Neutrino-Oxygen Neutral-Current Elastic Interaction as a Background - - PowerPoint PPT Presentation

SLIDE 1

Yosuke ASHIDA (Kyoto University)

for the T2K Collaboration 16th International Conference on Topics in Astroparticle and Underground Physics

September 9–13, 2019 / Toyama, Japan

Neutrino-Oxygen Neutral-Current Elastic Interaction as a Background in Supernova Relic Neutrino Search

SLIDE 2

2

Supernova Relic Neutrinos

• Neutrinos from all the past core-collapse supernovae have been accumulated.
• Detecting supernova relic neutrinos (SRNs) would provide a lot of information about

supernova mechanism, star formation history, heavy nucleosynthesis, etc.

• World most sensitive search has been conducted using Super-Kamiokande detector.
• K. Nakazato et al., Astrophys. Jour., 804, 75 (2015).

Inverted ordering normal ordering

SLIDE 3

3

Neutral-Current Elastic Background

Supernova relic neutrino (IBD) Atmospheric neutrino (NCQE) νe e+ n p

• r

H Gd γ γ

(2.2 MeV) (~8 MeV)

16O

ν γ n

• r

H Gd γ γ

(2.2 MeV) (~8 MeV)

• “Neutron tagging” analysis is implemented to obtain higher sensitivity.
• Delayed coincidence: e+ & γ from n capture
• SK: 2.2 MeV gamma-ray by H (efficiency ~20%)
• SK-Gd: ~8 MeV gamma-rays by Gd (efficiency ~80% @ 0.1%-Gd load)
• Many backgrounds can be reduced by neutron tagging, however, NC remains.
• NC at Eν > 200 MeV usually involves nucleon knock-outs (“NCQE”).
• This is an irreducible background, so must be measured precisely (current: 100%!).

SLIDE 4

4

T2K Experiment

• T2K is a long baseline neutrino experiment.
• Beams produced at J-PARC (8 bunch beam structure being separated by 581 ns).
• Neutrinos detected at 295 km away Super-Kamiokande.
• Flux peak ~630 MeV is close to the atmospheric neutrino flux peak.
• Beam timing information can reduce large amount of low energy backgrounds.
• So far, T2K has accumulated both neutrino and antineutrino data.
• FHC (neutrino mode) 15.12 × 1020 protons-on-target
• RHC (antineutrino mode) 16.51 × 1020 protons-on-target

Super‐Kamiokande J‐PARC Near Detectors

Neutrino Beam 295 km

• Mt. Noguchi‐Goro

2,924 m

• Mt. Ikeno‐Yama

1,360 m

1,700 m below sea level

SLIDE 5

5

Previous Result (Run 1–3 FHC)

• Flux-averaged cross section [Ref.: Phys. Rev. 072012 (2014)]
• Error size is very large:
• Statistical error: +/–25.5%
• Systematic error: +41.9/–21.3%

Large uncertainty & Result only for neutrinos

SLIDE 6

6

Event Simulation

• 1. NEUTRINO FLUX

[GeV]

ν

E 2 4 6 8 10

• POT]

21

/50-MeV/10

2

Flux [/cm

3

10

4

10

5

10

6

10

µ

ν

µ

ν

e

ν

e

ν

T2K Run 1-9 Flux at SK (FHC)

[GeV]

ν

E 2 4 6 8 10

• POT]

21

/50-MeV/10

2

Flux [/cm

2

10

3

10

4

10

5

10

6

10

µ

ν

µ

ν

e

ν

e

ν

T2K Run 1-9 Flux at SK (RHC)

• 30 GeV/c protons are injected onto a graphite target.
• Hadronic interactions are simulated by FLUKA with

reweighing by the NA61/SHINE experiment.

• Transportation and decay are simulated by GEANT3.

