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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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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.


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