Measuring 13 with ReactorsStuart Freedman

University of California at Berkeley

SLAC Seminar September 29, 2003

I am going to argue that --

the fastest and cheapest way to determine the value of Sin2213 is to

measure two big things and subtract the results.

- =

How to Weigh Dumbo’s Magic Feather

1313

Neutrino LANDscape

Constraints from most recent Experiments

€

U =

Ue1 Ue2 Ue3

Uμ1 Uμ 2 U μ 3

Uτ1 Uτ 2 Uτ 3

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

=

cosθ12 sinθ12 0

−sinθ12 cosθ12 0

0 0 1

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟×

cosθ13 0 e−iδ CP sinθ13

0 1 0

−e iδCP sinθ13 0 cosθ13

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟×

1 0 0

0 cosθ23 sinθ23

0 −sinθ23 cosθ23

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟×

1 0 0

0 e iα / 2 0

0 0 e iα / 2+iβ

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

12 ~ 30° 23 ~ 45°tan2 13 < 0.03 at 90% CL

UMNSP Matrix

Mass Hierarchy

Slide Courtesy of B. Kayser

What do we know and how do we know it

Is it important to measure 13?

Testimonials

L. Wofenstein

S. Glashow

B. Kayser S. Bilenky

A Smirnov

Measuring 13 Accelerator Experiments

• appearance experiment• measurement of e and e yields 13,CP

• baseline O(100 -1000 km), matter effects present

Reactor Neutrino Oscillation Experiment

• disappearance experiment • but: observation of oscillation signature with 2 or multiple detectors• look for deviations from 1/r2 • baseline O(1 km), no matter effects

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

€

Pee ≈1− sin2 2θ13 sin2 Δm312L

4Eν+

Δm212L

4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟cos4 θ13 sin2 2θ13

€

e →ν x

e

ee

€

→ e

€

Pμe ≈ sin2 2θ13 sin2 2θ23 sin2 Δm312L

4Eν+ ...

decay pipehorn absorbertargetp detector

+

+ +

Minakata and Nunokawa, hep-ph/0108085

Figuring out CP for leptons

€

P(ν μ →ν e ) − P(ν μ →ν e ) = −16s12c12s13c132 s23c23 sinδ sin

Δm122

4EL

⎛

⎝ ⎜

⎞

⎠ ⎟sin

Δm132

4EL

⎛

⎝ ⎜

⎞

⎠ ⎟sin

Δm232

4EL

⎛

⎝ ⎜

⎞

⎠ ⎟

Basic Idea for a Disappearance Experiment

?

ReactorDetector 1Detector 2

d2

d1

Experimental Design

First Direct Detection of the Neutrino

Reines and Cowan 1956

€

E prompt ≅ Eν − En − 0.8 MeV

)2.2( MeVdpn γ+→+

nepe +→+ +

sτ 210≈e ne+

2.2MeV~210 ms

Scintillator

Inverse Beta Decay Cross Section and Spectrum

Neutrino Spectra from Principal Reactor Isotopes

235U fission

1m

Poltergeist

Chooz4 m

KamLAND20 m

Long Baseline Reactor Neutrino Experiments

CHOOZ

CHOOZ

20

15

10

5

0

reactor neutrinos geo neutrinos background

25

20

15

10

5

086420

Prompt Energy (MeV)

2.6 MeVanalysis threshold

KamLAND data no oscillation best-fit oscillation

sin22 = 1.0 Δm2= 6.9 10x -5 eV2

KamLAND

KamLAND

from 12C(n, γ )

τcap = 188 +/- 23 sec

Inverse Beta Decay Signal from KamLAND

13 at a US nuclear power plant?

Site Requirements

• powerful reactors

• overburden

• controlled access

Diablo Canyon Power Station

scintillator e detectors

e + p e+ + n

coincidence signalprompt e+ annihilationdelayed n capture (in s)

