SNO+ plans to begin taking data in 2014. The main purpose of the SNO+ experiment will be the search for neutrinoless double beta. Electron recoil en backg.
Neutrinoless double beta decay ith SNO+ Prospects SolarwNeutrino Nasim Fatemighomi for the SNO+ collabora@on
Erin O’Sullivan, on beh
Queen’s University, Kingston, Ontario, Canada
Queen’s University, Kingston, On
SNO+: A Multipurpose
Double beta decay physics
SNO+ Solar Neutrino Sens
The SNO+ detector Neutrino Detector
SNO+ situated at 6800 underground at SNOLAB, Situatedis 6800 feet underground in thefeet SNOLAB facility in Sudbury, Ontario, the SNO+ is the nextof the experiment is to Sudbury, Ontario. The experiment primary goal generation of the SNO project. Still under construction, search for to0begin νββ taking with e-‐loaded liquid scin@llator. SNO+ plans dataTin 2014.
Discovery of neutrinoless double beta decay (0νββ) will answer:
Advantages%of%130Te%
Ø If neutrinos are Majorana or Dirac Ø What the scale of the neutrino mass is Ø If neutrino masses follow inverted or normal hierarchy ( A, Z ) → ( A, Z + 2) + 2e −
Acrylic Vessel - 12 m diameter
This process violates lepton number conserva@on and the rate is given by: hm⌫ i 2 0⌫ 1 4 (T ) = G0⌫ gA |M 0⌫ |2 | | 1/2 m
Other physics goals: • 34%&natural&abundance&& Ø Low energy solar neutrinos Ø Reactor/geo an@-‐neutrinos – Can&load&high&amount&of&natural&isotope& Ø Supernova neutrinos – Rela6vely&inexpensive&compared&to&an&enriched& Where T is the half-‐life, G is the phase space factor, g is the Axial-‐Vector coupling constant of tisotope& he weak interac@on, is the effec@ve neutrino mass. • 2νββ&rate&is&low&(~&100&6mes& SNO+ Te-‐loaded liquid scin9llator LAB+PPO+Surfactant+H2O+Te Liquid scin@llator approach: 150 Ø Economical wsmaller&than& ay to build a detector with a large Nd)& amount of 0νββ isotope Ø Low background environment can be achieved (purifica@on, scaled PMT response self-‐shielding and β-‐α rejec@on techniques) • No&inherent&op6cal& At its ini@al phase, SNO+ plans to run with 0.3% natural Te absorp6on&lines& (~ 790 kg of Te). MSB Peryl The advantage of Te is: Ø High natural abundance (34%) – No&a&priori&limit&on&loading& The Te-‐loaded cocktail: Nd Ø Low two neutrino double beta decay half-‐life Ø LAB + wavelength shiiers (factor of 100 lower than Nd, the previous isotope of choice) Ø H2O concentra6on& Ø No natural absorp9on peaks Ø A surfactant (Liquid scintillator - 780 t LAB) Phototube sphere
1/2
Electron recoil energy spectrum of expected signal and backgrounds in the solar neutrino phase
- ~ 9500 20 cm Hamamatsu PMTs
Statistical errors (signal with backgrounds) o solar neutrino flux measurements after one years of running:
Water shielding
e
- 1700 t inner - 5300 t outer
(stat)! pep! 8B! 7Be! pp! CNO!
Urylon liner
A
- radon seal
The main purpose of the SNO+ experiment will be the search for neutrinoless double beta decay with tellurium-130.
1 year! 9.1%! 7.5%! 4%!
2y 6. 5. 2.
A few %?! ~ 15%?!
Assuming Borexino-level backgrounds are reached!
