Recent Results and Future Prospects of Neutrino Oscilla5on
Experiments

Roger Wendell
Kyoto University
2017.01.06
KMI Symposium 2017, Nagoya

Introduc5onnRecently there has been a lot of progress in understanding neutrino mixing inoscilla5on experiments using a variety of sourcesn Atmosphericn Accelerator: both long- and short-baselinen Reactor neutrinosn

In this talk I will discuss the most recent results and prospects for the near- andmid-term futurenN.B. There is a worldwide program dedicated to resolving ques5ons in neutrino
oscilla5on physics
n I will touch brieﬂy on the whole, but emphasis will be placed on the Japanese
programn

Apologies to those projects that I don’t cover in detail!
n INO, JUNO, ORCA – to name a few

2

Status of Neutrino Oscilla5ons

Atmospheric

Solar
Esteban, I et al: 1611.01514

nThree mixing angles, two independent
mass diﬀerences (Δm221 , Δm232), and a
CP viola5ng phase δcp

Currently, all parameters have beenmeasured, though δcp is the least wellconstrained and the topic of muchinterest
n However, several open ques5ons
remainn3

Status of Neutrino Oscilla5ons

Atmosphericn

Three mixing angles, two independent
mass diﬀerences (Δm221 , Δm232), and a
CP viola5ng phase δcp

Currently, all parameters have beenmeasured, though δcp is the least wellconstrained and the topic of muchinterest
n However, several open ques5ons
remainn Maximal Mixing?

Solar
Is Atmospheric Mixing Maximaln4Status of Neutrino Oscilla5ons

Atmosphericn

Three mixing angles, two independent
mass diﬀerences (Δm221 , Δm232), and a
CP viola5ng phase δcp

Currently, all parameters have beenmeasured, though δcp is the least wellconstrained and the topic of muchinterest
n However, several open ques5ons
remainn Neutrino Mass hierarchy?

Solar
Mass Ordering is UnknownnΔm232 > 0Δm232 < 05

Status of Neutrino Oscilla5ons

Atmosphericn

Three mixing angles, two independent
mass diﬀerences (Δm221 , Δm232), and a
CP viola5ng phase δcp

Currently, all parameters have beenmeasured, though δcp is the least wellconstrained and the topic of muchinterest
n However, several open ques5ons
remainn Neutrino Mass hierarchy

Solar
Is CP Violated in Neutrino Mixing?

nEsteban, I et al: 1611.01514

6

Experimental Program: Dates
2026

2020

2020

2002

2010

2002
2009
2020
1996/2026

Δm221

Δm232

AtmosphericLong-baseline
ReactorMany experiments ongoing and plannedn Mass hierarchy and δcp measurements rely on the similar techniques, for the7most partnDetermina5on of The MH and δcp
For the purposes of today’s Talk:nn

Maeer Eﬀects

MHAppearanceδcp

Dominant oscilla5on mode for measurements is the appearance channel
n νµ
νe
n

This mode was established in 2012 by T2K and conﬁrmed with NOνAn

Notable excep5on is the JUNO experiment (backup)

Addi5onal sensi5vity from disappearance mode νµνµMass Hierarchy Determina5on: Maeer-Eﬀects
Normal Hierarchy

P(νµ →νe)

P(νµ →νe)n

Maeter induces asymmetric oscilla5ons between electron-type neutrinos andan5neutrinos
n If the baseline is long enough the asymmetry can be large (NOvA, DUNE, HKK)n

For atmospheric neutrinos: enhanced oscilla5ons for either neutrinos oran5neutrinos (not both), depending upon the mass hierarchyn Muon nuetrinos also sensiJve (ICAL-INO)

9

Measuring δcp Parameter : Long-baseline

Modula5on of the electron neutrino appearance probability is the dominantchannel with sensi5vity to δcp
n Neutrino/an5neutrino sign selec5on provides direct proben

T2K baseline : 295 km
n NOνA baseline : 810 kmn

10Measuring θ23 and δcp Parameter : Long-baseline“Atmospheric” Mixing

Maeer Eﬀect

Leading Term

CPV Here:

It is not suﬃcient to just search for electron neutrino appearance to study
neutrino CP
n Experiments u5lize constraints (in-situ measurements) from the disappearance
channel to improve sensi5vity ton Equally relevant for atmospheric neutrinos!
n11Current Experiments

