[PPT] - Long Baseline Neutrino Physics with Theia 70m 18m Mike Wilking PowerPoint Presentation

SLIDE 1

THEIA25

70m 20m 18m

Long Baseline Neutrino Physics with Theia

Mike Wilking Stony Brook University MOOD Workshop November 12th, 2019

SLIDE 2

Challenges in DUNE LBL Physics

Subtle mistakes in our modeling of ν-Ar interactions on argon

can produce large biases on neutrino oscillation parameters

Missing energy (e.g. neutrons) cause feed-down in Erec vs

Etrue

Mismodeling the shape of this feed-down can cause biases
Understanding the detector uncertainties is also critical

(e.g. in hadronic energy measurements)

ν

Ar μ

fully reconstructed

p

Energy measurement

n n

Missing energy

π0 π+

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 (GeV)

Rec.

E 10 20 30 40 3.5 kt-yr ×

like Events / 40

e

ν Selected

π+

Erec for selected Etrue bins

SLIDE 3

DUNE-PRISM to the Rescue?

DUNE-PRISM can provide strong constraints on ν-Ar interaction modeling
By measuring a continuously varying set of neutrino energy spectra, the Etrue ->

Erec relationship can be constrained

However, challenges still remain
Differences in detector efficiency and resolution between the ND (ArgonCube +

Muon spectrometer) and FD still must be precisely understood

Since the FD is on-axis, DUNE-PRISM cannot sample higher energies to constrain

high-Eν feed-down (other strategies, such as changing the horn current are under investigation)

Uncertainties in the neutrino flux prediction must be well constrained

(beamline geometry, wrong-sign backgrounds, etc.)

SLIDE 4

Advantages of Adding a WbLS Detector

A WbLS detector provides several complementary features

to the DUNE LBL program

A different (simpler?) target nucleus
Different detector systematic uncertainties (and

coupling of detector modeling to cross section modeling)

Improved neutron detection
Good energy resolution
Fast timing
In the era of systematics limitations (i.e. when a 4th

detector would come online), providing extra constraints

n systematic uncertainties will be a high priority

SLIDE 5

Theia LBL Sensitivity Studies

The initial LBL studies have focused on a pure

water (Cherenkov-only) phase

The additional benefits of WbLS have not yet

been included (hadronic energy measurements, neutron tagging, etc.)

Previous studies of a Water Cherenkov detector in

the LBNF beam occurred in LBNE

These studies used older (“SK1”) reconstruction

tools and analysis techniques

An updated set of studies has been conducted for

Theia based on the latest Water Cherenkov analysis tools

SLIDE 6

Neutrino&running&

Reconstructed Energy (GeV) Number of Events

NUEQE=562 ANUEQE=4 NUENQE=684 ANUENQE=7 NC=1390 BEAM NUE=289 NUMU CC=75

50 100 150 200 250 300 2 4 6 8

Reminder of LBNE Studies

LBNF beam with a water Cherenkov

detector at Homestake

Prior studies (LBNE) made the following

assumptions:

1. Only single-ring events are selected

(~20% νe-CCnQE efficiency)

Largest interaction mode at DUNE

energies of ~2-3 GeV is resonance (CCπ) events

2. Neutral current background rejection

is based on older reconstruction tools  (pre-FiTQun and even pre-POLFit)

Both of these assumptions have been

revisited with updated reconstruction tools

(GeV)

E
1

10 1 10

2

10

/ GeV)

2

cm

38

(10

cross section / E
0.2

0.4 0.6 0.8 1 1.2 1.4 (GeV)

E
1

10 1 10

2

10

/ GeV)

2

cm

38

(10

cross section / E
0.2

0.4 0.6 0.8 1 1.2 1.4

TOTAL QE DIS RES

SLIDE 7

Advances in Cherenkov Reconstruction

Since the LBNE WC studies, the FiTQun

event reconstruction package has been implemented in T2K & SK

A likelihood-based fitter that generates

charge and time PDFs for all PMTs for any proposed set of final state particles

Substantial improvements are seen in

e/μ separation and NC (π0) rejection

FiTQun is now exclusively used for all T2K
scillation analyses, and in the latest SK

atmospheric analysis

FiTQun can naturally incorporate

scintillation light, but this has not yet been implemented

Visible energy [MeV]

100 200 300 400 500 600 700 800 900 1000

Miss-ID rate [%]

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

µ

FiTQun apfit

(MeV) γ True Energy of the Less Energetic

10 20 30 40 50 60 70 80 90 100

Rejection Efficiency π

0.2 0.4 0.6 0.8 1

fiTQun POLFit

MC π0 events 0 to 500 MeV/c

Fraction of μ misIDed as e Improved low-E γ Detection

SLIDE 8

FiTQun π0 Rejection

Goal: identify a low-E photon in the

presence of a high-E photon

To reject π0: Compare best fit likelihoods of π0 fit &

single-e fit (as a function of reconstructed π0 mass)

