Neutrinoless Double Beta decay search with 76 Ge status and prospects with LEGEND Valerio D’Andrea on behalf of the LEGEND Collaboration Universit` a degli Studi dell’Aquila Moriond 2019 Rencontres de Moriond, La Thuile March 16 - 23, 2019
Why search for Neutrinoless Double Beta (0 νββ ) decay Powerful method to study the unknown neutrino properties Observation of 0 νββ decay implies: u u d d neutrino ν has Majorana nature W W e e ¯ ν e lepton number violation (∆ L = 2) ν M ¯ ν e e determination of ν absolute mass e W W (nuclear model dependent) u u d d 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 2 / 20
Why search for Neutrinoless Double Beta (0 νββ ) decay Powerful method to study the unknown neutrino properties Observation of 0 νββ decay implies: u u d d neutrino ν has Majorana nature W W e e ¯ ν e lepton number violation (∆ L = 2) ν M ¯ ν e e determination of ν absolute mass e W W (nuclear model dependent) u u d d Half life of 0 νββ (in case of light Majorana neutrino exchange): 1 / 2 ) − 1 = ( T 0 ν 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 2 / 20
Why search for Neutrinoless Double Beta (0 νββ ) decay Powerful method to study the unknown neutrino properties Observation of 0 νββ decay implies: u u d d neutrino ν has Majorana nature W W e e ¯ ν e lepton number violation (∆ L = 2) ν M ¯ ν e e determination of ν absolute mass e W W (nuclear model dependent) u u d d Half life of 0 νββ (in case of light Majorana neutrino exchange): 1 / 2 ) − 1 = G 0 ν × ( T 0 ν Phase Space Integral : well known quantity 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 2 / 20
Why search for Neutrinoless Double Beta (0 νββ ) decay Powerful method to study the unknown neutrino properties Observation of 0 νββ decay implies: u u d d neutrino ν has Majorana nature W W e e ¯ ν e lepton number violation (∆ L = 2) ν M ¯ ν e e determination of ν absolute mass e W W (nuclear model dependent) u u d d Half life of 0 νββ (in case of light Majorana neutrino exchange): 1 / 2 ) − 1 = G 0 ν × | M 0 ν | 2 × ( T 0 ν Phase Space Integral : well known quantity Nuclear Matrix Element : most critical ingredient, produces uncertainty in the determination of m ββ (quenching problem) 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 2 / 20
Why search for Neutrinoless Double Beta (0 νββ ) decay Powerful method to study the unknown neutrino properties Observation of 0 νββ decay implies: u u d d neutrino ν has Majorana nature W W e e ¯ ν e lepton number violation (∆ L = 2) ν M ¯ ν e e determination of ν absolute mass e W W (nuclear model dependent) u u d d Half life of 0 νββ (in case of light Majorana neutrino exchange): 1 / 2 ) − 1 = G 0 ν × | M 0 ν | 2 × ( m ββ ( T 0 ν m e ) 2 Phase Space Integral : well known quantity Nuclear Matrix Element : most critical ingredient, produces uncertainty in the determination of m ββ (quenching problem) Neutrino Effective Mass : by measuring T 0 ν 1 / 2 , m ββ can be estimate 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 2 / 20
Search for 0 νββ decay signature : sharp peak at Q -value of the decay Counts / keV Counts / keV GERDA 18-06 4 3 Experimental sensitivity 10 2 1800 2000 2 10 Energy (keV) 10 1 ⋅ enriched detectors - 53.9 kg yr 25 ν β β ⋅ 0 (T = 1.0 10 yr) 1/2 ν β β ⋅ 21 2 (T = 1.93 10 yr [EPJC 75 (2015) 9]) − 1/2 1 10 500 1000 1500 2000 Energy (keV) 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 3 / 20
Search for 0 νββ decay signature : sharp peak at Q -value of the decay Counts / keV Counts / keV GERDA 18-06 4 3 Experimental sensitivity 10 2 1800 2000 2 10 Energy (keV) 10 in case of background-free: 1 ( N bkg < 1 at full exposure) ⋅ enriched detectors - 53.9 kg yr 25 ν β β ⋅ 0 (T = 1.0 10 yr) 1/2 ν β β ⋅ 21 S ∝ a ε · M · t 2 (T = 1.93 10 yr [EPJC 75 (2015) 9]) − 1/2 1 10 500 1000 1500 2000 Energy (keV) 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 3 / 20
