Latest Results from the T2K Neutrino Oscillation Experiment and Future Plans for the Neutrino Program at J-PARC

CPAN Days, November 28-30, 2016, Zaragoza

Alexander Izmaylov

Instituto de Fisica Corpuscular, IFIC (CSIC&UV)

Latest Results from the T2K

Neutrino Oscillation Experiment and Future Plans for the Neutrino Program

at J-PARC

Neutrino Oscillations Phenomena

The evidence that neutrinos have mass comes from oscillations

•  interference between flavor and mass states

•  different flavor detected after a distance L

“Appearance”

channel

“Disappearance”

channel

L

Neutrino Oscillation Parameters and PMNS Matrix

Pontecorvo-Maki-Nakagawa-Sakata matrix (CKM analogue from quarks)

90%CL: δ_CP (-π, 0.15π) and (0.87π, π)

Accelerator

Atmospheric Reactor Solar

PDG 2015

•  Δm²₁₂ = 7.54 ± 0.16 x 10^-5 eV²

•  |Δm²₂₃| = 2.43 ± 0.06 x 10^-3 eV²

•  sin²θ₁₃ = 0.0240±0.002 normal

•  sin²θ₂₃ = 0.437±0.033 mass

•  sin²θ₁₂ = 0.308±0.017 ordering

•  2 mass diff`s Δm²_ij=m²_j-m²_i

•  three angles θ₁₂, θ₂₃, θ₁₃

•  CP-phase δ_CP

Open Questions

•  CP-violation in lepton sector?

à the value of δ_CP?

•  θ₂₃ “maximal”? octant? (< or > 45^o)

•  Additional (sterile) neutrinos?

•  Mass states ordering?

à sign of Δm²₂₃ ?

•  Dirac or Majorana nature?

•  “New” physics?

•  CPT violation

•  Lorentz violation effects in neutrino oscillations

•  Heavy (~1 GeV) neutrinos

Three Flavor Oscillations

Three flavor oscillations + matter effects à difficult to disentangle parameters

Concept of Long-Baseline Accelerator Experiment

Neutrino beam

produced by

accelerator (PS)

•  protons on target, E~O(GeV)

Near Detector

•  measurements of neutrino beam prior to oscillations

•  constrain flux, cross-sections “in situ”

Far Detector

•  measurements of neutrino beam after oscillations

•  retrieve oscillation parameters

T2K (Tokai-to-Kamioka) Collaboration

The T2K Neutrino Experiment

•  J-PARC 30 GeV proton synchrotron

•  Off-axis muon (anti)neutrino beam (2.5^o)

•  Near and far detectors

Kamioka

KEK

Tokai

295 km

MR

Neutrino Oscillations in T2K

Neutrino Oscillations in T2K

Leading term defines the octant

•  θ₂₃<45^o, θ₂₃>45^o or θ₂₃=45^o

δ_CP gives ±10-30% effect for T2K

•  δ_CP=-π/2 enhances ν_e and suppresses anti-ν_e appearance

•  δ_CP=π/2 suppresses ν_e and enhances anti-ν_e appearance

Similar effect from mass hierarchy ~±10%

•  normal (NH) enhances ν_e and suppresses anti-ν_e appearance

•  inverted (IH) suppresses ν_e and enhances anti-ν_e appearance

T2K Detectors

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“Pre-oscillation” Neutrino Beam Monitor T2K Near Detector ND280

on-axis detector (INGRID):

- direct neutrino beam day-by-day monitoring

- beam profile and center position monitoring (crucial for off-axis) - neutrino beam intensity

monitoring

-  scintillator+iron modules

ND280 off-axis: sub-detectors operated inside magnetic field

•  UA1 CERN magnet, B=0.2 T

•  3 Time-Projects Chambers( TPCs)

•  2 Fine-Grained Detectors (FGDs)

•  π⁰ detector, P0D

•  Electromagnetic calorimeters

•  Muon range detector in magnet slits

T2K Off-Axis Detector ND280

Key element to measure the neutrino beam properties prior to oscillations + unique opportunities for neutrino interaction studies

Current analysis based on tracker data: FGDs + TPCs

Far Detector Super-Kamiokande (SK)

•  e-like (“fuzzy”) vs µ-like rings separation

•  but no charge sign info

•  background from gamma- producing (e.g. NC-π⁰) events

•  Water Cherenkov detector

•  50 kT (22.5 kT FV)

•  11146 20-inch PMTs (Inner Detector)

•  1885 8-inch PMTs (Far Detector)

•  Optimized for single-events:

•  CCQE interactions at T2K energies

39 m

42 m

Far Detector Super-Kamiokande (SK)

T2K Neutrino Oscillation Analysis

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January 2010 –

start of T2K data taking

Neutrino Data Taking in T2K

Data by May 2016:

•  Neutrino data: 7.48x10²⁰ POT

•  Antineutrino data: 7.47x10²⁰ POT

Physics results

~420 kW achieved!

