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??????-??????????????( Event generator )

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• Contents
• Introduction
• Neutrino interactions above 100MeV
• Why important?
• Neutrino-nucleon/nucleus interaction
• simulation programs ( event generators)
  used in the experiments
• General structure of the simulation program (
  event generator )
• Neutrino interactions
• Nuclear effects ( Final state interactions of
  hadrons )
• Summary

2
1. Introduction
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Charged current interactions with nucleus n N
? l N ( X ) N, N nucleus
l charged lepton X hadrons ( p, K, W,
nucleons etc )
???????????????????????
3
2. Neutrino interactions above 100MeV
Charged current quasi-elastic scattering

• m n ?m- p

Neutral current elastic scattering

• m N ?n N

Single p,h,K resonance productions
nm N ?l N p (h,K)
Coherent pion productions
nm X ?l X p
Deep inelastic scattering
nm N ?l N mp(h,K)
(l lepton, N,N nucleon, m integer)
Cross-sections
Cross-sections
Total (NCCC)
CC Total
CC Total
CC quasi-elastic
s/E (10-38cm2/GeV)
DIS
DIS (CC)
CC single p
NC single p0
En (GeV)
4
3. Why important?
Example 1 ??????????????????
????????????
Case 1 En 100 1 GeV
Select charged current quasi-elastic scattering
events
n N ? l N
?????????????????????? ????????????????
?????????? ? Selection efficiency ? purity /
background contamination
???????????????????
Case 2 En gt several GeV
Charged current deep inelastic scattering events
dominate.
n N ? l N hadrons
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??????????????????
Precise knowledge of the primary neutrino
interactions and the secondary hadron
interactions is important.
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3. Why important?
Example 2 ????????????
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Example 3 ????????
?????????????????p ? e p0??? single p
production???????????????? (????????????)
?????????????????? ?????????p?????? ??????????
????????????.
( p n ? p0 p etc. )
Precise knowledge of the primary neutrino
interactions and the secondary hadron
interactions is important.
6
4. Neutrino-nucleon/nucleus interaction
simulation programs ( not complete. )
1. NEUT ????????????????????? ????????????Super-
Kamiokande, K2K SciBooNE, T2K ??????????????
2. NUANCE IMB??SK?????????????????????? MiniBoo
NE, Minelna, SK?????????????
3. NUGEN ???SUDAN???????????? ????????????MINOS?
??????????
4. GENIE ??????????????????????????? ???????????
??????? (Object oriented, C based program
library) ???MINOS?????????????????
7
4. Neutrino-nucleon/nucleus interaction
simulation programs used in the experiments.
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Water Cherenkov detector Sampling
calorimeter Full active scintillator detector
8
5. General structure of the simulation
program ( Event generator )

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??????????????? neutrino flux ( f (E) ) ? total
cross-section ( stotal (E) ) ??????????????

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Recent and near-future neutrino scattering
experiments

• K2K experiment
• Water Cherenkov detector
• High sensitivity for e, m, low momentum p0
• Threshold for p is rather high ( 1GeV/c)
• SciFi detector (Scintillating fiber detector with
  water target )
• Lower threshold for p. ( 600MeV/c )
• Tracking detector to identify CC quasi-elastic
  scattering.
• SciBar detector ( Fully active scintillator
  detector )
• Low threshold for p. ( 400MeV/c )
• Tracking detector to identify interactions.

