13 measurement with JHF-

F.Sánchez

Universitat Autònoma de Barcelona

IFAE

Disclaimer• The talk is mainly based on the JHF-

proposal (Y.Itow et al., hep-ex/0106019 )

• My only contribution is the compilation and some updated plots.

JHF-

Off-axis conventional beam

E < 1 GeV.

Base line of 295Km to SuperKamiokande.

JHF (Japan Hadron Facility)

High intensity proton

accelerator

50 GeV

0.75 MW (to be proven!)

High intensity neutrino flux with

<E>~ 0.7GeV at maximum of

the - oscillation for

m223~0.003 eV2

JHF- beamPrimary Proton beamline

Target Station

Decay

Volume

SK Beam Axis

50GeV PS

pit

JHF- NuMI

(FNAL)

Ep(GeV) 50 120

Int.(1012ppp) 330 40

Rate (Hz) 0.275 0.53

Power (MW) 0.75 0.41

Japan Hadron Facility is a multipurpose p accelerator covering

items from CP violation in K, hyperon

production to nuclear physics.

Relevant parameters for beam

130day/year x 3.3 1014 ppp x 2.5 104p/day ~ 1021pot/year

Off-axis beam

• Almost monochromatic beam. • Higher flux at the maximum of

the oscillation than wide band option.

TargetHornsDecay Pipe

Far Det.

OA3°OA2°OA1°

)()cos1(

033.0GeVE

• In a two body decay:

Off-axis beam

JHF

Maximum energy as a function of the off-axis value

Beam Monte Carlo simulation• All calculations are done with a simple two horns

GEANT simulation with a long decay pipe (80m).

• Includes polarization.

HORN 2 HORN 1

Simila

r to K

2K.

Not optim

ized!!!

Neutrino energy spectra for 2º off-axis

e

Main contribution: →

K→ contributes to the large energy tails,

)cos1(

235.0

GeV

EIt was

0.033GeV for

Intrinsice does not “peak”. Originated from 3 body decays:

• →ee

•K+e3 and Kºe3 contributing to the

large energy tails.

Neutrino Fluxes

OA2º OA1º WBB

2.1 x 107

(2.0 x 106)

2.2 x 107

(2.4 x 107)

2.2 x 107

(5.1 x 107)

e1.3 x 105

(1.1 x 105)

1.6 x 105

(1.8 x 105)

1.5 x 105

(2.3 x 105)

Ratio 6.2 x 10-3 7.2 x 10-3 6.8 x 10-3

Similar flux in the region of interest but:

1. Flatter for lower off-axis values (lower sensitivity).

2. Higher flux in WBB above 1.2 GeV (higher backgrounds from NC & CC production).

Neutrino flux for E < 1.2 GeV (> 1.2 GeV)

e background below 1%. Similar spectra in all cases (mainly from the 3-body decay).

Normalizing the flux: close detector

• To normalize the flux an off-axis detector at 2km is planned (1 KTon water Čerenkov detector –100 Ton fiducial volume-).

• Standard problem of different angular coverage between far and close is diluted by beam dispersion:

Far 50m x 50m x,y ~ 50/295000. = 0.17 mrad

2km 10m x 10m x,y ~ 10/2000 = 5 mrad

~ 10 mrad (beam dispersion)

Angle from the beam to SK.

In the K2K case, the claim is 5% systematic from normalization.

Normalizing the flux

Similar energy spectra in both the close and far detectors. In the region of interest, deviations are

below 1%.

Unexpected similar result for e. (mainly from 3-body decays)

Normalizing the flux

Other functionalities of 2km detector

• Measurement of neutrino cross-section:Neutral current.

Charge currents quasi-elastic and non-quasi-elastic.

• Interaction topologies and multiplicities:single ±/ production.

• Measurement e contamination.

The 2km detector will be probably similar to the K2K experiment:

• water Čerenkov detector. • fine grained calorimeter.• spectrometer.

disappearance I: E reconstruction

• E < 1 GeV, mainly Quasi-elastic interactions: n → p • Energy of neutrino can be recovered:

energy resolution: 3%. angular resolution: 3º.

