NOvA Near Detector: Performance and Physics Hongyue Duyang For the NOvA collaboration

1 Οutline

• Introduction to the NOvA near detector. • Rock-muon induced EM showers.

• νe-CC inclusive cross-section measurement.

• Coherent π0 cross-section measurement.

• Neutrino-electron elastic scattering for absolute flux constraint.

• Summary

2 Introduction

• NOvA is a long-baseline neutrino experiment designed to measure νμ to νe oscillation. (See Adam Aurisano’s talk for the first result!)

• The principal task of the NOvA near detector is to constrain systematics for oscillation measurement.

• In addition, the NOvA near detector provides an excellent opportunity for the measurement of various neutrino interactions.

• Neutrino interactions have their own physics, and are important for oscillation experiments to reduce systematics.

• This talk will highlight some measurements using NOvA’s early data:

• νe-CC inclusive cross-section measurement.

• Coherent π0 cross-section measurement.

• Neutrino-electron elastic scattering for absolute flux constraint.

3 The NOνA Near Detector NOνA Near Detector Construction NO�A NO�A Far Detector (Ash River, MN) MINOS Far Detector (Soudan, MN) A broad physics scope • • Detector construction and instrumentation0.3 kton, completed4.2mX4.2mX15.8m, Aug.Using ��→�e , � ͞ �→� ͞ e … Determine the � mass hierarchy Determine the � octant 2014 • 1 km from source, underground at Fermilab.23 Constrain �CP

• PVC cells filled with liquid scintillatorUsing ��→�� , � ͞ .�→ � ͞ � … • Neutrinos observed within seconds of turning on! Precision measurements of 2 2 sin 2�23 and m 32. • Alternating planes of orthogonal (Exclude view. �23=�/4?) Over-constrain the atmos. sector Results (four oscillation channels) Also … Neutrino cross sections at the NO�A Near Detector Sterile neutrinos Bin to bin correlation matrix: Supernova neutrinos Fermilab Other exotica

Ryan Patterson, Caltech • Low-Z, fine-grained (1 plane ~ 0.15X0), highly- active tracking calorimeter, optimized for EM shower reconstruction. Mass weight of detector component: C12 Cl35 H1 Near DetectorTi48 O16 Others 11 0.3 kton Jonathan M. Paley 66.8% 16.4% 10.5% 206 3.3%layers 2.6% 0.4% 4 cm ⨯ 6 cm 4 The measured inclusive cross section from Gargamelle, T2k, and NOvA as shown. There is also shown the predicted cross section for nue on carbon from GENIE. There is large correlation between the energy bins for NOvA results (see Top table). Our detector material is dominant by the carbon, chlorine, and hydrogen.

11/17 NuInt 2015 Xuebing Bu (Fermilab) 28 NuMI off-axis beam

NO�A detectors are sited NuMI NuMI Beam Beam 14 mrad off the NuMI The NuMI Beam beam axis

With the medium-energy NuMI tune, yields a narrow 2-GeV spectrum at the NO�A detectors

➔ Detectors are installed by being ➔ Detectorsoff beam are installed axis by being off beam axis on axis → Reduces NC and �e CC ➔ Narrow band beam peaked at 2 GeV

backgrounds in the ➔ 14 mrad Narrow➔ bandNear maximumbeam peaked oscillation at 2 GeV oscillation analyses (NO�A) ➔ Near ➔maximumReduced oscillation NC background while maintaining high � flux at 2 GeV. ➔ Reduced➔ Electron NC background neutrino flux counts ~1% � of total flux. ➔ Electron neutrino flux counts ~1% of total flux.

Ryan Patterson, Caltech 7 Fermilab JETP, August 6, 2015 • Narrow11/17 NuInt 2015band neutrino beam peakXuebing Buat (Fermilab) ~2GeV. 5

11/17 •NuIntDominated 2015 by νμ (94%), withXuebing small Bu (Fermilab) contribution from νe (1%). 5

5 Near Detector: 10 �s of readout during NuMI beam pulse (color ⇒ time of hit)Neutrino Interaction in ND

• Introduction to the NOvA near detector. • Rock-muon induced EM showers.

• νe-CC inclusive cross-section measurement.

• Coherent π0 cross-section measurement.

• Neutrino-electron elastic scattering for absolute flux constraint.

• Summary

Ryan Patterson, Caltech 10µs of readout during16 NuMI beam pulse.Fermilab JETP, August 6, 2015

6 Οutline

• Introduction to the NOvA near detector. • Rock-muon induced EM showers.

• νe-CC inclusive cross-section measurement.

• Coherent π0 cross-section measurement.

• Neutrino-electron elastic scattering for absolute flux constraint.