30 GeV/c proton hadrons (π, K, …) neutrinos

FLUKA Simulation + External Data (NA61/SHINE) GEANT3/GCALOR

graphite

SLIDE 7

ν ν’

neutron proton

potential p1/2 p3/2 s1/2

7

Event Simulation

• 2. NEUTRINO INTERACTION + PRIMARY-GAMMA PRODUCTION
• 3. SECONDARY INTERACTIONS + DETECTOR RESPONSE
• A dedicated generator “NEUT” is used until the final state

interaction (NCQE model = spectral function).

• Gamma-ray emission is based on a theoretical calculation (*).

(*) A. M. Ankowski et al., Phys. Rev. Lett. 108, 052505 (2012).

ν

16O

γ γ

n

NEUT GEANT3

Important is “neutron” simulations.

• Neutrons with <20 MeV: ENDF/B-V nuclear library
• Neutrons with >20 MeV: Intra-nuclear cascade model

≤ 10 MeV ≤ 10 MeV

SLIDE 8

SK Inner Detector Reconstructed vertex Reconstructed direction

effwall dwall

SK Outer Detector

8

Event Reconstruction

• SK low energy fitter is used to reconstruct events.
• Vertex: PMT hit timing information is used.
• Direction: Cherenkov ring pattern of hit PMTs is used.
• Energy: Number of hit PMTs is used.
• Fitter performance is checked by various calibrations.
• Important variables = { Erec, dwall, effwall, ovaQ, θC }.
• vaQ = GV2 – GA2

GV : Vertex goodness (quality of reconstructed vertex) GA : Angular badness (quality of reconstructed direction) θC: Cherenkov opening angle

SLIDE 9

s] µ dt0 [

1 − 1 2 3 4 5

s µ Events/0.05-

1 10

9

Event Selection

• 1. Energy window: 4 ≤ Erec < 30 MeV
• 2. Good spill selection
• 3. Timing cut: dt0 being required to be ±100 ns w.r.t the beam bunch center.
• 4. Decay-e cut: events having the pre-activity are cut (see backup for the post-activity).
• 5. Fiducial volume cut: dwall ≥ 200 cm
• 6. Ambient low energy background cut: Optimized { dwall, effwall, ovaQ } for each run to

remove beam-unrelated events.

• 7. CC interaction cut: optimized cut based on the Erec–θC 2D distribution.

Only for Data Both for Data and MC FHC

Neutron tagging is not applied in this analysis, while it is in the SRN analysis.

SLIDE 10

[MeV]

rec

E 4 4.5 5 5.5 6 6.5 dwall [cm] 160 180 200 220 240 260 280 300 Optimized dwall for Run 8 Optimized dwall for Run 8 [MeV]

rec

E 4 4.5 5 5.5 6 6.5 effwall [cm] 200 400 600 800 1000 Optimized effwall for Run 8 Optimized effwall for Run 8 [MeV]

rec

E 4 4.5 5 5.5 6 6.5

• vaQ

0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26 Optimized ovaQ for Run 8 Optimized ovaQ for Run 8

10

Ambient Low Energy Background Cut

• Three parameters { dwall, effwall, ovaQ } are optimized based on the figure-of-merit (FOM).
• Beam-unrelated events are taken from off-timing data (–500 µs ≤ dt0 ≤ –5 µs) and

normalized to the on-timing time scale (495 µs → 200 ns × bunch#).

On-timing data Off-timing data dt0

–500 µs –5 µs

~ ~ ~ ~

SLIDE 11

[MeV]

rec

E

5 10 15 20 25 30

Events/MeV

2 −

10

1 −

10 1 10

2

10

3

10

4

10

T2K Run 1-9 FHC Off-timing data (before FV cut) Off-timing data (after all cuts) MC (before FV cut) MC (after all cuts)

11

Background Rejection Power

neutrino events beam-unrelated events

SLIDE 12

0.5 1 1.5 2 2.5 3

• NCQE (FHC)

ν

[MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

• NCQE (FHC)

ν

0.05 0.1 0.15 0.2 0.25 0.3 0.35

CCQE (FHC)

[MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

CCQE (FHC)

12

CC Interaction Cut

• θC ~ 34 deg. for µ / θC ~ 42 deg. for e or single-γ / θC > 70 deg. for multiple-γ
• There are remaining events by CC interaction with decay-e which were not cut by the pre-

activity cut.

