NOnA in the context of of future n oscillations projects

1
NOnA in the context of of future n
oscillations projects

• 
  Leslie Camilleri
• CERN,
  PH
• Lausanne,
  May 15, 2006

2
Plan of the talk

• A very brief theory of neutrino oscillations.
• The Past The discovery of oscillations in
• Solar and Atmospheric neutrino
  experiments.
• The Present programmes
• Double-b decay
• Reactors
• Accelerator long baseline experiments.
• NOnA

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Theory 2
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Theory 3
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The PAST

• Discovery of Oscillations

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Solar spectrum
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Real Time

• Charged Current (CC) reactions on nucleons
• ne n ? p e- At quark level ne d ?
  u e-
• Sensitive ONLY to f(ne), the flux of ne
• Neutral Current (NC) reactions on nucleons
• nx n ? n nx
• Sensitive to flux from ALL flavours, f(ne, nm,
  nt)

CC and NC on nucleons negligible in WATER due to
Oxygen being very tightly bound (gt15
MeV) Important in HEAVY WATER deuterium binding
energy only 2 MeV.
Sensitive to f(ne) only

• Elastic Scattering (ES) on electron
• ES is large in WATER
• and HEAVY WATER

Sensitive to flux from ALL flavours, f(ne, nm,
nt) But rate smaller than W exch.
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Super-Kamiokande The Detector
50000 tons ultra-pure water
22500 tons fiducial volume
1 km overburden 2700 m.w.e.
Sensitive to Elastic Scattering ONLY
Mostly nes
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Suppression relative to Standard Solar Model
Suppression relative to Standard Solar Model is
observed in all experiments.
Is it due to a misunderstanding as to how the
sun works ? Standard solar model. Or are the
neutrinos disappearing ?
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SNO (Heavy water)Sensitive to CC, NC,
ES.Calculate flux from each.
ne only ne mostly ne, nm, nt
Using ALL neutrinos Fully Consistent with
Standard Solar Model
CC
Neutrinos DO NOT disappear.
They just Change Flavour ! Driven by
enhanced oscillations in the dense matter
of the sun.
NC
SSM
fmt
ES SK
ES
fe
13
Confirmed by KAMLAND Reactor antineutrinos to
detector at Kamioka
KAMLAND
Solar Experiments
KamLAND Solar Completely consistent
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Atmospheric Neutrinos ne and nm
Produced by p and K decays in upper atmosphere
Zenith angle ? Baseline
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m/e identification Super-Kamiokande
Detect through neutrinos through their charged
current interactions. nm X ? m
ne X ? e

• sharp ring

e fuzzy ring due to many particles in shower
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Suppression of nm zenith angle and energy
dependent
No oscillations
Oscillations
Explained by oscillations Similar results
from MACRO
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Suppression of nm in accelerator experiments
K2K, MINOS
They look for nm disappearance to observe
oscillatory pattern in energy spectrum.
Measure Dm2 and q23
MINOS (NUMI beam) 732km
K2K 232 km
Fermilab to Soudan Mine Same beam as NOnA. Will
concentrate on MINOS
KEK to SuperKamiokande Water Cerenkov Detector
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The MINOS/NOnA Neutrino beam NUMI.
Move horn and target to change energy of
Beam
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MINOS detector
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Near detector results
The NUMI beam is well understood.
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Far detector results II
Ratio of
Observed over
Expected with no oscillations
Suppression of events at low energy
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New MINOS measurements
(Experiment ended)
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3-family oscillation matrix
S sine c cosine

• d CP violation phase.
• q12 drives SOLAR oscillations sin2 q12 0.314
  0.056-0.047 (- 16)
• q23 drives ATMOSPHERIC oscillations sin2 q23
  0.44 0.18-0.10 (44 -22)
• q13 the MISSING link ! sin2 q13 lt 0.03 Set by a
  reactor experiment CHOOZ.

