Overview

for an European Strategy for neutrino Physics

Yves Déclais

CNRS/IN2P3/UCBL

IPN Lyon

• Measuring the neutrino mixing matrix• Reactor experiments• NUMI off axis• Combined sensitivity for JPARC, NUMI and reactors• Conclusions

CHIPP – Neutrino CH – June 22th - Neuchatel

Neutrino Oscillation : 3 neutrinos formalism

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

θsol

θ13, δθatm

The oscillation probability including matter effect

A

A

A

A

A

A

A

A

A

A

A

A

2ˆ

ˆsin2sincos

ˆ1

ˆ1sinˆ

ˆsincoscossin

ˆ1

ˆ1sinˆ

ˆsinsinsinsin

ˆ1

ˆ1sinsin2sin

2

122

2322

13

13

2

2

232

132

CP

CP

eP

)1(2sin2sincos 231213

213

221

m

m

2-3 10-2

213

22ˆm

EnGA eF

Matter effect sensitive to :• Sign of Δm2

13 • neutrino versus anti-neutrino

E

Lm

4

213

Oscillation phase

All effects are driven by θ13 !

dominant « on peak »Neutrinos +Anti Nu -

Neutrino Mixing Matrix Study : which Road Map

Nuclear reactors as neutrino source

• Minimum energy for the primary signal is 1.022 MeV from Minimum energy for the primary signal is 1.022 MeV from ee++ee−− annihilation at process threshold.annihilation at process threshold.

• Two part coincidence signal is crucial for background reduction.Two part coincidence signal is crucial for background reduction.

Arb

itra

ry

Flux Cross

Sectio

n

Observable Spectrum• The observable The observable ee spectrum is the product spectrum is the product

of theof the fluxflux and theand the cross sectioncross section..

• The spectrum peaks around ~3.6 MeV.The spectrum peaks around ~3.6 MeV.

• Visible “positron” energy implies Visible “positron” energy implies νν energy energy

From Bemporad, Gratta and Vogel

• Nuclear reactors are a very intense sources of Nuclear reactors are a very intense sources of ννee deriving from deriving from

the the -decay of the neutron-rich fission fragments.-decay of the neutron-rich fission fragments.

• A typical commercial reactor, with 3 GW thermal power, A typical commercial reactor, with 3 GW thermal power, produces produces 66×10×102020 ee/s/s

EEνν = E = Ee e + 0.8 MeV ( + 0.8 MeV ( ==mmnnmmpp++mmee1.022)1.022)

Backgrounds in reactor neutrinos experiment

There are two types of background…There are two types of background…

1.1. Uncorrelated Uncorrelated − Two random events that occur close together − Two random events that occur close together in space and time and mimic the parts of the coincidence.in space and time and mimic the parts of the coincidence.

This BG rate can be estimated by measuring the singles rates.This BG rate can be estimated by measuring the singles rates.

2.2. Correlated − One event that mimics both parts of the Correlated − One event that mimics both parts of the coincidence signal.coincidence signal.

These may be caused fast neutrons (from cosmic These may be caused fast neutrons (from cosmic ’s) that ’s) that strike a proton in the scintillator. The recoiling proton mimics strike a proton in the scintillator. The recoiling proton mimics the the ee++ and the neutron captures. and the neutron captures.

Or they may be cause by muon produced isotopes like Or they may be cause by muon produced isotopes like 99Li and Li and 88He which sometimes decay to He which sometimes decay to ββ++n.n.

Estimating the correlated rate is much more difficult!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

Many Sites have been investigated as potential hosts Many Sites have been investigated as potential hosts to a reactor neutrino experiment.to a reactor neutrino experiment.

This is appropriate since getting the cooperation of the reactor This is appropriate since getting the cooperation of the reactor company is the main challenge.company is the main challenge.

