1

First Results from Double Chooz

• Current Status of Neutrino Oscillations and θ13 • Recent Double Chooz Results

On behalf of the Double Chooz Collaboration

MIAMI 2011 Conference

December 16th 2011

Brandon White, University of Tennessee

Double Chooz Collaboration

2 2

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Oscillations •  PMNS matrix describing the relationship between mass and flavor

eigenstates. •  θ12, θ23, Δm2

21, and Δm231 oscillation parameters are now

experimentally known.

Atmospheric Super Kamiokanda & MINOS

Solar SNO & KamLand

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s232 = sin2θ23 = 0.50−0.06

+0.07

Δm312 = 2.40−0.11

+0.12 ×10−3eV 2

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s122 = sin2θ12 = 0.318−0.016

+0.019

Δm212 = 7.59−0.18

+0.23 ×10−5eV 2

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U =

1 0 00 c23 s230 −s23 c23

⎡

⎣

⎢ ⎢ ⎢

⎤

⎦

⎥ ⎥ ⎥

c13 0 s13e−iδ

0 1 0−s13e

−iδ 0 c13

⎡

⎣

⎢ ⎢ ⎢

⎤

⎦

⎥ ⎥ ⎥

c12 s12 0−s12 c12 00 0 1

⎡

⎣

⎢ ⎢ ⎢

⎤

⎦

⎥ ⎥ ⎥

θ13 parameter is small making measurements difficult

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Measuring θ13 •  From reactor neutrino experiments looking for

survival of electron anti-neutrinos.

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P νµ →νe( ) ≈ sin2θ23 sin2 2θ13sin2(Δ 31 −αL)(Δ 31 −αL)

2 Δ 312 + 2sin2θ13 sin2θ23 sin2θ12 cosθ13

sin(Δ 31 −αL)(Δ 31 −αL)

Δ 31

∗sin(αL)(αL)

Δ 21⋅ (cosΔ 32 cosδ − sinΔ 32 sinδ) + cos4 θ13 cos2θ23 sin

2 2θ12sin2(αL)(αL)2

Δ 212

•  From accelerator neutrino experiments looking for appearance of electron neutrinos from muon neutrino beams.

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Reactor Neutrinos •  Much cleaner measurement.

Eν = 4MeV Δm213 = 2.5 10-3 eV2

Short baseline reactor experiment sensitivity

Longer baseline reactor experiments KamLand sensitivity range Black sin2 2θ13= 0

Red sin2 2θ13= 0.1

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CHOOZ Experiment

•  The original CHOOZ Experiment was designed to measure θ13. First results in 1998.

•  Due to limited statistics and high systematic uncertainty of the absolute neutrino flux, only upper limits were set for sin2 2θ13 .

M. Apollonio[CHOOZ Collaboration], PLB 466 1999 415

sin2 2θ13 < 0.19 @ Δm213 = 2.0 10-3 eV2

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New Generation of Reactor Experiments

•  Near and Far detectors are used in the new generation of detectors. •  The relative rates between near and far will eliminate the reactor flux

uncertainty. Double Chooz: Far detector data taking since April 2011 First results presented at LowNu11 in November 2011 Near detector running early 2013

Reno: Both near and far detectors running since August 2011

Daya Bay: First Near Hall running since August 2011 Full running Summer 2012

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Accelerator Neutrino Experiments

•  T2K: Running (delayed now due to the earthquake and tsunami) •  MINOS: Running •  Noνa: Under Construction

MIN

OS

: arX

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108.

0015

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T2K

: arX

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106.

2822

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Double Chooz •  Double Chooz was designed on improvements of

the first CHOOZ experiment. •  Two identical detectors will be deployed, one at

the previous CHOOZ site (~1.05km from reactors) and a near detector (~400m from reactors).

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Detector Design

Target area: 10.3m3 liquid scintillator doped with Gd

Gamma Catcher: 22.3m3 liquid scintillator

Buffer Area: 110m3 non-scint. mineral oil

Inner Veto: 90m3 liquid scintillator

Outer Muon Veto:

Scintillator Plastic

15cm Steel Shielding

•  Reactor electron anti-neutrinos are detected by inverse beta decay reactions inside the target area.

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Detecting Reactor Anti-Neutrinos •  The electron anti-neutrinos are detected with inverse beta decay

reactions.

