Background identification for neutrinoless double beta decay detection with the DARWIN experiment Yanina Biondi on behalf of the DARWIN collaboration, Universität Zürich 12.09.2019 www.darwin-observatory.org
THE WIMP LANDSCAPE 2019 Spin independent Cross Section for WIMPs 38 − The highest sensitivity to WIMPs above 10 CRESST-II 5GeV/C 2 comes from experiments using DAMIC 39 − ] 10 2 DAMA/I SI WIMP-nucleon cross section [cm liquid noble gases are as target (Xe,Ar). 40 − 10 DAMA/Na CDMSlite PICO-60 CF3I CRESST-II 41 − 10 DarkSide-50 (nq) Lower cross sections will require much PICO-60 C3F8 42 − 10 larger detectors. DARWIN with 40t aims to SuperCDMS 43 − 10 DarkSide-50 increase 100-fold the current sensitivity XENON100 44 − 10 PandaX-II -floor ν Current limits 45 − LUX 10 XENON1T 46 − 10 Future sensitivities XENONnT / LZ (proj) − 47 10 DARWIN Ultimate reach before reaching the neutrino 48 − 10 -floor (Billard, 2014) floor ν 49 − 10 1 2 3 5 10 20 30 50 100 200 500 1000 2 WIMP mass [GeV/c ]
2019 XENON EVOLUTION 5.9 t 2017 2 t 2012 100 kg 2008 10 kg XENON100 XENON10 XENON1T XENONnT � 3
2019 XENON EVOLUTION 5.9 t 2025 2017 40 t 2 t 2012 100 kg 2008 10 kg XENON100 XENON10 XENON1T XENONnT DARWIN � 3
DARWIN DESIGN: AMBITIOUS 50 TONS LXE TPC OBSERVATORY ✦ Dual-phase Time Projection Chamber (TPC). ✦ 50t total (40 t active) of liquid xenon (LXe). ✦ Dimensions : 2.6 m diameter and 2.6 m height. ✦ T wo arrays of photosensors (top and bottom). ✦ PMTs, SiPM and other technologies are being considered ✦ Drift field ~0.5 kV/cm. ✦ Low-background double-wall cryostat. ✦ PTFE reflector panels & copper shaping rings. ✦ Outer shield filled with water (14 m diameter) ✦ Neutron veto For more details see Carla Macolino General talk DARWIN Collaboration, JCAP 1611 (2016) 017 � 4 at 16:10 room 202
DARWIN SCIENCE PROGRAM: MORE THAN DARK MATTER SEARCHES Given its projected low background and large mass, DARWIN will be sensitive to other rare physics processes such as: Solar Axions and Axion Like Particles ER Low energy Solar Neutrinos: pp, 7 Be Neutrinoless Double Beta Decay Coherent Neutrino Nucleus Scattering NR Supernova Neutrinos � 5
DARWIN SCIENCE PROGRAM: MORE THAN DARK MATTER SEARCHES 20/08/2019 2nbb (1).svg Given its projected low background and large mass, DARWIN will be sensitive to other rare physics processes such as: e − Solar Axions and Axion Like Particles W − ER Low energy Solar Neutrinos: pp, 7 Be ν e = ν e ¯ W − Neutrinoless Double Beta Decay e − Yanina Biondi Coherent Neutrino Nucleus Scattering Exchange of a Majorana neutrino NR ℒ L ( x ) = − 1 c ( x ) + h . c . 2 ∑ l ′ � l ( ν lL ) ν l ′ � L ( x ) M L Supernova Neutrinos file:///Users/yanina/Downloads/2nbb (1).svg 1/1 l ′ � , l � 5
NEUTRINOLESS DOUBLE BETA DECAY: A WINDOW TO NEW PHYSICS DARWIN provides the opportunity to study this process for free 136 Xe has a natural abundance of 8.9% in natural Xe, ~3.5 t in 40t 136 Xe Q = (2457.83 ± 0.37) keV Above the region of interest for WIMPs Expected Energy resolution of ~0.8% at 2.5 MeV M ⋅ t T 0 ν 1/2 ∝ f ⋅ a ⋅ ϵ ⋅ Ultra-low background environment achieved via B ⋅ Δ E xenon purification and screening campaigns Signal coverage ~ 0.76 for FWHM Natural abundance 8.9% Efficiency 90% � 6
ENERGY RESOLUTION IN LXE TPC XENON Collaboration The XENON1T Collaboration reached an unprecedented energy resolution, below 1% at Q-value, in a dual phase TPC. Improvements for high-energies: - Saturation Correction - Peak clustering Energy resolution fit - After-pulse removal σ a E = + b E [ keV ] � 7
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Materials Contaminants in LXe 2 νββ Cosmogenic Solar neutrinos � 8
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Mostly gammas from detector components Kenji Ozone PhD Thesis, 2015 with low attenuation in LXe due to their Materials energy Contaminants in LXe 2 νββ Cosmogenic Solar neutrinos � 8
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Mostly gammas from detector components Kenji Ozone PhD Thesis, 2015 with low attenuation in LXe due to their Materials energy Contaminants in LXe 222 Rn in the LXe 2 νββ Cosmogenic Solar neutrinos � 8
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Mostly gammas from detector components Kenji Ozone PhD Thesis, 2015 with low attenuation in LXe due to their Materials energy Contaminants in LXe 222 Rn in the LXe T 1/2 = (2.165 ± 0.075) × 10 21 y 2 νββ Cosmogenic Solar neutrinos � 8 EXO Collaboration, J.B. Albert et al., Phys. Rev. C 89 (2014) 015502.
