How to measureneutrinoless double-beta decay
nuclear matrix elements?
Javier MenéndezUniversity of Barcelona
Neutrinos ElectroWeak interactions and SymmetriesNEWS Colloquium
23rd April 2021
Nuclear matrix elements for new-physics searchesNeutrinos, dark matter studied inexperiments using nuclei
Nuclear structure physicsencoded in nuclear matrix elementskey to plan, fully exploit experiments
0νββ:(
T 0νββ1/2
)−1∝ g4
A
∣∣M0νββ∣∣2 m2
ββ
Dark matter:dσχNdq2 ∝
∣∣∣∑i
ci ζi Fi
∣∣∣2CEνNS:
dσνNdq2 ∝
∣∣∣∑i
ci ζi Fi
∣∣∣2M0νββ : Nuclear matrix elementFi : Nuclear structure factor
2 / 37
Outline
0νββ decay: huge potential, great challenge
Nuclear structure data as test of 0νββ calculations
Double Gamow-Teller transitions and 0νββ decay
γγ transitions and 0νββ decay
2 / 37
Outline
0νββ decay: huge potential, great challenge
Nuclear structure data as test of 0νββ calculations
Double Gamow-Teller transitions and 0νββ decay
γγ transitions and 0νββ decay
/ 37
Lepton-number conservationLepton number is conservedin all processes observed
β decay, ββ decay...
Uncharged massive particleslike Majorana neutrinos (ν)allow lepton number violation
Neutrinoless ββ (0νββ) decay3 / 37
ββ decaySecond order process in the weak interactionOnly observable in nuclei where (much faster) β-decay is forbiddenenergetically due to nuclear pairing interaction
BE(A) = −av A + asA2/3 + acZ (Z − 1)
A1/3+
(A− 2Z )2
A+
−δpairing N,Z even0 A oddδpairing N,Z odd
or where β-decay is very suppressed by ∆J angular momentum change
-76
-74
-72
-70
-68
-66
30 31 32 33 34 35 36 37
Bin
din
g e
nerg
y (
MeV
)
Atomic number, Z
76Se
76Ge
76As
76Br
76Kr
76Ga
β-
β+
β+
β-β
-
48Ca→ 48Ti76Ge→ 76Se82Se→ 82Kr96Zr→ 96Mo100Mo→ 100Ru110Pd→ 110Cd116Cd→ 116Sn124Sn→ 124Te130Te→ 130Xe136Xe→ 136Ba150Nd→ 150Sm
4 / 37
0νββ decay rate0νββ rate depends on kinematics and physics at very different scales:
1T 0νββ
1/2
(0+
i → 0+f
) = G01 g4A
∣∣M0νββ∣∣2(mββ
me
)2
G01 is the phase space factor, kinematics:accurate calculations; depends on Qββ , charge number Z , electrons...
gA is the coupling to the nucleonhard to compute (lattice QCD) but can be measured in other decays
M0νββ is the nuclear matrix element (NME)nuclear structure of the initial and final nuclei
mββ = |∑U2ek mk |, new physics responsible for lepton-number violation
For 0νββ rate dominated by different new physics, same structuredifferent values of G, g, M and mββ ∼ 1/Λ, v3/Λ3, v5/Λ5
5 / 37
Next generation experiments: inverted hierarchyDecay rate sensitive toneutrino masses, hierarchymββ = |∑U2
ek mk |T 0νββ
1/2
(0+ → 0+
)−1= G0ν g4
A
∣∣M0νββ∣∣2 m2
ββ
Matrix elements assess ifnext generation experimentsfully explore "inverted hierarchy"
(eV)lightestm4−10 3−10 2−10 1−10
3−10
2−10
1−10
1
IH
NH
A50 100 150
Ca
Ge
SeZr
Mo
CdTe
Te
Xe
Nd
(eV)
m
KamLAND-Zen, PRL117 082503(2016)
6 / 37
Nuclear matrix elements
Nuclear matrix elements needed in low-energy new-physics searches
〈Final |Lleptons−nucleons| Initial 〉 = 〈Final |∫
dx jµ(x)Jµ(x) | Initial 〉
• Nuclear structure calculationof the initial and final states:Shell model, QRPA, IBM,Energy-density functionalAb initio many-body theoryGFMC, Coupled-cluster, IMSRG...
