Measuring 13 with ReactorsStuart Freedman

HEPAP July 24, 2003Bethesda

ReactorDetector 1Detector 2

d2

d1

€

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

MNSP Matrix

Mass Hierarchy

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

⎛

⎝ ⎜

⎞

⎠ ⎟

?

€

Pee ≈1− sin2 2θ13 sin2 Δm312L

4Eν+

Δm212L

4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟cos4 θ13 sin2 2θ13

1/r2

Pee, (4 MeV)

e fl

ux

The Basic Idea

First Direct Detection of the Neutrino

Reines and Cowan 1956

e+

nE = 2200 keV

e E = 511 keV

E = 511 keV

€

E prompt ≅ Eν − En − 0.8 MeV

)2.2( MeVdpn +→+

nepe +→+ +

sτ 210≈

Neutrino Spectra from Principal Reactor Isotopes

Inverse Beta Decay Cross Section and Spectrum

from 12C(n, )

τcap = 188 +/- 23 sec

Inverse Beta Decay Signal from KamLAND

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=1.0Δm2=6.9 10x -5eV2

KamLAND

detector 1

Future 13 Reactor Experiment

detector 2

Ratio of Spectra

Energy (MeV)

Two Detector Reactor Experiment

Spectral Ratio

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

Sensitivity to sin2213

Ref

: H

uber

et a

l., h

ep-p

h/03

0323

2

• sin2213 < 0.01-0.02 @ 90 CL within reach of reactor 13 experiments• Knowing 13 is useful for the “intelligent design” of a CP experiments. 10-110-210-3

Reactor Neutrino Measurement of 13

• No matter effect

• Correlations are small, no degeneracies

• Independent of solar parameters 12, Δm212

We need accelerators and reactors--Reactors first!

Huber

et

al hep-p

h/0

30

30

23

2

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

Kr2Det: Reactor 13 Experiment at Krasnoyarsk

Lnear= 115 m, Lfar=1000 m, Nfar = 16000/yr

Rat

io o

f Spe

ctra

Rat

io o

f Spe

ctra

Ref: Marteyamov et al., hep-ex/0211070.Energy (MeV)

Kashiwazaki -7 nuclear power stations, World’s most powerful reactors

- requires construction of underground shaft for detectors

near near

far

Kashiwazaki-KariwaNuclear Power Station

Proposal for Reactor 13 Experiment in Japan

near near

far

70 m 70 m

200-300 m

6 m shaft, 200-300 m depth

Kashiwazaki: Proposal for Reactor 13 Experiment in Japan

13 at a US nuclear power plant?

Site Requirements

• powerful reactors

• overburden

• controlled access

Berkeley 230 miles

Pasadena200 miles

• Powerful: Two reactors (3.1+ 3.1 GW Eth) • Overburden: Horizontal tunnel could give 800 mwe shielding• Infrastructure: Construction roads. Controlled access. Close to wineries.

Diablo Canyon Nuclear Power Plant

1500 ft

2 underground detectors

Detector Concept

~60,000

~10,000

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

~250,000

Detector Event Rate/Year

Requirements: Overburden and Large Detectors

Neutrino Detectors at Diablo Canyon

Possible location

Crowbar Canyon Parallel to Diablo Canyon

Existing road access

Possibility for good overburden

Tunnels in radial direction

from reactor

• 2 neutrino detectors, railroad-car size

• in tunnels at (variable) distance of

NEAR/FAR I: 0.5-1 kmFAR II: 1.5-3 km

Crowbar Canyon parallel to Diablo Canyon

FAR: ~ 600-800 mwe

NEAR: ~ 300-400 mwe

Overburden

MC Studies‘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

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

4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟

⎧ ⎨ ⎩

⎫ ⎬ ⎭

Timescale and Size of a 13 Reactor Project

Moderate Scale ( < $50M ) Medium-size, low-energy experiment Little R&D necessary

(KamLAND, SNO, CHOOZ) Construction time ~ 2-3 yrs Start in

2007/2008?

2000 2005 2010

The Particle Physics Roadmap (in the US)

Δm223, 23

Reactor 13

13 CP

Reactor results will define the future of CP searches in the lepton sector and complement accelerator experiments

Conclusions•Top priorities in neutrino physics include pinning down

MNS matrix elements and discovering CP violation.

• We will need a number of experiments to resolve ambiguities from matter effects and correlations.

• Reactor experiments and accelerator experiments are complementary.

• Reactor experiments have the potential of being faster, cheaper and better for establishing the value of 13.

• Executing a reactor experiment at an appropriate site should be put on a fast track.