ν_e app.

2.5 σ ν_µ 1^st release

ν_e app.

3.1 σ ν_e app.

7.3 σ

1^st constraint on δ_CP ν_µ highest precision on θ₂₃

first anti-ν results

Neutrino 2016 New

Data

ND data

Hadron Production Data

NA61 CERN x-section data

Beam monitors + INGRID

SK data

ND model

x-section model

Flux model

SK model

External data T2K data MC models Data fits

+

ND fit

FD fit

T2K Oscillation Analysis Method

Oscillation parameters

ND280 Data for Oscillation Analysis

•  Select muon neutrino and anti-neutrino (ν_µ àµ^±) charged-current (CC) events

•  Use the data to constrain flux and neutrino interaction model parameters

§  neutrino mode: enhanced CC0π, CC1π and CC-other (mainly DIS)

§  antineutrino mode: 1-track and N-track (non CC0π) samples (work to further split the samples is on-going)

ν_µ CC samples in FGD1:

CC0π, CC1π and CC-other

Anti-ν_µ 1/N-track CC samples in FGD1 same selection to constrain wrong-sing background (~30% ν_µ in beam)

Oscillation Analysis at Far Detector

•  Joint analysis of four samples at far detector

§  ν_µ, anti-ν_µ, ν_e and anti-ν_e candidates

•  Frequentist and Bayesian analysis

Near Detector Constrains on Systematics

•  Significant reduction of systematics uncertainties due to ND

•  Less effect at low energy due to neutral current interactions (NC)

Neutrino vs Anti-Neutrino Results ν_µ Disappearance, CPT Probe

•  In “standard” neutrino framework (PMNS) expect no differences in disappearance channels (no +/- terms)

•  If observed à a clear hint for CPT violation, New Physics (e.g. non- standard interactions, decays)

•  Check sin²θ₂₃ and |Δm²₃₂| parameters for neutrino and anti-neutrino modes

§  constrain other parameters from PDG (2015) and set δ_CP to zero

?

Neutrino vs Anti-Neutrino Results ν_µ Disappearance, CPT Probe

•  Consistent results between neutrino and anti-neutrino

•  Best measurement for oscillation parameters for anti-neutrinos (with anti-neutrino data only)

•  Good agreement with other experiments

(Anti-) ν_µ à ν_e Oscillations Studies

•  Test the presence of anti- ν_µ à ν_e oscillations

•  Parameter β to turn ON/OFF P(ν_µàν_e)

•  Fit all 4 data samples (e.g. significant contribution from ν_e events) Switch On/OFF

antineutrino P(ν_µàν_e)

Constrain θ₁₃ from reactor data

•  No evidence for antineutrino P(ν_µàν_e) oscillations

•  Results consistent with backgrounds

Full Joint Analysis for “Atmospheric” Parameters

•  Full 4-sample analysis to constrain θ₂₃ and Δm²₃₂ parameters

•  Data consistent with maximal mixing

•  General agreement between experiments

Full Joint Analysis for CP-Violation, δ_CP

•  Best fit for δ_CP = -1.89 for NH

•  Exclude δ_CP = 0 at 2σ and π is excluded at 90% CL

•  @ 90% CL:

§  NH – [-3.13, -0.39]

§  IH – [-2.09, -0.74]

T2K and J-PARC Prospects

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T2K Plans: Current

•  In order to further improve sensitivity to oscillations params need to both increase the statistics and decrease the systematics

•  T2K steadily takes data: expect to have x2 neutrino data by summer 2017

•  Work to include new SK samples: ν_e CC1π à ~10% increase in the statistics

•  Try to decrease the model dependency + further reduce the systematics:

increase the phase-space in ND280 analysis à 4π

T2K Future Plans: Medium

•  Approved ~7.8x10²¹ P0T, expected to achieve by 2021

•  Approved (1^st stage from J-PARC PARC ) to further upgrade to T2K-II:

§  keep data taking until ~2025

§  increase the beam power with accelerator upgrade à~ 1MW

§  aim to reach 3σ sensitivity to δ_CP

T2K Future Plans: Medium

•  Need to further decrease systematics and constrain interaction models

•  Now considering ND280 upgrade in order to enhance 4π/low-energy analysis à

collaboration is being formed

§  rotated/vertical TPCs considered

§  new fine-grained (water-)scintillator as target à target prototype already

taking data at J-PARC (full proposal in backup)