12

Beam Experiments:
Target

π+

νµ
νµ
νµ
νµ

νe
νµ
ντ
ντ

πProton Accelerator

Magne5c HornsnOﬀ-axis beam used to create anarrow neutrino energy
n Baseline op5mized for
maximum oscilla5on eﬀectnNear detectors are used toconstrain ﬂux and interac5onmodel at the far detectornChanging magne5c horn polarity
allows one to create either aneutrino or an5neutrino enhanced
beam

Near Detector

Far Detector

13

Beam Experiments:
Target

π+

νµ
νµ
νµ
νµ

νe
νµ
ντ
ντ

πProton Accelerator

Magne5c Horns

Near Detector

Far Detector

T2K

NOνA

Japan / J-Parc

U.S.A. / FNAL

Beam Power

400 kW

560 kW

Proton Energy

30 GeV

120 GeV

Baseline Length

295 km810 kmNear Detector

Tracker: FGD, TPC

Lq. Scin5llator

TargetCarbonCarbonFar Detector

Super-K 50kton

Lq. Scin5llator

Target

Water

CarbonOﬀ-axis Angle

2.5 deg / 44 mrad

0.8 deg / 14 mrad

Peak ν Energy~600 MeV~2 GeV

Loca5on14

Atmospheric Neutrino Experiments:

Diverse range of energies
n Produced nearly isotropically
about the EarthnBoth electron and muon neutrinosn Both neutrinos and an5neutrinosn No “Horn” to focus one or theothernOscilla5ons
Super-Kamiokande
IceCube/DeepCore

No knowledge of neutrino
produc5on point or precise
direc5onn No near detector to control
15
interac5on systema5csnAtmospheric Neutrino Experiments:

40m

1 km

Super-Kamiokande

IceCube50,000 Ton Ultrapure Water

1 km3 of Antarc5c Ice

11,000 20” PMTs (ID) 1885 8” (OD)

5100 Digital Op5cal Modules (DOM)

Ring-Imaging“String” Imaging

40% Cathode Coverage

86 Strings, 17m / 7m DOM Spacing

0.1 ~ 103 GeV

10 ~ 105 GeV

Excellent e/µ PID, MIS PID 1%

Cascade (e/NC) and Track (µ)

Both are Cherenkov detectors without event-by-event ν/ν separa5on16

Atmospheric Mixing

17

Atmospheric Mixing: Muon Neutrino Disappearance

Experiment

Null Osc.

Observed

Best Fit

Comment

T2K (ν-mode)

522

135

135.3

7.5e20 POT

T2K (ν-mode)

185

66

64.1

7.5e20 POT

NOνA

437

78

82

6.05e20 POT

IceCube

6830

5174

---

AtmosphericNOνA currently rejec5ng maximal mixing at 2.5σ

18n

Atmospheric Mixing + δcp: Super-Kamiokande
Muon Samples

Electron Samples
Preliminary
Inverted Ordering
Normal Ordering

Multi-GeV e-like νeCompara5vely weak constraint on atmospheric mixingn Observe an excess of upward-going electron neutrino
events weakly favoring the normal hierarchyn Δχ2 ( NH – IH ) = -4.3
n P(NH|IH) : 3.1%nnWeak hint for δcp ~1.33π( Up - Down ) / ( Up + Down )

0.4
0.4

NormalInverted

0.2
0.2

0

-0.2
-0.2

-0.4
-0.4
3

2×103

3.5

44
10
2×104
Lepton P [ MeV ]19

Electron Appearance And δcp

Recall: νµ -> νe oscilla5ons are mode with dominant sensi5vity
However: oscilla5on dependence on atmospheric mixing
necessitates use of disappearance sample as an in-situ constraint

20

NOνA : Appearance Sample

J.Hartnell NOW2016nWith 6.1e20 POT observe 33 events in the far detectorn BG: 8.2 +- 0.8 expected (3.7 NC, 3.1 Intrinsic)
n Signal systema5c uncertainty is 5%

Expect 28.2 events for NH, δcp = 3π/2n Expect 11.2 events for IH, δcp = π/2n21NOνA : Full AnalaysisnCombined analysis of appearance anddisappearance samplesn