• Cut criteria are optimized based on 2D distributions and FOM.

SLIDE 13

[MeV]

rec

E

5 10 15 20 25 30

Events/MeV

10 20 30 40 50

Data (T2K Run1-9 FHC)

• NCQE

ν

• NCQE

ν NCother CC Beam-unrelated

[degree]

C

θ

10 20 30 40 50 60 70 80 90

Events/2.7-degree

5 10 15 20 25 30 35 40

Data (T2K Run1-9 FHC)

• NCQE

ν

• NCQE

ν NCother CC Beam-unrelated

13

Selected Final Samples (FHC)

Event# (Fraction) All nu NCQE nubar NCQE NCother CC Beam-unrelated T2K Run1-9 FHC MC 238.4
 (100%) 178.6
 (74.9%) 4.8
 (2.0%) 42.5
 (17.8%) 8.9
 (3.7%) 3.6
 (1.5%) Data 204 – – – – –

multiple-γ single-γ

SLIDE 14

[degree]

C

θ

10 20 30 40 50 60 70 80 90

Events/2.7-degree

2 4 6 8 10 12 14 16 18

Data (T2K Run1-9 RHC)

• NCQE

ν

• NCQE

ν NCother CC Beam-unrelated

[MeV]

rec

E

5 10 15 20 25 30

Events/MeV

2 4 6 8 10 12 14 16 18 20 22

Data (T2K Run1-9 RHC)

• NCQE

ν

• NCQE

ν NCother CC Beam-unrelated

Event# (Fraction) All nu NCQE nubar NCQE NCother CC Beam-unrelated T2K Run1-9 RHC MC 94.3
 (100%) 17.9
 (19.0%) 56.4
 (59.9%) 15.5
 (16.5%) 2.3
 (2.5%) 2.1
 (2.2%) Data 97 – – – – –

14

Selected Final Samples (RHC)

multiple-γ single-γ

SLIDE 15

15

Systematic Uncertainty

Polarity Type nu NCQE nubar NCQE NCother CC Beam-unrelated FHC Event fraction 74.9% 2.0% 17.8% 3.7% 1.5% Neutrino flux 6.7% 8.6% 7.3% 6.4%

• Neutrino interaction

3.0% 3.0% 8.2% 16.5%

• Primary-γ production

11.0% 10.6% 6.0% 6.6%

• Secondary-γ production

13.5% 13.4% 19.5% 17.6%

• Oscillation parameter
• 4.1%
• Detector response

3.4% 3.4% 2.0% 5.2% 3.4% Total error 19.2% 19.7% 23.3% 26.7% 3.4% RHC Event fraction 19.0% 59.9% 16.5% 2.5% 2.2% Neutrino flux 7.0% 6.4% 7.0% 6.5%

• Neutrino interaction

3.0% 3.0% 10.8% 38.2%

• Primary-γ production

12.2% 11.3% 2.3% 0.5%

• Secondary-γ production

13.6% 13.1% 19.3% 21.4%

• Oscillation parameter
• 3.1%
• Detector response

3.4% 3.4% 2.0% 5.2% 3.4% Total error 20.1% 19.0% 23.4% 44.7% 3.4%

SLIDE 16

16

Cross Sections Extraction

• Errors for these scale factors are determined by the toy MC.
• All the errors are treated uncorrelated but for the primary- and secondary-γ emission errors.
• These are treated fully positive correlated for all the interactions and both modes.

