Overview
for an European Strategy
for neutrino Physics
Yves Déclais
CNRS/IN2P3/UCBL
IPN Lyon
CHIPP – Neutrino CH – June 22th - Neuchatel
•
•
•
•
•
Measuring the neutrino mixing matrix
Reactor experiments
NUMI off axis
Combined sensitivity for JPARC, NUMI and reactors
Conclusions
Neutrino Oscillation : 3 neutrinos formalism
0  c13
 e   1 0
  

     0 c23 s23  0
   0  s c   s ei
23
23 
13
  
θatm
θsol
0 s13e i  c12 s12 0  1 

 
1
0   s12 c12 0  2 
0 c13  0
0 1  3 
θ13, δ
The oscillation probability including matter effect
All effects are driven by θ13 !
P   e
  
m L

4E
 
sin Aˆ   sin 1  Aˆ  
  sin   sin  sin 
1  Aˆ 
Aˆ
sin Aˆ   sin 1  Aˆ  
  sin   cos  cos 
1  Aˆ 
Aˆ
sin Aˆ  
  cos  sin 2
sin 2 1  Aˆ 
 sin 213 sin  23
2
ˆ
1 A
2
Neutrinos +
Anti Nu -
2
2
13
Oscillation phase
dominant « on peak »
13
CP
13
CP
2
2
2
2
23

12
Aˆ 2
E
ˆ
A  2 2GF ne
m132
m
m
2-3 10-2
2
21
2
13
  cos13 sin 212 sin 2 23  (1)
Matter effect sensitive to :
• Sign of Δm213
• neutrino versus anti-neutrino
Neutrino Mixing Matrix Study : which Road Map
Nuclear reactors as neutrino source
• Nuclear reactors are a very intense sources of νe deriving from
the b-decay of the neutron-rich fission fragments.
• The observable e spectrum is the product
of the flux and the cross section.
Arbitrary
• A typical commercial reactor, with 3 GW thermal power,
From Bemporad, Gratta and Vogel
produces 6×1020 e/s
Observable  Spectrum
• The spectrum peaks around ~3.6 MeV.
• Visible “positron” energy implies ν energy
Eν = Ee + 0.8 MeV ( =mnmp+me1.022)
• Minimum energy for the primary signal is 1.022 MeV from e+e−
annihilation at process threshold.
• Two part coincidence signal is crucial for background reduction.
Backgrounds in reactor neutrinos experiment
There are two types of background…
1. Uncorrelated − Two random events that occur close together
in space and time and mimic the parts of the coincidence.
This BG rate can be estimated by measuring the singles rates.
2. Correlated − One event that mimics both parts of the
coincidence signal.
These may be caused fast neutrons (from cosmic ’s) that
strike a proton in the scintillator. The recoiling proton mimics
the e+ and the neutron captures.
Or they may be cause by muon produced isotopes like 9Li and
8He which sometimes decay to β+n.
Estimating the correlated rate is much more difficult!
How to improve the sensitivity
Reactor exp. = Disappearance exp.
• compare total flux (and spectrum) with the
no- oscillation hypothesis
• one depends on systematic uncertainties, like:
absolute source strength,
cross section,
detection efficiency,
fuel development over time...
Basic idea:
• use 2 identical detectors to cancel uncertainties on neutrino flux and cross sections
• excellent monitoring of calibrations and efficiencies (including analysis cuts)
to reduce the systematics on detectors
• large statistics to see small effects
Proposed sites
Site
Power
Baseline
Shielding
Sensitivity
(GWthermal)
Near/Far (m)
Near/Far (mwe)
90% CL
Krasnoyarsk, Russia
1.6
115/1000
600/600
0.03
Kashiwazaki, Japan
24.0
300/1300
150/250
0.02
Double Chooz, France
8.4
150/1050
30/300
0.03
Diablo Canyon, CA
6.7
400/1700
50/700
0.01
Angra, Brazil
5.9
500/1350
50/500
0.02
Braidwood, IL
7.2
200/1700
450/450
0.01
11.5
250/2100
250/1100
0.01
Daya Bay, China
Many Sites have been investigated as potential hosts
to a reactor neutrino experiment.
This is appropriate since getting the cooperation of the reactor
company is the main challenge.
Double-Chooz : site
2 identical detectors goal : σrelative