So far neutrino mode onlynPreference for Normal hierarchyn Δχ2 = 0.47
n δcp = 1.49π
n sin2(θ23) = 0.40n3σ exclusion of IH with δcp = 0.5π

J.Hartnell NOW2016

22

T2K : Appearance Samples
Neutrino Mode (FHC)n

An5neutrino Mode (RHC)

With 7.5e20 POT for both neutrino mode (FHC) and an5neutrino mode (RHC)n FHC : 33 eventsn RHC:
4 events
Expecta5on23

T2K: First Hints of Leptonic CP-Viola5on?

Allowed region for δcp at 90% C.L.
n NH: [ -3.13 , 0.39 ]n IH : [ -2.09 , -0.74 ]n CP-conserving values 0, π are (just) outsideof this range!
n24

Into the Future25

Into the Future
Super-K Preliminaryn

T2K, NOvA, and Super-K show consistent preferences
for normal hierarchy and δcp = 3π/2
As of 2016

Hierarchy Δχ2 (NH-IH)

δcp / πSuper-K

-4.30

1.33

T2K

-1.40

1.50

NOνA

-0.47

1.49
26

Into the Future: Combining T2K-SK?

Normal Hierarchy

Preliminary
SK
T2K Model
SK+T2K Model

Super-K collabora5on has used publicly available informa5on to model and ﬁt
the T2K experiment together with atmospheric neutrinosn Atmospheric mixing constraint improves NH preferencen Δχ2 ( NH – IH ) = -5.1 (-4.3 SK Only)n P(NH|IH) : 2.7%nBeeer constraint with correlated systema5cs between experiments: future?!
27
n T2K + NOνA combina5on also in discussionnNear Future : Hierarchy with Atmospheric Neutrinos
PINGU – IceCube Upgrade

PINGU
Lower energy threshold of DeepCore/IceCube to ~5 GeV, by
addi5on of densely instrumented strings
Improved resolu5on, PID and sensi5vity to electroncomponent of ﬂux
If funded begin data taking with full detector in 2020+* N.B. : Similar project in mediteranean sear, ORCA, also expects 4σ sensi5vity (backup)

28

Mass Hierarchy Sensi5vity SummarynAssuming 2nd octant of θ23

Experiment2020

2025-6

Super-K

2.5σ

3.0σ

NOvA

3.4σ

4.4σ

KM3NeT

0.5σ

4.0σ

2030

2035

T2K /-II

IceCube (Pingu)>4.0σ

JUNO *

4.0σ

ICAL-INO

2.0σ

3.0σ

~4σ

DUNE

3.0σ

5.0σ

~7σ

4.0σ

~6σ

Hyper-Kn29
Currently , not all are funded but good chance for a determina5on in 10 years

Near Future : CP Viola5on
NOvA Sensi5vity, sin2θ23 = 0.6

T2K – CPV Sensi5vity

2016

Full POT

As of 2016:
n T2K : 7.5 × 1020 P.O.T. ν and 7.5 × 1020 P.O.T. ν
n NOvA : 6.1 × 1020 P.O.T. ν
n For 2017
n T2K : Plan to double ν P.O.T.
n NOvA : Addi5onal 3.0 × 1020 P.O.T. ν and 3.0 × 1020 P.O.T. νn30

The Future of T2K : T2K-II
Hints for CP-viola5on can be probed early on with more P.O.T.
n T2K-II Proposaln Accumulate 20 × 1021 P.O.T by ~2026
n Bridge the gap between T2K and Hyper-K
n Stage-1 approval with J-PARC PAC
n More than just an extended run!
n Upgrade all parts of the experimentn Accelerator, and neutrinno beamlinen

J-PARC

31

The Future of T2K : T2K-II
Hints for CP-viola5on can be probed early on with more P.O.T.
n T2K-II Proposaln Accumulate 20 × 1021 P.O.T by 2025-2026
n Bridge the gap between T2K and Hyper-K
n Stage-1 approval with J-PARC PAC
n More than just an extended run!
n Upgrade all parts of the experimentn Reduce systema5c errors to 4%： Upgrade near detector
n