• Summary

7 Rock-Muon Induced EM Showers

• Rock muons induce EM showers in the detector via bremsstrahlung radiation. • A muon-removal technique is developed to isolate those EM showers. • Provide a data-driven method to Check EM shower modeling and reconstruction for measurements involving EM showers. 8 Rock-Muon Induced EM Showers

• Rock muons induced EM showers in the detector via bremsstrahlung radiation. • A muon-removal technique is developed to isolate those EM showers. • Provide a data-driven method to Check EM shower modeling and reconstruction for measurements involving EM showers. 9 ReconstructionEM Shower of shower Angular directions Resolution

θshw - θμ (rad) • A “measured” angular resolution in data by comparing the 36 Jonathan M. Paley reconstructed EM shower direction to the muon direction. • The NOvA ND has good angular resolution (~0.02rad) for EM showers. • Important to measurements such as neutrino-electron elastic scattering and coherent π0 cross-section measurement.

10 Οutline

• Introduction to the NOvA near detector. • Rock-muon induced EM showers.

• νe-CC inclusive cross-section measurement.

• Coherent π0 cross-section measurement.

• Neutrino-electron elastic scattering for absolute flux constraint.

• Summary

11 νe-CC Inclusive Cross-Sectionνe + A CC Interactions Measurement in the NOνA Near Detector

NOνA Simulation 10 Full phase-space 1 50 p.o.t.)

8 21

/nucleon) 0.8 • Inclusive cross-section 2 40

- cm

measurement: νe + N => Χ + e 6 CC flux -39 30 e 0.6 T2K ν flux ν from µ 10 e /50 MeV/10

• × There are very few electron NEUT νe prediction 2 0 0 ± ( 4 from KL, K , and K 20 GENIE νe prediction 0.4 S σ NEUT average neutrino cross section νe /cm 9 GENIE νe average CC 10

Gargamelle data Fraction of measurements at GeV scale. ν νe 10 2 × 0.2 T2K νe data T2K νµ data flux (

0 0 e

0 1 2 3 4 5 6 7 8 9 10 ν 2 4 6 8 10 E (GeV) E (GeV) νe PRL 113, 241803 (2014) ν • Very limited world data • Beam electron neutrino interactions are irreducible backgrounds for the electron neutrino appearance analysis.• NOvA has a unique opportunity to make a clean measurement of ν • Measuring the electron neutrino inclusivee CC cross inclusive section, cross in sectionparticular in the 1 – 3 GeV energy region is important• Will restrict for long-baseline to 1-3 GeV range for the time being experiment, like DUNE. 24 Jonathan M. Paley

12 Event display νe-CCfor Inclusive nue candidate Cross-Section in Measurement data

11/17 NuIntThe 2015 signal events areXuebing νe-CC Bu (Fermilab) events with EM showers 32 induced by the electrons in the final state.

13 BDT output distributions BDT output distributions νe-CC Inclusive Cross-Section: Event Selection

• Pre-selection cuts on fiducial, containment, shower length and energy, fraction of MIP hits, andLeft EM plot likelihood shows theapplied. shape distributions of BDT output for the nue CC signal and numu CC and NC background. • Build multi-variantLeft plot showsBoost D theecision shape Tree distributions (BDT) algorithm of BDT based output upon for shower the nue CC signal Right plot shows the BDT output distributions after event selection from data, properties to reduce background:and numu CC and NC background. Right plot shows thesignal BDT and output various distributions backgrounds. after event selection from data, • Fraction of MIP hitsAll in eventssub-leading are selected prong with preselection cuts. signal and various backgrounds. • 11/17Fraction NuInt 2015 of energy in ±4cmAll events transverseXuebing are selected Buroad (Fermilab) with preselection cuts. 13 • Maximal fraction of energy in 6-continuous planes •11/17Fraction NuInt 2015 of energy in first 10 planes Xuebing Bu (Fermilab) 13 • Fraction of energy in 2nd, 3rd and 4th plane. νe-CC: Rock Muon EM Showers 20 2.6 × 1020 POT NOνA Preliminary 2.6 × 10 POT NOνA Preliminary 0.3

Brem EM Data Brem EM Data 0.25 0.25 Brem EM MC Brem EM MC 0.2 0.2 νe MC νe MC

0.15 0.15

0.1 0.1 Fraction of Events Fraction of Events

0.05 0.05

0 0 1 1.5 2 0 200 400 600 Shower Energy (GeV) Shower Length (cm)

2.6 × 1020 POT NOνA Preliminary • Use rock muon EM showers to 2000 check EM shower modeling and Data BDT algorithm. 1500 MC

