1. Fakultät Mathematik und Naturwissenschaften, Institut für Kern- und Teilchenphysik
Various new measurements related to DBD Kai Zuber Institute for Nuclear- and Particle Physics
, Erice 2017

2. Contents Introduction Nuclear matrix elements (exp.) Quenching of gA
I‘m sure you‘ve heard it all before - Oasis
Introduction
Nuclear matrix elements (exp.)
Quenching of gA
Excited states and double EC
Charged lepton flavour violation
Summary

3. Double EC and DBD Mass parabola (isobar) There are 35 double beta
(and ECEC) emitters out
of which 6 are double
positron emitters
Depending on Q-value competing with double
Positron and EC/positron
decay
- Both modes can occur with/without neutrinos
- Also transitions into excited states are possible

4. Master equation 1 / T1/2 = PS * NME2 * (<m> / me)2 Measurement
Nuclear Physics
Measurement
Exact calculation
Complex calculations
Quantity of interest
Severe nuclear structure issue
J. Kotila, F. Iachello, PRC (2012)
S. Stoica, M. Mirea, arXiv:

5. Several new techniques applied in last years
Matrix element
Rescaled as people use different gA (1-1.25) and R0 ( fm)
would do it
A. Dueck, W. Rodejohann, K. Zuber,
arXiv: , PRD 83, (2011)
Several new techniques applied in last years

6. Supportive measurements
Working packages
Precise Q-value measurements
Charge exchange reactions
Ordinary muon capture
Double electron captures
Neutrino-Nucleus scattering
Nucleon transfer reactions
Consensus Report:
K. Zuber, nucl-ex/

7. NME – Intermediate states
1+ states up to about Q-value
All multipoles up to about 100 MeV

8. Experimental approaches
0nbb decay rate scales with Q only those with Q>2000 keV
11 isotopes of interest
Isotope
Nat. abund. (%)
Q-values 2016
Ca-48
0.187
± 0.84
Ge-76
7.44
± 0.050
Se-82
8.73
± 0.3
Zr-96
2.80
± 0.086
Mo-100
9.63
± 0.17
Pd-110
11.72
± 0.64
Cd-116
7.49
± 0.13
Sn-124
5.79
± 0.39
Te-130
33.80
± 0.013
Xe-136
8.9
± 0.37
Nd-150
5.64
± 0.20
Candles
GERDA, Majorana, LEGEND
SuperNEMO, LUCIFER
MOON, AMore
COBRA
Tin.Tin
CUORE, SNO+, CuPID
nEXO, KamLAND-Zen, NEXT, XMASS
MCT, SuperNEMO(?)
All Q-values measured to an error of less than 1 keV!

9. Charge exchange reactions
128,130Te(3He,t)128,130I
Best resolution at RCNP Osaka
using Grand Raiden spectrometer
P, Puppe et al. PRC 86, (2012)
Double charge exchange reactions -> Talk by H. Lenske

10. Neutrino-less DBD How to probe high lying excitations?
Courtesy H. Lenske
How to probe high lying excitations?

11. Ordinary muon capture
D. Zinatulina, MEDEX 2017

12. Nucleon transfer reactions
J. Schiffer et al. , PRL 2008

13. Deformation
Not all nuclei are spherical...

14. Quenching of gA
Deppisch, Suhonen, arXiv:

15. The case of 113Cd 4-fold forbidden non-unique beta decay (1/2+9/2+)
COBRA double beta decay experiment (64 CdZnTe detectors)
Q-value:
113Cd
Preliminary
J. V. Dawson et al., Nucl. Phys. A 818,264 (2009)
AME 2012 value: keV
Penning trap value: (27) keV
N. D. Gamage et al., Phys. Rev. C 94, (2016)
Shape depends on gA
M. T. Mustonen, M. Aunola, J. Suhonen , PRC 73, (2006)
M. T. Mustonen, J. Suhonen,, PLB 657,38 (2007)
Status: COBRA modified for low threshold, data taking has started end of july

16. Excited state transitions
First excited 0+ states have only been seen in Mo-100 and Nd-150
GERDA phase I : First (and only) multi-detector analysis in GERDA
Die blauen Baender sind Seitenbaender fuer die Background estimation T^
M. Agostini et al., J. Phys. G (2015)

17. Excited state transitions
More measurements :
„Our“ measurements
J. Phys. G 43, (2016)
More half-life limits exist but most of them are below 1020 years

18. Double EC and DPD
Theory predictions are lacking for neutrinoless double EC:
- Internal bremsstrahlungs gamma (monoenergetic)
Pair production in nuclear field
Internal conversion
M. Doi, T. Kotani, Prog. Theo. Phys. 89,130 (1993)
(GERDA and „our“ measurements)
Eur. Phys. J C 76, 652 (2016)
Again more measurements exist
NB: Q-value is reduced by 2mec2 for a positron

19. 2nu double EC
Suggestion: Use LXe dark matter detectors for search (124,126Xe)
N. Barros, J. Thurn, K. Zuber, J. Phys. G 41, (2014)
Xenon-collab: T > years, (124Xe) Phys. Rev. C 95, (2017)
XMASS-collab.: T > years (124Xe)
T > years (126Xe) , Phys. Lett. B 759,64 (2016)
Russian collab.: T > years (124Xe), Phys. Part. Nucl. 48, 38 (2017)
More to come - more data, larger detectors like DARWIN and others

20. Charged lepton flavour violation (CLFV)
DBD limits have improved by about a factor 10 in 15 years (optimistic)
If you want to have fun: Factor in 8 years
Mu2e
Focus: Coherent muon – electron conversion on nuclei (coherent = via ground state)

21. CLFV
Aim : R about 10-17

22. (My) Questions 
What fraction in muon-electron conversion is mediated
via excited states (GDR)? Thanks Petr, Alex
This would be most interesting for Aluminum (COMET, Mu2e)
How does this depend on the element/nucleus, i.e. target?   
Could there be spin dependent and spin independent
reactions like in dark matter?
See Phys. Lett. B 771, 242 (2017)

23. Total lepton number violation
Neutrino-less double beta decay 
μ- - e+ conversion on nuclei
T. Geib, A. Merle, K. Zuber, PLB 764,157 (2017) 
Neutrino-less double muon decay of the kaon
(< 8.6 x 10-11)
K. Zuber, Phys. Lett. B 479,33 (2000) J. Barley et al., Phys. Lett. B 769,67 (2017)
In general: BSM physics

24. COMET
Major aim: coherent muon-electron conversion on nuclei (CLFV), will be performed at J-PARC, start 2019
Phase 1 setup:
Which would be best target for μ- - e+ ?
Major background: Radiative muon capture
Phase I: Improvement of factor 100,
Phase 2: Another factor 100
B. Yeo, Y. Kuno, M. Lee, K. Zuber, arxiv: , acc. PRD

25. Summary
Q-values for all relevant DBD isotopes are measured with less than a keV uncertainty
More measurements have been obtained or will be persuit (3He,t), OMC, nucleon transfer reactions..) to provide good date for NME calculations
Spectral shape searches in highly forbidden beta decay sounds
interesting for learning about quenching of gA
Various new half-lives for excited states in double beta decay and radiative double EC have been obtained
 Big progess expected in the next years in charged lepton flavour violation processes