• Lepton-nucleus interaction:Hadronic current in nucleus:phenomenological,effective theory of QCD
7 / 37
0νββ decay nuclear matrix elementsLarge difference in nuclear matrix element calculations: factor ∼ 2− 3⟨0+
f
∣∣∑n,m
τ−n τ−m
∑X
HX (r) ΩX∣∣0+
i
⟩ ΩX = Fermi (1), GT (σnσm),TensorH(r) = neutrino potential
0
1
2
3
4
5
6
7
48 76 82 100 116 130 136 150
M0
ν
A
CC
IMSRG
NSM
QRPA
IBM
EDF
Engel, JM, Rep. Prog. Phys. 80 046301 (2017), updated8 / 37
Uncertainty in physics reach of 0νββ half-lives
0
1
2
3
4
5
6
7
8
M0
ν
SM St-M,Tk
SM Mi
IBM-2
QRPA CH
QRPA Tu
QRPA Jy
R-EDF
NR-EDF
1028
1029
1030
1031
48 76 82 96 100 116 124 130 136 150
T1/20ν m
ββ
2 [y m
eV
2]
A
Nuclear matrix elementtheoretical uncertainty criticalto anticipate mββ sensitivityof future experiments
Order of magnitudeuncertainty in T 0ν
1/2needs to be reduced!
Engel, JM,Rep. Prog. Phys. 80 046301 (2017)
9 / 37
Pairing correlations and 0νββ decay0νββ decay favoured by proton-proton, neutron-neutron pairing,but it is disfavored by proton-neutron pairing
Ideal case: superfluid nucleireduced with high-seniorities
0
2
4
6
8
10
12
0 4 8 12
M0ν
ββ
sm
A=48A=76A=82
A=124A=128A=130A=136
Caurier et al. PRL100 052503 (2008)
Addition of isoscalar pairingreduces matrix element value
-10
-5
0
5
10
0 0.5 1 1.5 2 2.5 3
M0ν
gT=0/gT=1
GCM SkO′QRPA SkO′GCM SkM*
QRPA SkM*
Hinohara, Engel PRC90 031301 (2014)
Related to approximate SU(4) symmetry of the∑
H(r)σiσjτiτj operator10 / 37
Outline
0νββ decay: huge potential, great challenge
Nuclear structure data as test of 0νββ calculations
Double Gamow-Teller transitions and 0νββ decay
γγ transitions and 0νββ decay
/ 37
Nuclear shell modelNuclear shell model configuration spaceonly keep essential degrees of freedom
• High-energy orbitals: always empty
• Valence space:where many-body problem is solved
• Inert core: always filled
H |Ψ〉 = E |Ψ〉 → Heff |Ψ〉eff = E |Ψ〉eff
|Ψ〉eff =∑α
cα |φα〉 , |φα〉 = a+i1a+
i2...a+iA |0〉
Shell model diagonalization:∼1010 Slater dets. Caurier et al. RMP77 (2005)&1024 Slater dets. with Monte Carlo SM
Otsuka, Shimizu, Y.Tsunoda
Heff includes effects of
• inert core
• high-energy orbitals13 / 37
Tests of nuclear structureSpectroscopy well described: masses, spectra, transitions, knockout...
Theory Exp0
500
1000
1500
2000
2500
Ex
cita
tio
n e
ner
gy
(k
eV)
4+
6+
0+
3+
4+
6+
2+5
+
2+
0+
2+
4+
2+
6+
3+,4
+6+
2+ 2
+5(4
+)
136Xe
0
0
0.5
1
Ex (
MeV
)
0+2+
4+
6+
8+
0+2+
4+
6+
8+
0+
2+
4+
0+
2+
4+
6+
204
292
325
345
115(2)
175(1)
212(12)
236(11)
98
151
181
55.8(25)
112(12)
Theory Exp. Theory Exp.150Nd 150Sm
Schiffer et al. PRL100 112501(2009)Kay et al. PRC79 021301(2009)...Szwec et al., PRC94 054314 (2016)
Rodríguez et al. PRL105 252503 (2010)...Vietze et al. PRD91 043520 (2015)
14 / 37
β–decay Gamow-Teller transitions: “quenching”β decays (e− capture): phenomenology vs ab initio
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
T(GT) Th.
T(G
T)
Ex
p.