2) MiniBooNE experiment Mineral oil
Cherenkov detector High sensitivity for e, m,
low momentum p0 High purity CC QE Single pi
sample. ( Owing to the lower energy beam )
10
Recent and near-future neutrino scattering
experiments
3) SciBooNE experiment SciBar detector ( Fully
active scintillator detector ) Low threshold for
p. ( 400MeV/c ) Tracking detector to identify
interactions. High purity CC QE Single pi
sample. ( Owing to the lower energy beam
Use same neutrino beamline as MiniBooNE )
4) MINERnA Use various target ( Hydrogen,
Carbon, Oxygen, Argon .. ) Use MINOS
beamline. Rather high energy beam.
Study CCQE, Single pi, DIS and various nuclear
effects.
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Status of SciBooNE (K. Hiraide)
New experiments using Booster Neutrino Beam
Measure cross-sections with full-active
scintillator detector
12
6. Expected interaction rates ( neutrino mode )
Beam time June 2007 Summer 2008 ( Now running
) Protons on target 1 x 1020 for neutrino 1 x
1020 for anti neutrino
of nm events /10tons/1E20POT Fraction
CC-QE 41,100 41.0
CC-1pi 23,500 23.5
CC-coherent 1,500 1.5
CC-other 5,500 5.5
NC-1pi 8,500 8.5
NC-coherent 900 0.9
NC-other 1,700 1.7
NC-elastic 17,400 17.4
Dominant
DIS etc. Small fraction
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The MINERnA neutrino interaction
experiment (R. Gran)
MINERnA Measure neutrino interaction
cross-sections with various targets ( Pb, Fe,
C,He ) _at_ 5 level for CC and _at_ 10
level for NC. Exclusive final state! Study
form factors, structure functions and
nuclear effects.
Full active plastic scintillator inner detector
2009 Start with MINOS LE Beam 2012
Change over to NonA ME beam
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The MINERnA neutrino interaction
experiment (R. Gran)
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6. Charged Current Quasi elastic scattering
? N ? l N
Cross-section calculations
Free nucleon C.H.L. Smith (Phys. Rep.
3,261(1972))
(MV0.84GeV/c)
In the original article, both vector and
axial-vector form factors are assumed to be
dipole. Also, GEn is set to 0.
Recently, non-dipole form vector factor and
non-zero GEn obtained from the recent
electron scattering experiments are used
in some simulation programs. ( Re-evaluation
of MA is also required. )
16
6. Charged Current Quasi elastic scattering
? N ? l N
?µ n ? µ- p
?µ p ? µ n
As for the bound nucleons, most
implementation uses the one by Smith and Moniz.
(Nucl.Phys.B43 605(1972),erratum-ibid.B101
547(1975))
Recently, several new improved models are
proposed. From Simple Fermi-Gas model (
Smith-Moniz ) to the model with spectrum
functions or based on the many-body theorem
etc..
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6. Charged Current Quasi elastic scattering
NEUT(Smith-Moniz)Nieves et al.solid n,
dashed n
ne 16O ? e- X
Nieves model is lower than S-M by 10 at 500MeV
both in ve,vmRatio Nieves/S-M is within /-25
above 200MeV Systematic error for CCQE is newly
evaluated with these models? Takenaga-sans
analysis considers these errors
nm 16O ? m- X
Currently, this model is available until 500MeV,
so is not used for ATMPD/T2K vector
17
18
7. Single meson production via resonances
? N ? l N p (K ,h)
Based on D.Rein, and L.M.Sehgal, Ann. of Phys.
133(1981)
? N ? l D (N)
?(N) ? p N
Resonances up to 2GeV are taken into account.
Some simulation programs include the absorption
of D in nucleus.
?µ n ? µ- p p
?µ n ? µ- p p
?µ n ? µ- p p
En (GeV)
En (GeV)
En (GeV)
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7. Single meson production via resonances
Simulation result -Integrated cross section-
Berger and Sehgal add the pion-pole term in the
hadronic current. This effect is the almost same
as in the coherent-p production hep-ph/0709.
4378
nm p ? m- p p
Black neRed nm Gren nt
Lepton mass / Original ()
Lepton mass / Original ()
An amount of reduction depends on lepton flavor
and energyThese values are consistent with the
description in references
20
7. Single meson production via resonances
Simulation result -Kinematics-
Pm(GeV)
cosqm
Lepton momentum has no significant changeLepton
scattering angle has suppression in forward
directionPion and nucleon kinematics are not
changed
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8. Deep Inelastic scattering
? N ? l hadrons
Dominant interaction in the high energy region (gt
several GeV )
n
m
W
Hadrons
N
Parton distribution functions ( F2 and xF3 ) are
extracted from the accelerator experiments.
However, major parton distribution functions
can not be used not applicable in the small W or
q2 region.
( If we use the PDF as-is, excess was observed
in the small q2 region. )
1) Use experimental results of neutrino
scattering in that region. 2) Apply corrections
to the existing parton distribution functions.
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8. Deep Inelastic scattering
? N ? l hadrons
Corrections proposed by Bodek and Yang
( hep-ex/0203009, hep-ex/0308007 )
1. Bjorken scaling x? xw
A target mass effect higher twist effectB
photoproduction limit(Q20)
2. Correction to the structure function F2
to fit both intermediate-x and low-x
3. d/u ratio dv ? dv(dv,uv) uv ? uv(dv,uv)
Correction to the conversion from F2d to F2n
4. Longitudinal R
Corrections for the spin of the target.
These correction parameters are obtained by
fitting various existing experimental results.
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8. Deep Inelastic scattering
( G. Mitsuka )
nm Charged current cross sections
nm
GRV94GRV94 (with correction)GRV98GRV98 (with
correction)
nm
En(GeV)
q2 distribution ( atmospheric n flux )
GRV94GRV94 (with correction)Enlt5GeV5ltEnlt20GeV
With the correction, cross-section is
suppressed and small q2 region is also
suppressed.
of events
sqrt(q2(GeV2/c2))
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9. Coherent pion productions
? X ? ? X p0
p production without breaking the target nucleus
n
Model by Rein Sehgal (Nucl.Phys.B22329,1983)
n
p