A description of the 3+1 light How behav sterile neutrino model
130
The 3+1 sterile neutrino model described here is for a very light sterile neutrino that would affect the Electon recoil energy spectrum of expected signal and backgrounds in the oscillation behaviour in the solar neutrinoless double beta decay phase neutrino energy range. It is based on The SNO+ liquid scintillator cocktail will consist of: 150 the 2+1 sterile neutrino model first Linear Alkylbenzene (a liquid scintillator) + PPO (a proposed in de Holanda and wavelength shifting fluor) + 130Te (in the neutrinoless Smirnov 2002, and more recently double beta decay phase only) A glossa Ø Natural 2013D09D19& 9& Nasim&Fatemighomi,&Queen’s&University& explored in de Te Holanda and model te Other SNO+ physics goals include: Smirnov 2010. This 3+1 sterile ν0: the m -low energy solar neutrinos, specifically the CNO and neutrino model accounts for the sterile n pep neutrinos (discussed in this poster) three active neutrinos and proposes α: the ac (analogo -reactor neutrinos: a measurement of neutrino mixing one sterile neutrino species (ν0) R: the r parameters which can mix with one of the active the activ How multi-component much of the Earth’s heatingscintillator is due * -geoneutrinos: Based on model extrapolating labo neutrino mass eigenstates (ν1). The differen to radioactivity? How much comes from the core and measurements of absorption, emission and intrinsic of ofboth 3+1 modellight takes yield the form the the Depicted inf how much from the mantle? survival prob but properly neutrino sur mixture and individual constituents. Validity2+1ofmodel, the model wasaccounts verifiedelectron by neutrinos: information on neutrinosurv Purifica@on: mul9-‐stage dis9lla9on of the liquid scin9llator, re-‐crystalliza9on o-supernova f the telluric acid gives using nitric acid for θ13. LMA model matter interactions as well to as known the core-collapse The ana pep neu performance estimates scintillator experiments and from an (solid green). and removing surface impuri@es with ethanol, QuadraSil scavengers to purify the surfactant supernova mechanism
130
Backgrounds
Studies suggest average light levels of ~200-300 hits/Me
8B solar neutrino and 2νββ
Internal radioac9vity and cosmogenics: reduced by Ø
light production from one liter of scintillator contained in an acrylic co
Ø In-‐situ analysis: All 214Bi-‐214Po (238U) and 212Bi-‐212Po (232Th) events that are in two separate trigger windows can deployed in the SNO detector during 2008. be tagged and removed. The rest of the events (pile-‐up) are removed via likelihood ra9o and PMT 9me residuals
External γs and radon:
60Co was removed by factor of
Ø Removing background events by fiducializa9on Ø PMT 9me residuals can be used to reduce AV 208Tl Ø Reducing radon ingress with a new sealed cover gas system
>104 aier two passes
α-‐n: Neutrons produced by 210Po and 214Po/212Po α interac@on with 13C can interact with protons and give 2.2 MeV γs.
Sensi9vity with 0.3% Te loading
Op@mized region of interest 22.2 expected background events/year
UK)CoOleading)Development)Group)
Expected Average Spectra of Contributing Backgrounds for Two Live Years of Data
SNO+ future
0ν
25
90% CL T1/2 Sensitivity (10 y)
Ongoing R&D towards future SNO+ phases...
11 10 9
1st phase (now!)
8
5
0.3%
4 3
Expected energy spectrum
1
1.5
2
2.5
3
3.5
4
4.5 5 Live time (y)
Half-‐life sensi@vity @90%CL
Figure 4: The sensitivity of SNO+ as a function of live time.
[1] J. Barea et al. Phys. Rev. C 87, 014315 (2013) [2] J. Ko@la, F. Iachello. Phys. Rev.C 85, 034316 (2012) 104 104 103 103 eV bin
Ø 200 hits/MeV light yield Ø Factor of 50 reduc@on of BiPo pile-‐up events Ø =200 meV[1][2] Ø 3.5 m fiducial volume cut
Future phase
7 6
Sum
Sum, background 0ν β β (80 meV)
0.5%
1%
Increasing sensi@vity by
3%
Jeff)Hartnell,)IoP/RHUL,)Apr.)'14)
Ø Higher loading Ø Increasing light yield: improving loading techniques and using higher QE PMTs Ø Using a low background bag to reduce external background
5%
31)