2016

32

The Future of T2K : T2K-II
Hints for CP-viola5on can be probed early on with more P.O.T.
n T2K-II Proposaln Accumulate 20 × 1021 P.O.T by 2025-2026
n Bridge the gap between T2K and Hyper-K
n Stage-1 approval with J-PARC PAC
n More than just an extended run!
n Upgrade all parts of the experimentn Reduce systema5c errors to 4%： Upgrade near detectornCurrent Concept:

Installa5on goal 2020
33

The Future of T2K : T2K-II
Hints for CP-viola5on can be probed early on with more P.O.T.
n T2K-II Proposaln Accumulate 20 × 1021 P.O.T by 2025-2026
n Bridge the gap between T2K and Hyper-K
n Stage-1 approval with J-PARC PAC
n More than just an extended run!
n Upgrade all parts of the experimentn Eﬀec5ve sta5s5cal increases (+50%) with FD reconstruc5on upgrades, andthe introduc5on of new analysis samples (mul5ple-rings, invisible decays)ntowallwall

34

T2K-IIn

3σ measurement of CPV possible !

nOdds improve greatly with if thehierarchy is known

By external experiment!

35

Farther Future: Next Genera5on Experiments
Hyper-K

DUNEJapan / J-PARC

U.S.A. / FNAL

Proton Energy

30 GeV

120 GeV

Beam Power

1.2 MW

1.2MW

Baseline Length

295 km1300 km

Near Detector

Tracker: FGD, TPC

FGT, STT, Pl. Sci.

TargetCarbon, Water

Ar, C, Fe

Far Detector

360 kton WC

40 kton Lq. Ar TPC

Target

Water

Argon

Oﬀ-axis Angle

2.5 deg / 44 mrad

0 deg (on-axis)

Peak ν Energy~600 MeV

2.5 GeV

Neutrino Data

2025~262025~26

Loca5onnN.B. Both projects are more than oscilla5on experiments
n Nucleon Decay, Astrophysical neutrinos, precision cross sec5on36

Hyper-Kamiokande37

Hyper-Kamiokande38

Hyper-Kamiokande: Oscilla5ons

Observa5on of CPV at 5σ for 60% of phase spacen Measure atmospheric mass splixng to less than 1%
n Atmospheric mixing angle, sin2θ23, to less than 3%

n

39

n

Unique in its ability to study but beam and atmospheric
neutrinos due to its sizenCombina5on with beam neutrinos allows mass
hierarchy determina5on in 1~4 years if not already
known

n

3s determina5on of the q23 octant if |θ23 – 45°| > 3°40

Hyper-K: Second Detector in Korea?
nWith the staged design it ispossible to place second
detector outside of Kamioka,
n Korea is an op5on underserious considera5on (Mt.
Bisul ~ 1100 km baseline)n

Improved CP asymmetry alonger baselines via 2nd
oscilla5on maximumnLarger maeer eﬀects forhierarchy sensi5vitynOp5mize second detector asnecessarynTruly internaJonal experiment41

Hyper-K, Korea – Beam

42

CP Viola5on Sensi5vity Summary
T.Nakaya NuFact2016

2035: HK 10 years, staged
2033: Dune 7 years full conﬁgura5on2027: T2K-II, 20e20 POT w/ improvements
2020: T2K + NOvA full statsn

Several complementary measurements planned in the years aheadnDeﬁni5ve δcp measurement 10~20 years?
43

A Word about Tau Neutrinos
PINGU

Hyper-Kamiokande

Achieve 7% uncertainty on tau cross sec5onnormaliza5on with 560 Mton-year exposure ofHyper-Kn PINGU is similar, but fastern These samples will be useful for tes5ng crosssec5on modeling as well as providing direct probe
of |Uτ3|2nSummary and Prospects:n

The race is on for the neutrino mass hierarchyn Several compe5ng ideasn Expect a 3~4σ determina5on within 10 yearsnCP viola5on measurements are similarly drawing a lot of interest
n Require large detectors and more beam powern A precise determina5on will likely take another 10 or 20 years, but is in the
cards

n

Many projects on-going or planned to address these issues!
n Its an exci5ng 5me for neutrino physics, with a lot of ac5vity
n Apologies I could not give each suﬃcient detail in this talk45

46