# Presentation: 825238

## SNO+

- PANIC Neutrino Satellite Meeting
- Santa Fe, NM
- October 29, 2005

*Mark Chen*
- Queen’s University

## Fall 04 to Dec 06: SNO Phase III
3He proportional counter array now in place
dedicated Neutral Current Detectors (NCDs)
taking production data
data taking end date: 31 Dec 2006
will bring total uncertainty on 8B solar  NC signal below 5%
physics with heavy water will be complete
in 2007, heavy water will be returned to Atomic Energy of Canada Limited

what should be done with the detector after?

- 3He proportional counter array now in place
- dedicated Neutral Current Detectors (NCDs)
- taking production data
- data taking end date: 31 Dec 2006
- will bring total uncertainty on 8B solar  NC signal below 5%
- physics with heavy water will be complete
- in 2007, heavy water will be returned to Atomic Energy of Canada Limited
*what should be done with the detector after?*

- Beyond SNO

## SNO plus liquid scintillator → physics program
pep and CNO low energy solar neutrinos
tests the neutrino-matter interaction, sensitive to new physics
geo-neutrinos
240 km baseline reactor oscillation confirmation
supernova neutrinos
double beta decay?

*pep* and CNO low energy solar neutrinos
- tests the neutrino-matter interaction, sensitive to new physics
- geo-neutrinos
- 240 km baseline reactor oscillation confirmation
- supernova neutrinos
- double beta decay?

- Fill with Liquid Scintillator

## complete our understanding of neutrinos from the Sun
		pep, CNO, 7Be
probe the neutrino-matter interaction which is sensitive to new physics

- complete our understanding of neutrinos from the Sun
- 		*pep*, CNO, 7Be
- probe the neutrino-matter interaction which is sensitive to new physics

- Low Energy Solar Neutrinos

- from Peña-Garay

- vacuum-matter transition

- best-fit oscillation parameters suggest MSW occurs
- but we have no direct evidence of MSW
- day-night effect not observed
- no spectral distortion for 8B ’s

## Will SNO Phase III Show MSW?

- Day-Night Effect
- SNO I-II combined Ae = (+3.7 ± 4.0)%
- Super-K equivalent Ae = (+3.3 ± 3.7)%
- best-fit oscillation parameters predict: Ae = +2.7%
- 		where Ae = 2*(N−D)/(N+D) for the electron flavour
- Spectral Distortion
- NCD phase breaks
- 	CC-NC correlations
- helps reduce systematics
- 	at low energies
- still, will be difficult to see
- 	spectral distortion

## SSM pep flux:
	uncertainty ±1.5%
known source → precision test

*pep* 

- SNO CC/NC

- m2 = 8.0 × 10−5 eV2
- tan2 = 0.45

- SSM pep flux:
- 	uncertainty ±1.5%
- known source → precision test

- Survival Probability Rise

- sensitive to new physics:
-  non-standard interactions
-  solar density perturbations
-  mass-varying neutrinos
-  CPT violation
-  large 13
-  sterile neutrino admixture

- improves precision on 12

*observing the rise confirms MSW and that we know what’s going on*

- stat + syst + SSM errors estimated

## non-standard interactions
MSW is linear in GF and limits from -scattering experiments  g2 aren’t that restrictive
mass-varying neutrinos

- MSW is linear in GF and limits from -scattering experiments  g2 aren’t that restrictive
- mass-varying neutrinos

- Friedland, Lunardini, Peña-Garay, hep-ph/0402266

- Barger, Huber, Marfatia, hep-ph/0502196

- pep solar neutrinos are at
- the “sweet spot” to test for new physics

- New Physics

- NC non-standard Lagrangian

- CHARM limit

- Miranda, Tórtola, Valle, hep-ph/0406280

**solar density fluctuations:**
- Guzzo, Reggiani, de Holanda, hep-ph/0302303
- see also Burgess et al., hep-ph/0310366
-    and also Balantekin et al.

## Event Rates (Oscillated)

**3600 pep/year/kton >0.8 MeV**

**2300 CNO/year/kton >0.8 MeV**

- 7Be solar neutrinos

- using BS05(OP)
- and best-fit LMA

- resolution with
- 450 photoelectrons/MeV

## 11C Cosmogenic Background

- these plots from the KamLAND proposal

**muon rate in KamLAND: 26,000 d****−****1**** compared with **
**SNO: 70 d****−****1**

- 11C Cosmogenic Background

## Real KamLAND Backgrounds

**external**

- pep window

## radiopurity requirements
40K, 210Bi (Rn daughter)
85Kr, 210Po (seen in KamLAND) not a problem since pep signal is at higher energy than 7Be
U, Th not a problem if one can repeat KamLAND scintillator purity
14C not a problem since pep signal is at higher energy