1000

• Good agreement between data Events

and MC. 500 • Take the data/MC difference in −0.4 −0.2 0 0.2 0.4 selection efficiency as systematics. 1.5 1 0.5

Data / MC −0.4 −0.2 0 0.2 0.4 15 BDT output νe-CC: Background Normalization 2.6 × 1020 POT NOνA Preliminary 2.6 × 1020 POT NOνA Preliminary 1400 2500 Data Data CC νe 1200 CC νe 2000 ROCK + CC ROCK + CC νe 1000 νe NC NC 1500 800 CC νµ CC νµ

Events Events 600 1000 400 500 200

0.4 0.45 0.5 0.55 0.6 0.65 0.7 −0.3 −0.25 −0.2 −0.15 −0.1 1.2 1 1 0.9 0.8 0.8 0.6 0.7 0.6 Data / Bkg 0.4 Data / Bkg 0.4 0.45 0.5 0.55 0.6 0.65 0.7 −0.3 −0.25 −0.2 −0.15 −0.1 Fraction of MIP hits BDT output

• Use 2 Sideband samples for background normalization: • Fraction of MIP hits > 0.45. • BDT < -0.1 • MC over predict backgrounds: choose a normalization factor of 0.95±0.2.

16 νe-CC: Flux NOνA Simulation 1

• νe flux comes from muon and kaon decay 0.8 muon • Systematics from beam transport and kaon CC flux

e 0.6 hadron production. ν • Use external data (MIPP and NA49) to 0.4

constraint the hadron production uncertainty. Fraction of 0.2 • Scale down flux by 5~8% in 1~3GeV, with 2 4 6 8 10 uncertainty ~10%. Electron Neutrino Energy (GeV)

NOνA Preliminary NOνA Preliminary

0.4 1.2

0.2

1.1

0

1 Flux weight −0.2

0.9 Uncertainty on flux weight −0.4

2 4 6 8 10 2 4 6 8 10 Electron Neutrino Energy (GeV) Electron Neutrino Energy (GeV) 17 Results νe-CC Inclusive Cross-Section: Result and Systematics

Bin to bin correlation matrix:

Mass weight of detector component: C12 Cl35 H1 Ti48 O16 Others 66.8% 16.4% 10.5% 3.3% 2.6% 0.4% • Dominate systematics: flux, backgroundThe normalization,measured inclusive hadron cross energy, section and event from Gargamelle, T2k, and NOvA as shown. selection efficiency.There is also shown the predicted cross section for nue on carbon from GENIE. • Presented atThere NuInt15. is large Looking correlation forward betweento publishing the energysoon. bins for NOvA results (see Top table). Our detector material is dominant by the carbon, chlorine, and hydrogen. 18 11/17 NuInt 2015 Xuebing Bu (Fermilab) 28 Οutline

• Introduction to the NOvA near detector. • Rock-muon induced EM showers.

• νe-CC inclusive cross-section measurement.

• Coherent π0 cross-section measurement.

• Neutrino-electron elastic scattering for absolute flux constraint.

• Summary

19 Coherent π0 Measurement

• Neutrinos can coherently scatter off target nucleus via charge/ neutral current interaction and produce pions. • Small momentum transfer. No quantum number exchange. • Single forward-going pion in the final state, no vertex activity.

• Background to νe appearance. • Physics in its own right: Partially Conserved Axial Current (PCAC), used in Berger-Seghal model and in most neutrino event generators such as GENIE. 20 Coherent π0: World Measurement

100

80 /Nucleus)

2 There are relatively few

cm 0

-40 60 coherent π measurement,

GENIE

) (10 most suffer from large 0 40 NOMAD Worldπ Data Aachen-Padova uncertainty. Gargamelle 20

(COH CHARM

σ SKAT 0 0 10 20 30 Neutrino Energy (GeV)

40 2 Experiments A < E⌫ > (10 cm /N) /(⌫µ-CC) /(RS) Aachen-Padova 27 2 29 10 ± Gargamelle 31 2 31 20 ± CHARM 20 30 96 42 ± SKAT 30 7 79 28 4.3 1.5 ± ± 15’ BC 20 20 0.20 0.04s ± NOMAD 12.8 24.8 72.6 10.6 3.21 0.46 ± ± MiniBooNE 12 0.8 0.65 0.14 ± SciBooNE 12 0.8 0.9 0.20 ± NO⌫A 10.6 2.7 13.7 1.9 21 ±

Coherent ⇡0 Hongyue Duyang 44 Coherent π0: Topology

• Focusing on 2-prong topology: π0 => γγ, both reconstructed.