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CHOOZ A reactor experiment to measure q13

• Excellent source of MeV antineutrinos.
• If they oscillate to nm or nt they would NOT
  have enough energy to create
• ms or ts via CC interactions.
• Cannot study oscillations through an appearance
  experiment.
• Must study oscillations via ne disappearance.
• Pee 1 sin2 2q13 sin2 (Dm232L)/(4En) Same
  Dm2 as atmospheric.
• With a detector at 1 km, L/E 1km/1MeV
• same as atmospheric 1000km/1GeV.
• Can probe same Dm2

Distortion of the ne energy spectrum Oscillation
effects are SMALL Must know ne energy
spectrum well to control SYSTEMATIC CHOOZ
Systematic uncertainty 2.7 Mostly from flux and
n cross sections.
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Technique
Measured through inverse b decay ne p
e n

• Detectors Liquid scintillator loaded with
  gadolinium Neutron capture ? photons

e annihilates with e- of liquid MeV
ne
n captured by Gadolinium 8 MeV of photons
emitted within 10s of msec.
Delayed Coincidence of 2 signals
Did NOT find any distrortions. Set an upper
limit sin22q13 lt 0.12 or sin2 q13 lt
0.03 for Dm2atm 2.5 x 10-3 eV2

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Mass hierarchySign of Dm223
ne
nm
nt
Normal Hierarchy
Inverted Hierarchy
Dm122 7.9 x 10 -5 eV2
m3
m2 m1
gt 0.05 eV2
Dm232 2.4 x 10-3 eV2
Dm232 2.4 x 10-3 eV2
m2 m1
Dm122 7.9 x 10 -5 eV2
m3
Oscillations only tell us about DIFFERENCES in
masses Not the ABSOLUTE mass scale Direct
measurements or Double b decay Upper limit
Tritium b decay mass (ne) lt 2.2 eV Lower limit
(2.4 x 10-3)1/2 gt 0.05 eV
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Why are neutrino masses so low????
Other particles
Fascinating to me !!!!!!
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Whats needed next?

• Determine q13.
• Determine the mass hierarchy.
• Any CP violation in the neutrino sector?

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Correlations in Oscillation Probability
From M. Lindner
Measuring P (nmne) does NOT yield a UNIQUE value
of q13 . Because of correlations between q13, dCP
and the mass hierarchy (sign of Dm231) CP
violation Difference between Neutrino and
Antineutrino Oscillations Mass hierarchy
accessible through Matter effects.
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8-fold degeneracies

• q13 - d ambiguity.
• Mass hierarchy two-fold degeneragy

A measure of Pme can yield a whole range of
values of q13 Measuring with ns as well reduces
the correlations

• q23 degeneracy
• For a value of sin2 2q23, say 0.92, 2q23 is
  67o or 113 o and q23 is 33.5o or 56.5
• In addition if we just have a lower limit on sin2
  2q23, then all the
• values between these two are possible.

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Matter Effects

• In vacuum and without CP
  violation
• P(nm-ne)vac sin2 q23 sin2 2q13 sin2
  Datm
• with Datm 1.27 Dm232 (L/E)
• For Dm232 2.5 x 10-3 eV2 and for maximum
  oscillation
• We need Datm p/2 ? L(km)/E(GeV)
  495
• For L 800km E must be 1.64 GeV, and
  for L 295km E 0.6 GeV
• Introducing matter effects, at the
  first oscillation maximum
• P(nm-ne)mat 1 - (2E/ER)
  P(nm-ne)vac
• with ER 12 GeVDm232/(2.5x10-3)2.8
  gm.cm-3/r 12 GeV
• - depends on the mass hierarchy.
• Matter effects grow with energy and
  therefore with distance.
• 3 times larger (27) at NOnA (1.64
  GeV) than at T2K (0.6 GeV)

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The NEAR Future
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Neutrinoless Double-b decay
(A,Z) ? (A,Z2) 2 e-
(A,Z) ? (A,Z2) 2 e- 2n
Standard 2-neutrino double b decay
Neutrinoless double b decay
Can only happen if the neutrino
is reabsorbed as an Antineutrino
Helicity must flip ? non-zero mass If the
neutrino is its own Antiparticle Majorana
e-
e-
e-
e-
ni
ni
ni
N
N
W-
W-
W-
W-
N
N
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Detection
Look for a peak at the end point of
the2-neutrino spectrum
New experiments will use 130Te, 132Xe, 76Ge,
100Mo Will observe the 2 electrons
through bolometric, calorimetric or tracking
techniques Sensitivity down to 100-300 meV
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q13 with Reactors How to reduce systematics
Pee 1 sin2 2q13 sin2 (Dm232L)/(4En) near
oscillation maximum
Advantage NO dependence on dCP or mass
hierarchy No ambiguities.
Disadvantage Cannot determine them!
How to reduce systematics ?

