SUMMARY OF θ13 MEASUREMENTS AND PROSPECTS

AAP 2012 meeting, Honolulu Jelena Maricic University of Hawaii October 4, 2012

Executive Summary

Summary of θ13 measurements from reactors 2011-2012 Daya Bay θ13 ~8.7° (~8 σ zero exclusion)

RENO

θ13 ~9.8° (~6 σ zero exclusion)

Double Chooz

θ13 ~9.6° (~3 σ zero exclusion)

Summary of θ13 measurements from beams MINOS T2K

2CP 23

213

213

213

213

213

for δ =0, sin (2θ )=1,

sin (2θ ) = 0.053 at best fit

0.01 < sin (2θ ) < 0.12 at 90% C.L.

sin (2θ ) = 0.094 at best fit

0.03 < sin (2θ ) < 0

normal hierarcy:

inv

.19 at 90% C.L.

sin

erted hierarc

(2θ )

y:

= 0 excluded at 96% C.L.

θ13 ~7° (NH) θ13 ~9° (IH)

θ13 ~9° (NH) θ13 ~10° (IH)

~2 σ zero exclusion

~3 σ zero exclusion

Summary of θ13 measurements

Global fit from Daya Bay, RENO, Double Chooz and T2K:

1

2

3

4

Nσ

Fogli, Lisi, Marrone, Montanino, Palazzo, Rotunno: hep-ph/1205.5254 (2012)

Sin2 θ13 = 0.0241 ± 0.0025 (NH) Sin2 θ13 = 0.0244 ± 0.0025 (IH)

θ13 = 8.9°± 0.9° (~10% relative uncertainty)

Prospects

θ13 measured to be non zero with > 7σ C.L.

In the next 3 years expected to be known with 5% uncertainty

Going from the unknown to the best measured neutrino mixing angle: 2003-2012 But there is more to this measurement…

Outline

Introduction

Review of the experiments

Results of measurement θ13

Prospects

Material adopted from presentations from NOW2012 and ISNP 2012, from members of MINOS, T2K, Double Chooz, Daya Bay and RENO

Introduction

Starting point in 2003: CHOOZ

Last non-measured neutrino mixing angle!

Only the upper limit on the value of angle θ13

was set!

CHOOZ experiment constraint:

(νe → νe disappearance exp)

@∆m2atm = 2.3 10-3 eV2

sin2(2θ13) < 0.15

(90% C.L)

CHOOZ experiment R = 1.01 ± 2.8%(stat)±2.7%(syst)

νe → νx

M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374 M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374

θ13 < 11°

θ13 central to fundamental questions CP-violation phase and mass hierarchy

12 12 13 13

12 12 23 23

13 13 23 23

cos sin 0 cos 0 sin 1 0 0sin cos 0 0 1 0 0 cos sin

0 0 1 sin 0 cos 0 sin cos

CP

CP

i

i

eU

e

δ

δ

θ θ θ θθ θ θ θ

θ θ θ θ

− = − × ×

− −

“Solar” θ12 ~ 30° “Atmospheric” θ23 ~ 45° (SK + MINOS)

“Little mixing angle” θ13 < 11° (circa 2011)

(CHOOZ)

Value of θ13 directly influences prospects of

measuring CP violation phase in the weak sector!

θ13 impacts measurements on ~few 100 m scale and above Interesting for nuclear reactor monitoring with neutrinos

Δm221=(7.50+0.19

-0.20)×10-5 eV2

(KamLAND) Δm2

32=(2.32+0.12-0.08)×10-3 eV2

(MINOS)

Hints on θ13 from global fits in 2005/2008

Fogli, Lisi, Marrone, Palazzo, Rotunno: hep-ph/0806.2649v2 (2008)

sin2θ 13 = 0.9+2.3−0.9 × 10−2

Fogli, Lisi, Marrone, Palazzo: hep-ph/0506083 (2005)

sin2 θ 13 = 0.016 ± 0.010

θ13 ~ 5°

θ13 ~ 7°

Large uncertainty and low non-zero exclusion level.

Global fit from KamLAND in March 2011

KamLAND collaboration: hep-ex/1009.4771

sin2 θ 13 = 0.020 ± 0.016

θ13 ~ 8°

Large uncertainty and low non-zero exclusion level.