D: Data, M: MC

In the case with the observed events and the nominal MC values: f_nu = 0.80 f_nubar = 1.11

SLIDE 17

[GeV]

ν

E 0.5 1 1.5 2 2.5 3 ]

2

cm

• 38

10 × [

NCQE

σ 0.5 1 1.5 2 2.5 3

T2K Neutrino Data (Run1-9) NEUT NEUT Flux-averaged Flux (Run1-9) ν T2K FHC

[GeV]

ν

E 0.5 1 1.5 2 2.5 3 ]

2

cm

• 38

10 × [

NCQE

σ 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

T2K Antineutrino Data (Run1-9) NEUT NEUT Flux-averaged Flux (Run1-9) ν T2K RHC

17

Cross Sections Results

• Both results for neutrino and antineutrino are compared with a theory (NEUT).
• They are consistent to each other within the errors.

Neutrino Antineutrino

Run 1–3: σ = 1.55 × 10–38 cm2

SLIDE 18

18

Impact to SRN Search & Prospects

• This time antineutrino-oxygen NCQE cross section is measured for the first time.
• Now get prepared for constraining NCQE background estimation in the SRN search.
• Expected precision …
• T2K measurement error: ~30%
• Atmospheric neutrino flux error: ~20%
• Difference in different flux shape and according cross section model: ≤30% (?)


→ Estimation with <50% precision is possible !! (such work is on-going)

• Further possible improvement is to apply the neutron-tagging to this sample.
• This will provide almost the same phase space as the SRN analysis.
• Many errors can be reduced since only the final state is compared.
• SK-Gd can achieve this with higher statistics.

(Run 1–3: σ = 1.55 × 10–38 cm2)

SLIDE 19

19

Summary

• Detecting supernova relic neutrinos is a key to understanding star formation history,

supernova mechanism, nucleosynthesis, etc.

• The current search sensitivity is limited by a large uncertainty of the NCQE interaction.
• Both of neutrino and antineutrino NCQE interactions on oxygen were measured at Super-

Kamiokande using T2K beams.

• The world most precise measurements
• First measurement for antineutrinos
• It seems that SRN background precision can be improved to half of the current 100%.

Thank you for your attention!

SLIDE 20

BACKUP SLIDES

SLIDE 21

21

Analysis Flow Chart

NEUT SKDETSIM LOWFIT

Monte Carlo Simulation Data

Neutrino Flux MC T2K Beam Data

Off-timing cut [–500, –5] µs

Optimization of cut criteria (from dwall, effwall, ovaQ)

On-timing cut spill center ±100 ns

+

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neutrino interaction + FSI SI + detector response reconstruction

LOWFIT Good spill selection

N beam-related

sig

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N beam-related

bkg

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N beam-unrelated

bkg

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Nobs

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Npred

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=

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Data from Run1–9 FHC (14.94 × 1020 POT) and RHC (16.35 × 1020 POT) are used.

SLIDE 22

22

Neutrino Oscillation Effect

νµ νµ νe ντ

wgte wgtµ wgtτ × P(νµ→νµ; Eν) × P(νµ→νe; Eν) × P(νµ→ντ; Eν) × σCC(νe; Eν)/σCC(νµ; Eν) ~ 1 × σCC(ντ; Eν)/σCC(νµ; Eν) × 1

(–)

(–) (–) (–) (–)

(–) (–) (–) (–) (–) (–) (–) (–) (–)

• For CC events, the neutrino oscillation effect should be considered.
• Only νµ to νµ/νe are taken into account, which is justified by flux and cross sections.

T2K 2017OA best fit with reactor constraint Parameter Nominal Error sin2θ13 0.0211 ±0.0008 sin2θ23 0.541 +0.027/–0.037 Δm232 [×10–3 eV2] 2.469 +0.073/–0.071 νµ and νe CC cross sections are assumed to be same.

SLIDE 23

23

Primary-γ Production

ν ν’

neutron proton

potential p1/2 p3/2 s1/2

Spectroscopic factors by Ankowski et al. [Phys, Rev. Lett. 108, 052505 (2012).]