- 40K, 210Bi (Rn daughter)
- 85Kr, 210Po (seen in KamLAND) not a problem since *pep* signal is at higher energy than 7Be
- U, Th not a problem **if** one can repeat KamLAND scintillator purity
- 14C not a problem since pep signal is at higher energy

*pep* Solar  Backgrounds

## SNO+ pep

- SNOLAB is the only deep site that exists where the *pep* solar neutrinos could be measured with precision.
- First observation of the CNO solar neutrino would be important for astrophysics.

|  | sensitive probe neutrino-matter interaction? | precision measurement (SSM flux)? |
| --- | --- | --- |
| pp |  |  |
| 7Be |  |  |
| pep |  |  |

## Geo-Neutrinos

- can we detect the antineutrinos produced by natural radioactivity in the Earth?

- Image by: Colin Rose,
- Dorling Kindersley

- radioactive decay of heavy elements (uranium, thorium) produces antineutrinos

- assay the entire Earth by
- looking at its “neutrino glow”

- e

## Earth’s Heat Flow

- models of Earth’s heat sources suggest that radioactivity contributes 40-100% towards Earth’s total heat flow

- the radiogenic portion is not
- that well known!

- geophysicists want to understand Earth’s thermal history

- H.N. Pollack, S.J. Hurter and J.R. Johnson,
*Reviews of Geophysics*** 31**(3), 267-280, 1993

## Geo-Neutrino Signal

- terrestrial antineutrino event rates:
-  Borexino: 10 events per year (280 tons of C9H12) / 29 events reactor
-  KamLAND: 29 events per year (1000 tons CH2) / 480 events reactor
-  SNO+: 64 events per year (1000 tons CH2) / 87 events reactor

- SNO+ geo-neutrinos and reactor background

- _KamLAND_ geo-neutrino
- detection...July 28, 2005 in Nature

*based on Rothschild, Chen, Calaprice*
*Geophys. Res. Lett. ****25****, 1083 (1998)*

- geo- in
- SNO+

- KamLAND

## Fundamental Geophysics

- SNO+ geo-neutrinos: a good follow-up to KamLAND’s first detection
- potential to really constrain the radiogenic heat flow
- potential for geochemistry (U and Th separation)
- tests models of Earth’s chemical origin
- simple geological configuration (smaller uncertainties)

## 1 kton organic liquid scintillator would maintain excellent supernova neutrino capability
 e + p 				    [large rate]
 e + 12C (CC)
 e + 12C (CC)
 x NC excitation of 12C (NC)
 x + p elastic scattering (NC)	    [large rate]
see Beacom et al., PRD 66, 033001(2002)

-  e + p 				    [large rate]
-  e + 12C (CC)
-  e + 12C (CC)
-  x NC excitation of 12C (NC)
-  x + p elastic scattering (NC)	    [large rate]
- see Beacom *et al.*, PRD **66**, 033001(2002)

- Supernova Neutrinos

## leverage existing investment in SNO to get new physics for relatively low cost

SNO+ is uniquely positioned to make several  measurements (due to depth, geology, appropriate distance to reactors, low backgrounds)

costs are:
liquid scintillator procurement
mechanics of new configuration, AV certification
fluid handling and safety systems
scintillator purification
electronics/DAQ spares or upgrades?

- SNO+ is uniquely positioned to make several  measurements (due to depth, geology, appropriate distance to reactors, low backgrounds)
- costs are:
- liquid scintillator procurement
- mechanics of new configuration, AV certification
- fluid handling and safety systems
- scintillator purification
- electronics/DAQ spares or upgrades?

- Extension of SNO Science

## SNO+ Technical

- liquid scintillator selection and design
- AV engineering
- cover gas, fluid handling, safety
- scintillator purification
- electronics/DAQ (spares, upgrade...)

**to be tackled next year**

## SNO+ Technical Issues

- liquid scintillator selection
- compatibility with acrylic vessel
- high light yield, long attenuation length
- reversing the acrylic vessel mechanics
- SNO: AV contains heavy water, must hold up
- SNO+: AV contains scintillator,  < 1 g/cm3, must hold down

## Acrylic Vessel Hold-down

- “rope net” being designed to hold down 15% density difference (buoyancy)

**SNO**

**SNO+**

## Scintillator Design

- high density (>0.85 g/cm3)
- chemical compatibility with acrylic
- high light yield, long attenuation and scattering lengths
- high flash point
- low toxicity
- low cost

