Cross-section measurements at the NOvA near detector Linda - - PowerPoint PPT Presentation

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cross section measurements at the nova near detector
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Cross-section measurements at the NOvA near detector Linda - - PowerPoint PPT Presentation

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Sandbox Studio, Chicago Cross-section measurements at the NOvA near detector Linda Cremonesi for the NOvA Collaboration Outline Overview of the NOvA beam, detector and simulation Inclusive measurements Pion production measurements

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SLIDE 1

Linda Cremonesi for the NOvA Collaboration

Cross-section measurements at the NOvA near detector

Sandbox Studio, Chicago

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SLIDE 2
  • L. Cremonesi “Cross-sections at NOvA ND”
  • Overview of the NOvA beam, detector and

simulation

  • Inclusive measurements
  • Pion production measurements
  • NC coherent π0 results
  • Summary and outlook

Outline

2

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SLIDE 3
  • L. Cremonesi “Cross-sections at NOvA ND”

Beam at NOvA

  • NOvA detectors are 14 mrad off the

NuMI beam axis.

  • narrow 2-GeV spectrum
  • small flux shape uncertainties


(hadron production uncertainties are mostly normalisation effect)

  • 95% pure νμ beam

3

On-Axis A) ν 14.6 mrad Off-Axis (NO

[GeV]

π

E

10 20 30 40

[GeV]

ν

E

2 4 6 8 10

= 0 mrad θ A) ν = 14.6 mrad (NO θ

[GeV]

ν

E

5 10 15

CC / 6E20 POT / kton / 0.1 GeV

µ

ν

6

10

5 10 15 20 25

On-Axis A) ν 14.6 mrad Off-Axis (NO

FLUKA11

A Simulation ν NO

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SLIDE 4
  • L. Cremonesi “Cross-sections at NOvA ND”

Reconstructed Neutrino Energy(GeV)

1 2 3 4 5

Events/(8.09E+20 POT)

0.05 0.1 0.15 0.2 0.25

6

10 ×

NOvA Simulation

CC Res

µ

ν CC DIS

µ

ν CC QE

µ

ν CC MEC

µ

ν CC Coh

µ

ν NC

1 10

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

00 150 200 250 300 350

X

  • µ

→ N

µ

ν X

+

µ → N

µ

ν

100

(GeV)

ν

E

/ GeV)

2

cm

  • 38

(10

ν

/ E

CC

σ

CDHS, ZP C35, 443 (1987) GGM-SPS, PL 104B, 235 (1981) GGM-PS, PL 84B (1979) IHEP-ITEP, SJNP 30, 527 (1979) IHEP-JINR, ZP C70, 39 (1996) MINOS, PRD 81, 072002 (2010) NOMAD, PLB 660, 19 (2008) NuTeV, PRD 74, 012008 (2006) SciBooNE, PRD 83, 012005 (2011) SKAT, PL 81B, 255 (1979) T2K (Fe) PRD 90, 052010 (2014) T2K (CH) PRD 90, 052010 (2014) T2K (C), PRD 87, 092003 (2013) ArgoNeuT PRD 89, 112003 (2014) ArgoNeuT, PRL 108, 161802 (2012) ANL, PRD 19, 2521 (1979) BEBC, ZP C2, 187 (1979) BNL, PRD 25, 617 (1982) CCFR (1997 Seligman Thesis)

Beam at NOvA

  • NOvA is sensitive to many different nu+A interaction channels.
  • Cross sections in NOvA’s energy range suffer from high uncertainties in

neutrinos and no measurements below 3 GeV for antineutrinos.

  • Nice overlap with currently running experiments, as well as future

experiments in the US.

4

T2K + MicroBooNE + NOvA + MINERvA

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SLIDE 5
  • L. Cremonesi “Cross-sections at NOvA ND”

s) µ Hit time (

215 220 225 230

hits / 50ns

3

10

5 10 15 20

A ND Data ν NO

Preliminary

A ND Data ν NO

The NOvA Near Detector

  • Tracking calorimeter
  • 77% hydrocarbon by mass, 16% chlorine, 6%

TiO2

  • Muon catcher (steel + NOvA cells) at downstream

end to range out ~2GeV muons.

  • O(10) ns single hit timing resolution.

5

Beam

Wavelength- shifting fibres routed to a single cell on an Avalanche Photodiode

~1 hour


  • f data!