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ν e + p = n + e+

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Δt ≅ 30µs

Reactor Spectrum

Thermal Power from EDF Time Evolved Fission Rates

- Th.A. Mueller et al, Phys.Rev. C83(2011) 054615. - P. Huber, Phys.Rev. C84 (2011) 024617

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Calibration Data

68Ge In Gamma Catcher

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252Cf Source Spontaneous fission neutrons deployed in Target

Preliminary Data H Gd

Gd + H Gd + Gd

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Far Detector Outer Veto Outer Veto and Chimney

Muons tagged by OV and Inner Detector

Preliminary

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Inner Veto

Muon rates from Inner Veto Michel Electrons after tagged stopping Muons

Detector Timing working well down to the µs level

Preliminary

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Events Following Muons

H neutron Capture

Gd neutron Capture

Preliminary

Visible Energy Spectrum Rate of neutron capture on Hydrogen following Muons

Preliminary

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Backgrounds Accidental:

Gamma from radioactive contamination followed by a thermalized neutron from an untagged muon. Rate 0.332 0.004 day-1

Long lived Muon induced isotopes: Beta + n decay of 9Li and 8He Rate 2.3 1.2 day-1

Muon induced fast neutrons: Recoil proton followed by thermalized neutron. Rate 0.7 0.5 day-1

γ µ

n

µ

nβ

n

p +

+

+

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Two Reactors Off Data

•  Double Chooz had the unique opportunity to have ~1 day of running with both reactors off.

Preliminary

•  Two recorded events during this time within IBD prompt visible energy. •  9.8 MeV (200ms after high

energy Muon) •  4.8 MeV (241ms after high

energy Muon)

Consistent with background estimations from data

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Inverse Beta Decay •  Neutrino event candidates via Inverse Beta Decay

Reactions: –  Prompt Event (0.7-12 MeV visible energy) –  Delay Event (6-12MeV visible energy) –  Delta T between prompt and delay(2-100µs) –  Veto events 1ms after tagged muons. –  Multiplicity conditions

•  No event 100µs before prompt events •  Only delay event 400µs after prompt events

–  Cut of PMT spontaneous light emission •  Ratio of max charge/total charge •  RMS of PMT hit time

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Timing and Spatial Distribution

•  Time between Prompt and Delay events

•  Distance between Prompt and Delay events

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Candidate Position Reconstruction

•  No Cuts made on position

•  Cuts are made for delay events to capture on Gd

•  Well contained in target

Prompt Events

Delay Events

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Inverse Beta Decay Rates

Day0 20 40 60 80 100 120 140

)-1

Neu

trin

o R

ate

(day

0

20

40

60

80

rate�Expected

rate�Measured

Neutrino rate (background subtracted)

Double Chooz preliminary

Day0 20 40 60 80 100 120 140

Rat

e D

ata-

MC

rat

io

0.0

0.5

1.0

1.5

2.0

2.5

Neutrino Rate Data-MC ratio (background subtracted)

Double Chooz preliminary

24 Visible Energy Spectrums

Delayed energy [MeV]6 7 8 9 10 11 12

Eve

nts

/0.2

5 M

eV

0100200300400500600700800900

1000

Data

Neutrino MC

Double Chooz preliminary

Delayed energy [MeV]6 7 8 9 10 11 12

Eve

nts

/0.2

5 M

eV

0100200300400500600700800900

1000

Energy [MeV]2 4 6 8 10 12

Even

ts

0

100

200

300

400

500

600

700

PRELIMINARY

Double Chooz

DataNo Oscillation

) = 0.08513θ(22Best Fit: sin2 = 2.4e-3 eV13

2 mΔ @ Lithium-9Fast nAccidentals

Energy [MeV]2 4 6 8 10 12

Even

ts

0

100

200

300

400

500

600

700

Prompt Delay

Rate + Shape Analysis Rate Only Analysis

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sin2 2θ13 = 0.085 ± 0.029(stat) ± 0.042(syst)

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sin2 2θ13 = 0.093 ± 0.029(stat) ± 0.073(syst)

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Results Presented

First at LowNu11 Conference November 2011

More recently presented on CBS “The Big Bang Theory” December 2011

Episode: “The Speckerman Recurrence” Images Copyright CBS http://www.cbs.com/shows/big_bang_theory/video

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Combined Results

0

10

20

30

Δχ2

T2K+MINOS+CHOOZ+DCT2K+MINOS+CHOOZCHOOZDCDC+CHOOZ

★

0 0.1 0.2 0.3 0.4 0.5sin22θ13

-1

-0.5

0

0.5

1

δ / π

normal orderingΔm2

DC = 2.35e-3 eV2

68%, 95% CL (2 dof)

curves: T2K+MINOS +CHOOZshaded: T2K+MINOS +CHOOZ+DC

3σ

2σ

A non-zero θ13 value above 3σ.