Far detector : using existing infrastructure
0.6% from the previous experiment @ 1050 m
• LOI : hep-ex/0405032
• detector cost 7.5 Meuros
• civil engineering ~5 Meuros (not studied)
• LOI accepted
• need for a proposal within 6 months
Near detector @100-200 m from the nuclear cores
in discussion with EDF
Double CHOOZ : detector structure
Same concept as CHOOZ :
• the target mass is defined by
the Gd loaded scintillator mass
• the efficiency is defined by neutron capture
efficiency on Gd
7m
Target cylinder (f = 2.4m, h = 2.8m)
filled with 0.1%Gd loaded liquid scintillator (12.7 Tons)
Gamma catcher inside Acrylic Vessel, thickness : 60cm
Non scintillating buffer 
7m
new !
mechanical structure to house PMTs
7m
existing pit
Performances (expected):
• S/B : 10  100
• target : 5.5  12.7 m3
• analysis errors : 1.5%  0.2%
Muons VETO of scintillating oil , thickness :60 cm
Shielding : main tank , steel thickness 15cm
But the changes would probably worsen the bkgd:
• large increase of passive material (including high Z)
• active target less protected
due to the increase of the target volume
Double CHOOZ : Gd loaded scintillator
LENS R&D  new metal β-diketone molecule (MPIK)
Stable: 0.1% Gd-Acac (few months)
Baseline recipe ~80% mineral oil + ~20% PXE + Fluors + wavelenght shifters
In-loaded scintillators (0.1 %, 5% loading) are counting @Gran Sasso
Spare stable recipes available (MPIK, INFN/LNGS)
0,020
0,018
Stability 0,1 % Gd in PXE
29.09.
06.10.
25.10.
03.11.
17.11.
0,016
3+Gd
absorbance
0,014
0,012
0,010
0,008
0,006
0,004
Gd-Acac molecule
0,002
0,000
420
440
460
480
500
520
540
560
580
600
wavelength [nm]
Completion of the R&D first half of 2004
 Choice of the final scintillator
 Stability & Material compatibility  Aging tests (MPIK, Saclay)
Warning : long term stability and acrylic vessel damage
Double CHOOZ: close detector
~10-15 m
Dense material
Overburden ~50mwe
Additional water buffer
around the detector
• similar conditions to PaloVerde (46 mwe)
• large dead time for muon veto : 50%
• can a massive detector work at such a shallow depth ?
PaloVerde and Bugey was segmented
and used dedicated signature for neutron and positron
Double CHOOZ : Background and signal
Ratio at the far detector
The baseline is too short
to see the L/E pattern
• no direct measurement
• accidental miscorrection
may mimic or suppress an effect
• fake neutron capture signal rate
underestimated
Reactor experiment sensitivity
sin22θ13 Sensitivity
The sensitivity may be pushed lower with large detectors
sensitive to a shape deformation.
90%CL
at Δm2 = 3×10-3 eV2
From Huber, Lindner,
Schwetz and Winter
Exposure (GW·ton·years)
The location of the transition from rate to shape depends on the
level of systematic error.
Double CHOOZ sensitivity
3 10-2
To be conclusive a reactor experiment which intend
to reach few 10-2 in sin22θ should be able to show
an L/E effect according to the value of δm2
( which will be known at a high level of accuracy )
and to the disappearance rate measured
NUMI off-axis
NOVA detector : TASD
160 M$
νe + n  p + e- + π0
Goals of the NOνA experiment
• sensitivity to sin2(2θ13) down to ~0.01
• measurement of sin2(2θ23) to 2% accuracy
• contribute to resolution of mass hierarchy via matter effect
• contribute to study CP violation in the neutrino sector
• NC background reduced by a narrow band beam (off axis)
• increase mass with cost/kiloton reduced by a factor 3
• sampling 1/3 X0 per plane for better electron id
• choose long baseline to enhance matter effects
For 5years @ 4 1020 pot/year, 50kton detector, sin2(2θ13) = 0.1
νμ CC
Beam unoscillated
Beam oscillated
After cuts
Beam νe
NC
signal
22858
10594
229
5758
10593
229
853
3.6
15.4
19.1
175
Nova : tentative schedule
MINOS run ? (goal : 16. E20 pot
5 M$/year to improve proton intensity:
• Booster cycle 3  7-10 hz
• decrease losses
•…
N0νA
sensitivity
Mass
Hierarchy
CP
Violation
Reactor contribution to CP violation (Shaewitz)
Input:
• sin22θ13=0.058
• δCP = 270°
• sin22θ23=10.06
The θ23 Degeneracy Problem
Atmospheric neutrino measurements are sensitive to sin22θ23
2


1
.
27

m
2
2
23 L

P(    x )  sin 2θ 23 sin 
E


But the leading order term in νμ→νe oscillations is
sin2
2


1
.
27

m
2
2
2
13 L

P(    e )  sin θ 23 sin 2θ13 sin 
E


If the atmospheric oscillation is not exactly maximal
(sin22θ23<1.0) then sin2θ23 has a twofold degeneracy
sin22θ23
sin2θ23
θ
45º
θ
2θ
90º
2θ
Solving the θ23 degeneracy with reactor (Shaewitz)
Input:
• sin22θ13=0.058
• δCP = 270°
• sin22θ23=10.06
European Strategy (Venice , december 03)
4 phases program for 13 and 
1) CNGS/MINOS
(2005-2010)
2) JPARC and Reactor(?) (2008-2013)
3) Superbeam/betabeam (>2014
)
4) Neutrino factory
(>2020 )
 Are Phase 3 (and 4) needed in case of a signal seen in JPARC
 Can we disentangle all parameters with the superbeam /betabeam option

Should we go directly to phase 4 in case of no signal seen in JPARC


shift in time for Superbeam/betabeam due to funding profile in Europe
is the low energy the optimum choice to measure Θ13 , δ , sign(Δm2)

the choice on the strategy defines not only the needed R&D on accelerators
but also for the detectors
In any case a MW machine is central
Concluding on european activities (and dreams …)
SPL
330
EURISOL
200
PS/SPS upgrade
70
Decay Ring
340
Super beam
70
UNO like detector
Grand total
500
1510
Cost in Meuros
no manpower, no contingencies
could be provided
by Nuclear physics
Concluding remarks by CERN management at MMW
• CERN will reimburse LHC loan up to 2011
• in 2008 new round of negotiations with members state
for support for new R&D (not only neutrinos …)
• CERN machines (quite old) upgrade will cost
• Staff number will decrease from 2500  2000 in 5 years
More international coordination is mandatory
The choice will imply consequences on Machines AND Detectors R&D