0.77
0.744
Martinez-Pinedo et al. PRC53 2602(1996)
〈F |∑
i
[gA σiτ−i ]eff |I〉 , [σiτ ]eff ≈ 0.7σiτ
Standard shell modelneeds σiτ “quenching”
Gysbers et al. Nature Phys. 15 428 (2019)
Ab initio calculations includingmeson-exchange currents
do not need any “quenching”15 / 37
Gamow-Teller strength distributionsGT strength distribution complements β-decay beyond Q-value region
Frekers et al.NPA916 219 (2013)
Iwata et al. JPSCP6 3057 (2015) Caurier et al. PLB711 62 (2012)
dσdΩ
(θ = 0) ∝∑
σiτ±⟨
1+f
∣∣∑geffA σiτ
±i
∣∣0+gs⟩, geff
A ∼ 0.57gA for 136Xe
Similar “quenching” q= 0.57 needed in GT decays in xenon mass regionSmaller “quenching” q= 0.42 needed in 2νββ of 136Xe
16 / 37
Two-neutrino ββ decay, 2νECEC2νββ decay same initial, final states , similar operator (στ ) as 0νββComparison of predicted 2νββ decay vs data
Shell modelreproduce 2νββ dataincluding “quenching”
Prediction previous to48Ca measurement!Caurier, Poves ZukerPLB 252 13(1990)
M2νββ =∑
k
⟨0+
f
∣∣∑n σnτ
−n∣∣1+
k
⟩ ⟨1+
k
∣∣∑m σmτ
−m∣∣0+
i
⟩Ek − (Mi + Mf )/2
Table 2
The ISM predictions for the matrix element of several 2ν double beta decays
(in MeV−1). See text for the definitions of the valence spaces and interactions.
M2ν (exp) q M2ν (th) INT
48Ca→48Ti 0.047± 0.003 0.74 0.047 kb3
48Ca→48Ti 0.047± 0.003 0.74 0.048 kb3g
48Ca→48Ti 0.047± 0.003 0.74 0.065 gxpf1
76Ge→76Se 0.140± 0.005 0.60 0.116 gcn28:50
76Ge→76Se 0.140± 0.005 0.60 0.120 jun45
82Se→82Kr 0.098± 0.004 0.60 0.126 gcn28:50
82Se→82Kr 0.098± 0.004 0.60 0.124 jun45
128Te→128Xe 0.049± 0.006 0.57 0.059 gcn50:82
130Te→130Xe 0.034± 0.003 0.57 0.043 gcn50:82
136Xe→136Ba 0.019± 0.002 0.45 0.025 gcn50:82
Caurier, Nowacki, Poves, PLB 711 62 (2012)17 / 37
Two-neutrino ECEC of 124XePredicted 2νECEC half-life:shell model error bar largely dominated by “quenching” uncertainty
SuhonenJPG 40 075102 (2013)
Pirinen, SuhonenPRC 91, 054309 (2015)
Coello Pérez, JM,SchwenkPLB 797 134885 (2019)
Shell model, QRPA and Effective theory (ET) predictionssuggest experimental detection close to XMASS 2018 limit
18 / 37
Two-neutrino ECEC of 124XePredicted 2νECEC half-life:shell model error bar largely dominated by “quenching” uncertainty
SuhonenJPG 40 075102 (2013)
Pirinen, SuhonenPRC 91, 054309 (2015)
Coello Pérez, JM,SchwenkPLB 797 134885 (2019)
XENON1TNature 568 532 (2019)
Shell model, QRPA and Effective theory (ET) predictionsgood agreement with XENON1T measurement of 2νECEC!
18 / 37
Effective theory of ββ decay
Effective theory (ET) for ββ decay:spherical core coupled to one nucleon
Couplings adjusted to experimental data,uncertainty given by effective theory(breakdown scale, systematic expansion)
Use β-decay datato predict 2νββ decayGood agreement, large error(leading-order in ET)
Coello-Pérez, JM, SchwenkPRC 98, 045501 (2018)
19 / 37
Electron spectrum in two-neutrino ββ decayPrecise 2νββ half-life, next term in expansion of energy denominator
(T 2ν1/2)−1 ' g4
A
∣∣(M2νGT )2G2ν
0 + M2νGT M2ν
GT−3G2ν2 + ...
∣∣M2ν
GT =∑
j
〈0+f |∑
l σlτ−l |1
+j 〉〈1
+j |∑
l σlτ−l |0
+i 〉
∆,
M2νGT3 =
∑j
4〈0+f |∑
l σlτ−l |1
+j 〉〈1
+j |∑
l σlτ−l |0
+i 〉
∆3,
∆ = [Ej − (Ei + Ef )/2]/me
Electron differential decay rate:
dΓββ
dTee∼
dG0
dTee+
M2νGT
M2νGT−3
dG2
dTee
Exp. sensitivity to ξ2ν31 = M2ν
GT−3/M2νGT Šimkovic et al.
