @0.6% Achievable “intrinsically” by using 2 identical detectors Similar estimation as KASKA - Second generation projects aim at 0.3%

Backgrounds Correlated bkg will dominate as in CHOOZ Upper bound given by CHOOZ (real) data

Double CHOOZ sensitivity: Far Detector ONLY: sin2(213)<0.06-0.1 (after 1 year) sin2(213)<0.02-0.03 (3 years, 2 detectors)

Complementarity with the Beam programs Future oscillation physics based on 13 true value!

An early 13 information would boost the program towards -CPOptimisation of Neutrino/Antineutrino run of superBeams experiments

Reactor/Accelerator provide 2 independent measurements Double Chooz (far) will tell wether second generation of reactor neutrino is feasible (Daya Bay, Braidwood, Angra)

Summary

CS-IN2P3 20-21 Mars 2006 Thierry Lasserre (CEA/Saclay & APC) Pour la collaboration Double Chooz

Documents

Transcript of CS-IN2P3 20-21 Mars 2006 Thierry Lasserre (CEA/Saclay & APC) Pour la collaboration Double Chooz