Status of neutrinoless double beta decay search most recent limits on the half-life, sensitivity and m ββ (at 90% C.L.) 1 / 2 [10 25 yr] 1 / 2 [10 25 yr] T 0 ν S 0 ν isotope m ββ [meV] experiment 76 Ge 9 11 104–228 Gerda 76 Ge 2.7 4.8 157–346 Majorana 130 Te 1.5 0.7 162–757 CUORE 136 Xe 1.8 3.7 93–287 EXO-200 136 Xe 10.7 5.6 76–234 KamLAND-Zen 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 4 / 20
Status of neutrinoless double beta decay search most recent limits on the half-life, sensitivity and m ββ (at 90% C.L.) 1 / 2 [10 25 yr] 1 / 2 [10 25 yr] T 0 ν S 0 ν isotope m ββ [meV] experiment 76 Ge 9 11 104–228 Gerda 76 Ge 2.7 4.8 157–346 Majorana 130 Te 1.5 0.7 162–757 CUORE 136 Xe 1.8 3.7 93–287 EXO-200 136 Xe 10.7 5.6 76–234 KamLAND-Zen ⇓ 1 / 2 ∼ 10 27 –10 28 yr and the future goal is reach sensitivities of S 0 ν improve the limit on the effective Majorana neutrino mass to m ββ ∼ 10 meV 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 4 / 20
76 Ge based 0 νββ decay experiments HPGe detectors enriched up to ∼ 88% in the 76 Ge ββ emitter (Nat. ∼ 8%) source = detector → high detection efficiency excellent energy resolution (FWHM ∼ 0 . 1% at Q ββ ) background-free experiments ( N bkg < 1 at full exposure) → S ∝ M · t RUNNING M ∼ 40 kg 1 / 2 � 10 26 yr T 0 ν 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 5 / 20
76 Ge based 0 νββ decay experiments HPGe detectors enriched up to ∼ 88% in the 76 Ge ββ emitter (Nat. ∼ 8%) source = detector → high detection efficiency excellent energy resolution (FWHM ∼ 0 . 1% at Q ββ ) background-free experiments ( N bkg < 1 at full exposure) → S ∝ M · t RUNNING M ∼ 40 kg MID TERM 1 / 2 � 10 26 yr T 0 ν M ∼ 200 kg 1 / 2 � 10 27 yr T 0 ν LEGEND-200 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 5 / 20
76 Ge based 0 νββ decay experiments HPGe detectors enriched up to ∼ 88% in the 76 Ge ββ emitter (Nat. ∼ 8%) source = detector → high detection efficiency excellent energy resolution (FWHM ∼ 0 . 1% at Q ββ ) background-free experiments ( N bkg < 1 at full exposure) → S ∝ M · t RUNNING M ∼ 40 kg MID TERM LONG TERM 1 / 2 � 10 26 yr T 0 ν M ∼ 200 kg M ∼ 1 ton 1 / 2 � 10 27 yr 1 / 2 � 10 28 yr T 0 ν T 0 ν LEGEND-200 LEGEND-1000 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 5 / 20
The Majorana Demonstrator 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 6 / 20
Majorana Demonstrator [Adv. High Energy Physics, 365432 (2014)] operating underground at the 4850’ level of the Sanford Underground Research Facility (SURF) demonstrate background low enough to justify a future 1 ton experiment detectors : p-type point-contact, 29.7 kg of 88% enr. 76 Ge, 14.4 kg of nat Ge energy resolution : 2.5 keV FWHM at 2039 keV (best in the field) low background : 2 independent cryostat made of ultra-clean electroformed Cu and a compact Cu and Pb shield with active muon veto 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 7 / 20
Majorana Demonstrator : background rejection Multi Site Events p-type point-contact detectors have a localized weighting potential the ampitude of current pulse is reduced for a multi-site event w.r.t. a single-site event with the same energy Alpha Background this background (e.g. 210 Po) is on surfaces close to the point contact charge trapped at passivated surface, slowly released into bulk a distinctive waveform allows a high-efficiency cut (99%) 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 8 / 20
Majorana Demonstrator : results Data releases: 2017 Release: 9.95 kg · yr [PRL 120 132502 (2018)] 2018 Release: 26 kg · yr [Neutrino 2018, arXiv:1902.02299] Full exposure results (26.0 kg · yr) Background : 15 . 4 ± 2 . 0 cts/(FWHM · t · yr) Median Sensitivity : 1 / 2 = 4 . 8 · 10 25 yr (90% C.L.) S 0 ν Limit on 0 νββ decay : 1 / 2 > 2 . 7 · 10 25 yr (90% C.L.) T 0 ν Lowest background configuration (21.3 kg · yr) : Background : 11 . 9 ± 2 . 0 cts/(FWHM · t · yr) (4 . 7 ± 0 . 8) · 10 − 3 cts/(keV · kg · yr) ⇒ 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 9 / 20
The Gerda Experiment 0 νββ decay search with 76 Ge Valerio D’Andrea (Universit` a dell’Aquila) Moriond 2019 - La Thuile 10 / 20
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