10 μs
 NuMI pulse

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SLIDE 6
  • L. Cremonesi “Cross-sections at NOvA ND”

Simulation

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Beamline+Flux: G4NuMI nu interactions &
 FSI modelling: GENIE Detector response:
 GEANT4 Readout electronics & DAQ: Custom simulation routines

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SLIDE 7
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC inclusive

  • σ(E) and flux-averaged double differential cross section in muon

kinematics variables

7

  • σ(E) measurements are kinematically restricted this phase space

due to limited statistics and low efficiency

µ

θ Reco Cos

0.5 0.6 0.7 0.8 0.9 1

Reco Muon Kinetic Energy (GeV)

0.5 1 1.5 2 2.5

Events/(8.09E+20 POT)

1 10

2

10

3

10

4

10

NOvA Simulation

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SLIDE 8
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC inclusive: Reco + Selection

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Top View Side View Beam Muon Catcher Muon Catcher

  • Hits associated in time and space are used to form a candidate interaction.
  • Vertices, tracks and showers are reconstructed from these hits.
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SLIDE 9
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC inclusive: Reco + Selection

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Top View Side View Beam Muon Catcher Muon Catcher

  • Solid box is Fiducial Volume
  • Containment uses nearest projected distance to an edge (dashed box is rough approximation).
  • Events with hadronic activity in or near the muon catcher are excluded
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SLIDE 10
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC inclusive: PID

  • Use a kNN to separate signal and background tracks based on 4

variables:

  • track length
  • dE/dx along track
  • scattering along track
  • fraction of track planes w/ single 


particle dE/dx

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dE/dx Log-likelihood

3 − 2 − 1 − 1

Events

0.0 0.2 0.4 0.6

6

10 × Simulated Selected Events Simulated Background Data

  • syst. range

σ Full 1- POT

20

10 × ND POT norm., 3.72

Muon ID

0.2 0.4 0.6 0.8 1

Events

3

10

4

10

5

10

6

10

7

10

Simulated selected events Simulated background Data

  • syst. range

σ Shape-only 1- POT

20

10 × ND area norm., 3.72

NOvA Preliminary

Length of primary track (m)

5 10 15

Events

3

10

20 40 60 80

Simulated selected events Simulated background Data

  • syst. range

σ Shape-only 1- POT

20

10 × ND area norm., 3.72

NOvA Preliminary

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SLIDE 11
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC inc: efficiency and background

  • Selection efficiency is dominated by containment cut.
  • Backgrounds are small near the 2 GeV peak, larger in the tails of the

spectrum.

  • Uncertainties are at the level of a few %.

11 Reconstructed Neutrino Energy (GeV)

1 2 3 4

  • like

µ

ν

  • like /

µ

ν Non-

0.1 0.2 0.3

µ

ν /

µ

ν Anti-

0.05 0.1 0.15 0.2 0.25 0.3

NOvA Simulation

True Neutrino Energy (GeV)

1 2 3 4

Purity

0.2 0.4 0.6 0.8

Efficiency

NOvA Simulation

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SLIDE 12
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC inc: Summary of Uncertainties

  • Statistical uncertainties are typically <2%.
  • Systematics are still being assessed, but we expect for the differential

measurement ~10% highly correlated (normalisation) flux uncertainties, and all the other systematics combined to be 5-8%

  • σ(E) measurement systematics will be similar, although systematics from energy

scale uncertainties will be larger on the rising and falling edges of the spectrum.

12

µ

θ Reco Cos

0.5 0.6 0.7 0.8 0.9 1

Reco Muon Kinetic Energy (GeV)

0.5 1 1.5 2 2.5

Statistical Uncertainty

0.02 0.04 0.06 0.08 0.1

NOvA Simulation

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SLIDE 13
  • L. Cremonesi “Cross-sections at NOvA ND”

νe CC inclusive: Overview

  • Challenging because (by design) there are ~1% of νe.
  • We have shown preliminary results on this channel in the past.

That analysis is now superseded with a different event identification developed in the oscillation analysis.

13

  • σ(E) and flux-averaged single

differential cross-section as a function

  • f the electron kinematics for energies

between 1 and 3 GeV.

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SLIDE 14
  • L. Cremonesi “Cross-sections at NOvA ND”

νe CC inclusive: CVN

  • NOvA uses a Convolutional Neural Network (CNN) where a series
  • f image filters are applied to hit map images to extract features

associated with an interaction

  • Not limited to features chosen a priori
  • CNNs extract features of varying complexity and learn correlations
  • 30% effective increase in exposure
  • First CNN implementation on a HEP result
  • Inputs are image representations of our events where “RGB”

calibrated hit information

  • Does not require previous reconstruction: no reconstruction

inefficiencies

  • Inspired by animal visual cortex
  • Kernels, Filters or Convolutional Layers extract features of varying

levels of complexity

14

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SLIDE 15
  • L. Cremonesi “Cross-sections at NOvA ND”
  • A convolutional visual network (CVN) is then trained on these

filters.