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Mostly gammas from detector components Kenji Ozone PhD Thesis, 2015 with low attenuation in LXe due to their Materials energy Contaminants in LXe 222 Rn in the LXe T 1/2 = (2.165 ± 0.075) × 10 21 y 2 νββ 137 Xe from cosmogenic activation underground Cosmogenic Solar neutrinos � 8 EXO Collaboration, J.B. Albert et al., Phys. Rev. C 89 (2014) 015502.
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Mostly gammas from detector components Kenji Ozone PhD Thesis, 2015 with low attenuation in LXe due to their Materials energy Contaminants in LXe 222 Rn in the LXe T 1/2 = (2.165 ± 0.075) × 10 21 y 2 νββ 137 Xe from cosmogenic activation underground Cosmogenic Irreducible 8 B solar neutrinos Solar neutrinos � 8 EXO Collaboration, J.B. Albert et al., Phys. Rev. C 89 (2014) 015502.
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Critical components for the background are fully simulated in detail Materials Elements under consideration: Photosensors (PMT, SiPM,…) XENON Collaboration, Eur. Phys. J. C (2017) 77: 881. Materials Mass [kg] 226 Ra* 228 Th* 60 Co* 1 per cm 2 Outer cryostat 2 per unit 5717.7 <0.09 0.23 <0.03 Ti * mBq/kg Electronics 301.2 0.07 <0.06 <0.02 PTFE 1199.3 <0.035 <0.026 <0.02 Cu 7.6 17.7 3 <0.10 Cirlex 5.7 <0.0075 <0.0092 - SiPM 1 Field shaping rings Photosensors 378.8 0.6 0.6 0.84 PMT 2 Study performed by the engineering group to optimise size and materials for the Photosensors holder cryostat Filler Volume PTFE panels Inner cryostat � 9 LZ Collaboration, Physics 96 (2017): 1-10.
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Critical components for the background are fully simulated in detail Materials Elements under consideration: Photosensors (PMT, SiPM,…) XENON Collaboration, Eur. Phys. J. C (2017) 77: 881. Materials Mass [kg] 226 Ra* 228 Th* 60 Co* 1 per cm 2 Outer cryostat 2 per unit 5717.7 <0.09 0.23 <0.03 Ti * mBq/kg Electronics 301.2 0.07 <0.06 <0.02 PTFE 1199.3 <0.035 <0.026 <0.02 Cu 7.6 17.7 3 <0.10 Cirlex 5.7 <0.0075 <0.0092 - SiPM 1 Field shaping rings Photosensors 378.8 0.6 0.6 0.84 PMT 2 Study performed by the engineering group to optimise size and materials for the Photosensors holder cryostat Filler Volume PTFE panels Inner cryostat � 9 LZ Collaboration, Physics 96 (2017): 1-10.
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Background contribution per material component Materials 40 tonnes, no fiducial cut Cryostat was optimised with Ti material and stiffeners Single Scatter ~ 15 mm resolution (very conservative) for low mass ~99% of signal events end in SS spectra Different photosensors: SiPM, PMTs (shown below) Superellipsoid fiducial volume cut Background counts 6 tonnes Preliminary � 10
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE 137 Xe from cosmogenic activation underground Cosmogenic e − 136 Xe 137 Xe 137 Cs 3.82 min 30.1 year 137 Xe beta decays with a Q-value of 4173 keV P 137 Ba Uniform background inside the detector Stable Primary background from betas ν ¯ N Yanina Biondi Neutrons from natural radioactivity in the rock/concrete Neutron from natural radioactivity in detector’s materials Production rate for 137 Xe in LNGS: 6.7 atoms/t/y Muon induced neutrons in the rock and concrete Muon induced neutrons in the materials of the detector 137 Xe is mainly produced when muon-induced neutrons are captured by 136 Xe � 11
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE Contaminants in LXe The noble gas 222 Rn (T 1/2 ≈ 3.8 days) from 226 Ra (T 1/2 ≈ 1600 years), mixes with the xenon with beta decays from this chain. 214 Pb and daughters a dhere to material surfaces ( plate-out ) and can lead to ( α , n) reactions Contamination assumption 0.1 μ Bq / kg XENON Collaboration Bi-Po : 99.8% tagging e ffi ciency and suppression XENON Collaboration, Eur. Phys. J. C (2017) 77:358 Removal by cryo-distillation columns More info in Michael Murra’s Poster � 12
BACKGROUND CONTRIBUTIONS AROUND 136 XE Q-VALUE 2 νββ Solar neutrinos Bahcall, J. Serenelli, A.,Basu, S Irreducible 8 B solar neutrinos Astrophys. J . 621 : L85–L88 Double beta decay of two neutrons: ν + e → ν + e ( Z , A ) → ( Z + 2, A ) + e − 1 + e − 2 + ¯ ν e 1 + ¯ ν e 2 Neutrino electron scattering with the target LXe ϕ ν e = 5.82 × 10 6 cm − 2 s − 1 P e = 0.534 σ ν e ( σ νμ ) = 59.4 × 10 − 45 (10.6 × 10 − 45 ) cm 2 Baudis, L., et al. "Neutrino physics with multi-ton scale liquid xenon detectors." JCAP 2014.01 (2014): 044. � 13
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