Review of θ13 experiments

θ13 Measurement Strategies

Use muon neutrinos from accelerator: appearance search for electron neutrinos MINOS T2K

Use electron antineutrinos from nuclear reactor: disappearance search CHOOZ Double Chooz Daya Bay RENO

θ13 and Beam Experiments

MINOS

T2K

T2K uses off-axis beams to achieve: -Increased flux near oscillation max -Reduced high energy NC bkg

νµ

νµ

νe

νe

θ13 and Reactor Experiments

Reactor Near Detector Far Detector

( ) [ ][ ]

∆−=→

MeVm27.1sin2sin1

2312

132

ν

θννE

LmP ee

Eν ~ 4 MeV

(Flux)L2

L ~1.5km

< 14%

No Oscillations

Oscillated

νe νe

High precision measurement required: systematic error ~0.5%

θ13 & Beam Experiments Appearance probability :

dependences in sin(2θ13), sin(θ23), sign(∆m231), δ-CP phase in [0,2π]

θ13 & Reactor Experiments • <Eν> ~ a few MeV only disappearance experiments sin2(2θ13) measurement independent of δ-CP

• P(νe→ νe) = 1 - sin2(2θ13)sin2(∆m231L/4E) + O(∆m2

21/∆m231)

weak dependence in ∆m221

• a few MeV νe + short baselines negligible matter effects (O[10-4] )

sin2(2θ13) measurement independent of sign(∆m213)

Results of measurement θ13 with beams

MINOS Experiment

735 km νµ

MINOS - Main Injector Neutrino Oscillation Search

Two functionally identical detectors to reduce systematics

Near Detector • 1 km from target • 94 m underground, 225 mwe • Measures the energy spectrum and beam composition

Far Detector • 735 km from target • 700 m underground, 2070 mwe • Re-measures the neutrino beam

composition Near Detector

980 tons Far Detector

5,400 tons

Steel/scintillator tracking calorimeters • Alternate orthogonal orientation planes • Steel absorber 2.54 cm thick • Scintillator strips 4.1 cm wide, 1.0 cm thick • 1 GeV muons penetrate 28 layers • Longitudinal sampling = 1.4 radiation lengths • Optical WLS fiber readout to multi-anode PMTs

Detector Technology

Multi-anode PMT

Extruded PS scint. 4.1 x 1 cm

WLS fiber

Clear Fiber cables

2.54 cm Fe

U V planes +/- 450

Magnetized • <B> = 1.3T • Muon energy from

range/curvature • Distinguish μ+ from μ-

tracks

Neutrino Interactions in Detectors tr

ansv

erse

dire

ctio

n

ν e-

µ-

beam direction color scale represents energy deposition

νµ Charged Current νx Neutral Current νe Charged Current

long μ track & possible hadronic activity at vertex

short with compact EM shower profile

short with diffuse shower

120 GeV protons

Focusing Horns

2 m

675 m 15 m 30 m

νµ = 91.7%ν µ = 7.0%

νe +ν e =1.3%

Target

Neutrino mode Horns focus π+, K+

Decay Pipe

π-

π+

νμ

νμ

Monte Carlo

Neutrino Mode

Antineutrino Mode

120 GeV protons

Focusing Horns

2 m

675 m 15 m 30 m

νµ = 91.7%ν µ = 7.0%

νe +ν e =1.3%

Target

Neutrino mode Horns focus π+, K+

Decay Pipe

π+

π-

νμ

νμ

Monte Carlo Monte Carlo Antineutrino mode Horns focus π-, K-

ν µ = 39.9%νµ = 58.1%

νe +ν e = 2.0%

( )ν ν

→ ≈ +

2

2

2 2 312

23 13sin ( )sin ( ) sin m LP

E1.267 Δ

θ θμ e

νe Appearance Measurement

( )eν ν

→ ≈ +

2

2

2 2 3123

213sin ( )sin ( ) sin LP

E1.267 Δm

θ θμ

sensitive to neutrino mixing angle θ13, δCP, mass ordering

( ) ( )if 0, eCP eP P µµδ ν ν ν ν≠ → ≠ → In matter, νe CC scattering modifies oscillation probability ~30% in MINOS

10.6×1020 POT (ν mode)

Electron Appearance in FHC and RHC Beam

3.3×1020 ( ν mode) ν mode Expected (LEM>0.7):

69.1 (background, if θ13=0) 26.0 (signal, if sin2(2θ13)=0.1)

Observe:

88 events

ν mode Expected (LEM>0.7):

10.5 (background , if θ13=0)

3.1 (signal, if sin2(2θ13)=0.1)

Observe:

12 events

Library Event Matching (LEM)

2CP 23

213

213

213

213

213

for δ =0, sin (2θ )=1,

sin (2θ ) = 0.053 at best fit

0.01 < sin (2θ ) < 0.12 at 90% C.L.

sin (2θ ) = 0.094 at best fit

0.03 < sin (2θ ) < 0

normal hierarcy:

inv

.19 at 90% C.L.

sin

erted hierarc

(2θ )

y:

= 0 excluded at 96% C.L.