SiteSitePowerPower

(GW(GWthermalthermal))BaselineBaseline

Near/Far (m)Near/Far (m)

ShieldingShieldingNear/Far (mwe)Near/Far (mwe)

SensitivitySensitivity90% CL90% CL

Krasnoyarsk, RussiaKrasnoyarsk, Russia 1.61.6 115/1000115/1000 600/600600/600 0.030.03

Kashiwazaki, JapanKashiwazaki, Japan 2424.0.0 300/1300300/1300 150/250150/250 0.020.02

Double Chooz, FranceDouble Chooz, France 8.48.4 150/1050150/1050 30/30030/300 0.030.03

Diablo Canyon, CADiablo Canyon, CA 6.76.7 400/1700400/1700 50/70050/700 0.010.01

Angra, BrazilAngra, Brazil 5.95.9 500/1350500/1350 50/50050/500 0.020.02

Braidwood, ILBraidwood, IL 7.27.2 200/1700200/1700 450/450450/450 0.010.01

Daya Bay, ChinaDaya Bay, China 11.511.5 250/2100250/2100 250/1100250/1100 0.010.01

Double-Chooz : site

Near detector @100-200 m from the nuclear coresin discussion with EDF

Far detector : using existing infrastructure 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

2 identical detectors goal : σrelative 0.6%

Double CHOOZ : detector structure

existing pit

7 m

7 m

7 m

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 new !

mechanical structure to house PMTs

Muons VETO of scintillating oil , thickness :60 cm

Shielding : main tank , steel thickness 15cm

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

Performances (expected):• S/B : 10 100• target : 5.5 12.7 m3

• analysis errors : 1.5% 0.2%

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

420 440 460 480 500 520 540 560 580 6000,000

0,002

0,004

0,006

0,008

0,010

0,012

0,014

0,016

0,018

0,020

ab

sorb

an

ce

wavelength [nm]

29.09. 06.10. 25.10. 03.11. 17.11.

Stability 0,1 % Gd in PXE

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 shiftersIn-loaded scintillators (0.1 %, 5% loading) are counting @Gran SassoSpare stable recipes available (MPIK, INFN/LNGS)

Gd-Acac molecule

Completion of the R&D first half of 2004 Choice of the final scintillator Stability & Material compatibility Aging tests (MPIK, Saclay)

3+Gd

Warning : long term stability and acrylic vessel damage

Double CHOOZ: close detector

Dense material

~10-15 m

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 signalRatio at the far detector

• no direct measurement • accidental miscorrection

may mimic or suppress an effect• fake neutron capture signal rate underestimated

The baseline is too short to see the L/E pattern

Reactor experiment sensitivity

The location of the transition from rate to shape depends on the The location of the transition from rate to shape depends on the level of systematic error.level of systematic error.

90%CL 90%CL at at ΔΔmm22 = 3×10 = 3×10-3-3 eV eV22

From Huber, Lindner, Schwetz and Winter

Statistical error only

Fit uses spectral shape only

Exposure (GW·ton·years)

sin2 2

θ 13 S

ensi

tivi

tyThe sensitivity may be pushed lower with large detectors The sensitivity may be pushed lower with large detectors sensitive to a shape deformation.sensitive to a shape deformation.

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

νμ CC NC Beam νesignal

Beam unoscillated 22858 10594 229

Beam oscillated 5758 10593 229 853

After cuts 3.6 15.4 19.1 175

For 5years @ 4 1020 pot/year, 50kton detector, sin2(2θ13) = 0.1

Nova : tentative schedule

5 M$/year to improve proton intensity:• Booster cycle 3 7-10 hz• decrease losses• …

MINOS run ? (goal : 16. E20 pot

N0νA sensitivity

MassHierarchy

CPViolation

Reactor contribution to CP violation (Shaewitz)

Input:• sin22θ13=0.058• δCP = 270°• sin22θ23=10.06

The θ23 Degeneracy Problem

Atmospheric neutrino measurements are sensitive to sin22θ23

But the leading order term in νμ→νe oscillations is

If the atmospheric oscillation is not exactly maximal (sin22θ23<1.0) then sin2θ23 has a twofold degeneracy

E

LmP x

2232

232 27.1

sinθ2sin)(

E

LmP e

2132

132

232 27.1

sinθ2sinθsin)(

45º 90º2θ 2θθθ

sin2 sinsin2222θθ2323

sinsin22θθ2323

Solving the θ23 degeneracy with reactor (Shaewitz)

Input:• sin22θ13=0.058• δCP = 270°• sin22θ23=10.06

European Strategy (Venice , december 03)4 phases program for and

1) CNGS/MINOS (2005-2010)2) JPARC and Reactor(?) (2008-2013)3) Superbeam/betabeam (>2014 )4) Neutrino factory (>2020 )

In any case a MW machine is central

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

Concluding on european activities (and dreams …)

SPL 330

EURISOL 200

PS/SPS upgrade 70

Decay Ring 340

Super beam 70

UNO like detector 500

Grand total 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