## Linear Alkylbenzene

## LAB Advantages

**1**

**1**

**0**

- compatible with acrylic (e.g. Bicron BC-531 is 95% LAB)
- “BC-531 is particularly suited for intermediate sized detectors in which the containers are fabricated with common plastic materials such as PVC and acrylics.  The scintillator provides over twice the light output of mineral oil based liquids having similar plastic compatibility.”
- high flash point 130 °C
- low toxicity                                  (pseudocumene 2 4 0)
- cheap, (common feedstock for LAS detergent)
- plant in Quebec makes 120 kton/year, producer has been very accommodating
- high purity

## SNO+ Monte Carlo

- light yield simulations

| KamLAND scintillator in SNO+ | 629 ± 25 pe/MeV |
| --- | --- |
| above no acrylic | 711 ± 27 pe/MeV
 |
| KamLAND scintillator and 50 mg/L bisMSB | 826 ± 24 pe/MeV
 |
| above no acrylic | 878 ± 29 pe/MeV |
| KamLAND (20% PC in dodecane, 1.52 g/L PPO) | ~300 pe/MeV for 22% photocathode coverage |

- SNO+ has 54% PMT coverage; acrylic vessel only diminishes light ouput by ~10%

## LAB Scintillator Optimization

- “safe” scintillators

**LAB has 75% greater light yield **
**than KamLAND scintillator**

## Light Attenuation Length

**Petresa LAB**
**as received**
**attenuation length exceeds 10 m**

- ~10 m

- preliminary measurement

## Default Scintillator Identified

- LAB has the smallest scattering of all scintillating solvents investigated
- LAB has the best acrylic compatibility of all solvents investigated
- density  = 0.86 g/cm3 acceptable
- ...default is Petresa LAB with 4 g/L PPO, wavelength shifter 10-50 mg/L bisMSB
- because solvent is undiluted and SNO photocathode coverage is high, expect light output (photoelectrons/MeV) ~3× KamLAND

## SNO+ is an NSERC-funded R&D project
SNO+ endorsed by the SNOLAB Experiment Advisory Committee

“Exploit low-energy solar neutrinos for precision neutrino physics 
and stellar physics”

“We endorse development toward SNO+ for pep solar neutrinos 
and geo-neutrinos.  We applaud the technical progress in developing 
the liquid scintillator and encourage continued R&D, development of 
the necessary collaboration and proposal to secure funding. We look 
forward to a receiving a full technical proposal.”

- SNO+ endorsed by the SNOLAB Experiment Advisory Committee
- “Exploit low-energy solar neutrinos for precision neutrino physics
- and stellar physics”
- “We endorse development toward **SNO+** for pep solar neutrinos
- and geo-neutrinos.  We applaud the technical progress in developing
- the liquid scintillator and encourage continued R&D, development of
- the necessary collaboration and proposal to secure funding. We look
- forward to a receiving a full technical proposal.”

- SNO+ Status

## SNO+ in 2006

- SNO+ in Fall 2005 “proof of principle”
- liquid scintillator identified
- preliminary design to holddown the acrylic vessel
- need more collaborators
- project management
- scintillator purification R&D
- electronics/DAQ plans...
- full TDR by Fall 2006
- including process engineering and AV mechanics
- proposals to funding agencies by Fall 2006

## SNO+ in 2007

- start of capital funding
- construction of hold-down net
- access detector after D2O removed
- scintillator procurement contracts
- ...and *on to converting SNO into an operating, **multi-purpose**, liquid scintillator detector with **unique** physics capabilities*

## Queen’s
	M. Chen*, M. Boulay, X. Dai, K. Graham, A. Hallin, C. Hearns, C. Kraus,    C. Lan, J.R. Leslie, A. McDonald, V. Novikov, P. Skensved, A. Wright,        U. Bissbort, S. Quirk
Laurentian
	D. Hallman, C. Virtue 
SNOLAB
	B. Cleveland, R. Ford, I. Lawson
Brookhaven National Lab
	A. Garnov, D. Hahn, M. Yeh
Los Alamos National Lab
  	A. Hime
LIP Lisbon
	J. Maneira

potential collaborators from outside SNO (Italy, Germany, Russia) have indicated some interest
new collaborators welcome

- 	M. Chen*, M. Boulay, X. Dai, K. Graham, A. Hallin, C. Hearns, C. Kraus,    C. Lan, J.R. Leslie, A. McDonald, V. Novikov, P. Skensved, A. Wright,        U. Bissbort, S. Quirk
- Laurentian
- 	D. Hallman, C. Virtue
- SNOLAB
- 	B. Cleveland, R. Ford, I. Lawson
- Brookhaven National Lab
- 	A. Garnov, D. Hahn, M. Yeh
- Los Alamos National Lab
-   	A. Hime
- LIP Lisbon
- 	J. Maneira
- potential collaborators from outside SNO (Italy, Germany, Russia) have indicated some interest
- new collaborators welcome

- SNO+ Collaboration

- only a subset of the SNO collaboration will continue with SNO+

## DepthMatters!