• (p1/2)–1: ground state (no γ-emission)
• (p3/2)–1: ~100% gamma emission (6.18 MeV, 6.32 MeV, etc)
• (s1/2)–1: particle (p, n, α, etc) decay + gamma emission
• others: short range correlation (← No data nor calculation about the final state)
• The ‘others’ is integrated into (s1/2)–1 state in the nominal setting.

Spectroscopic factors (p1/2)–1 (p3/2)–1 (s1/2)–1

• thers

Simple shell model 0.25 0.50 0.25 Ankowski’s calculation 
 based on LDA 0.158 0.3515 0.1055 0.385 This analysis 0.158 0.3515 0.4905

One of the excited states is selected after the neutrino interaction (any interaction).

SLIDE 24

24

Primary-γ Production

SLIDE 25

25

Primary-γ Production

SLIDE 26

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045

CCother (FHC) [MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

CCother (FHC)

0.05 0.1 0.15 0.2 0.25 0.3 0.35

CCQE (FHC) [MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

CCQE (FHC)

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045

CC 2p2h (FHC) [MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

CC 2p2h (FHC)

0.1 0.2 0.3 0.4 0.5 0.6

(FHC) π NC1 [MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

(FHC) π NC1

0.01 0.02 0.03 0.04 0.05

NCother (FHC) [MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

NCother (FHC)

0.02 0.04 0.06 0.08 0.1

• NCQE (FHC)

ν

[MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

• NCQE (FHC)

ν

0.5 1 1.5 2 2.5 3

• NCQE (FHC)

ν [MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

• NCQE (FHC)

ν

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24

Beam-unrelated (FHC) [MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90

Beam-unrelated (FHC)

26

CC Interaction Cut

SLIDE 27

27

Background Rejection Power

[MeV]

rec

E

5 10 15 20 25 30

Events/MeV

2 −

10

1 −

10 1 10

2

10

3

10

4

10

T2K Run 1-9 FHC Off-timing data (before FV cut) Off-timing data (after all cuts) MC (before FV cut) MC (after all cuts)

SLIDE 28

28

Neutrino Interaction Parameters

SLIDE 29

]

2

[(GeV/c)

2

Q 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 (area normalized)

2

Events/0.02-(GeV/c)

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04

T2K Run 1-9 FHC No cut After FV cut After dwall cut After effwall cut After ovaQ cut After CC interaction cut

]

2

[(GeV/c)

2

Q 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 (area normalized)

2

Events/0.02-(GeV/c)

0.01 0.02 0.03 0.04 0.05

T2K Run 1-9 FHC No cut After FV cut After dwall cut After effwall cut After ovaQ cut After CC interaction cut

29

Momentum Transfer

• Signal Q2 distributions before and after cuts are not so different.
• No need to take the systematics about signal efficiency by interaction model into account.

neutrino antineutrino

SLIDE 30

30

Secondary-γ Production Error

C

N

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

selected

P

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

FHC

C

N

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

selected

P

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

RHC

• Previously, two gamma emission models (GCALOR and NEUT) are compared. 


The boundary of neutron interaction picture (non-QE from QE) was assumed to be 30 MeV.

• Recent RCNP measurements didn’t see any peak considered from QE process even at 80

MeV [*] and 250 MeV. Then, it may be dangerous to set such a boundary.

• This analysis focuses only on the number of Cherenkov photons (NC).
• 1. Calculate probabilities of an event being selected in a [4, 30] MeV region for each NC.
• 2. Change NC coming from the secondary process, and apply the probabilities above.

[*] Y. Ashida et al., arXiv:1902.08964

Changed by 65% (×1.65 or 0.35)

SLIDE 31

31

Secondary-γ Production Error

• Secondary-γ production = neutron-16O interaction + gamma emission
• Neutron-16O interaction
• The previous proton-12C study [*] shows a correction factor of 1.229±0.075 from the

intra-cascade cross section.

