Long-baseline neutrino oscillation with NOvA and T2K - Indico

May 16, 2022Zoya Vallari | NDM22 1

The 7th Symposium on Neutrinos and Dark

Matter in Nuclear Physics (NDM22)

Zoya Vallari

May 16, 2022

[ [email protected] ]

Long-baseline neutrino oscillation withNOvA and T2K


Neutrinos have mass!

Ø Discovery of neutrino oscillations proved the surprising hypothesis that neutrinos have mass!

Ø Massive neutrinos suggest new fundamental symmetries and fields, but we do notyet know what those might be?

• Requires further experimental inputs!

Image by Symmetry Magazine


The Neutrino Oscillation

1

2

3Mixing Matrix

Flavor Eigenstates Mass Eigenstates

Solar Reactor Accelerator Atmospheric

Measured from the following neutrino sources




1

2

3Mixing MatrixFlavor Eigenstates Mass Eigenstates

Measured Value :

Precision : [NuFit 5.1 arXiv:2007.14792]


http://arxiv.org/abs/2007.14792



1

2


Measured Value :

Precision :

dCP : Unknown ?

Do neutrinos violate CP : sin dCP = 0?CP violation in leptonic sector could provide a path towards explaining the baryon asymmetry in the early universe.




1

2


Measured Value :

Precision :

CKM PMNS

Vs




1

2


Measured Value :

Precision :

n1 n2 n3

Is the q23 mixing maximal?

q23 = 45o → |Uµ3| = |Ut3|

Mass Eigenstates




Solar

Normal Ordering Inverted Ordering

Precision ~ 2.8%

Precision ~ 1.1%

Mass Ordering: Normal or Inverted?

Does the symmetry that determines the mass of

charged leptons influences n1 to be the lightest

neutrino or does the inverse hold?

Reactor

Accelerator Atmospheric

L : distance (baseline)E : neutrino energy

Optimize baseline L for a given neutrino source of energy E.

Oscillations are sensitive to neutrino mass splitting squared andto the sign of mass splitting via the matter-effect.

(mas

s)2



Neutrino masses

and their ordering?How do

neutrinos get mass?

Are neutrinos Majorana or Dirac?

Existence of sterile neutrinos

?

Do neutrinos

violate CP?

Open Questions

Contrast b/w CKM & PMNS matrix?

CKM PMNS

1

2

3



Normal Ordering Inverted Ordering

dCP: Do neutrinos violate CP?

?

?Mass Ordering:

Normal or Inverted?

q23 : Is the mixing maximal?

?

Long-baseline oscillation physics scope


Long-baseline (LBL) measurement

neutrino beam

Near DetectorFar Detector

nµ / nµLong baseline O(~100 km)

n? / n?

ne appearance

µ-

nµ disappearance = 1 - nµ survival


LBL Oscillations : nµ disappearance

nµ survival /nµ disappearance

§ Leading order dependence on ∆m!"" and sin2 q23

§ Aims to answer the question of maximal mixing in q23


LBL Oscillations : ne appearance

0 1 2 3 4 5Reconstructed neutrino energy (GeV)

0

10

20

30

40

50

Eve

nts

NOvA Simulation

ne Signal eventsBackground events

ne appearance

NOvA: L=810 km, E=2.0 GeV

%eν→µνP0 2 4 6 8

%eν

→ µνP

0

2

4

6

8 =0.08513θ22sin2eV-310×|=2.442

32m∆|=0.404,0.62323θ2sin

=0δ /2π=δπ=δ /2π=3δ

0.404

0.623

0.404

0.623

NOvA: L=810 km, E=2.0 GeV

OCTAN

T

Mass Ordering

d CP

§ Dependence on q13, q23, dCP and the neutrino mass ordering through the matter effect. Constraint on q13 via the reactor neutrino experiments.

§ Comparing the rate of ne appearance with neappearance provides a measurement of dCP and mass ordering.


The experiments


Long-Baseline Experiments

2010 2020 2030

K2K

T2K collects first beam data. NOvA collects

first beam data.

Today’s results show data

analyzed until 2020 by both experiments.

Both NOvA and T2K are scheduled to run until ~ 2026-27.