• Solution Use 2 detectors
• Additional NEAR detector measure flux and cross
  sections BEFORE oscillations.
• Even better interchange NEAR and FAR detectors
  part of the time
• to reduce detector systematics

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Proposed experiments
CHOOZ systematics was 2.7
Experiment Location Sites Systematics Limit
Double CHOOZ France Near/Far 0.6 0.03
Braidwood USA Near/Far 0.3 0.005
Daya Bay China Near/Mid/Far 0.36-0.12 0.009-0.006
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Future (Accelerators)
T2K (Japan) 295km
NOnA (NUMI beam) 810km
Both projects are Long Baseline Off-axis
projects. They search for nm ne oscillations by
searching for ne appearance in a nm
beam. Determine that q13 is non-zero. Measure
it? Mass hierarchy?
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OFF-AXIS Technique
Most decay pions give similar neutrino energies
at the detector The Neutrino Energy Spectrum is
narrow know where to expect ne appearance Can
choose the off-axis angle and select the mean
energy of the beam. ( Optimizes the
oscillation probability)
q 0o
q 2o
q 3o
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T2K
0.7 GeV

• New 40 GeV Proton Synchrotron (JPARC)
• Reconstructed Super-K
• Near detector to measure unoscillated flux
• distance of 280 m (Maybe 2km also)
• JPARC ready in 2008
• T2K construction 2004-2008
• Data-taking starting in 2009

nm
ne
ne from K decays (hashed) and m decays
0.4 background at peak . Irreducible
background to a nm ? ne search.
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nm disappearance Dm232 and q23.
Position of dip
Dm232 to an accuracy of 10-4 eV2
Depth of dip
Sin22q23 to an accuracy of 0.01 Factor of 10
improvement in both
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Measurement of q13.

• ne appearance

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Sensitivity, correlations, degeneracies
Limit on sin2 2q13 if we take into account
correlations and degeneracies
Sin2 2q13 0.01 - 0.04
-150 0 dCP
150
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T2K II Hyper-Kamiokande
One megaton Water Cerenkov and 4MW accelerator.
Improvement by more than an order of magnitude on
q13 sensitivity

• All degeneracies included

0.01
sin22q13
0.001
d
150o
-150o
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T2K II Sensitivity to dCP
Definition For each value of sin2 2q13 The
minimum d for which there is a difference Of 3s
between CP and NO CP violation
Limited by statistics
d
50o
CP violation asymmetry (n,n difference)
decreases with increasing sin2 2q13
20o
0.0001
0.01
Sin2 2q13
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NOnA Detector
Given relatively high energy of NUMI beam,
decided to optimize NOnA for resolution of the
mass hierarchy Detector placed 14 mrad (12 km)
Off-axis of the Fermilab NUMI beam (MINOS). At
Ash River near Canadian border (L 810km) New
site. Above ground. Fully active detector
consisting of 15.7m long plastic cells filled
with liquid scintillator Total mass 30
ktons. Each cell viewed by a looped WLS fibre
read by an avalanche photodiode (APD)
760 000 cells
TiO2 Coated PVC tubes
n
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NOnA
The quantum efficiency of APDs is much higher
than a pms 80 . Especially at the higher
wave lengths surviving after traversing the
fibre.
Asic for APDs 2.5 pe noise ? S/N 12
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Avalanche Photodiode
Photon

• Hamamatsu 32 APD arrays

• Pixel size 1.8mm x 1.05mm
• (Fibre 0.8mm diameter)
• Operating voltage 400 Volts
• Gain 100
• Operating temperature -15o C
• (reduces noise)