€

Pee ≈1− sin2 2θ13 sin2 Δm312L

4Eν+

Δm212L

4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟cos4 θ13 sin2 2θ12

• disappearance experiment • look for rate deviations from 1/r2 and spectral distortions• observation of oscillation signature with 2 or multiple detectors• baseline O(1 km), no matter effects

e< 1 km

e,,τ~ 1.5-2.5km

Overburden Essential for Reducing Cosmic Ray Backgrounds

~60,000

~10,000

Statistical error: stat ~ 0.5% for L = 300t-yr

~250,000

Detector Event Rate/Year

Statistical Precision Dominated by the Far Detector

2 or 3 detectors in 1-1.5 km tunnel

Diablo Canyon

Variable Baseline

Ge

Issues

- folding may have damaged rock matrix- steep topography causes landslide risk- tunnel orientation and key block failure- seismic hazards and hydrology

Geology

I

II

IIIaIIIb

liquid scintillatorbuffer oil

muon veto

passive shield

Detector Concept

5 m

1.6 m

Variable baseline to control systematics and demonstrate oscillations (if |13| > 0)

acrylic vessel

Movable Detectors

5 m~12 m

• Modular, movable detectors• Volume scalable• Vfiducial ~ 50-100 t/detector

610

1-2 km

Kashiwazaki: 13 Experiment in Japan

- 7 nuclear reactors, World’s largest power station

near near

far

Kashiwazaki-KariwaNuclear Power Station

near near

far

70 m 70 m

200-300 m

6 m shaft hole, 200-300 m depth

Kashiwazaki: Proposal for Reactor 13 Experiment in Japan

Ref: Marteyamov et al, hep-ex/0211070

Reactor

Detector locations constrained by existing infrastructure

Features - underground reactor - existing infrastructure

~20000 ev/year~1.5 x 106 ev/year

Kr2Det: Reactor 13 Experiment at Krasnoyarsk

%Total LS mass 2.1Fiducial mass ratio 4.1Energy threshold 2.1Tagging efficiency 2.1Live time 0.07Reactor power 2.0Fuel composition 1.0Time lag 0.28e spectra 2.5

Cross section 0.2

Total uncertainty 6.4 %

Systematic Uncertainties

E > 2.6 MeV

Systematics

Reactor Flux • near/far ratio, choice of detector location

Best experiment to date: CHOOZ

Target Volume & • well defined fiducial volume

Backgrounds • external active and passive shielding for correlated backgrounds

Detector Efficiency • built near and far detector of same design • calibrate relative detector efficiency variable baseline may be necessary

Ref: Apollonio et al., hep-ex/0301017

Total syst ~ 1-1.5%

rel eff ≤ 1%

target ~ 0.3%

n bkgd < 1%

flux < 0.2%

acc < 0.5%

.

MC Studies

Normalization: 10k events at 10km

‘far-far’ L1=6 km L2=7.8 km

‘near-far’ L1 = 1 km L2 = 3 km

Oscillation Parameters:sin2213 = 0.14Δm2= 2.5 x 10-3 eV2

Optimization atLBNL

P νe → νe( )≈sin4θ13+cos4θ13 1−sin2(2θ12) ⋅sin2 Δm122 L

4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟

⎧ ⎨ ⎩

⎫ ⎬ ⎭

Sensitivity to sin2213 at 90% CL

Reactor-I: limit depends on norm (flux normalization)

Reactor-II: limit essentially independent of norm

statistical error only

fit to spectral shape

cal relative near/far energy calibration

norm relative near/far flux normalization

Reactor I12 t, 7 GWth, 5 yrs

Reactor II250 t, 7 GWth, 5 yrsChooz 5 t, 8.4 GWth, 1.5 yrs

Ref

: H

uber

et a

l., h

ep-p

h/03

0323

2

statistics StatisticsSystematicsCorrelationsDegeneracies

Ref

: H

uber

et a

l., h

ep-p

h/03

0323

2

Expected Constraints on 13

Experiment sin2(213) 13 When?

CHOOZ < 0.11 < 10

NUMI Off- Axis (5 yr) < 0.006-0.015 < 2.2 2012

JPARC-nu (5 yr) < 0.006-0.0015 < 2.3 2012

MINOS < 0.06 < 7.1 2008

ICARUS (5 yr) < 0.04 < 5.8 2011

OPERA (5 yr) < 0.06 < 7.1 2011

KR2DET (Russia) < 0.016 < 3.6 ?

Kashiwazaki (Japan) < 0.026 < 4.6 [2008]

Penly/Cruas (France) < 0.025 < 4.5 [2010]

Diablo Canyon (US) < 0.01-0.02 < 2.9 [2009]

Upper limits correspond to 90% C.L.