22 Neutral Current π0 Selection

• Select events with 2 EM shower prongs by calculating log-likelihoods against muons, protons and charged pions. • Invariant mass plot show good data/MC agreement: also serve as a calibration check. • Good statistics for a coherent π0 measurement. • Non-coherent background comes from Resonance (RES), Deep- Inelastic Scattering (DIS) and charge-current events. Coherent π0: Analysis Strategy

• Select NC π0 events, including coherent and non-coherent (RES, DIS). • Define a control sample, dominated by non-coherent π0 s, and a signal sample with coherent events. • The control sample will be used for background tuning (shape and normalization).

24 Coherent π0 Analysis: Control Sample and Signal Sample

Control Sample Signal Sample

• Select NC π0 events, including coherent and non-coherent (RES, DIS). • Define a control sample, dominated by non-coherent π0 s, and a signal sample with coherent events. • The control sample will be used for background tuning (shape and normalization).

25 Coherent π0 Measurement

• ζ = E*(1-cosθ) is a variable indicating the “forwardness” of the π0. • Coherent has small ζ: define coherent region as ζ < 0.1GeV. • Apply the normalization and ζ shape tuning from control sample to non- coherent π0 MC in signal sample • Will get a measurement by looking at data event excess over non-coherent π0 MC in the coherent region. • Expect ~15% uncertainty (stat + syst) using current data (2.6E20 POT): a very competitive result. 26 Οutline

• Introduction to the NOvA near detector. • Rock-muon induced EM showers.

• νe-CC inclusive cross-section measurement.

• Coherent π0 cross-section measurement.

• Neutrino-electron elastic scattering for absolute flux constraint.

• Summary

27 Neutrino-ElectronMotivation Elastic Scattering

• Neutrinos can elastically scatter off atomic electrons. • • -eA scatteringpure leptonic is process pure leptonic: the cross-section process is whichvery well can known be calculated accuratelyfrom electroweak (~1%). theory. So it can be used to absolutely constrain flux.• On the other hand, the neutrino flux is poorly known in accelerator neutrino experiments such as NOνA. • Because of the small Q2, the scattered electron is very forward. • We can get an absolute neutrino flux constraint by So measuringthe signal ν-e is scattering be a very in theforward detector. single electron. • The cross-section is very low (~10-4 of total), so PID and background rejection is very28 important to identify the signal. Initially, this channel can also be used to validate electron

identification with early ND data. 3 Neutrino-Electron Elastic Scattering

50 100 150 200 250 300 350 400 450

−20

−40 x (cm)

−60

0

−20

−40 y (cm)

−60

−80 50 100 150 200 250 300 350 400 450 z (cm) NOvA - FNAL E929 2 Run: 10500 / 50 102 10 hits hits Event: 1694 / -- 10 10 1 1 UTC Wed Jun 26, 1974 0 100 200 300 400 500 10 102 103 01:20:33.175032704 t (µsec) q (ADC)

• ν-e scattering has very small Q2 transfer => very forward electron • The signal signature is unique: one single, forward EM shower in the detector, with nothing else.

29 Neutrino-Electron Elastic Scattering: Analysis

NOA Simulation 60

MC -on-e signal

POT MC Beam e 20 40 10 MC µ CC + NC ×

20 Events / 1.66

0 0 0.01 0.02 0.03 0.04 E2 (GeV × rad2) E 2 distribution after event selection for ND neutrino MC, where E • Cross-sectionθ is small: PID algorithms developed to reduce is the shower energy for the electron candidate and θ is the angle backgroundsof the (electronνe-CC, candidates νμ-NC). with regard to beam direction. 2 • The electron is very forward: Limit in E*θ < 2me. • Expect to get a clean sample for flux constraint soon.

30 Other Measurementsνµ CC InteractionsUnderway in the NOνA Near Detector

InteractionsNO histogramsνA Simulation 20 • Even with a narrow-band QE • Inclusive νμ-CC cross-section. Res beam, NOvA still has DIS access to all FSI types. • CC Quasi-elastic. POT 15 Coh 20

10 • Too many Ph.D. topics here

+ × • Resonance (CC 1 π ). to list… • 10 2p2h. • νµ CC QE and CC inclusive cross section • And more! Events / 4.2 3

10 5 measurements are underway

0 0 1 2 3 4 5 Neutrino Energy (GeV)

22 Jonathan M. Paley

31 Summary and Outlook

• Neutrino interaction cross-sections are important to oscillation experiments. • Several analysis with NOvA’s early data:

• νe-CC inclusive • Coherent π0 • ν-e elastic scattering • NOvA has great opportunities for various neutrino interaction measurements with high-statistics, high-quality data in the next few years. • Stay tuned!

32 The NOνA Collaboration

Thank you!

A growing collaboration of over 200 scientists and engineers from 38 institutions and 7 countries.33

2 Jonathan M. Paley