• Observation of the oscillation dip → Good resolution in m2

23

→ Confirmation of oscillation.

lllN

llN

pEm

mEmE

cos

2/2

Resolution limited by:

1. Fermi motion (smearing of ~200 MeV).

2. Non-QE background subtraction.

3. Coherent nuclear effects (Nucleus as a target).

4. Energy shape prediction.

kmnoscillationopredicted

kmmeasured

295

295

Quasi elastic events in JHF-

Fraction of QE provided byNuance Monte Carlo.

JHF off axis

Reconstructed vs. true energy in SuperKamiokande

for QE events (no Fermi motion).

disappearance I: E reconstruction

• E < 1 GeV, mainly Quasi-elastic interactions: n → p • Energy of neutrino can be recovered:

energy resolution: 3%. angular resolution: 3º.

• Observation of the oscillation dip → Good resolution in m2

23

→ Confirmation of oscillation.

lllN

llN

pEm

mEmE

cos

2/2

Resolution limited by:

1. Fermi motion (smearing of ~200 MeV).

2. Non-QE background subtraction.

3. Coherent nuclear effects (Nucleus as a target).

4. Energy shape prediction.

kmnoscillationopredicted

kmmeasured

295

295

)2sin1( 232

disappearance II: flux normalization

• Sensitivity to 23 enhanced by off-axis technique.• The normalization error is highly suppressed (5% in K2K):

• Systematic errors:Neutrino energy shape uncertainties.Knowledge of energy resolution in far detector (Far/near resolution

comparison). Non-QE background subtraction.

Principle of 13 measurement• In the assumption of two maximal mixing (12 and 23) the 1 ↔ 3

oscillation will lead to a e ↔ oscillation which needs of a high energy intense e beam.

• However, there is a subdominant oscillation: → e that can be detected in conventional intense beams. The signature is the appearance of e.

• The number of e is function of 13 via:

disappeare

disappearappear NNNe 2sin2sin

2

1 213

2

e

m2 = 0.003 eV2

Sin2 e = 0.05

E = 0.7 GeV

e appearance: background I• The signal is expected to be small, so the background will limit the

sensitivity to 13.

Intrinsic background: 1. CC with → e (E below threshold).2. e contamination of the beam. ( < 6 ‰ )

3. e appearance from 12 mixing (~ 1 ‰ ) →

10max1

max2

e

e

13=0

First maximum

e

0 →e misidentification.0 identification from 2 Č. rings.

Background:1. Missing ring2. Overlapped ring.

e appearance: background II

→e misidentification. Id. from ring shape arguments.

Detector related backgrounds

2 invariant m

ass

data

e

0 →e separation cuts:

1. Angle between e and e. (0 more forward)2. Energy fraction of lower energy ring.3. Double ring likelihood (low energy ring shadowed by

light diffusion).4. Invariant mass of 2 photons.

e appearance: background III

Tested in the realistic Superkamiokande Monte Carlo

Sensitivity to 13 in JHF-bck estimates

OAB 2º NC+CC e Oscillated e

Detected 14793 292 301

e-like 261.3 68.4 204

e/º sep. 26.5 21.9 152

0.4<E<1.2 11.1 (0.7‰) 11.1 (3.8%) 123.2(41%)

From beam simulation and SK Monte Carlo (5 years exposure):

Mainly from NC

m2 = 0.003 eV2

Sin2 e = 0.05

From E range

In absence of signal:

Bck ~ 22 events

..%90003.005.0123

2264.12sin 2 LCe Expected signal

QE!!!!

Sensitivity to 13 in JHF-

5 Years (~ 5 1021 pot)Three options:1. Wide Band2. OAB 2º3. NBB 2 GeV.

Old resultfrom JHF-

proposal.

003.02sin 2 e

Sesitivity contour from a full oscillation analysis.

Sensitivity is enhanced around the expected value of m2 for both off-axis andnarrow band beam.

But!, low energy means: • Low cross-section. (bad for e appearance)• Large energy uncertainty from Fermi motion worsening 2m resolution for .

Conclusions

• Superkamiokande is a known-good detector around 1GeV: – Good angular and energy resolution.– Good particle id. capabilities. – + All accumulated experience.

• Off-axis technique: maximum sensitivity & low background. • energy reconstruction from QE.• High intensity proton beam (1012 pot/year).• Near (2km) detector:

– Optimal flux normalization.– Characterization ofN interactions at these energies.

JHF-will measure sin2 2 e with a sensitivity of 0.003 @ 90% C.L. after 5 years of operation in the appearance of e from a beam.