Large improvement in finding low energy 2nd ring
~70% reduction in π0 background relative to POLFit

(but not even POLFit was used in the LBNE studies)

Vertex Photon Conversions

π0 γ γ

Mass (MeV/c) π

20 40 60 80 100 120 140 160 180 200 50 100 150 200 250 300 350 fiTQun POLFit

T2K νe Background

(MeV) γ True Energy of the Less Energetic

10 20 30 40 50 60 70 80 90 100

Rejection Efficiency π

0.2 0.4 0.6 0.8 1

fiTQun POLFit

MC π0 events 0 to 500 MeV/c

)

2

Mass (MeV/c π

50 100 150 200 250

)

e

/L

π

ln(L

50 100 150 200 250 300 350 400

Signal

e

ν Background π

SLIDE 9

Multi-Ring Events

FiTQun can currently reconstruct up to 6

rings in a staged approach

Each step sequentially adds a “track-

like” (π+) or “shower-like” (e) ring

The chain terminates when adding a

ring does not sufficiently improve the fit

Ring counting & PID are significantly

improved

Atmospheric MC Event

Reconstructed charge Predicted charge

10

Hit Charge Distribution

Atmospheric MC Event

Reconstructed charge Predicted charge

10

Reconstructed “Mean” Charge

π e ee eπ πe ππ eee No Improvement Fit Improves eeπ πee πeπ

Sample Fit Sequence

eeπe eeππ πeπe πeππ Fit Improves Fit Improves πeππe πeπππ ππe πππ ππee ππeπ πππe ππππ

SLIDE 10

“1-Ring” νe-CCπ+ in T2K

The newest T2K νe sample is νe-CCπ+

where the π+ is below Cherenkov threshold

Still a 1-ring event, but with a Michel

electron

Previously, these events were

contaminated with νμ-CC background

Improved e/μ separation now allows

for a high purity 1-ring, 1-Michel νe selection

Eventually, Theia may have a better tag
f below Cherenkov pions via

scintillation (if separable from protons, etc.), but this is not yet included

e CC1

selection: reconstructed energy

Reconstructed energy distribution of CC1

enriched

e sample.

FiTQun selection yields a much smaller numu CC background, which has a large systematic uncertainty. fiTQun APfit

energy (MeV) ν Reconstructed 500 1000 Number of events

0.5 1 1.5

POT)

20

10 × (7.48 CC

e

ν Osc. CC

e

ν Osc. CC

µ

ν /

µ

ν CC

e

ν /

e

ν Beam NC =0.0217

13

θ

2

MC w/ sin

Xiaoyue Li fiTQun event selection February 10, 2017 19 / 69

e CC1

selection: reconstructed energy

Reconstructed energy distribution of CC1

enriched

e sample.

FiTQun selection yields a much smaller numu CC background, which has a large systematic uncertainty. fiTQun

energy (MeV) ν Reconstructed 500 1000 Number of events

0.5 1 1.5

POT)

20

10 × (7.48 CC

e

ν Osc. CC

e

ν Osc. CC

µ

ν /

µ

ν CC

e

ν /

e

ν Beam NC =0.0217

13

θ

2

MC w/ sin

APfit

Xiaoyue Li fiTQun event selection February 10, 2017 19 / 69

SLIDE 11

Theia νe Samples (0 vs 0+1 Decay-e)

By adding in the new “1-ring” CCπ+ sample, we

see a very large gain in νe CC non-QE efficiency

More than 50% increase in the 2-3 GeV region
These events have the largest cross section at

the DUNE oscillation maximum

nue&QE& nuebar&QE& nue&NQE& nuebar&NQE& NC& numu&CC&

0 decay Electrons ≤1 decay Electrons

FiTQun FiTQun

x 25%

SLIDE 12

Boosted Decision Tree π0 Cut

The best-fit likelihoods and reconstructed kinematics of the

multi-ring fits were combined into a boosted decision tree

The primary goal of this cut is to remove neutral current

(π0) background (as in the LBNE analysis)

THEIA collaboration meeting

NC νe

SLIDE 13

1-Ring Event Samples

The 1-ring, 0-decay-e sample has a

substantially reduced NC background

The new 1-ring, 1-decay-e sample increases

the statistics by ~30%

The purity of this sample is also higher

Neutrino&running&

Reconstructed Energy (GeV) Number of Events

NUEQE=562 ANUEQE=4 NUENQE=684 ANUENQE=7 NC=1390 BEAM NUE=289 NUMU CC=75

50 100 150 200 250 300 2 4 6 8

1-ring, 0 decay e 1-ring, 1 decay e

SLIDE 14

Multi-ring Samples

Additional 2- and 3-ring samples also have controllable

backgrounds

Selections have not yet been optimized for CP sensitivity

SLIDE 15

Sensitivity

Sensitivities produced with the

same GLoBES framework used for the DUNE CDR analysis

Systematic assumptions are also

consistent with the CDR  (2% signal, 5% background, uncorrelated among all samples)

