# Measuring q 13 with Reactors Stuart Freedman University of California at Berkeley - PowerPoint PPT Presentation

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Measuring q 13 with Reactors Stuart Freedman University of California at Berkeley SLAC Seminar September 29, 2003. q 13. How to Weigh Dumbo’s Magic Feather. I am going to argue that --

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Measuring q 13 with Reactors Stuart Freedman University of California at Berkeley

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#### Presentation Transcript

Measuring q13 with Reactors

Stuart Freedman

University of California at Berkeley

SLAC Seminar September 29, 2003

q13

How to Weigh Dumbo’s Magic Feather

I am going to argue that --

the fastest and cheapest way to determine the value of Sin22q13 is to measure two big things and subtract the results.

-

=

Neutrino LANDscape

Constraints from most recent Experiments

UMNSP Matrix

12 ~ 30°

tan2 13 < 0.03 at 90% CL

23 ~ 45°

Mass Hierarchy

What do we know and how do we know it

Slide Courtesy of B. Kayser

Is it important to measure q13?

L. Wofenstein

B. Kayser

S. Bilenky

S. Glashow

A Smirnov

Testimonials

absorber

decay pipe

detector

p

target

horn

+

+

+

e

e

e

### 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

Figuring out CP for leptons

Minakata and Nunokawa, hep-ph/0108085

Basic Idea for a Disappearance Experiment

?

d2

d1

Detector 2

Detector 1

Reactor

Experimental Design

First Direct Detection of the Neutrino

Scintillator

ne

e+

n

2.2MeV

n

m

Reines and Cowan 1956

Inverse Beta Decay Cross Section and Spectrum

235U fission

Neutrino Spectra from Principal Reactor Isotopes

20 m

KamLAND

4 m

Chooz

1m

Long Baseline Reactor Neutrino Experiments

Poltergeist

CHOOZ

CHOOZ

KamLAND

KamLAND

Inverse Beta Decay Signal from KamLAND

from 12C(n, g )

tcap = 188 +/- 23 msec

q13 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 signal

prompt e+ annihilation

delayed n capture (in s)

e,,

~ 1.5-2.5km

e

< 1 km

• • No degeneracies

• • No matter effects

• • Practically no correlations

• E = Ee + mn-mp

• Eprompt = Ekin + 2me

• 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

Overburden Essential for Reducing Cosmic Ray Backgrounds

Detector Event Rate/Year

~250,000

~60,000

~10,000

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

Statistical Precision Dominated by the Far Detector

Diablo Canyon

Variable Baseline

2 or 3 detectors in 1-1.5 km tunnel

IIIb

IIIa

Ge

Geology

II

I

• Issues

• folding may have damaged rock matrix

• - steep topography causes landslide risk

• tunnel orientation and key block failure

• seismic hazards and hydrology

### Detector Concept

muon veto

acrylic vessel

5 m

liquid scintillator

buffer oil

1.6 m

passive shield

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

6

10

5 m

Movable Detectors

1-2 km

~12 m

• Modular, movable detectors

• Volume scalable

• Vfiducial ~ 50-100 t/detector

### Kashiwazaki:13 Experiment in Japan

- 7 nuclear reactors, World’s largest power station

far

near

near

Kashiwazaki-Kariwa

Nuclear Power Station

### Kashiwazaki:Proposal for Reactor 13 Experiment in Japan

far

near

near

70 m

70 m

200-300 m

6 m shaft hole, 200-300 m depth

~20000 ev/year

~1.5 x 106 ev/year

### Kr2Det: Reactor 13 Experiment at Krasnoyarsk

Features

- underground reactor

- existing infrastructure

Detector locations constrained by existing infrastructure

Reactor

Ref: Marteyamov et al, hep-ex/0211070

Systematic Uncertainties

%

Total LS mass2.1

Fiducial mass ratio4.1

Energy threshold2.1

Tagging efficiency2.1

Live time0.07

Reactor power2.0

Fuel composition1.0

Time lag0.28

e spectra2.5

Cross section0.2

Total uncertainty6.4 %

E > 2.6 MeV

.

flux < 0.2%

rel eff ≤ 1%

target ~ 0.3%

acc < 0.5%

nbkgd< 1%

### Systematics

Best experiment to date: CHOOZ

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

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

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

Target Volume &• well defined fiducial volume

Backgrounds • external active and passive shielding for correlated backgrounds

Total syst ~ 1-1.5%

Optimization at

LBNL

‘near-far’ L1 = 1 km

L2 = 3 km

‘far-far’ L1=6 km

L2=7.8 km

### MC Studies

Normalization:

10k events at 10km

Oscillation Parameters:

sin2213 = 0.14

m2= 2.5 x 10-3 eV2

Sensitivity to sin2213at 90% CL

cal relative near/far energy calibration

norm relative near/far flux normalization

Reactor I

12 t, 7 GWth, 5 yrs

Reactor II

250 t, 7 GWth, 5 yrs

Chooz5 t, 8.4 GWth, 1.5 yrs

fit to spectral shape

Ref: Huber et al., hep-ph/0303232

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

Reactor-II: limit essentially independent of norm

statistical error only

Ref: Huber et al., hep-ph/0303232

statistics

Statistics

Systematics

Correlations

Degeneracies

### Expected Constraints on13

Upper limits correspond to 90% C.L.