NBI Workshop @ KEK
2003/11/8

Hadron Production Model Dependenceof Neutrino Flux Estimation
Univ. of Tokyo Ryosuke Ishida& JHF-nu Working Group1

Contents
 Introduction
 Neutrino Beam Simulation
 Hadron Production Model Dependence ofPredicted Neutrino Spectra Conclusion

2

Introduction〜Hadron production uncertainty
K2K
JHF-nu→Direct measurement of hadron (pion) spectrum.
→Impossible due to high momentum and high intensity.
→Estimated by Simulation !

In order to predict the Neutrino Spectrum at SK, we need tounderstand the uncertainty of Hadron Production and its effect tothe prediction of neutrino beam spectrum.

We study the Hadron Production Model Dependence of Neutrino flux.

3Neutrino Beam Simulation
Jnubeamneutrinos

hadrons
protontargetHorns&decay volume
Hadron Production

MARS
FLUKA

GEANT3

To estimate the Hadron production uncertainty we use two Hadron
Production Models (MARS and FLUKA) and compare them.

4

Neutrino Beam Simulation<Simulation Parameters>
Proton Energy : 50[GeV] Target material : Carbon
 Proton On Target : 3.3×1014[#/spill]→1021[#/year] Decay Pipe : 130[m] Off Axis Angle : 2.0 deg. for SK
 Distance to SK : 295km , to ND : 280m
 ND size : 3×3[m2]5

Neutrino Beam Simulation
This study(J-PARC)

・ 90[cm] length ,1.5[cm] radius target
・ three sets of horns

The previous study (LOI)・ 45[cm] length ,0.32[cm] radius target
・ two sets of horns

6Comparison between LOI and J-PARC
LOI
J-PARC

Neutrino Energy Spectrum
@ND

@SK02
Eν[GeV]

02
Eν[GeV]A little difference between two geometries. (~3.1% peak difference)
Total flux of neutrino is about 16% more than LOI.
7

Hadron Production Model
Dependence on Neutrino Spectrum
π+ momentum contributing to νx102

Energy of muon neutrino

x10 3
1600

MARS
FLUKA

1400

10000

1200

8000
1000

6000

800
600

4000

400

2000
200

0
00

1234

56

78

9

10

10

Pπ[GeV]00

0

0.2 0.4

0.6 0.81

1.2 1.4

1.6 1.

2

Eν[GeV]

Peak

Mean

π contributing to ν

9.1%

6.8%(5.4%)

νenergy3.1%

3.0%(1.4%)

MARS model is harder than FLUKA model.

Flux15.7%(14.9%)

Full range

0.4<Eν<1.28Model Dependence of Far/nearratio
2.5pπ

OA 2 deg.

MARSFLUKAν

ND280mSK295km

Flux @SK = Flux @ND ×[Far/near ratio]

From MC simulation
The Difference of Far/near ratio is〜1.9±0.4%

00

10.8
012Eν [GeV]
Double ratio (FLUKA/MARS)
1.21.0(Energy range:0.4〜1.2[GeV])
2Eν[GeV]9

<Absolute Value>
Model Dependence ofNeutrino Flux at On Axis ND
π+ momentum contributing toνEnergy of muon neutrino
MARS
FLUKA

0510Pπ[GeV]

02.5PeakMean

π contributing to ν

13.3%

5.3%

νenergy

16.6%

6.8%

5Eν[GeV]
Flux
26.6%
10

<The shape>
Model Dependence ofNeutrino Flux at On Axis ND<Histograms are normalized by the total entories>
π+ momentum contributing toν Energy of muon neutrino

000510Pπ[GeV]

05Eν[GeV]

There are some shape differences in both spectra: peak ~15% mean ~5%11In the case of 2km Detector
Far/near ratio

1.5〜Far/near ratio Model DependenceMARS
FLUKA

1.0Very flat

0.502 Eν[GeV]
Double ratio (FLUKA/MARS) The Difference of Far/near ratio is
1.2〜0.2±0.4%(Energy range:0.4〜1.2[GeV])
1.00.802

Very small model dependence!!

Eν[GeV]
12

Introduction〜Neutrino Beam
Bombarding 50 GeV proton beam to Carbon Target
Secondary hadrons are focused by horns

Off Axis Beam
(2~3 degree)

They decay in the decay pipe.

Super-K.

Target Horns

Decay Pipeθ

13

Conclusion
We study the Hadron Production Model Dependence ofpredicted Neutrino Flux.

○Model dependence on(@SK)
total flux~15%π+ momentum ~9%ν energy~3% Off Axis effect○Model dependence on Far/near ratio~1.9% @280m~0.2%@2km14