Theia disappearance samples

are not included here (impact is minimal)

Both the CP and mass hierarchy

sensitivity are similar for a 10 kt LAr module, and a 17 kt Theia module

π /

CP

δ

1 -0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1

2

χ ∆ 5 10 15 20 25 30

Mass Ordering Sensitivity

π /

CP

δ

1 -0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1

2

χ ∆ 5 10 15 20 25 30

Theia 70 kt Theia 17 kt DUNE 10 kt (CDR) Mass Ordering Sensitivity Normal Ordering 7 years Mass Ordering Sensitivity

π /

CP

δ

1 -0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1

2

χ ∆ = σ 1 2 3 4 5 6 7

CP Violation Sensitivity

π /

CP

δ

1 -0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1

2

χ ∆ = σ 1 2 3 4 5 6 7

Theia 70 kt Theia 17 kt DUNE 10 kt (CDR)

CP Violation Sensitivity Normal Ordering 7 years

CP Violation Sensitivity

SLIDE 16

Role of the Near Detector

DUNE will have a high granularity C

target in the near detector (3DST)

This is the same detector

technology that is being used for the T2K ND280 upgrade

The goal is to achieve 4π muon

acceptance, and study short tracks near the vertex

Similar to T2K, the 3DST could

provide strong LBL constraints for Theia

Several possibilities exist to add

water or WbLS targets in the 3DST as well

SLIDE 17

Summary I

Theia provides a set of LBL events that are complementary to the

LAr samples

Different nucleus, detector systematics, neutron detection,

energy resolution, timing, etc.

Advances in Water Cherenkov reconstruction techniques provide

substantial improvements over the those assumed in LBNE studies

Improved reduction of NC background and the addition of new

multi-particles samples have substantially improved the CP sensitivity of a water-based detector in the LBNF beam

A 17 kt Theia module can provide similar sensitivity in both CP &

MH to a 10 kt LAr module

This does not include any improvements from the scintillation

light Theia would provide

Many opportunities for many aspects of such a detector (optical

configuration, DAQ, electronics, calibrations, slow controls, etc.)

SLIDE 18

Theia can enhance the LBL program, and expand DUNE’s physics reach!

Directional fit (cf. Super-Kamiokande)

Solar CNO Flux @ 10% uncertainty

LEGEND-1000 CUPID CUPID-reach SNO+II PandaX-III-1000 KamLAND2-Zen NEXT-HD nEXO CUPID-1T Theia-Te NEXT-BOLD Theia-Xe

2 −

10

1 −

10 [eV]

β β

discovery sensitivity on m σ 3

0νββ: mββ @ ~6 meV

150

100
50
50

100 150

) ° ( f D

80

60
40
20
20

40 60 80

) ° ( q D

1 2 3 4 5 6 7 8 9

Entries 600 / ndf 2 c 380.6 / 1795 norm 10.24 ± 110 ) ° ( q 1.239 ± 0.5753 ) ° ( f 1.193 ± 0.8371 ) ° ( s 0.8488 ± 10.6 const. 0.02005 ± 0.3462 Entries 600 / ndf 2 c 380.6 / 1795 norm 10.24 ± 110 ) ° ( q 1.239 ± 0.5753 ) ° ( f 1.193 ± 0.8371 ) ° ( s 0.8488 ± 10.6 const. 0.02005 ± 0.3462

Michael Wurm (Mainz)

eES 200 IBD 4000 tag eff. 90% θ0 0.57±1.24 ϕ0 0.84±1.19

Reconstructing ES electron direction

SN Pointing @ 2°

12

Signal/BG spectra and observation window

5σ Observation

f DSNB

π /

CP

δ

1 -0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1

2

χ ∆ = σ 1 2 3 4 5 6 7

CP Violation Sensitivity

π /

CP

δ

1 -0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1

2

χ ∆ = σ 1 2 3 4 5 6 7

Theia 70 kt Theia 17 kt DUNE 10 kt (CDR)

CP Violation Sensitivity Normal Ordering 7 years

CP Violation Sensitivity

Confirm CPV w/ different systematics

SLIDE 19

Supplement

SLIDE 20

Increased Fiducial Volume

Previously in Super-K, event vertices required

“wall” > 2 m

The T2K event selection is now based on

“wall” and “towall”

An event with small “wall”, but large

“towall" can be perfectly well reconstructed

Reconstruction performance degrades with

small “towall”, even if “wall” > 2 m

New, expanded FV increases oscillated νe

events by ~25%

In the latest SK atmospheric analysis (2019),

a wall cut of 50 cm was used, increasing the FV even further

This improvement has not yet been

incorporated into the Theia analysis

track towall wall

Wall [cm] Towall [cm]

)

T2K νe

CCQE CCnQE NC Entering MisID (CC νμ)