Asic for APDs 2.5 pe noise ? S/N 30/2.5 12
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Fibre/Scintillator cosmic ray test
Inserted looped 15.7m long fibre in 60 cm
long PVC tube filled with liquid
scintillator. Exposed to cosmic rays.
Measured 20 p.e. For a mip signal at the far end.
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The Proton Beam as of today
2.8 x 1013 ps per spill
(2.2 secs)
For a Fermilab year of 2 x 107 secs 2.4
x 1020 pots/year. MINOS baseline 3.4 x 1020
pots/year.
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The Beam

• PROTONS 6.5 x 1020 protons on target per year.
• Greatly helped by
• Cancellation of BTeV
• Termination of Collider programme by 2009.
• A gain of a factor of gt 2 in numbers of protons
  delivered.
• As of today, this extrapolates to 4.8 x 1020
• Longer term Construction of an 8 GeV proton
  driver x 4
• 25.2 x 1020 protons on target per year is the
  goal.

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The Beam Same NUMI beam as MINOS
Can select low, medium and high energy beams by
moving horn and target Best is the Medium
energy beam
14 mrad
14 mrad
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Beam spectra
nm ? nt
Signal Sin2 2q13 0.04
Beam ne background 0.5
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nm- ne separation
Low energy
High energy
Electrons (shower)
Electrons (shower)
Muons
Muons
po in NC also a problem. Signal ne efficiency
24. nm CC background 4 x 10-4
nm NC background
2 x 10-3
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Summary of backgrounds
Background Events Error Error
Beam ne 11.9 7 0.8
Nm CC 0.5 15 0.08
NC 7.1 5 0.4
Total 19.5 5 0.9
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Signal and Backgrounds

• Statistical Power why this is hard and we need
  protons

0.01 0.05 0.1
0.01 0.05 0.1
For sin2 2?13 0.1 ? S142.1, B19.5 ?
S 71.8, B12.1
5 yrs at 6.5E20 pot/yr, efficiencies included
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3 s discovery limits for q13 0
2.5 years each n and n.
5 years n

• Discovery limit is better than 0.02 for ALL ds
  and BOTH mass hierarchies.

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3 s discovery limits for q13 0Comparison with
Proton Driver
2.5 years each n and n.
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3 s discovery limits for q13 0Comparison with
T2K and 2 Reactor experiments
T2K
Braidwood Double Chooz
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Resolution of mass hierarchy

• Fraction of d over which the mass hierarchy can
  be resolved at 2s.
• Equal amounts of neutrino and antineutrino
  running 3 years each assuming Phase I.
• Near the CHOOZ limit the mass hierarchy can be
  resolved over 50 of the range of d.
• T2K Phase I can only resolve the hierarchy in a
  region already excluded by CHOOZ.
• Because of its lower energy.
• Some small improvement if we combine T2K and NOnA
  results

T2K
CHOOZ limit
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Looking further ahead

• With a proton driver, Phase II, the mass
  hierarchy can be resolved over 75 of d near the
  CHOOZ limit.
• In addition to more protons in Phase II, to
  resolve hierarchy a second detector at the second
  oscillation maximum can be considered
• Datm 1.27 Dm232 (L/E) 3p/2.
• L/E 1485, a factor of 3 larger than at 1st max.
• For the same distance, E is 3 times
  smaller
• matter effects are smaller by a factor of
  3
• 50 kton detector at 710 km.
• 30km off axis (second max.)
• 6 years (3 n 3 n)

Determines mass hierarchy for all values of
d down to sin2 2q13 0.02
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CP reach

• To look for CP violation requires the proton
  driver.
• But combining with a
• second detector is what really becomes
• SIGNIFICANT.