  • 30% effective increase in exposure in the Far Detector for the
  • scillation analysis

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νe CC inclusive: CVN

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SLIDE 16
  • L. Cremonesi “Cross-sections at NOvA ND”
  • Currently using a cut (CVN > 0.85) that optimises

the FoM of S/√(S+B)

  • Backgrounds are significant, and we are

investigating potential driven data constraints.

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Interaction Fraction(%) νeCC 51.2 ¯ νeCC 4.4 νµCC 21.1 NC 23.0 Other 0.18

νe CC incl: PID

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SLIDE 17
  • L. Cremonesi “Cross-sections at NOvA ND”
  • Xsec, FSI and calibration systematics included in error bands.
  • Uncertainties on efficiency and backgrounds is between 5-10%.
  • Data-driven constraints on the efficiency and backgrounds are

being explored.

17

νe CC incl: Efficiency and Purity

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SLIDE 18
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC π0

18

  • Signal: νμ-CC events with at least one primary π0 in the final state.
  • π0 production vital for νe appearance searches
  • Flux-averaged differential cross sections in final state kinematics
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SLIDE 19
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC π0: PID

19

Use non-muon shower variables to form a π0 identifier:

  • Bragg peak identifier.
  • Energy per hit.
  • Photon gap from vertex.
  • Number of missing planes.

Fit signal and background MC to data in each kinematic bin.

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SLIDE 20
  • L. Cremonesi “Cross-sections at NOvA ND”

νμ CC π0

20

  • Signal is dominantly RES (38.3%)

and DIS (61.3%).

  • Uncertainty (~15%) is systematic

dominant.

  • Plan to report flux-averaged

differential cross section in final state muon and pion kinematics.

  • Αt final stage of internal review.

Results soon!

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SLIDE 21
  • L. Cremonesi “Cross-sections at NOvA ND”

NC Coherent π0

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  • Neutrino coherent scattering = small

momentum transfer.

  • Single forward-going pion, without other

pions or nucleons. To identify the NC π0 sample:

  • Absence of muon.
  • Two showers identified as photons by

dE/dx-based likelihoods.

  • Cut on invariant mass to select π0s

Main background is RES and DIS π0s.

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SLIDE 22
  • L. Cremonesi “Cross-sections at NOvA ND”

NC Coherent π0

22

Divide the NC π0 into two sub-samples:

  • Signal sample: events with most of their

energy in the 2 photon showers and low vertex energy: it has >90% of the signal.

  • Control sample: the events with extra

energy other than the photons or in the vertex region, dominated by non- coherent π0 s (RES and DIS).

Control Sample Signal Sample

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SLIDE 23
  • L. Cremonesi “Cross-sections at NOvA ND”

NC Coherent π0

23

  • Fit the backgrounds to control sample data

in π0 energy vs angle 2D space.

  • Background fit result are applied to the

backgrounds in the signal sample.

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SLIDE 24
  • L. Cremonesi “Cross-sections at NOvA ND”

NC Coherent π0

24

  • Renormalised background using energy and angle 2D space.
  • Measured flux-averaged cross-section using background subtraction:

σ = 14.0 ± 0.9(stat.) ± 2.1(syst.)x10-40cm2/nucleus

  • Total uncertainty 16.7%, systematic dominant

Measurements scaled to 12C by A2/3

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SLIDE 25
  • L. Cremonesi “Cross-sections at NOvA ND”

Summary and future plans

  • The NOvA experiment has excellent opportunities to make high

precision measurements of neutrino-nucleon/nucleus interactions

  • 8x1020 POT neutrino ND dataset:
  • systematics-limited inclusive and CC neutral pion production

measurement to be released this year

  • CC charged pion production and NC neutral pion production

measurements are in progress

  • 3x1020 POT antineutrino ND dataset —> inclusive measurement

are high priority for NOvA

  • Stay tuned for results soon!

25

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SLIDE 26

Thank you!