• To cover this, a conservative 40% is assigned to neutron-16O cross section.
• (Neutron-16O interaction +) Gamma emission
• In SK Li9 study [**], no serious difference between Data and MC.
• A 50% error is expected to be enough.

Totally a 65% error is assigned for the inclusive cross section. → This produces a ~13% error.

Energy after muon spallation

[*] W. Y. Ma et al., J. Phys. Conf. Ser. 888, 012171 (2017). [**] Y. Zhang et al., Phys. Rev. D 93, 012004 (2016).

SLIDE 32

• NCQE

ν

f

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 10000 20000 30000 40000 50000

) ν Statistical Error ( nominal (0.80) (+/-0.08) σ +/-1

• NCQE

ν

f

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 22000

) ν Statistical Error ( nominal (1.11) (+/-0.18) σ +/-1

200 400 600 800 1000

• NCQE

ν

f

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

• NCQE

ν

f

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Statistical Error nominal (0.80, 1.11)

f_nu = 0.80±0.08 f_nubar = 1.11±0.18

32

Toy MC Results: Statistical Error

SLIDE 33

• NCQE

ν

f

0.5 1 1.5 2 2.5 3 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

) ν Systematic Error ( nominal (0.80) (+0.24/-0.18) σ +/-1

• NCQE

ν

f

0.5 1 1.5 2 2.5 3 2000 4000 6000 8000 10000 12000 14000 16000

) ν Systematic Error ( nominal (1.11) (+0.29/-0.22) σ +/-1

100 200 300 400 500 600

• NCQE

ν

f

0.5 1 1.5 2 2.5 3

• NCQE

ν

f

0.5 1 1.5 2 2.5 3

Systematic Error nominal (0.80, 1.11)

f_nu = 0.80+0.24/–0.18 f_nubar = 1.11+0.29/–0.22

33

Toy MC Results: Systematic Error

SLIDE 34

34

Flux-averaged Cross Sections

(integration over flux before oscillation up to 10 GeV) (FHC Φ(nu) for neutrino, RHC Φ(nubar) for antineutrino)

SLIDE 35

0.0296149

• 0.00545748
• 0.00545748

0.0253014

ν

σ

ν

σ

ν

σ

ν

σ

]

2

/oxygen)

2

cm

• 38

(10 × [

0.005 − 0.005 0.01 0.015 0.02 0.025

Statistical Error

0.226975 0.0947279 0.0947279 0.0583337

ν

σ

ν

σ

ν

σ

ν

σ

]

2

/oxygen)

2

cm

• 38

(10 × [

0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22

Systematic Error

35

Covariance of Cross Sections

SLIDE 36

36

Model Comparison

• Ref. [A. Ankowski et al., Phys. Rev. C 92, 025501 (2015)] provides some model predictions.
• Spectral function (SF)
• Relativistic mean field (RMF)
• Superscaling (SuSA)
• Relativistic Green’s function with EDAI potential (RGF, EDAI)
• Relativistic Green’s function with democratic potential (RGF, Democratic)
• Relativistic plane wave impulse approximation (RPWIA)
• Measured results are compared with them.
• Caution
• Any of above models does not consider 2p2h, while the measured may contain it.
• Measurement was done based on NEUT differential cross section, then direct comparison

is not an ideal way actually (starting from the event generation is ideal).

