Neutrino Physics with SNO+ Freija Descamps for the SNO+ collaboration

Transcription

1 Neutrino Physics with SNO+ Freija Descamps for the SNO+ collaboration NOW 2014, Otranto, Lecce, Italy September 7-14, 2014

2 Intro Neutrino physics with the SNO+ detector 2

3 Intro What we know:! Neutrinos have mass! Neutrinos oscillate between flavour states! Squared mass differences between mass eigenstates!! Neutrino physics with the SNO+ detector 2

4 Intro What we know:! Neutrinos have mass! Neutrinos oscillate between flavour states! Squared mass differences between mass eigenstates!! Challenges:! What is their mass and what is the mass hierarchy?! Majorana vs. Dirac nature of neutrinos! What are the precise oscillation parameters?! What can ν s tell us about Earth, Sun, Universe? Neutrino physics with the SNO+ detector 2

5 Intro What we know:! Neutrinos have mass! Neutrinos oscillate between flavour states! Squared mass differences between mass eigenstates!! Challenges:! What is their mass and what is the mass hierarchy?! } Majorana vs. Dirac nature of neutrinos! What are the precise oscillation parameters?! What can ν s tell us about Earth, Sun, Universe? Neutrino physics with the SNO+ detector 2

6 SNOLAB and SNO+ SNO+ = successor to Sudbury Neutrino Observatory (SNO)! Located in SNOLAB inside the Creighton mine near Sudbury, Canada! Depth = 2070m (6000m.w.e)! ~70 muons/day in SNO+! Class-2000 clean room Neutrino physics with the SNO+ detector 3

7 SNOLAB and SNO+ Deck with DAQ SNO+ operator ~780T LAB liquid organic scintillator! + PPO acrylic vessel! 12m! 5cm thick SNO+ = successor to Sudbury Neutrino Observatory (SNO)! Located in SNOLAB inside the Creighton mine near Sudbury, Canada! Depth = 2070m (6000m.w.e)! ~70 muons/day in SNO+! Class-2000 clean room ~9500 PMTs! 54% coverage ~7kT ultrapure water shield rock Neutrino physics with the SNO+ detector 3

8 SNOLAB and SNO+ Deck with DAQ SNO+ operator ~780T LAB liquid organic scintillator! + PPO acrylic vessel! 12m! 5cm thick SNO+ = successor to Sudbury Neutrino Observatory (SNO)! Located in SNOLAB inside the Creighton mine near Sudbury, Canada! Depth = 2070m (6000m.w.e)! ~70 muons/day in SNO+! Class-2000 clean room ~9500 PMTs! 54% coverage ~7kT ultrapure water shield rock Neutrino physics with the SNO+ detector 3

9 Liquid scintillator Solvent: Linear AlkylBenzene (LAB)! Long attenuation length (~20m)! Safe: low toxicity and high flash point! Chemically compatible with acrylic! α-β separation through decay-time! 2g/L fluor 2,5 diphenyloxazole (PPO)! High light yield ~10000γ/MeV Petresa plant! Bécancour, QC NIM A640, (2011) Neutrino physics with the SNO+ detector 4

10 LAB purification plan! Multi-stage distillation! Removes heavy metals! Improves UV transparency! Dual-stream PPO distillation! N2/steam stripping! Removes Rn, Kr, Ar, O2! Water extraction! Removes Ra, K, Bi! Metal scavenging! Removes Bi, Pb! Micro-filtration! Removes dust Target levels:! 85 Kr! : g/g! 40 K! : g/g! 39 Ar! : g/g! U! : g/g! Th! : g/g Neutrino physics with the SNO+ detector 5

11 SNO+ physics goals Neutrino physics with the SNO+ detector 6

12 SNO+ physics goals Geo-neutrinos Neutrino physics with the SNO+ detector 6

13 SNO+ physics goals Geo-neutrinos Darlington reactor, Canada Reactor neutrinos Neutrino physics with the SNO+ detector 6

14 SNO+ physics goals Supernova! neutrinos Geo-neutrinos Darlington reactor, Canada Reactor neutrinos Neutrino physics with the SNO+ detector 6

15 SNO+ physics goals Supernova! neutrinos Geo-neutrinos Solar neutrinos Darlington reactor, Canada Reactor neutrinos Neutrino physics with the SNO+ detector 6

16 SNO+ physics goals Supernova! neutrinos neutrino-less double beta decay Geo-neutrinos Solar neutrinos ν e Darlington reactor, Canada Reactor neutrinos Neutrino physics with the SNO+ detector 6

17 SNO+ physics goals Supernova! neutrinos neutrino-less double beta decay Geo-neutrinos Solar neutrinos ν e Darlington reactor, Canada invisible nucleon decay Reactor neutrinos Neutrino physics with the SNO+ detector 6

18 SNO+ phases Neutrino physics with the SNO+ detector 7

19 SNO+ phases Water Nucleon spring fall 2015 Neutrino physics with the SNO+ detector 7

20 SNO+ phases Scintillator Water Solar after 0νββ Nucleon spring fall 2015 Neutrino physics with the SNO+ detector 7

21 SNO+ phases Scintillator Water Solar after 0νββ Nucleon spring fall νββ 2016 Scintillator Te Neutrino physics with the SNO+ detector 7