Tough schedule: installation and commissioning planned for 2020

T2K Future Plans: Long-Term Projects @ J-PARC

•  Hyper-Kamiokande water Cherenkov detector (TK2-HK)

•  2 tanks, 260 kton (187 kton FV): x10 Super-Kamiokande

•  reach physics programs of oscillations, SN, solar nu`s and proton decay

•  New intermediate detectors @ ~1km distance

•  Proposed 2^nd tank in Korea to check second oscillation maximum

Conclusion

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•  T2K data for physics analysis: (7.5(nu)+7.5(antinu))x10²¹ POT statistics

•  Results of first joint fit with four samples: (anti-)ν_µ and (anti-)ν_e

§  Prefer max disappearance for (anti-)ν_µ + best experimental limits for atmospheric oscillations parameters

§  At 90% CL exclude no CP violation for neutrinos

•  7.8x10²¹ P0T approved and plan to reach in 2021

•  Many on-going analyses: neutrino interaction studies (can help to constrain interaction models, improve systematics) +

search for new physics

•  T2K-II with 20x10²¹ POT @ J-PARC accelerator upgrade proposed

•  Plan to reach 3σ sensitivity for δ_CP ~ π/2 and NH (further profits from combining with other experiments, NOVA)

•  Consider ND280 upgrade to further reduce systematics

Stay tuned for new T2K results!

Backup Slides

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“Pre-oscillation” Neutrino Beam Monitor T2K Near Detector ND280

A set of sub-detectors (280 m from target) operated inside a magnetic field

•  UA1 Magnet -  0.2 T field

•  Time Projection Chambers (TPCs) -  momentum and charge info -  particle ID (PID) via dEdX

•  Fine-Grained Detectors (FGDs)

-  plastic scintillators: neutrino target -  pure CH and CH+H₂O module

•  π⁰ Detector (P0D)

-  plastic scintillators + brass and lead -  NC-π⁰ events study

•  Electromagnetic Calorimeter (ECal)

-  lead+scintillator sampling detector -  track (muon) vs shower (e, γ, p, π) separation

•  Side-Muon Range Detector (SMRD)

-  scintillator bars in magnet air gaps -  cosmic trigger + reconstruction of

tracks with high-angles w.r.t. neutrino beam

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T2K Neutrino Beam Content

Antineutrino mode running (horn polarity)

Neutrino mode running (horn polarity)

Neutrino oscillations in T2K

Off-axis beam optimized for oscillation studies E_nu ~ 600 MeV

!CCQE/0π interactions are dominant at T2K energy à T2K signal

Background increases with energy: CC1p, NC1p, DIS, intrinsic ν_e à

reduced due to off-axis beam

!

µ(e)

Cross Section Model

•  CCQE events dominant and T2K energies à signal is CC0π

•  Testing, tuning of MC models for signal and background

•  Multi-nucleon processes

•  CC1π and CC-DIS

•  FSI

J-PARC T2K neutrino beamline

PS proton beam to Super-K

Graphite, Φ26 x 900 mm long

Helium cooling

~96 m long

3 Horns w/

250kA Si array

+ IC array

intensity, position profile

T2K ν_e CC-0π event candidate

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ND280 neutrino events

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DIS candidate

CC1π candidate

CC0Pi candidate

Sand muon + DIS candidate

DsECAL

P0D

TPC1

TPC2

TPC3

FGD2

FGD1

“Exotic” Physics with ND280

•  Short-baseline oscillations in ND280 (L~280 m)

•  ν_e disappearance (published)

•  ν_µ disappearance – analysis on-going (IFAE)

•  Search for heavy (O(GeV)) neutral leptons in ND280 (IFIC)

•  Kàe/µ+Nàe/µ+π

•  Potential to improve previous limits

•  PS191 (CERN)

•  “Theory”

•  T2K beam MC

Latest Highlights from T2K ND280 Cross Section Measurements

T2K Future Plans

•  Approved ~7.8x10²¹ P0T, expected to achieve by 2021

•  Steadily taking data: expect to double neutrino data

•  Combination with NOVA can improve sensitivity for δ_CP ≠ 0

Neutrino Cross-Section Studies in ND280

ND280 provides reach capabilities for ν cross section studies

ν_e CC inclusive on CH.

Phys.Rev.Lett. 113 (2014)24, 241803

ν_µ CC inclusive on CH.

Phys.Rev. D87 (2013) 9, 092003

ν_µ CC coherent on CH. ν_µ CC-1π on CH (IFAE)

Event Selection in Super-Kamiokande

Event Selection in Super-Kamiokande

Daya Bay Δm²_ee