Introduction to THEIA and low-energy neutrino program 70m 18m - - PowerPoint PPT Presentation

Introduction to THEIA and low-energy neutrino program

THEIA25

70m 20m 18m

MooD Workshop BNL, Nov 12, 2019 Michael Wurm (JGU Mainz) for the THEIA proto-collaboration

What is THEIA?

THEIA 2

Novel target medium: Water-based Liquid Scintillator Novel light sensors: LAPPDs, dichroicons Large volume detector able to exploit both Cherenkov+Scintillation signals → Enhanced sensitivity to broad physics program Long-Baseline Oscillations Solar neutrinos Supernova neutrinos Diffuse SN neutrinos Neutrinoless Double-Beta Decay scintillation Cherenkov Novel reconstruction techniques

THEIA Technology

Michael Wurm (Mainz) THEIA 3

scintillation Cherenkov → how to generate (and preserve!) scintillation and Cherenkov photons?

102 103 104 25 50 75 100 125 Water (SK,SNO) Scintillator Borexino KamLAND Water-based Liquid Scintillator Water-like § >70% water § Cherenkov+ scintillation § cost-effective Oil-like § loading of hydrophilic elements

Photon yield (MeV) Attenuation length (m)

WbLS mycels

S u f f i c i e n t l y t r a n s p a r e n t t

• e

x t r a c t C h e r e n k

• v

p h

• t
• n

s ! → target medium can be adjusted to physics goals!

THEIA Technology

Michael Wurm (Mainz) THEIA 4

scintillation Cherenkov Timing

“instantaneous chertons”

• vs. delayed “scintons”

→ ns resolution or better

Spectrum

UV/blue scintillation vs. blue/green Cherenkov → wavelength-sensitivity

Angular distribution

increased PMT hit density under Cherenkov angle → sufficient granularity

→ how to separate the Cherenkov/scintillation signals? → how to generate (and preserve!) scintillation and Cherenkov photons?

LAPPDs: ~60ps timing

THEIA Technology

Michael Wurm (Mainz) THEIA 5

scintillation Cherenkov Timing

“instantaneous chertons”

• vs. delayed “scintons”

→ ns resolution or better

Spectrum

UV/blue scintillation vs. blue/green Cherenkov → wavelength-sensitivity

Angular distribution

increased PMT hit density under Cherenkov angle → sufficient granularity

→ how to separate the Cherenkov/scintillation signals? → how to generate (and preserve!) scintillation and Cherenkov photons? Dichroic filters

→ talk by Tanner Kaptanoglu

Standard PMTs

LAPPDs: ~60ps timing

THEIA Technology

Michael Wurm (Mainz) THEIA 6

scintillation Cherenkov Timing

“instantaneous chertons”

• vs. delayed “scintons”

→ ns resolution or better

→ how to separate the Cherenkov/scintillation signals? → how to generate (and preserve!) scintillation and Cherenkov photons? Large Area Picosecond Photon Detectors

§Area: 20-by-20 cm2 §Amplification of p.e. by two MCP layers §Flat geometry: ultrafast timing ~65ps §Strip readout: spatial resolution ~1cm §Commercial production by Incom, Ltd.

THEIA R&D and friends

THEIA 7

→ test of THEIA-related technologies

→ talk by Adam Bernstein

WATCHMAN-AIT ANNIE @ Fermilab BNB → demonstrator for LAPPDs → WbLS upgrade foreseen Selected examples of on-going R&D:

CHESS setup at UC Berkeley: Image Cherenkov rings from WbLS + C/S timing timing in rings → Dichroicons at U.Penn Simultaneous but discriminating detection

• f chertons & scintons

→ talk by T. Kaptanoglu Toplogical reconstruction at U.Hamburg Using (Wb)LS volume as “photon TPC“ by tracking back photons for enhanced emission probability ß 0.5GeV µ in WbLS+LAPPDs

THEIA25 as the Module of Opportunity

Michael Wurm (Mainz) THEIA 8

THEIA25

70m 20m 18m

Detector specifications

§ Total mass: 25 kt of WbLS § Fiducial mass: 17-20 kt (depends on physics) § Photosensors in Phase 1 (LBL): 22,500x 10’’ PMTs → 25% coverage w/ high QE 700x 8’’ LAPPDs → 3% coverage → equals the current photon collection of SK! § Background levels: Radiopurity (H2O): ~10-15 g/g in 238U, 232Th, 40K Rock shielding: 4300 m.w.e. → muon flux only ~10% of LNGS

THEIA25 : Staged Approach

Michael Wurm (Mainz) THEIA 9

THEIA25

70m 20m 18m

Staged Approach Phase 1 Long-baseline neutrinos (LBNF) with ”thin” WbLS (1-10%) Phase 2 Low-energy neutrino

• bservation with “oily” LS

Phase 3 multi-ton scale 0νββ search with loaded LS in suspended vessel and added photocoverage Physics Goals § Long-Baseline Oscillations § Proton decay → K+ν/π0e+ § Supernova neutrinos § Diffuse SN neutrinos § Solar neutrinos § Geoneutrinos § 0νβ νββ search

