K2K near detector:

Measurement of the flux in absence of oscillations and of the beam direction

3 different detectors:

1 Kton Water Čerenkov: Small replica of Super-K; Fiducial mass 25 ton.

Scintillating fiber detector in water

(SciFi): fine grained water target CCQE identification Fiducial mass 6 ton.

SciBar

Muon range detector:MRD: Iron target 330 ton fiducial massNeutrino beam monitor:Momentum and direction of muons

Since October 2003 the Lead Glass has been replaced with a scintillating bars 2.5x1.3x300 cm detector, 11 ton Fid.Study of low energy neutrino interactions (osc. Max. @ 0.6 GeV)

Pro

bab

ilit

y#

of i

nte

rac

tio

ns

No oscillationOscillated

dip

Oscillationmaximum

(ideal energy reconstruction)

Events:

1) WC: only muon id.2) SCIFI (water) 1 or 2 tracks, muon id.3) SCIBAR (plastic scint.) 1 or 2 tracks, muon id.

For the events with 2 tracks make a classification in QE andnQE just looking at the angle of the track wich is not the muon

WC SCIFI SCIBAR

Fid. mass 5.59 ton 9.38 ton

Muon thresh. 200 MeV/c 400-550 MeV/c 450 MeV/c

events 52110 (66% QE)

17935 11030

Energy scale 2.7% 2.7%

Momentum resolution

2.0-2.5% 80 MeV/c

Angular resolution

1.05° 1.6°

70% H20

21.8% Al

Energy measurement of the in SuperKamiokande using the 1R sample under the hypothesis of the quasi-elastic scattering (dominant process at low energy): + n – + p

–

Proton undetectablebelow Čerenkov threshold

Incoming direction known

Under the assumption that the initial neutron was at rest the kinematics of QE-CC can be used to find the energy of the incoming :

cos

5.0 2

pEM

mMEE

E~60MeV<10% measurement

E(reconstructed) – E(true)

QE

inelastic

For the events with 2 tracks make a classification in QE andnQE just looking at the angle of the track wich is not the muon, should be within 25° from the expected proton direction

Scibar

For the 3 classes of events fit the muon variables data vs MC in bins of energy

Analysis based on the muon apart from the division in classes, no proton id, no measurement of prton energy

WC

SCIFI

SCIBAR

No significative differences SCIFI-SCIBAR, large difference in WC

Formation Zone Intranuclear Cascade:

First application to neutrino interactions by Battistoni, Lipari, Ranft, Scapparonehep-ph 9801426

The formation length was introduced in analogy to the Landau Pomeranchuk effect to explain the suppression of the intranuclear cascade at high energies

The tracking of hadrons trhough the nucleus with known cross sections is performed only for hadrons formed inside the nucleus. Formation time in the rest frame of the hadron sampled from an exponential with average:

0 is of the order of a few fm/c. In the lab frame =S s only low energy hadrons participate

Z. Phys C 43 (1989) 439

Z. Phys C 52 (1991) 643

The FZIC code performs a complete sampling of the nucleus in the impulse approximation assigning momenta and positions to the nucleons and then propagates the hadrons trough the nuclear medium developing the cascade

D.Autiero NUINT04

Spectrometer: p/p = ±% for p < GeV/c

ECAL resolution: %1%2.3

EEE

The NOMAD detector

WANF neutrino beam: <E>=24 GeV for 48 GeV for CC

Nomad typical events:

+ N – + X

e + N e– + X

e + N e+ + X

– track

Energy depositions in the ECAL

Proton and neutron yields increase with the INC (DIS, Nomad beam and target, pure MC level):

p

n

Momentum (GeV/c)

Momentum (GeV/c) Angle wrt incoming neutrino (rad)

Angle wrt incoming neutrino (rad)

Low momentaLarge angles 1 fm/c

2 fm/c

5 fm/c

No INC

Look for the protons in order to tune the model

Formation time tuning, after fragmentation tuning: INC improves the agreement data-MC, (minimum found at 2 fm/c)

Charged hadrons multiplicity Charged hadrons multiplicity

No INC

No INC

Total event charge Total event charge

2 fm/c

2 fm/c

Hadrons angular dist. (rad) Hadrons angular dist. (rad)

Hadrons momenta (GeV/c) Hadrons momenta (GeV/c)

Hadrons spectra and angular distributions

No INC

No INC

2 fm/c

2 fm/c+ +

++- -

--

Hadron with largest angle (rad)