PRC98 064325 (2018)20 / 37
Electron spectrum in 136Xe ββ decay
Present 0νββexperiments observe∼10000 2νββ decays,major background
KamLAND-Zen 2νββanalysis excludes largervalues of ξ2ν
31
KamLAND-Zen, PRL122 192501 (2019)21 / 37
Ratio of leading/subleading ββ matrix elementsShape of ββ spectrum constrains matrix element ratio ξ2ν
31 = M2νGT−3/M2ν
GT
0 0.005 0.01 0.015 0.02 0.025 0.03
M2ν
GT-3
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
gef
f
A
shell model (GCN)
shell model (MC)
QRPA (CD-Bonn)
QRPA (Argonne)
ξ 2ν
31 = 0.26
excluded, KamLAND-Zen
ξ2ν
31 = 0.10
ξ2ν
31 = 0.17(1σ)
(90% C.L.)
ξ 2ν
31 = 0.05
Theory deficiencies in M2νGT
fixed adjusting gA(“quenching”)
ξ2ν31 measurement
test theoretical models
Theory-experiment work withKamLAND-Zen collaborationTheory: JM, Dvornicky, Šimkovic
Shell model ξ2ν31 predictions
consistent with 90% C.L. limitKamLAND-Zen et al.PRL122 192501 (2019)
22 / 37
Outline
0νββ decay: huge potential, great challenge
Nuclear structure data as test of 0νββ calculations
Double Gamow-Teller transitions and 0νββ decay
γγ transitions and 0νββ decay
/ 37
Double Gamow-Teller strength distributionMeasurement of Double Gamow-Teller (DGT) resonancein double charge-exchange reactions 48Ca(pp,nn)48Ti proposed in 80’sAuerbach, Muto, Vogel... 1980’s, 90’s
Recent experimental plans in RCNP, RIKEN (48Ca), INFN CataniaTakaki et al. JPS Conf. Proc. 6 020038 (2015)Capuzzello et al. EPJA 51 145 (2015), Takahisa, Ejiri et al. arXiv:1703.08264
Promising connection to ββ decay,two-particle-exchange process,especially the (tiny) transitionto ground state of final state
Shell model calculationShimizu, JM, Yako, PRL120 142502 (2018)
0 20 40 600
20
40
B(D
GT
)
Ex. (MeV)
SDPFMU J=2
SDPFMU J=0
GXPF1B J=2
GXPF1B J=0
B(DGT−;λ; i → f ) =1
2Ji + 1
∣∣∣∣⟨48Ti∣∣∣∣∣∣∣∣[∑
i
σiτ−i ×
∑j
σjτ−j
](λ)∣∣∣∣∣∣∣∣48Cags
⟩∣∣∣∣223 / 37
Double Gamow-Teller distribution and pairingStudy the sensitivity of Double GT distribution to pairing correlations
Add/remove pairing
H ′ = H + GJT PJT
like-particle (T=1) orproton-neutron (T=0)
Position of theDGT giant resonancevery sensitive tolike-particle pairing
DGT resonance widthprobes isoscalar pairingShimizu, JM, YakoPRL120 142502 (2018) 0 20 40
0
20
40
0
20
40
0
20
40
0 20 400
20
40
G(10)
= +0.5 MeV
Ex (MeV)
Jf=2+
Jf=0+
G(10)
= +0.25 MeV
G(10)
= -0.25 MeV
G(10)
= -0.5 MeV
G(01)
= +0.5 MeV
B(D
GT
)
Ex (MeV)
Jf=2+
Jf=0+
G(01)
= +0.25 MeV
G(01)
= -0.25 MeV
G(01)
= -0.5 MeV
(a) (b)
24 / 37
Correlation of 0νββ decay to DGT transitionsDouble GT transition to ground state MDGT =
⟨Fgs∣∣∣∣[∑
i σiτ−i ×∑
j σjτ−j
]0∣∣∣∣Igs⟩∣∣2
very good linear correlation with 0νββ decay nuclear matrix elements
0
2
4
6
8
10
0 1 2 3 4 5
42 ≤ A ≤ 238
MD
GT(0
+ gs,i →
0+ g
s,f)
*R(f
m)
M0νββ
(0+gs,i → 0
+gs,f)
QRPA
IBM (MDGT/2.0)
EDF
shell model
Double Gamow-Tellercorrelation with0νββ decay holdsacross nuclear chartShimizu, JM, YakoPRL120 142502 (2018)
Common to shell modelenergy-density functionalsinteracting boson model,disagreement to QRPA
Experiments atRIKEN, INFN, RCNP?access DGT transitions
25 / 37
Short-range character of DGT, 0νββ decayCorrelation between DGT and 0νββ decay matrix elementsexplained by transition involving low-energy states combined withdominance of short distances between exchanged/decaying neutronsBogner et al. PRC86 064304 (2012)
