K. Zuber, TU Dresden INT, Double beta decay experiments

Transcription

1 , TU Dresden INT, Double beta decay experiments

2 Double beta decay (A,Z) (A,Z+2) +2 e - + 2ν e (A,Z) (A,Z+2) + 2 e - - 2νββ 0νββ Unique process to measure character of neutrino The smaller the neutrino mass the longer the half-life Neutrino mass measurement via half-life measurement Requires half-life measurements well beyond yrs!!!! Only 35 isotopes in nature are able to do that!

3 Example - Ge76

4 0νββ Any L=2 process can contribute to 0νββ R p violating SUSY V+A interactions Extra dimensions (KK- states) Leptoquarks Double charged Higgs bosons Compositeness Heavy Majorana neutrino exchange Light Majorana neutrino exchange... Nice interplay with LHC 1 / T 1/2 = PS * NME 2 *ε 2

5 Light Majorana neutrinos ε m ν = 2 U ei m ν i i 1 / T 1/2 = PS * NME 2 * (<m ν > / m e ) 2 Schechter and Valle 1982: Independent of mechanism for neutrinoless DBD Majorana neutrino mass will appear in higher order!

6 3 Flavour mixing (PMNS) cosθ 12 sinθ 12 0 U = sinθ 12 cosθ Neutrinos mix as oscillation experiments have shown, hence Leptonic mixing (PMNS) matrix (including Majorana character) cosθ 13 0 sinθ 13 e iδ cosθ 23 sinθ 23 0 e iα 1 0 sinθ 13 e iδ 0 cosθ 13 0 sinθ 23 cosθ e iα 2 solar reactor atmospheric 2 m ν = U ei m ν i = c 12 2 c 2 13 m 1 + s 2 12 c 13 i From oscillation experiments 2 e iα 1 m + s e iα 2 m 3 sin 2 2θ 23 > 0.9 (90%CL), best fit θ 23 =45 sin 2 2θ 13 = 0.09 (90%CL), θ 13 = 9 normal inverted sin 2 θ 12 = 0.32,θ 12 =

7 Mass hierarchies and DBD 76 Ge T 1/2 = 1.19 x yr 1 H.V. Klapdor-Kleingrothaus et al. Phys. Lett. B 586, 198 (2004) 2 Claim of evidence yrs yrs yrs yrs 3 normal inverted 1.) Is the claimed evidence correct? GERDA phase I 2.) Can we probe the inverted hierarchy? 3.) What about the normal hierarchy?

8 Mass hierarchies and DBD With the known oscillation results everything is fixed General dependence Current data M. Lindner, A.. Merle, W. Rodejohann, Phys. Rev. D 73, (2006)

9 Mass hierarchies Adding a sterile Plot get s turned around... Barry, Rodejohann, Zhang (2011), Giradi, Meroni, Petcov (2013), Giunti, Zavanin, arxiv:

10 Other mass determinations Beta decay: Cosmology: Ω ν h 2 KATRIN Sensitivity about 0.2 ev m ν < 0.23eV (95%CL) + oscillation parameters

11 Cosmology Hint for NH? m ν = ± 0.081eV On 1 sigma level IH excluded R. Battye, A. Moss, PRL 112, (2014) Dell Oro et al., arxiv: , N. Palanque-Delabrouille et al. JCAP 1502,045 (2015)

12 Spectral shapes 0νββ: Peak at Q-value of nuclear transition Sum energy spectrum of both electrons Measured quantity: Half-life 1 / T 1/2 = PS * NME 2 * (<m ν > / m e ) 2 Energy resolution Experimental sensitivity depends on T 1 1/ 2 aε Mt ΔEB T 1 1/ 2 aεmt (BG limited) (BG free) Background If background limited m ν 4 ΔEB Mt

13 Perfect world experiment No background δ function as peak 100 % abundance 100% detection efficiency Infinite measuring time Infinite mass T 1 1/ 2 aε Mt ΔEB Life is easy, the rest is just details Kai Zuber K. 13 Zuber

14 Master equation 1 / T 1/2 = PS * NME 2 * (<m ν > / m e ) 2 Nuclear Physics Measurement Exact calculation Complex calculations Quantity of interest J. Kotila, F. Iachello, PRC (2012) S. Stoica, M. Mirea, arxiv: Severe nuclear structure issue

15 Phase space factors (new vs. old) Kotila, Iachello, PRC 85, (2012), Stoica, Mirea, arxiv: Kai Zuber 15

16 NME Intermediate states 2νββ 0νββ 2νββ

17 NME Intermediate states Differential cross section in forward direction directly linked to Gamow-Teller strength Charge exchange measurements at KVI and RCNP

18 Matrix element Rescaled as people use different g A (1-1.25) and R 0 ( fm) 4 ± 4 would do it Several new techniques applied in last years A. Dueck, W. Rodejohann,, arxiv: , PRD 83, (2011)

19 Items studied (examples) D. Frekers, H. Ejiri et al., RCNP Osaka TITAN-EC at TRIUMF D. Zinatulina, MEDEX 2013 J. Schiffer et al., Phys. Rev. Lett. 100, (2008)

20 Back of an envelope This is the 50 mev option, just add 0 s to moles and kgs if you want smaller neutrino masses Τ 1/2 = ln2 a N A M t / N ββ (τ>>t) ( Background free) For half-life measurements of yrs 1 event/yr you need source atoms This is about 1000 moles of isotope, implying about 100 kg Now you only can loose: nat. abundance, efficiency, background,...