νe Appearance:ν and ν Combined Contour

● Second generation long-baseline neutrino-oscillation experiment;

● High intensity almost pure νµ beam from Main Ring in J-PARC is shot toward the Super-Kamiokande detector 295km away.

●

from Tokai to Kamioka

● The physics data-taking started in Jan. 2010, and stopped in March 2011 by the earthquake. Resumed almost a year later.

J-PARC in JAEA

Tokai

Tokyo

Kamioka

KEK

T2K experiment

J-PARC in JAEA

Super-Kamiokande J-PARC

Results of measurement θ13 with reactors

Locations

Double Chooz Daya

Bay RENO

Configurations Double Chooz

Daya Bay

300 mwe 115 mwe

1 km 400 m

Reactor Neutrino Detection Signature • Reactors as neutrino sources:

Nν s−1( )= 6NFiss s−1( )≈ 2 ×1011P s−1( )Chooz: P =2x4.25 GWth ⇒Nν~2x1021s-1

Neutrino detection via inverse β decay

Distinctive two-step signature: -prompt event Photons from e+ annihilation Ee = Eν - 0.8 MeV + O(Ee/mn) -delayed event Photons from n capture on dedicated nuclei (Gd) ∆t ~ 30 µs E ~ 8 MeV Gadolinium

Target: Gd doped scintillator 1 g/l Gd in LS

¹ºe + p+ ! e+ + n

The Double Chooz Far Detector Outer Veto (OV) plastic scintillator strips

Outer Steel Shielding 250 t steel (15 cm)

Inner Veto (IV) 90 m3 of scintillator in a steel vessel (10 mm) equipped with 78 PMTs (8 inches)

Buffer 110 m3 of mineral oil in a steel vessel (3 mm) equipped with 390 PMTs (10 inches)

γ-Catcher (GC) 22.3 m3 scintillator in an acrylic vessel (12 mm)

Target 10.3 m3 scintillator doped with 1g/l of Gd compound in an acrylic vessel (8 mm)

~7m

Calibration Glove Box

Daya Bay

θ13 Measurement with DC Far

Interaction Cross-Section

• Recalculations of spectra introduced normalization shift; “anomaly”?

• Th.A. Mueller et al, Phys.Rev. C83(2011) 054615.

• P. Huber, Phys.Rev. C84 (2011) 024617

( )( )

( )∑=

××=

}2,1{Reactors

,2

exp ,4

),(R

Rf

Rf

Rth

R

p tEtE

tPL

NtEN σ

πε

ν

Reference Spectra + Bugey4 “Anchor”

Normalize to Total Rate Measurement of Bugey4

( )( )

( )∑=

××=

}2,1{Reactors

,2

exp ,4

),(R

Rf

Rf

Rth

R

p tEtE

tPL

NtEN σ

πε

ν

Reduces reactor normalization uncertainty

from 2.70% to 1.76%

Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV

Delayed signal Evis = [6.0, 12.0] MeV

Delayed Coincidence Δt = [2, 100] µsec

Require Δt μ > 1 msec

PMT light noise rejection cuts

• PMT hits approx. homogeneous

• PMT hits approx. coincident in time

Multiplicity conditions:

• No extra events around signal

Background rejection:

• No coincident signal in OV

• Require Δt μ > 500 msec if Eμ > 600 MeV

Plus three irreducible backgrounds:

• Accidentals

• Cosmogenic 9Li

• Fast neutrons/stopping muons

Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV

Delayed signal Evis = [6.0, 12.0] MeV

Delayed Coincidence Δt = [2, 100] µsec

Require Δt μ > 1 msec

PMT light noise rejection cuts

• PMT hits approx. homogeneous

• PMT hits approx. coincident in time

Multiplicity conditions:

• No extra events around signal

Background rejection:

• No coincident signal in OV

• Require Δt μ > 500 msec if Eμ > 600 MeV

Preliminary

Trigger efficiency • Threshold at 400keV (ε=50%) • ε=100% above 700keV

Minimum visible energy of ν signal Prompt

energy cut

Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV

Delayed signal Evis = [6.0, 12.0] MeV

Delayed Coincidence Δt = [2, 100] µsec

Require Δt μ > 1 msec

PMT light noise rejection cuts

• PMT hits approx. homogeneous

• PMT hits approx. coincident in time

Multiplicity conditions:

• No extra events around signal

Background rejection:

• No coincident signal in OV

• Require Δt μ > 500 msec if Eμ > 600 MeV

Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV

Delayed signal Evis = [6.0, 12.0] MeV

Delayed Coincidence Δt = [2, 100] µsec

Require Δt μ > 1 msec

PMT light noise rejection cuts

• PMT hits approx. homogeneous

• PMT hits approx. coincident in time

Multiplicity conditions:

• No extra events around signal

Background rejection:

• No coincident signal in OV

• Require Δt μ > 500 msec if Eμ > 600 MeV

Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV

Delayed signal Evis = [6.0, 12.0] MeV

Delayed Coincidence Δt = [2, 100] µsec

Require Δt μ > 1 msec

PMT light noise rejection cuts

• PMT hits approx. homogeneous

• PMT hits approx. coincident in time

Multiplicity conditions:

• No extra events around signal

Background rejection:

• No coincident signal in OV

• Require Δt μ > 500 msec if Eμ > 600 MeV

Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV

Delayed signal Evis = [6.0, 12.0] MeV

Delayed Coincidence Δt = [2, 100] µsec

Require Δt μ > 1 msec

PMT light noise rejection cuts

• PMT hits approx. homogeneous

• PMT hits approx. coincident in time

Multiplicity conditions:

• No extra events around signal

Background rejection:

• No coincident signal in OV

• Require Δt μ > 500 msec if Eμ > 600 MeV

• 41% of 9Li BG is rejected by additional muon veto (~5% live-time loss)

• 28% of fast neutron/stop μ BG is rejected by OV anticoincidence

Candidate Rate Variation

Before 9Li reduction cut, no OV anticoincidence applied

Not background-subtracted Rate consistent with expectation

Cross-check: Reconstructed Vertex Position

Events well-localized within target Note: no spatial cuts applied in candidate selection

Detector Calibration

1. PMT and electronics gain non-linearity calibration

LED light injection system

2. Correct for position dependence

Spallation neutron H captures

3. Correct for time stability Spallation neutron Gd captures

4. Energy scale Radioactive sources deployed

into ν-target and γ-catcher

Energy Calibration

Neutron Detection Efficiency Energy & time window, Gd fraction, spill in/out effects • 252Cf source deployed into ν-target and γ-catcher

Backgrounds Accidentals • Prompt: radiation hit on PMT • Delayed: spallation neutron capture • Prevented by radiopurity & shielding • Measured from off-time windows: 0.261 +/- 0.002 day-1

Cosmogenic 9Li • Prompt: beta emission • Delayed: neutrons from long-lived decays • Measured from Δtμ & spatial muon coincidence: 1.25 +/- 0.54 day-1

Fast-n & Stopping muons • Prompt: proton recoil or muon track • Delayed: neutron capture or muon decay • Measured from high-energy spectrum: 0.67 +/- 0.20 day-1

Backgrounds Accidentals • Prompt: radiation hit on PMT • Delayed: spallation neutron capture • Prevented by radiopurity & shielding • Measured from off-time windows: 0.261 +/- 0.002 day-1

Cosmogenic 9Li • Prompt: beta emission • Delayed: neutrons from long-lived decays • Measured from Δtμ & spatial muon coincidence: 1.25 +/- 0.54 day-1

Fast-n & Stopping muons • Prompt: proton recoil or muon track • Delayed: neutron capture or muon decay • Measured from high-energy spectrum: 0.67 +/- 0.20 day-1

Preliminary

Backgrounds Accidentals • Prompt: radiation hit on PMT • Delayed: spallation neutron capture • Prevented by radiopurity & shielding • Measured from off-time windows: 0.261 +/- 0.002 day-1

Cosmogenic 9Li • Prompt: beta emission • Delayed: neutrons from long-lived decays • Measured from Δtμ & spatial muon coincidence: 1.25 +/- 0.54 day-1

Fast-n & Stopping muons • Prompt: proton recoil or muon track • Delayed: neutron capture or muon decay • Measured from high-energy spectrum: 0.67 +/- 0.20 day-1

Backgrounds Accidentals • Prompt: radiation hit on PMT • Delayed: spallation neutron capture • Prevented by radiopurity & shielding • Measured from off-time windows: 0.261 +/- 0.002 day-1

