TITUS - An Intermediate Distance Detector for the Tokai-to

TITUS

An Intermediate Distance Detector for theTokai-to-Hyper-K Neutrino Beam

Nick Prouse

Institute of Physics Particle, Astroparticle, and Nuclear Physics Group MeetingUniversity of Manchester

31 March 2015

Nick Prouse (Queen Mary & Southampton) TITUS: An intermediate detector for Hyper-K IoP Meeting, 31 March 2015 1 / 12

Table of Contents

1 Overview of Hyper-K

2 Overview of TITUS

3 Gadolinium Doping

4 Muon Range Detector

5 Simulation & Reconstruction

6 Physics Potential

7 Summary


Overview of Hyper-K

See talk by M. Malek(PPAP Parallel: Neutrino

Oscillations I)

I 1 megaton water Cherenkov detector near Super-K site

I 295km from J-PARC neutrino beam, 2.5 degrees off-axis

I Rich physics programme:I Neutrino oscillations: CP violation, mass hierarchy, etc.I Neutrinos from astrophysical sources: local & relic supernova, dark matterI Proton decay: 1035 years at 3σ

I CP-violation requires reduced systematics as well as more statisticsI Require an improved near detector


Overview of TITUS

I TITUS: Tokai Intermediate Tank for Unoscillated Spectrum

I 2 kton Gadolinium doped water Cherenkovdetector ∼ 2km from J-PARC

I Main aim to reduce systematics for Hyper-K

I Location/design chosen to match Hyper-Kneutrino interactions and beam spectrum


Overview of TITUS

I TITUS: Tokai Intermediate Tank for Unoscillated Spectrum

I 2 kton Gadolinium doped water Cherenkovdetector ∼ 2km from J-PARC

I Main aim to reduce systematics for Hyper-K

I Location/design chosen to match Hyper-Kneutrino interactions and beam spectrum

I Baseline design:I 22m long, 11m diameter tankI Muon Range Detector partially enclosing downstream endI 0.1% Gadolinium doping for neutron capture signal

I Physics programme:I Precise measurement of J-PARC beam spectrum for Hyper-KI Cross-section measurementsI Neutron multiplicityI Sterile neutrinosI Detect supernova burst neutrinos for SN alarm


Gadolinium Doping

I Neutron capture on Gadolinium:I Cross section of 49,000b compared to 0.3b for HI 8MeV gamma cascade with 4-5MeV visible energyI 100% detection efficiency on Gd (<20% on H in SK)I 0.1% Gd doping: ∼90% of neutrons capture on Gd

I New signal to distinguish ν / ν̄ events and different interaction modes:νµ CCQE νµ + n→ µ− + p 0 neutrons

ν̄µ CCQE ν̄µ + p→ µ+ + n 1 neutron

νµ MEC νµ + (n+ n)→ µ− + p+ n 0.2 neutrons average

ν̄µ MEC ν̄µ + (p+ p/n)→ µ+ + n+ p/n 1.8 neutrons average

I Greatly enhanced sample purities:

I νµ CCQE: 36% → 67%I ν̄µ CCQE: 63% → 88%

I Feasibility of Gd in water Cherenkov detector being tested in EGADS

I arXiv:1201.1017


Muon Range Detector

I In nominal TITUS 18% of muons escapetank

I MRD consisting of layers of iron andscintillator partially covers tank downstreamof beam

I Allows momentum measurement for muonsstopped in MRD

I Addition of 1.5T magnetic field enablesmuon charge reconstruction

I Second method for ν/ν̄ discriminationI Use to calibrate and validate ν/ν̄

discrimination from Gd n-captureI Combination provides very accurate

separation → improved δCP sensitivity


Simulation & Reconstruction

I New fast simulation and reconstructionpackages being developed

I WChSandBox simulation simulationdeveloped in collaboration with ANNIE

I ANNIE: 20ton Gd-doped WC with MRDI Like scaled down TITUS: Collaborate for

detector R&D

I New low-E and high-E reconstruction packagesI Currently available reconstruction packages require

tuning for specific detector configurationsI New Low-E reconstruction using 4-hit algorithmI New High-E reconstruction using hit timing and

likelihood fitsI Single combined package for signals from e/µ or

n-capture

I Fast and convenient for changing tank size, coverage,photodetector type, etc.


Physics Potential

Physics Potential: CP sensitivity

I Reduced systematics for improved sensitivities at HKI Measure intrinsic νe component of J-PARC beamI ν/ν̄ discrimination provides measurement of ν contamination of beam in ν̄

mode

CPδ

3 2 1 0 1 2 3

)1

3θ

(22

sin

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.13

0.14

0.15

90% CI with neutron tagging

90% CI without neutron tagging

POT scale

110 1 10)

CP

δ(σ

0

0.1

0.2

0.3

0.4

0.5stat+syst without neutron tagging

stat+syst with neutron tagging

stat only without neutron tagging

Increased δCP sensitivity when including TITUS and neutron tagging in fit(preliminary results)


Physics Potential

Physics Potential: Cross-section measurements


mode

I Cross-section measurementsI Measure cross-sections as function of neutron multiplicityI Use neutron multiplicity to better distinguish interaction modesI Enhance Hyper-K proton decay searches through precise background

measurements

Beam in ν mode Beam in ν̄ mode


Physics Potential

Physics Potential


mode

I Cross-section measurementsI Measure cross-sections as function of neutron multiplicityI Use neutron multiplicity to better distinguish interaction modesI Enhance Hyper-K proton decay searches through precise background

measurements

I Sterile neutrino search via νe disappearance from ND280I Comparing NC and CC rates at ND280 at 280m and TITUS at 2km

I Supernova burst - expect ∼650 events for SN at 10kpcI Discriminate νe and ν̄e using GdI Use TITUS as independent SN alarm


Summary

I TITUS: proposed design for detector as part of Hyper-K projectI Match HK target material and beam spectrumI Main aim to reduce systematics for HK

I Gadolinium doping of water provides new signal for neutron taggingI Distinguish ν from ν̄ interactions - essential to improve CP-violation sensitivityI Neutron multiplicity allows better identification of interaction mode

I MRD partially covering downstream endI 18% of muons exit the tank - use MRD to reconstruct momentumI Magnetised MRD allows charge reconstruction of exiting muons

Thank you for your attention


Backup Slides


Backgrounds

I Cosmic sourcesI Spallation neutrons from cosmic ray muons give significant background for

Gadolinium doped water cherenkov

I Beam induced sourcesI Muons produced from interactions in sand and rock around TITUSI Resulting neutrons give largest backgroundI Upstream veto can remove mostI Investigating using outer detector for better background removal


Design Optimisation

I Work is ongoing to optimise detector accounting for costI Location - distance and off-axis angleI MRD coverage options

I Magnetic field for MRD: Need to shield PMTs from fieldI Photosensor coverage options

I Photosensor type: PMTs, HQE, LAPPDs


Reconstruction

I Low energy event reconstruction via 4-hitalgorithm

I Takes 4 hits and solves for vertex positionassuming point source

I Similar to BONSAI for SK and quad fitter forSNO

I High energy event reconstruction similar to SKalgorithm

I Vertex and direction using hit timinginformation

I Ring counting by modified Hough transformusing hit posisions and times

I PID using full likelihood based on Cherenkovphoton emission pdfs


TITUS Samples without n-tagging


TITUS Samples with n-tagging


Secondary interactions for n-tagging


Documents

TITUS - An Intermediate Distance Detector for the Tokai-to