A preliminary CC 0 event selection in SBND Rhiannon Jones - - - PowerPoint PPT Presentation

A preliminary νμCC 0π event selection in SBND

Rhiannon Jones - University of Liverpool, UK

On behalf of the SBND collaboration New Perspectives, Fermilab

Monday 10th June 2019

SBND MicroBooNE ICARUS

Baseline [m]

110 470 600

Argon mass [t]

112 89 476

The SBN Program

B

• s

t e r N e u t r i n

• B

e a m ( B N B )

ICARUS (FD) MicroBooNE S B N D ( N D ) BNB Target Hall

M i n i B

• N

E

The Short Baseline Near Detector, SBND

• Liquid argon time projection chamber

○

112 tonnes of liquid argon

○

4 x 4 x 5 m3

○

110 m from the neutrino source

• 500 V/cm electric field across the TPC

○

Neutrinos interact and ionise the argon

○

Field drifts ionisation electrons towards

• ne of the anode plane assemblies (APAs)
• 2 electron drift volumes

○

Connected at the centre by the cathode plane assembly

• All TPC components are now at Fermilab!

○

Installation will begin this year

○

Running by the beginning of 2021

Light detection system Anode wire planes Cathode plane Electric field x z y

νμ

TPC 1 TPC 2 e- drift e- drift Anode wire planes

2 of our APAs have been unpacked and aligned, the second 2 are here at Fermilab, awaiting the same

3

• Near detector in the SBN oscillation

analysis

○

Characterise the initial flux of the neutrinos

○

Confirm or rule out the existence of light sterile neutrinos

The physics program of SBND

sin22θμe sin22θμμ Δm2 (eV2)

arXiv:1503.01520

SBN sensitivity to νμ → νe oscillations SBN sensitivity to νμ → νx oscillations 4

• Unprecedentedly high statistics

○

~ 7,000,000 νμ events over 3 years

○

~20 times μBooNE, ~10 times ICARUS

• Will make high-precision cross-section

measurements of neutrino interactions with argon nuclei at ~1 GeV

0.5 1 1.5 2 2.5 3 20 40 60 80 100 x 103

Neutrino energy, [GeV] SBND event rate, 3 years of running

5

• G. Zeller, arXiv:1305.7513 [hep-ex], 2013

Neutrino scattering cross-section data

1.4 1.2 1.0 0.8 0.6 0.4 0.2 10-1 1 101 102

ν cross-section [10-38 cm2 GeV-1] Neutrino energy, [GeV]

Cross-sections in the few-GeV energy range

• Neutrino interactions in the few GeV

energy region are very interesting

○

Boundary between perturbative and non-perturbative regimes

■

QE, RES and DIS cross-over ○

Historically, very little data in this region

• Interactions on heavy nuclei are not yet

well understood

○

Many unconstrained models exist

• Datasets from recent experiments are

starting to help constrain these models

○ Such as MINERvA and MiniBooNE

SBND will provide data in this energy region with huge statistics giving us tighter constraints

• n these neutrino-nuclei models

6 0.5 1 1.5 2 2.5 3 20 40 60 80 100 x 103

Neutrino energy, [GeV]c SBND event rate, 3 years of running

Final state charged current topologies in SBND

νμ CC 0π in SBND

• LArTPC detector technology:

○

Bubble chamber resolution capability (~mm)

○

Automated event processing

○

Calorimetry

• Can distinguish individual

particles in the final state of the neutrino interaction

• νμ CC 0π is the most simple and

abundant final state in SBND: 1 muon and any number of protons

• Expect to see ~4,000,000

νμ CC 0π events in 3 years

https:/ /vms.fnal.gov/asset/detail?recid=1743008&recid=1743008

Bubble chamber

http:/ /news.fnal.gov/2015/10/microboone-sees-first-accelerator-born- neutrinos-2/

LArTPC

Using the νμ CC 0π final state in SBND

7

GENIE v02.12.10, Default+MEC

1 2 3 4 5 6 0.5 1 1.5 2 2.5 x 106

Proton multiplicity in the true νμ CC 0π final state SBND event rate, 3 years of running

A b s

• r

p t i

• n

FSI

π± μ- p νμ

Bound nucleon interactions

FSI

μ- p n νμ

• Nuclear target neutrino experiments don’t

necessarily observe the products of the initial interaction which took place

• Can use exclusive final state topologies,

such as νμCC 0π, to discriminate between neutrino-argon interaction models

○

Distinguishing power in the proton multiplicity of the final state

Multiple scattering

FSI

μ- p p n νμ

8

νμ CC 0π 3p signal event in the SBND MC sample

μ- p p p

Neutrino vertex

Time, TDC Wire number

‘Hammer’ signal event in the SBND MC sample

μ- p p

Neutrino vertex

Time, TDC Wire number

νμ CC 0π final state

particles in SBND

• Monte Carlo SBND

νμ CC 0π events

• Resolution allows for

straightforward particle identification by-eye

• Final states with interesting

physical characteristics Need to ensure our software can reconstruct and select these events