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Comparison to Theory

0

2

4

6

8

10

12

14

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Δχ2

arXiv:hep-ex/0410081v1

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Conclusion •  Double Chooz Far Detector has been running stably

since April of this year, publication coming soon. •  Double Chooz will continue to run with the Far detector

as the Near detector is built (completed 2013). •  A “clean” measurement of a large θ13 will impact current

and future accelerator neutrino experiments probing for CP-violating phase and mass hierarchy.

€

P νµ →νe( ) ≈ sin2θ23 sin2 2θ13sin2(Δ 31 −αL)(Δ 31 −αL)

2 Δ 312

+2sin2θ13 sin2θ23 sin2θ12 cosθ13sin(Δ 31 −αL)(Δ 31 −αL)

Δ 31

∗sin(αL)(αL)

Δ 21⋅ (cosΔ 32 cosδ − sinΔ 32 sinδ)

+cos4 θ13 cos2θ23 sin

2 2θ12sin2(αL)(αL)2

Δ 212

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Thank You

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Backup Slides

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Readout Threshold

Preliminary

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Data Analysed

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Spontaneous Light Emission Cut

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Prompt vs Delay

prompt E (MeV)0 2 4 6 8 10 12

del

ayed

E (M

eV)

6

7

8

9

10

11

12

0

1

2

3

4

5

6

7delayed vs EpromptE

Double Chooz preliminary

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Background There are unavoidable events that can mimic inverse beta decay

in our detector. Much care was taken in the detector construction to limit these

events. We must carefully determine the rate and energy spectrum of

these events to get a pure anti-neutrino spectrum.

€

ν e + p = n + e+

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Δt ≅ 30µs

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Accidental Background

–  Accidental background events come from prompt-like signal from radioactivity.

–  Muon induced long lived isotopes resulting in beta + n.

–  Fast Neutrons with recoil protons

γ

µ

n Gd

µ

9Li

n β

Gd n

p

Gd

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Accidental BG •  Accidental events are found by using an off time window between

prompt and delay events of Δt 1-100ms. •  Rate 0.332 0.004 day-1

Preliminary

+

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Correlated BG 9Li

•  For 9Li events, look for time since last high energy muon to prompt event.

Rate 2.3 1.2 day-1

Preliminary

+

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Correlated BG Fast Neutrons

•  For Fast Neutron events, look at high energy prompt spectrum above neutrino signal energy range.

Rate 0.7 0.5 day-1 Preliminary

+

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Reactor Spectrum

•  A total reactor errors of 1.74% remains for a far detector analysis only.

•  Having two identical detectors will cancel these uncertainties.

Preliminary

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Preliminary Data •  Stable Data taking at the Far Detector begain

April 13, 2011

Now over 100 days of physics data analyzed.

~75% physics data efficiency ~10% calibration data Preliminary

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Neutrino Future

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P ν µ →ν e( ) ≠ P νµ →νe( )For accelerator experiments compare appearance rates for neutrinos and anti-neutrinos.

arX

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710.

0554

v2

Noνa: Beam from Fermi Lab to detector in Ash River MN Baseline 810km

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Two Reactors Off Data •  Due to one reactor undergoing two month refueling period and

tests to the second reactor, one day of data was taken with both reactors off.

Preliminary

•  Three recorded events during this time with prompt visible energy < 30MeV •  2 events with prompt

visible energy within the IBD spectrum range (9.8 and 4.8 MeV).

•  1 event with high prompt visible energy (26.5 MeV)

Consistent with background estimations from data

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Included Theories

arXiv:hep-ex/0410081v1

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Preliminary Results

Preliminary

Rate + Shape Analysis Rate Only Analysis

€

sin2 2θ13 = 0.085 ± 0.029(stat) ± 0.042(syst)

€

sin2 2θ13 = 0.093 ± 0.029(stat) ± 0.073(syst)