• n <10meV scale

WbLS: Impact on MeV neutrino detection

Michael Wurm (Mainz) THEIA 10

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

Supernova Neutrinos

Michael Wurm (Mainz) THEIA 11

Galactic Supernovae (10kpc): Expected events: ~5,000, mostly ) 𝝃𝒇‘s from IBD § complementary to 𝜉- signal in argon § Same location: compare Earth matter effects § Provide fast trigger for Lar TPCs, especially for far-off Supernovae (LMC: ~200 ev. In THEIA) Detection channels can be separated due to neutron & delayed decay tags § some all-flavor (νe+νµ+ντ) information from NC reactions on oxygen § Enhanced SN pointing: ∼2° based on ES with IBD background subtraction

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

Reconstructing ES electron direction

Diffuse Supernova Neutrino Background

Michael Wurm (Mainz) THEIA 12

DSNB detection: § Low-flux 𝒫(102 cm-2s-1) ̅ 𝜉- signal → detectable by IBD: ~2 ev. per 10 kt∙yrs § Requires efficient BG discrimination, especially to atmospheric ν NC interactions § In THEIA:

• ring counting:
• Cherenkov/scintillation ratio
• delayed decay tags

→ signal efficiency: 95% → residual background: 1.7% very clean measurement cf. JUNO & SK-Gd

Cherenkov/scintillation ratio for BG discrimination Signal/BG spectra and observation window

THEIA25: 5 IBDs over 2.7 BG per year → 5σ discovery after 6 years

NC BG data by ANNIE!

Solar neutrinos

Michael Wurm (Mainz) THEIA 13

Objectives: § Precise measurement of CNO neutrino flux § Spectral upturn of low-energy 8B neutrinos → require efficient BG discrimination and sufficient light yield in 1-3 MeV range § THEIA25: 2D directional & spectral fit → CNO flux at 10% level after 5 yrs stellar physics, solar metallicity matter effects, BSM physics?

Spectral fit (cf. Borexino) Directional fit (cf. Super-Kamiokande)

• R. Bonventre, G.D. Orebi Gann, Eur. Phys. J. C (2018) 78:435

Neutrinoless double-beta decay

Michael Wurm (Mainz) THEIA 14

Insertion of subvolume holding 1.8kt of organic scintillator (LAB+PPO) loading:

• - 3% enriched Xe (89.5%)
• - 5% natural Te (~90t)

enhanced 1200 pe/MeV (cf. JUNO) photo-cov. → 3% energy resolution Sensitivity (90% CL) from spectral fit: § Te: T1/2 > 1.1x1028 yrs, mββ < 6.3 meV § Xe: T1/2 > 2.0x1028 yrs, mββ < 5.6 meV

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]

b b

discovery sensitivity on m s 3

Energy spectrum (ROI)

Plot by Yu. G. Kolomensky using methodology from Agostini, Benato, Detwiler: PhysRevD.96.053001

THEIA Whitepaper online!

15

THEIA proto-collaboration: groups from 35+ institutions and eight countries (CA, CN, DE, FI, IT, KR, UK, US) arXiv:1911.03501 Read more on: § Detector technology § Low energy neutrinos, e.g. geoneutrinos § Nucleon decay § LBL oscillations Mike Wilking’s talk

Backup Slides

16

THEIA25

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Supernova neutrino pointing

Toy-MC study § Realistic kinematics for ES § Flat for IBD (conservative) § “canonical“ SN model (used for JUNO) § eES events: 200 in 20kt § IBD events: 4000 § IBD tagging efficiency: 0% → 90% → 100% § Angular resolution (at 10MeV+) 10° → 15° → 20° § Results of a 2D analytical fit: IBD tag Angular resolution efficiency 10° 15° 20° 0% 1.55 1.55 2.05 90% 1.75 1.95 2.55 100% 2.95 5.45 11.35

DSNB – spectrum before cuts

scintillation p.e.

1 2 3 4 5 6

3

10 ´

100 p.e.) ´ events /(100 ktyr

3

• 10

2

• 10

1

• 10

1 10

2

10

3

10

visible scintillation energy (MeV) 5 10 15 20 25 30 35 40 45

DSNB Reactor BG AtmCC BG AtmNC BG Li9 BG FastN BG

DSNB Ring Counting

scintillation p.e.

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 50 100 150 200 250 300 350 visible scintillation energy (MeV) 5 10 15 20 25 30 35

One-Ring Multi-Ring No-Ring

AtmNC events

DSNB C/S ratio background rejection

5 10 15 20 25 30 35

S+B S/

2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6

yr) ´ AtmNC Rate /(100 kt

5 10 15 20 25 30 35

yr) ´ DSNB Rate /(100 kt

10 12 14 16 18 20 22 24 26

82% signal efficiency

Background Reduction [%] 1 2 3 4 5 6 7 8 9

DSNB Delayed decay tags

ß taggable ß taggable

DSNB Signal and Background Rates

DSNB Sensitivity : BG discrimination

yr] ´ exposure [kt

20 40 60 80 100 120 140 160

] s significance [

1 2 3 4 5 6 7 no unc. 5%

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 t [yr] 1 2 3 4 5 6 7 8

DSNB Sensitivity : DSNB models

Solar : angular resolution & WbLS fraction

Scintillation fraction (%) 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 CNO sensitivity (%) 2 4 6 8 10 12 14 angular resolution ° 25 angular resolution ° 35 angular resolution ° 45 angular resolution ° 55

Solar neutrinos – 7Li loading

0𝛏ββ ββ study for THEIA50

0𝛏ββ ββ backgrounds

Antineutrino spectrum

Proton decay sensitivity