Cosmogenic 9Li • Prompt: beta emission • Delayed: neutrons from long-lived decays • Measured from Δtμ & spatial muon coincidence: 1.25 +/- 0.54 day-1

Fast-n & Stopping muons • Prompt: proton recoil or muon track • Delayed: neutron capture or muon decay • Measured from high-energy spectrum: 0.67 +/- 0.20 day-1

Red: Best-fit Spectrum Grey: Tagged background events White: IBD Signal

Check Rate vs. Reactor Power

2 events observed in 0.84 days livetime with both reactors off (= 2.2 event/day)

→ Background rate consistent with estimation (2.2 ±0.6 event/day)

Best fit to expected rate: sin22θ13 = 0.19 ± 0.06 BG rate = 2.9 ± 1.1 event/day

arXiv:1207.6632

Summary of Rate Uncertainties

Source Uncertainty w.r.t. signal

Statistics 1.1%

Flux 1.7%

Detector

Energy response 0.3%

1.0%

Edelay containment 0.7%

Gd fraction 0.3%

Δt cut 0.5%

Spill in/out 0.3%

Trigger efficiency <0.1%

Target H 0.3%

Background

Accidental <0.1% 1.6% Fast-n + stop μ 0.5%

9Li 1.4%

Summary of Candidates Both Reactors On One Reactor

Pth < 20% Total

Livetime [days] 139.27 88.66 227.93 IBD Candidates 6088 2161 8249

Prediction Reactor B1 ν 2910.9 774.6 3685.5 Reactor B2 ν 3422.4 1331.7 4754.1

9Li 174.1 110.8 284.9 FN & SM 93.3 59.4 152.7

Accidentals 36.4 23.1 59.5 Total Prediction 6637.1 2299.7 8936.8

Data divided into two integration periods based on reactor power Allows use of changing signal/background ratio in fit

Double Chooz Prompt Spectrum

Data w/ Stat. Error Bars

Best Fit Prediction

(w/ Syst. Errors)

Null Oscillation Prediction

Backgrounds

Rate+Shape: sin22θ13= 0.109 ± 0.030 (stat.) ± 0.025 (syst.) χ2/d.o.f. = 42.1/35 Rate-only: sin22θ13 = 0.170 ± 0.035 (stat.) ± 0.040 (syst.) Frequentist analysis: sin22θ13 = 0 excluded at 99.8% (2.9σ) Presented in arXiv:1207.6632, accepted by PRD

RENO θ13 Measurement

Daya Bay θ13 Measurement

Result

Summary and Prospects

Summary of θ13 measurements from beams MINOS T2K

2CP 23

213

213

213

213

213

for δ =0, sin (2θ )=1,

sin (2θ ) = 0.053 at best fit

0.01 < sin (2θ ) < 0.12 at 90% C.L.

sin (2θ ) = 0.094 at best fit

0.03 < sin (2θ ) < 0

normal hierarcy:

inv

.19 at 90% C.L.

sin

erted hierarc

(2θ )

y:

= 0 excluded at 96% C.L.

θ13 ~7° (NH) θ13 ~9° (IH)

θ13 ~9° (NH) θ13 ~10° (IH)

~2 σ zero exclusion

~3 σ zero exclusion

Summary of θ13 measurements from reactors Daya Bay (June 2012) θ13 ~8.7° (~8 σ zero exclusion)

RENO (June 2012)

θ13 ~9.8° (~6 σ zero exclusion)

Double Chooz

θ13 ~9.6° (~3 σ zero exclusion)

Summary of θ13 measurements

Global fit from Daya Bay, RENO, Double Chooz and T2K:

1

2

3

4

Nσ

Fogli, Lisi, Marrone, Montanino, Palazzo, Rotunno: hep-ph/1205.5254 (2012)

Sin2 θ13 = 0.0241 ± 0.0025 (NH) Sin2 θ13 = 0.0244 ± 0.0025 (IH)

θ13 = 8.9°± 0.9° (~10% relative uncertainty)

Energy Spectra Spectral shape

contains some potentially peculiar features when compared to expectation.

Double Chooz

RENO

Daya Bay sin2(2θ13)=0.12

∆m2atm= 3.0 10-3 eV2

Far/Near ratio simulated

Summary and Prospects Better understanding of spectral shape: hint of new

physics?!?

θ13 measured to be non zero with > 7σ C.L. and 10% uncertainty

In the next 3 years expected to be known with 5% uncertainty

Going from the unknown to the best measured neutrino mixing angle: 2003-2012!