Looking for the presence of the protons from INC ….Hadron with the largest angle (wrt incoming neutrino) in the event

2 fm/c

2 fm/c

No INC

No INC

PositivesPositives

Negatives Negatives

Strong improvement of the agreement data-MC for the positives due to the INC protons

Hadron with largest angle (rad)

Hadron with largest angle (rad)

Hadron with largest angle (rad)

Looking for the presence of the protons from INC ….Spectra for hadrons with 0.5<<1.57

Negatives Negatives

Positives Positives

Momentum (GeV/c) Momentum (GeV/c)

Momentum (GeV/c)Momentum (GeV/c)

pp

No INC

No INC

2 fm/c

2 fm/c

Backward protons (kinematically forbidden for neutrino interactions on stationary nucleons) are a very sensitive observable for the tuning of INC

Protons can be identified by range looking in the sample of backward stopping particles

Nomad has published a paper on the production of backward particles: P.Astier et al. Nuc. Phys. B 609 (2001), see also M. Veltri Nuint01 proc.

Invariant cross section:

# of BP per DIS CC

NEG-N: invariant spectrum in NOMAD for various formation times

The slope is not affected by the formation time, the rate is quite sensitive to the formation time

Formation time NBP [350-800] MeV/c

Data 52.8 +-7 10-3

NO INC 2.1 10-3

5 fm/c 31.3 10-3

2 fm/c 53.0 10-3

1 fm/c 67.5 10-3

The formation time tuned on the hadronic distributions predicts the correct rate of BP.

On the contrary one can constrain the formation time from the measurement of BP which gives: 2 +0.9 –0.5 fm/c

Pi0 momentum spectrum

GeV/c

Ar

O/C

Ar O C No rescattering

Pi0 0.272/event

0.330 GeV/c

0.264

0.355 GeV/c

0.259

0.362 GeV/c

0.246

0.406 GeV/c

Pi+ 0.597

0.351 GeV/c

0.662

0.357 GeV/c

0.678

0.357 GeV/c

0.754

0.367 GeV/c

Pi- 0.014

0.294 GeV/c

0.008

0.336 GeV/c

0.007

0.324 GeV/c

None

n 0.779

0.425 GeV/c

0.482

0.457 GeV/c

0.424

0.569 GeV/c

0.230

0.850 GeV/c

p 1.428

0.480 GeV/c

1.223

0.528 GeV/c

1.114

0.546 GeV/c

0.769

0.689 GeV/c

50000 events /run Resonances Rein & Seghal modelParticles in the final state:

Ar vs O +3% Pi0 with a softer spectrum (-9%)Ar vs O +17% protons

Upper limit, neglecting completely nuclear effects (19%)

Upper limit II, fitting the invariant mass of the NEUT events with NUX (no nuclear effects) 18% discrepancy

When adding protons and detector mass isn’t enough…

For any of these experiments, detectors see different mixes of events between near and far. Cross section uncertainties don’t all cancel!

Looking for differences between and anti- probabilities of at most 15-20%…need to measure probabilities to 5% or better for a 3 determination!

Problem: no cross sections at these energies are known any better than about 20%...

Minera will provide precise measurements, but we still need anti- cross sections…

NOvA pre-PD rates

D. Harris, proton driver review

Some remarks:

1) The LAr detector will be the ideal detector to study the nuclear effects and accurately model the MC on Ar (MC validator):

Capability to measure exclusive statesParticle id (ionization)Energy measurementHomogeneus and hermetic detector, reconstruction systematics reduced

2) The ice target will allow to measure also the interactions on oxigen (on a subsample of the phase space) and cross-check the model

3) The WC detector will allow to correlate accurately the (beam*interaction model) data obtained in the LAr with the WC reconstruction, these beam data will be extrapolated to the far detector

a) A full systematic analysis has not been completed at the moment neither for the 280m nor for the 2Km LAr+WC (using assumption like 10% syst…)

b) WC alone vs SK is nevertheless based on some MC+flux assumptions, what if in reality they are wrong ? We need absolutely the LAr to cross-check the flux*interaction model

c) In real life it may take many years before reaching a good understanding of the systematics (e.g. NOMAD numu nue analysis ~ 5 years)

d) The WC detector has never been used at this level of precision, we absolutely need all the handles for the systematics, the LAr will be precious

Real QE events in the 50lLAr chamber exposed at WANF