Selecting ν-Ar interaction final state particles

Residual range [cm] dE/dx [MeV/cm] G4 MC Predictions Proton ―

Pion ― Muon ―

• Recorded stopping track

5 10 15 20 25 30 5 10 15 20 25 30 35 40

• Use calorimetry to distinguish protons from muons & pions
• Use case: Fit the bragg peak of a reconstructed track to the

theoretical peak under a certain particle hypothesis

• Fitting to the proton hypothesis has the strongest

discrimination power

ArgoNeuT, JINST 7, P10019, 2012

Protons are correctly distinguished from muons and pions 98% of the time when tested on a BNB sample!

Muons

50 100 150 200 250

χ2 under proton hypothesis Fraction of true particles [arb]

Protons Particle-gun samples

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Use geometrical features

• f the event to find

muons

5 . 5 % e v e n t s h a v e a s i n g l e e s c a p i n g t r a c k 9 5 . 9 % e s c a p i n g t r a c k s a r e μ

Selecting ν-Ar interaction final state particles

All tracks contained:

• Compare lengths of all

particles to determine if a muon exists

• Longest ⇒ muon

Single track escapes:

• Check if the neutrino

vertex is far from the exiting border

• Large ℒ ⇒ muon exits

π π p

Fiducial volume of the TPCs

p n νμ μ n ℒ

Performance of the selection in SBND

Purity: Signal / Total selected

Selected → ↓ True νμ CC Inclusive νμ CC 0π νμ CC 0π 39,100 32,650 νμ CC 1π 8,386 3,218 νμ CC Other 658 70 νμ NC 2,967 2,130 Efficiency 92.0% 76.9% Purity 94.2% 85.8% Main sources of topological impurities: Pion-proton mis-ID 8.5% in 0π Incorrect-muon finding 5.6% in 0π, 5.8% in Inc.

Efficiency: Signal / Total true

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No external backgrounds (cosmic rays and dirt muons) included in the selection yet

Summary

• SBND will drastically increase the amount of neutrino interaction data on

heavy nuclei in the few-GeV energy range

• The LArTPC detector technology allows us to observe final state particles

at bubble chamber resolution

○

We can utilise particle selections to produce high-precision cross-section measurements on exclusive final state topologies

○

Oscillation measurements can also be made using exclusive final states to help constrain the interaction systematic uncertainties

• Understanding neutrino interactions on argon will help future experiments

like DUNE probe new and interesting physics

12

Backup slides

13

Neutrino-nuclear interactions

• CC QE on free-nuclei is a theoretically well

understood process

𝜉μ + n → μ- + p

○

Models were built on neutrino interactions on free-nuclei

○

Don’t work for interactions on nuclear targets

○

Experiments use nuclear targets!

• Experiments such as MiniBooNE saw an

excess of events

○

Known as the quasi-elastic puzzle

○

The data is QE-like, not true QE

○

Tuning free model parameters & including the 2p-2h process helps fix this

CC QE on C12

• L. Alvarez-Ruso, arXiv:1012.3871 (Neutrino 2010)

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 1 2 3 4 5 6 7 8 σ [x 10-38 cm2] Neutrino energy, [GeV] 14

MiniBooNE data

15

μ vs. π: z-angle & momentum

• Took pions as the comparable particle

since they rival the individuality of the muon’s MIP property

• Looking at the characteristics of the

true particles, does this support the theory that the muon is most likely to escape when the neutrino vertex is sufficiently far from the fiducial border?

• Since the muons tend to have higher

momenta and are more forward going: Yes!

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Finding escaping muons

• In an event with 1

escaping particle, we can use the TPC to determine if this particle is a muon ○

Using its properties as a MIP and the neutrino primary final state lepton

• If a particle exists and the

neutrino interaction vertex is far from the border the particle exits from (ℒ is

large), ask if that particle is

likely to be a muon

Δy Δx

x z y

π p Fiducial volume of the TPC

ℒ

Tentative fiducial border definition: X = 10 Y = 20 Z = 10

17

Escaping track rates

When the neutrino vertex is further than ~50 cm from the escaping fiducial border, the escaping track becomes significantly more likely to be a muon

50 100 150 200 250 300 350 400 Distance of the neutrino vertex from the escaped fiducial border [cm]

The true muon is the escaping particle The true muon is not the escaping particle

• Arb. units

450 500

Quantities within this sample

Total events with contained, reconstructed neutrino vertex 65,830

True vertex also contained 96.3% Maximum 1 escaping track 99.9% Exactly 1 escaping track 5.5%

Of these, only the true muon escapes 95.9%

Adding cosmics has reduced the ‘free’ muons to be 4.9% of the sample

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