• Cross-section is smaller than
• the resonance-mediated mode.
• Direction of p has peak in forward

( Experimentally observed in the higher energy
neutrino experiments. )
? 12C? l? 12C p0
Recently, cross-section of charged current
coherent pion production was found to be very
small in ltGeV region.
M. Hasegawa et al.(K2K collaboration) (
hep-ex/0506008 )
25
10. Nuclear effects ( Final state interactions of
hadrons )
Large fraction of the p from single p
production are coming from the decay of D.
Cross-section of those p is large.
Interaction probability of p in
nucleus generated by the single p production is
large.
Momentum of p from p ? e p0 is
460ltMeV/c.
26
10. Nuclear effects ( Final state interactions of
hadrons )
re-scattering of pion, kaon, eta, omega and
nucleon in nucleus
Different models are used in each simulation
program.
Implementation in NEUT
Cascade model is used. Each particle is tracked
in the nucleus until it escapes from the
nucleus.
For low momentum pion ( lt 500MeV/c , so-called D
region ) Mean free paths of absorption and
inelastic-scattering are calculated based on a
model by L.Salcedo et al. . (Nucl. Phys.
A484(1998) 79)
These mean free paths are position and momentum
dependent. The Fermi surface momentum also has
radius dependence.
For the higher momentum pion ( gt 500MeV/c),
kaons, eta, omega and nucleons Results
from scattering experiments are used.
27
10. Nuclear effects ( Final state interactions of
hadrons )
Interaction probabilities of p
generated in 16O
Checked with p 16O scattering or photo - p
production experiments.
Monte-Carlo simulation reproduces various
distributions quite well.
Comparison with p 16O scattering experiment
28
10. Nuclear effects ( Final state interactions of
hadrons )
momentum of p0 (atmospheric n) _at_
SK (Simulation Vector level)
momentum of p0 _at_ K2K-1KT
Arbitrary unit
Blue Before FSI Red After FSI
preliminary
of FC 2ring p0 events
( MC is normalized by area )
p0 momentum (GeV/c)
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11. Summary
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? ? K2K?MiniBooNE????????? ???
SciBooNE?T2K(280m)?Minelna ?????? ???????????????
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Fin.
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6. Charged Current Quasi elastic scattering
(G.Mitsuka)
Comparison between the model by Smith-Moniz
and by Nieves et al.
?µ n ? µ- p
Cross-section
Black Smith-Moniz Nieves et al. modelBlue
????Red FSI??Pink RPA??Green
FSIRPA
Black Smith-Moniz Nieves et al. modelBlue
????Red FSI??Pink RPA??Green
FSIRPA
s(10-40 cm2)/oxygen nuclei
ds/dQ2(10-40 cm2/MeV2/c2)/oxygen nuclei
En500MeV
En(MeV)
Q2