Data collected:

NOvA : 2.6 x 1021 p.o.t (n:n ~ 1:1)T2K : 3.6 x 1021 p.o.t (n:n~ 6:5)

This talk

Next up …


Far DetectorFermilab

810 kmNear

Detector

nµ, ne, nt

Japan USA

◎ 200 collaborators◎ 50 institutions◎ 8 countries

◎ 500 collaborators◎ 69 institutions◎ 12 countries

The experiments


T2K NOvA

Neutrino flux

T2K NOvA

CCDIS

The experiments

<En> ~ 0.6 GeVL ~ 300 km

Mostly QE events

T2K

<En>~ 2 GeVL ~ 800 km

A mix of QE, RES and DIS events

NOvA

Formaggio, Zeller

https://arxiv.org/search/hep-ex?searchtype=author&query=Formaggio%2C+J

https://arxiv.org/search/hep-ex?searchtype=author&query=Zeller%2C+G


Measuring Oscillations: 1. Detect neutrino interactions.

2. Tag the flavor.

3. Reconstruct energy.


§ NOvA’s ND and FD are functionally identical detectors.

§ Segmented liquid scintillator detectors

§ Optimized for electron showers: § ~6 samples per X0 (40cm) & ~60% active volume

§ Spatial resolution: ~few cm (good rejection of cosmic events)

§ Timing resolution: few ns (to distinguish pile-ups)

Detecting neutrino interaction


Tag flavor & Reconstruct n Energy

Hadronic

Eν = f (Eµ, Ehad)

neEν = f (EEM, Ehad)

Muon energy comes from the track length and hadronic energy is calculated from calorimetry.

Calorimetric energy estimation is done for EM and hadronic clusters separately.

Muon track

EM Shower

nµ


Detecting neutrino interaction

§ 50 kton Water Cherenkov detector§ 11000 20” PMTs for inner detector; 2000 8” PMTs

for outer detector§ 40% photo-coverage.§ Charged particles produce Cherenkov light

detected by the PMTs.

Super-KamiokandeT2K’s Far Detector


Muon makes sharp Cherenkov ring

Tag flavor & Reconstruct n energy

electron makes fuzzy Cherenkov ring

Energy of the incoming neutrino is reconstructed from the lepton kinematics.

*for the CC1p+ sample mass of D resonance is used.


Using Near Detector in Oscillation Analysis


ND Data in Oscillation Analysis

neutrino beam

Near DetectorFar Detector

nµ / nµLong baseline O(~100 km)

n? / n?

§ Same flux exposure, high-statistics neutrino interactions and lack of oscillations at ND

make it a critical component to predict no-oscillation spectrum at the FD.

§ Provides indispensable constraints on flux, cross-section and detector systematics.

NOvA and T2K use very different strategies to incorporate ND Data but with very similar impact on oscillation measurements.

ND280ND

NOvA ND is functionally identical to its FD.T2K ND is an ensemble of scintillator and tracking detectors on various nuclear targets.



§ All charged current inclusive data from the functionally identical ND is used to predict both nµ and ne signal spectra at the FD.

§ The differences between the two detectors in flux, acceptance and cross-sections are modeled using simulations and related systematic uncertainties.

ND FD

neutrino beam neutrino beam


ND Data constrains the total systematic uncertainties in the FD neprediction from >15% to ~5%.

neutrino beam




§ Create many subsamples of ND data based on number of final state pions.

§ Isolate the ND data samples of different nuclear targets (water and plastic).

§ Fit cross-section, flux and detector response parameters to strongly constrain systematics.

Pre-ND Fit Post-ND Fit

C. Wilkinson, KITP 2022

https://online.kitp.ucsb.edu/online/neutrinos-c22/wilkinson/



Total prefit uncertainty on FD 1 e-like ring ne event rate goes from 13.0% to 4.7% after applying ND280 constraints.

Reduction in flux uncertainty from ND data shown as an example.

C. Wilkinson, KITP 2022

https://online.kitp.ucsb.edu/online/neutrinos-c22/wilkinson/


Far Detector Data Samples


neutrino beam neutrino beam

FD Data : nµ disappearance

§ The oscillation parameters change the no-oscillation prediction to best fit the FD data.