21 Experimental approaches Isotope Nat. abund. (%) Q-values 2012 Ca ± 0.84 Ge ± Se ± 0.3 Zr ± 2.2 Mo ± 0.17 Pd ± 0.64 Cd ± 0.13 Sn ± 0.39 Te ± Xe ± 0.37 Nd ± isotopes of interest Candles GERDA, Majorana SuperNEMO, LUCIFER MOON, AMore COBRA TinTin CUORE, SNO+ EXO, KamLAND-Zen, NEXT, XMASS MCT, SuperNEMO(?) There is no super-isotope

22 Evidence? T 1/2 = 2.23 ± 0.4 x yr H.V. Klapdor-Kleingrothaus et al., Phys. Lett. B 586, 198 (2004) Mod.Phys.Lett.A21: (2006) Background reduction by pulse shape analysis H.V. Klapdor-Kleingrothaus et al., Eur.Phys.J. A12 (2001) Very controversial discussion in the community If right, neutrino mass is around 0.3 ev and masses are almost degenerate

23 KamLAND - Zen Using 400 kg of Xe (91.7% enriched in Xe-136) A Gando et al., PRC 85, (2012) T 1/2 > 1.9 x years (90%CL) A. Gando, arxiv: Upgrade to 1 ton enriched Xe planned soon

24 EXO kg of enriched (80%) Xe-136 at hand Current half-life limit on 0nu decay : T 1/2 > 1.1 x years (90%CL) J. B. Albert et al., doi: /nature13432 (2014) First observation of 2nu decay of Xe-136, N. Ackerman et al., PRL 107, (2011) Future option: Barium tagging In conflict with positive claim for almost all matrix element calculations Uncertainties due to conversion

25 GERDA-Principal Setup Idea : Running bare Ge crystals in LAr 9

26 Phase I data taking

27 Phase I results Pulse shape discrimination: M. Agostini et al. Eur. Phys. J. C 71,2583 (2013) Result Phase 1: M. Agostini et al., PRL 111, (2013) Background model (flat background in region of 200 kev around signal after removing lines)

28 2 Tackling 50 mev (IH) Dependence on solar mixing angle Just to touch the IH 100 Mo and 150 Nd seems most promising sin 2 θ 12 Reminder: Factor 2 in mass implies factor 16 in experimental parameters better solar measurement SNO+??? Reactors (JUNO, RENO-50)??? A. Dueck, W. Rodejohann,, PRD 83, (2011)

29 3 Tackling the normal hierarchy No real proposal yet Will be tough and expensive > tonne scale detectors Needs more precise data from oscillations New background components (f.e. solar neutrino-electron elastic scattering) N. debarros,, arxiv: , JPG 38, (2011) More accurate matrix elements HOW??? Experiments which work for IH might not work for NH

30 Resonant double EC

31 Alternative modes (A,Z) (A,Z-2) + 2 e + (+2ν e ) β+β+ e - + (A,Z) (A,Z-2) + e + (+2ν e ) β+/ec 2 e - + (A,Z) (A,Z-2) (+2ν e ) EC/EC Resonant enhancement (*10 6 ) of 0nu ECEC if excited state in daughter is degenerate (within 200 ev) with initial ground state (-> Q-values) Q-4m e c 2 Q-2m e c 2 Q Enhanced if V+A is at work M. Hirsch et al, Z. Phys. A 347,151 (1994) Best candidate : 152Gd measured with SHIPTRAP at GSI J. Bernabeu, A. derujula, C. Jarlskog, Nucl. Phys. B 221,15 (1983) S. Zujkoswski, S. Wycech, PRC 70, (2004) S. Eliseev et al., Phys. Rev. Lett. 106, (2011)

32 "I hope you leave here and walk out and say, 'What did he say?'" George W. Bush Conclusion Double beta decay is of central importance for neutrino physics. Gold plated channel to probe fundamental character of neutrinos Interesting times as both LHC and double beta probe TeV scale Several next generation experiments started recently (Candles, GERDA, KamLAND-Zen, EXO) First exciting results from Xe-experiments and GERDA Further experiments are in the building up phase, several interesting experimental ideas are investigated To go below 50 mev requires hundreds of kilograms of enriched material, lot of ideas...to cover uncertainties at least 3-4 isotopes should be measured To support matrix element calculations as much experimental input as possible on nuclear structure is desired! We are only talking about 11 isotope pairs!!!