SLIDE 37

37

Model Comparison

[GeV]

ν

E 0.5 1 1.5 2 2.5 ]

2

cm

• 38

10 × [

NCQE

σ 0.5 1 1.5 2 2.5 3

'N) cross section ν , ν O(

16

NEUT SF RMF SuSA RGF, EDAI RGF, Democratic RPWIA

[GeV]

ν

E 0.5 1 1.5 2 2.5 3 ]

2

cm

• 38

10 × [

NCQE

σ 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 'N) cross section ν , ν O(

16

NEUT SF RMF SuSA RGF, EDAI RGF, Democratic RPWIA

Neutrino Antineutrino

SLIDE 38

]

2

cm

• 38

10 × [

• NCQE

ν

σ

0.5 1 1.5 2 2.5

RPWIA RGF, DEM RGF, EDAI SuSA RMF SF NEUT ]

2

cm

• 38

10 × [

• NCQE

ν

σ

0.2 0.4 0.6 0.8 1 1.2 1.4

RPWIA RGF, DEM RGF, EDAI SuSA RMF SF NEUT 38

Model Comparison

• Neutrino: Every model is consistent with the measurement.
• Antineutrino: SF, RMF, and SuSA are slightly disfavored but it is not significant at all.

Neutrino Antineutrino

SLIDE 39

39

Cherenkov Angle vs. Energy

[MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90 0.5 1 1.5 2 2.5 3 3.5

[MeV]

rec

E

5 10 15 20 25 30

[degree]

C

θ

10 20 30 40 50 60 70 80 90 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

FHC RHC

SLIDE 40

[degree]

C

θ

10 20 30 40 50 60 70 80 90

Events/2.7-degree

5 10 15 20 25 30 35 40

Data (T2K Run1-9 FHC)

• NCQE

ν

• NCQE

ν NCother CC Beam-unrelated

[degree]

C

θ

10 20 30 40 50 60 70 80 90

Events/2.7-degree

2 4 6 8 10 12 14 16 18

Data (T2K Run1-9 RHC)

• NCQE

ν

• NCQE

ν NCother CC Beam-unrelated

40

Nucleon Energy & Cherenkov Angle

• The θC distribution in RHC looks different from the one in FHC.
• High angle events seem more in RHC relative to ~42 deg. peak events.
• Peak height ratio between ~90 and ~42 deg. is clearly different between FHC and RHC.
• This is considered due to the difference in neutron energy after ν and anti-ν NCQE.
• In anti-ν case, the momentum transfer is relatively smaller and then nucleon momentum

becomes smaller (this is leading to less secondary-γ production?).

SLIDE 41

[MeV]

n

E

100 200 300 400 500 600 700 800 900 1000

Events/5-MeV (area normalized)

0.005 0.01 0.015 0.02 0.025 0.03

• n NCQE

ν

• n NCQE

ν

0.002 0.004 0.006 0.008 0.01

• n NCQE (FHC)

ν

[MeV]

n

E

100 200 300 400 500 600 700 800 900 1000

[degree]

C

θ

10 20 30 40 50 60 70 80 90

• n NCQE (FHC)

ν

0.05 0.1 0.15 0.2 0.25 0.3 0.35

• n NCQE (FHC)

ν

[MeV]

n

E

100 200 300 400 500 600 700 800 900 1000

[degree]

C

θ

10 20 30 40 50 60 70 80 90

• n NCQE (FHC)

ν

41

Nucleon Energy & Cherenkov Angle

FHC NCQE with Neutron

SLIDE 42

[MeV]

n

E

100 200 300 400 500 600 700 800 900 1000

Events/5-MeV (area normalized)

0.005 0.01 0.015 0.02 0.025 0.03 0.035

• n NCQE

ν

• n NCQE

ν

0.02 0.04 0.06 0.08 0.1 0.12 0.14

• n NCQE (RHC)

ν

[MeV]

n

E

100 200 300 400 500 600 700 800 900 1000

[degree]

C

θ

10 20 30 40 50 60 70 80 90

• n NCQE (RHC)

ν

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045

• n NCQE (RHC)

ν

[MeV]

n

E

100 200 300 400 500 600 700 800 900 1000

[degree]

C

θ

10 20 30 40 50 60 70 80 90

• n NCQE (RHC)

ν

42

Nucleon Energy & Cherenkov Angle

RHC NCQE with Neutron