22 SNO+ phases Scintillator Water Solar after 0νββ Reactor Geo Supernova Background studies Nucleon spring fall νββ 2016 Scintillator Te Neutrino physics with the SNO+ detector 7

23 0νββ with the SNO+ detector Neutrino physics with the SNO+ detector 8

24 0νββ with the SNO+ detector SNO+ approach: (add 0.3% of natural Te! = ~800kg of 130 Te) Trade-off energy resolution for! Higher statistics! Low backgrounds! External shielding! Scintillator self-shielding! LAB purification by distillation! Re-use existing detector! Scalable Neutrino physics with the SNO+ detector 8

25 0νββ with the SNO+ detector Loading Te in LAB SNO+ approach: (add 0.3% of natural Te! = ~800kg of 130 Te) Trade-off energy resolution for! Higher statistics! Low backgrounds! External shielding! Scintillator self-shielding! LAB purification by distillation! Re-use existing detector! Scalable Old loading technique Neutrino physics with the SNO+ detector 8

26 0νββ with the SNO+ detector Loading Te in LAB SNO+ approach: (add 0.3% of natural Te! = ~800kg of 130 Te) Trade-off energy resolution for! Higher statistics! Low backgrounds! External shielding! Scintillator self-shielding! LAB purification by distillation! Re-use existing detector! Scalable Old loading technique Dissolve telluric acid (H6 O 6 Te) in water! Combine with LAB using a surfactant! Good optical properties! Stable > 1 year explicitly demonstrated for 0.3% loading Neutrino physics with the SNO+ detector 8

27 0νββ with the SNO+ detector Loading Te in LAB SNO+ approach: (add 0.3% of natural Te! = ~800kg of 130 Te) Trade-off energy resolution for! Higher statistics! Low backgrounds! External shielding! Scintillator self-shielding! LAB purification by distillation! Re-use existing detector! Scalable Old loading technique Dissolve telluric acid (H6 O 6 Te) in water! Combine with LAB using a surfactant! Good optical properties! Stable > 1 year explicitly demonstrated New loading technique (M. Yeh et al., for 0.3% loading paper in progress) Neutrino physics with the SNO+ detector 8

28 130 Te advantages 34% natural abundance! Load high amount of natural isotope! Relatively inexpensive compared to enriched isotope! 2νββ rate is relatively low (~100 times lower than 150 Nd)! Lower background! Less sensitive to poor energy resolution! Improved optical properties! No inherent optical absorption lines! Higher intrinsic light yield! Nd-LS (0.5%): 8400γ/MeV! Te loaded LS scaled PMT response Nd loaded LS Te-LS (0.5%): 9400γ/MeV Neutrino physics with the SNO+ detector 9

29 Backgrounds Neutrino physics with the SNO+ detector 10

30 Backgrounds Cosmogenic! 60 Co, 131 I, 110m Ag, 124 Sb! 11 C Tellurium cocktail! 238 U, 232 Th, 210 Po! LAB+PPO! 238 U, 232 Th, 14 C! Thermal neutrons! Capture on H: 2.2MeV γ! Neutrino physics with the SNO+ detector 10

31 Backgrounds 8 B Solar neutrinos Tellurium 2νββ! Cosmogenic! 60 Co, 131 I, 110m Ag, 124 Sb! 11 C Tellurium cocktail! 238 U, 232 Th, 210 Po! LAB+PPO! 238 U, 232 Th, 14 C! Thermal neutrons! Capture on H: 2.2MeV γ! Neutrino physics with the SNO+ detector 10

32 Backgrounds 8 B Solar neutrinos Tellurium 2νββ! Cosmogenic! 60 Co, 131 I, 110m Ag, 124 Sb! 11 C Tellurium cocktail! 238 U, 232 Th, 210 Po! LAB+PPO! 238 U, 232 Th, 14 C! Fiducial! volume AV Thermal neutrons! Capture on H: 2.2MeV γ! Acrylic vessel (AV)! Radon daughters in AV ( 210 Pb, 210 Bi, 210 Po) PMTs External! 214 Bi and 208 Tl from AV, PMTs, H2O, ropes! Neutrino physics with the SNO+ detector 10

33 U and Th chains 2.6 MeV gamma from external 208 Tl suppressed by fiducialization! Purification techniques! LS target levels:! ~2.5 x g U /g cocktail! ~3 x g Th /g cocktail! Direct background α and β emissions! Coincidence techniques are under investigation, ex.:! β-α 214 Bi- 214 Po! β-α 212 Bi- 212 Po! α-β 212 Bi- 208 Tl Neutrino physics with the SNO+ detector 11

34 Cosmogenic isotopes Short and long living isotopes can be produced by cosmogenic activation of natural tellurium.! Isotopes (Q> 2 MeV, T1/2 > 20 days)! Rates from ACTIVIA, sea level (n,p)-flux from Armstrong and Gehrels.! For E<200 MeV: TENDL database for cross-sections. V. Lozza, J. Petzoldt, Cosmogenic activation of a natural tellurium target, Astropart. Phys. 61, Neutrino physics with the SNO+ detector 12