FD Data : nµ disappearance

§ Each neutrino mode data is divided into 4 quartiles of hadronic energy fraction which separates high-resolution events. This increases the sensitivity to the shape of the oscillation dip.

neutrino beam

neutrino beam211 events


FD Data : ne appearance

ne 82 events (27 background)

ne 33 events (14 background)

§ Separating in bins of Particle ID enhances oscillation sensitivity which is dependent on a better rejection of background events.

neutrino beam antineutrino beam


FD Data Samples:

CC quasielastic-like events (CC 0p) CC quasielastic-like events (CC 0p)

nµ disappearance ne appearance

1e – like ring sample in antineutrino beam

mode has 16 events.

1µ –like ring sample in antineutrino beam has

137 events. 2 electron like rings to detect CC1p+ candidate events

P. Dunne, Neutrino 2020

https://doi.org/10.5281/zenodo.3959558


Measuring Neutrino Oscillation


Mass splitting and mixing angle

§ All measurements are consistent with maximal mixing with weak preference for upper octant for q23.


dCP measurement

§ Both NOvA and T2K individually show a mild preference (~1-2 sigma) for normal ordering.

§ While inverted ordering is disfavored by both experiments alone, their contours areconsistent with each other in inverted ordering while present a mild tension in normal ordering.


dCP measurement

20 40 60 80 100 120Total events - neutrino beam

20

30

40

50

60

Tota

l eve

nts

- ant

ineu

trino

bea

m

= 0CPδ /2π= CPδ

π= CPδ /2π= 3CPδ

2eV-310×2.44−=232mΔ

IH

2eV-310×2.40+=232mΔ

NH

=0.4623θ2sin LO

=0.5723θ2sin UO

=0.08513θ22sinNOvA FD

)ν POT-equiv (2010×13.60)ν POT (2010×12.50

NOvA Preliminary

2020 best fit

NOvA Preliminary

§ T2K sees an asymmetry in their ne and ne appearance and their best fit is consistent with large CP violation for normal mass ordering.

P. Dunne, Neutrino 2020

https://doi.org/10.5281/zenodo.3959558


Outlook


Where are we?

2010 2020 2030

K2K

Global measurements on Dm232 and q23 agree well while measurements of dCP are in mild tension.


Where are we?

2010 2020 2030

K2K


2010 2020 2030

K2K

Coming this year: NOvA+T2K Joint Analysis

T2K NOvA

L = 295 km, E = 0.6 GeV L = 810 km, E = 2 GeV

Inverted OrderingNormal Ordering

Inverted OrderingNormal Ordering

1. The joint-fit will provide a significantly tighter statistical constraint.

2. Complementary features in NOvA and T2K experiments will be important for breaking degeneracies in the individual measurements.

Where are we?


2010 2020 2030

K2K

Where we might be in ~5 years?


Total Estimated Exposure

NOvA : 7.2 x 1021 p.o.tT2K : 10 x 1021 p.o.t

>2.5x increase in exposure for both experiments.

NOvA+T2K joint analysis with the full dataset of both experiments.

§ T2K will run with an upgraded beam and upgraded ND in near future (~2022-23).

§ NOvA Test Beam detector placed at Fermilab Test Beam Facility is collecting data to measure hadronic response and better understand the detector energy scale and response systematics.


2010 2020 2030

K2K



Total Estimated Exposure

NOvA : 7.2 x 1021 p.o.tT2K : 10 x 1021 p.o.t

>2.5x increase in exposure for both experiments.

NOvA+T2K joint analysis with the full dataset of both experiments.

Current sensitivity projections from individual experiments show that ne appearance driven measurements(dCP and nMO) will remain statistics limited for the current generation of oscillation experiments.


2010 2020 2030

K2K

Plot from R. Patterson, Snowmass Neutrino Colloquium


Disclaim

er

https://indico.fnal.gov/event/52707/contributions/238224/attachments/153866/199779/20220406_snowmass_nf_colloq_rbp_forweb.pdf


Where are we headed?

2010 2020 2030

K2K

The era of discovery and precision in the neutrino sector …

but

There is always room for surprises?

Thank you for listening!

Next up …

Long-baseline neutrino oscillation with NOvA and T2K - Indico

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