26

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SLIDE 27
  • L. Cremonesi “Cross-sections at NOvA ND”

Neutrino beam

  • 120 GeV protons extracted from the Main Injector at

Fermilab in 10 μs spills

  • Focus secondary pions using magnetic horns
  • Positive hadrons for neutrino beam
  • Negative hadrons for antineutrino beam
  • Decay kinematics mean a detector at 14.6 mrad sees

a narrowly peaked energy spectrum

  • Beam 97.5% νμ with 0.7% νe and 1.8% wrong-sign

NuMI Beam

27

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SLIDE 28
  • L. Cremonesi “Cross-sections at NOvA ND”

NuMI beam performance

  • Present results data collected between February 6, 2014 and May 2, 2016
  • Equivalent to 6.05x1020 protons-on-target in a full 14 kT detector
  • Beam had been running at 560 kW
  • Achieved 700 kW design goal, most powerful neutrino beam in the world

Detector Commissioning (Reduced Mass)

First Analysis 2.74x1020 POT-equiv Total Exposure 6.05x1020 POT

Switched to antineutrinos

  • n Feb 20th

2017

28

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SLIDE 29
  • L. Cremonesi “Cross-sections at NOvA ND”

NOvA detectors

  • Two functionally identical detectors
  • Extruded plastic cells alternating vertical and

horizontal orientation filled with liquid scintillator

  • Charged particles passing through cells produce

light which is collected.

15.5 m

3.9 m

29

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SLIDE 30
  • L. Cremonesi “Cross-sections at NOvA ND”

Cell hits coloured by recorded charge (~photoelectrons)

Far Detector 550 μs Readout Window

Beam direction

30

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SLIDE 31
  • L. Cremonesi “Cross-sections at NOvA ND”

Cell hits coloured by recorded charge (~photoelectrons)

Far Detector 10 μs NuMI Beam Window

Beam direction

31

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SLIDE 32
  • L. Cremonesi “Cross-sections at NOvA ND”

Cell hits coloured by recorded charge (~photoelectrons)

Far Detector Neutrino Interaction

Beam direction

32

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SLIDE 33
  • L. Cremonesi “Cross-sections at NOvA ND”

Event topologies

33

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SLIDE 34
  • L. Cremonesi “Cross-sections at NOvA ND”

Muon neutrino selection

  • Separate νμ CC interactions from NC and

cosmic-ray backgrounds

  • Use 4 variable k-Nearest Neighbour to select μ
  • Selection is 81% efficient and 91% pure
  • Containment cuts remove activity near walls
  • Additional Cosmic rejection from event topology

and Boosted Decision Tree

Number of events in the spill window

1 10

2

10

3

10

4

10

5

10

6

10

7

10

8

10 NC rejection Containment Cosmic rej. Data quality Good spills

NOvA Preliminary

Cosmic background Signal prediction (max. mixing)

Muon ID

0.2 0.4 0.6 0.8 1

Events

3

10

4

10

5

10

6

10

7

10

Simulated selected events Simulated background Data

  • syst. range

σ Full 1- POT

20

10 × ND POT norm., 3.72

NOvA Preliminary

dE/dx Log-likelihood

3 − 2 − 1 − 1

Events

0.0 0.2 0.4 0.6

6

10 × Simulated Selected Events Simulated Background Data

  • syst. range

σ Shape-only 1- POT

20

10 × ND area norm., 3.72

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SLIDE 35
  • L. Cremonesi “Cross-sections at NOvA ND”

Electron neutrino selection

  • 73% νe CC selection efficiency, 76% purity with CVN classifier
  • Good ND Data/MC agreement
  • CVN provides better cosmic rejection and similar systematics to 2015 classifiers
  • Bin analysis in 3 bins of CVN and 4 bins of energy

classifier

e

ν CVN

0.75 0.80 0.85 0.90 0.95 1.00

POT

20

10 × Events / 3.72

200 400 600 800 1000

ND data Total MC Flux Uncert. NC CC

e

ν Beam CC

µ

ν

NOvA Preliminary

Reconstructed neutrino energy (GeV)

1 2 3 4 5

POT

20

10 × Events / 3.72

1000 2000 3000

ND data Total MC Flux Uncert. NC CC

e

ν Beam CC

µ

ν

NOvA Preliminary 35

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SLIDE 36
  • L. Cremonesi “Cross-sections at NOvA ND”

NC Coherent pi0

36

RES in Control Sample RES in Signal Sample DIS in Signal Sample DIS in Control Sample

Fit the backgrounds to control sample data in π0 energy vs angle 2D space. Apply the background tuning to the signal sample.

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SLIDE 37
  • L. Cremonesi “Cross-sections at NOvA ND”

Bragg Peak Identifier

  • The Bragg Peak Identifier (BPI)

is a measure of the increase in dE/dx towards the end of a prong.

  • The BPI value is defined for

prongs with Nhit ≥ 4 as the ratio of average energy deposit in the furthest min(6, Nhit/2) hits from the prong start point to the average energy deposit in the rest of the prong.

  • Here, Nhit/2 is always rounded

down.

37