Proton driver
Proton driver 2nd detector
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Near Detector to understand the beam
262 T 145 T totally active 20.4 T
fiducial (central 2.5 x 3.25 m)
8-plane block 10.6 T full 1.6 T empty
9.6 m
5 m
Muon catcher 1 m iron
Shower containment region
Target region
3.5 m
Veto region
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Neutrino spectra at near and far detectors
Far Detector x 800
ne CC events
Site 1.5
Site 2
nm CC events
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Cost and schedule

• Total cost (Far and near detectors, building,
  admin etc)
• 225 M
  
• (including 50
  contingency)
• Status
• Approved by Fermilab Program Advisory Committee
  Stage 1 Approval, (April 2005).
• Prioritized by NuSAG.
• Critical Decision Zero (CD0) granted. Mission
  need.
• Granted 10M in RD for generic oscillation
  experiment.
• Obtained CD1 approval Range of Schedules and
  costs.
• CD2 next Final cost, schedule and TDR.
• Proton Driver CD0 shelved at this stage. But RD
  can continue.
• Schedule
• Assumption Approval in 2006.
• Building ready May 2009.
• First kiloton October 2009.
• Completion July 2011.

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The road ahead
66
Conclusions

• The neutrino oscillation programme is very rich.
• The smallness of neutrino masses is fascinating.
• The mass hierarchy must be determined.
• Is there any CP violation in the neutrino sector?
• The road to these is the observation of a
  non-zero q13.
• The NUMI beam is functioning well.
• NOnA has a well-developed long term research
  programme.

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Near Detector in MINOS Surface Building
6.5 x 1020 pot in 75 mrad off-axis beam
Kaon peak
45,000 nm CC events
2,200 ne CC events
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Matter effects Mikheyev-Smirnov-Wolfenstein
ne n m nt
ne n m nt
ne
e -
All n flavours
Only ne flavour
Zo
W-
e - , N
e -, N
e -
ne
Introduces extra potential for ne
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q13 with Reactors
Pee 1 sin2 2q13 sin2 (Dm232L)/(4En) near
oscillation maximum
Advantage NO dependence on dCP or mass
hierarchy No ambiguities.
Disadvantage Cannot determine them!
Measured through inverse b decay ne p
e n
Distortion of the ne energy spectrum Oscillation
effects are SMALL Must know ne energy
spectrum well to control SYSTEMATICS. CHOOZ One
detector at 1100m Systematic uncertainty 2.7
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SK-I 8B Solar Neutrino Flux
PLB539 (2002) 179
May 31, 1996 July 15, 2001 (1496 days )
Electron total energy 5.0-20MeV
22400 ? 230 solar n events
8B flux 2.35 ? 0.02 ? 0.08 x106/cm2/s
Data / SSMBP2004 0.406 ?0.004(stat.) 0.014
-0.013 (syst.)
Data / SSMBP2000 0.465 ?0.005(stat.) 0.016
-0.015 (syst.)
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Far detector results I
In time with beam spill
Uniform spatial distributions
Intermodule gap
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Limits
Rate (Ton ½)-1 (Phase space factor) x (Matrix
element)2 x ltmeegt2
ltmeegt Ue12m1 Ue22m2Ue32m3
Claim
Small if m3 is heaviest state, because multiplied
by Ue32 ( sin2 q13) which is small
(lt0.03). Better with inverted hierarchy
New experiments will go down 100-300 milli eV
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CHOOZ Limits on q13
Looked for distortions of the expected energy
spectrum or in the rate
Did not find any.
Set a limit on sin22q13 lt 0.12 for
Dm2atm 2.5 x 10-3 eV2 or sin2
q13 lt 0.03
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Detection
Look for a peak at the end point of
the2-neutrino spectrum
One claim not generally believed
New experiments will use 130Te, 132Xe, 76Ge,
100Mo Will observe the 2 electrons
through bolometric, calorimetric or tracking
techniques Sensitivity down to 100-300 meV
75
Proposed experiments
Example Double CHOOZ
Importance of systematics
0.035 0.027
1
CHOOZ systematics Was 2.7
0.4
Experiment Location Sites Systematics Limit
Double CHOOZ France Near/Far 0.6 0.03
Braidwood USA Near/Far 0.3 0.005
Daya Bay China Near/Mid/Far 0.36-0.12 0.009-0.006