35 Cosmogenic isotopes Short and long living isotopes can be produced by cosmogenic activation of natural tellurium.! Isotopes (Q> 2 MeV, T1/2 > 20 days)! Rates from ACTIVIA, sea level (n,p)-flux from Armstrong and Gehrels.! For E<200 MeV: TENDL database for cross-sections. 2 stage - purification:! Above ground: 2 passes! Dissolve Te(OH) 6 in water! Re-crystalize using nitric acid! Rinse with ethanol! Below ground: 2 passes! Dissolve in 80 C water! Cool down to re-crystalize thermally! 50% yield! 3-6 months cool-down >10 4 reduction >10 2 reduction V. Lozza, J. Petzoldt, Cosmogenic activation of a natural tellurium target, Astropart. Phys. 61, Neutrino physics with the SNO+ detector 12

36 Cosmogenic isotopes Short and long living isotopes can be produced by cosmogenic activation of natural tellurium.! Isotopes (Q> 2 MeV, T1/2 > 20 days)! Rates from ACTIVIA, sea level (n,p)-flux from Armstrong and Gehrels.! For E<200 MeV: TENDL database for cross-sections. 2 stage - purification:! Above ground: 2 passes! Dissolve Te(OH) 6 in water! Re-crystalize using nitric acid! Rinse with ethanol! Below ground: 2 passes! Dissolve in 80 C water! Cool down to re-crystalize thermally! 50% yield! 3-6 months cool-down >10 4 reduction >10 2 reduction => Cosmogenic isotopes negligible V. Lozza, J. Petzoldt, Cosmogenic activation of a natural tellurium target, Astropart. Phys. 61, Neutrino physics with the SNO+ detector 12

37 SNO+ 0νββ spectrum 0 (200 mev) 2 2 Internal! U Chain U Chain Internal U chain Optimized ROI: 18.6 events/yr 2 Internal! Th Chain Internal Th chain Th Chain 5 0.3% natural Te loading! Fiducial volume cut at 3.5m (20%)! T (MeV) 212 BiPo, 214 BiPo! Optimized ROI: 18.6 events/yr 8 B ES 8 B ES (, n) U Chain Th Chain External 100% efficient tagging for separate trigger windows! x 50 for in-window! External (, n) External (, n) Cosmogenics Counts/5 y/20 kev bin (200 mev) 2 8 B ES (, n) U Chain Th Chain External T (MeV) Neutrino physics with the SNO+ detector 13

38 0.3% natural Te sensitivity Sensitivity (y) T 1/ % confidence level for! 5 years:!! T 1/2 = 9.84 x yrs!! m ββ = 66.5 mev! 1 year:!! T 1/2 = 4.27 x yrs!! m ββ = mev 90% CL 3 CL NME = 4.03 (IBM-2)! G = 3.69 x y -1! ga = Live time (y) Neutrino physics with the SNO+ detector 14

39 Conclusion SNO+: a large liquid scintillator detector with broad physics program! 0νββ = primary goal! Natural Te will be added to the liquid scintillator! 0.3% loading (~800kg 130 Te)! Possibility of increased loading in future Schedule Water level just below acrylic vessel: now.! Water running: spring 2015.! Scintillator transition: fall 2015.! Introduction of Te: start of Neutrino physics with the SNO+ detector 15

40 Back-up slides

41 Reactor and geo neutrinos ν- e Mantle geoneutrino flux ( 238 U Th) Kamioka Gran Sasso Sudbury Detection through inverse beta decay! Delayed coincidence e + annihilation and n capture! Possible in all SNO+ scintillator phases! Reactor! Geo! 3 nearby reactors dominate flux! Favourable direction and distances! U, Th and K in Earth's crust and mantle! Investigate origin of the heat produced within Earth No oscillation All reactors oscillated No Bruce All over 700km distance Geoneutrinos Eν (MeV) Neutrino physics with the SNO+ detector 17

42 Supernova neutrinos! ν-p elastic scattering events (in LAB)! SNO+ plans to be part of SuperNova Early Warning System (SNEWS) Neutrino flux on Earth! 10kpc SN, 3x10 53 erg! Quenched SN ν-p elastic scattering spectrum True SN ν-p elastic scattering spectrum Neutrino physics with the SNO+ detector 18

43 Solar Neutrinos Assuming initial Borexino-level backgrounds are reached Figure adapted from Nature , 2014 SNO SNO: LETA SNO+ Solar neutrinos probe astrophysics and elementary particle physics models:! Solar metallicity (CNO)! Neutrino oscillations (pep)! SNO+ solar neutrino goal: pep/cno solar neutrino measurement! Low 11 C background thanks to depth (100 times lower than Borexino)! Low energy threshold thanks to LAB Critically dependent on 85 Kr and 14 C background levels Neutrino physics with the SNO+ detector 19

44 Borexino / SNO+ signal/bkg comparison Borexino SNO+

45 Cosmogenics half-life ~ 106d Neutrino physics with the SNO+ detector 21