-0.2
0
0.2
0.4
0.6
0 3 6 9 12 15
(a)
CG
T (
r jk)
[fm
-1]
rjk [fm]
0νββ decay
DGT
0 200 400 600
-0.001
0
0.001
0.002
0.003136
Xe
(b)
CG
T (q
) [MeV
-1]
q [MeV]
0νββ decay matrix elementlimited to shorter range
Short-range part dominantin double GT matrix elementdue to partial cancellationof mid- and long-range parts
Long-range part dominant inQRPA DGT matrix elements
Shimizu, JM, Yako,PRL120 142502 (2018)
26 / 37
Short-range character of DGT, 0νββ decayCorrelation between DGT and 0νββ decay matrix elementsexplained by transition involving low-energy states combined withdominance of short distances between exchanged/decaying neutronsBogner et al. PRC86 064304 (2012)
JM, JPSCP 23 012036 (2018) Šimkovic et al. PRC 98 064325 (2019)
In contrast to NSM, long-range dominates QRPA DGT matrix elements27 / 37
Contribution of S = 1 pairs to DGT NMENMEs are dominated by S = 0 pairs
In DGT QRPA, S = 1 pair contributions extremely suppressedlead to small MDGT = MDGT
S=0 + MDGTS=1 = 4MDGT
S=1 (isospin conserved)
In contrast, nuclear shell model MDGTS=1 small but not negligible
even between seniority-zero states (J = 0 pairs, isospin not conserved)
Šimkovic et al. PRC 98 064325 (2019) Linares, JM, in preparation28 / 37
0νββ decay NMEs in ET of β decayEffective theory of β decay can calculate DGT with uncertainties(similar to calculation of 2νββ, no energy denominator)DGT vs 0nbb correlation⇒ predict 0νββ NMEs with uncertainties
Because ET couplings fitted to β decay and GT strengthscorrect shell model DGT NMEs in correlationby “quenching” factor for these observables: q = 0.42− 0.65
0 0.5 1.0 1.5 2.0 2.5
M0νββ(0+gs,i −→ 0+
gs,f) · A−16
0
0.5
1.0
MD
GT
(0+ gs,
i−→
0+ gs,
f)
44 6 A 6 238fitSM
SM, 44 6 A 6 136
EDF
IBM (MDGT/2.0)
As a result, ET 0νββ NMEs76Ge: M0ν = 0.3− 1.582Se: M0ν = 0.3− 1.6
smaller than mostcalculationslarge uncertainty:LO in ET, fit, “quenching”Brase, Coello Pérez, JM, Schwenkin preparation29 / 37
Outline
0νββ decay: huge potential, great challenge
Nuclear structure data as test of 0νββ calculations
Double Gamow-Teller transitions and 0νββ decay
γγ transitions and 0νββ decay
/ 37
γγ decay of the DIAS of the initial ββ nucleusExplore correlation between 0νββ and γγ decays,focused on double-M1 transitions
MγγM1 M1 =
∑k
⟨0+
f
∣∣∑n(g l
nln + gsnσn)IV
∣∣1+k (IAS)
⟩⟨1+
k (IAS)∣∣∑
m(g lmlm + gs
mσm)IV∣∣0+
i (DIAS)⟩
Ek − (Ei + Ef )/2
-75
-74
-73
-72
31 32 33 34 35
76Se
76Ge
76As
76Ge double isobaric analogue state
β-β
- γ γ
Bin
din
g e
nerg
y (
MeV
)
Atomic number, Z
Similar initial and final statesbut both in same nucleusfor electromagnetic transition
M1 and GT operators similar,physics of spin operatorM1 also angular momentum
Different energy denominatorRomeo, JM, Peña-GarayarXiv:2102.11101
30 / 37
β decays and γ transitions from IASThe relation between electromagnetic decays from IAS and weak oneshas been used and tested many timesEjiri, Suhonen, Zuber, Phys. Rept. 797 1 (2019)Fujita, Rubio, Gelletly, Prog. Part. Nucl. Phys.66, 549 (2011)
And it is certainly not a novel idea...
PRL 21 373 (1968)
31 / 37
Correlation between M1M1 and 0νββ NMEsα
Mγγ(0 D
IAS
+⟶
0 gs+)[μ
N2Me
V-1 ]
TiCrFe
0
0.5
1.0
1.5
2.0
2.5
46 ≤ A ≤ 60
ZnSeGeKr
TeXeBa
1.0 1.5 2.0 2.5 3.00
0.5
1.0
1.5
2.0
2.5
M0νββ(0gs+ ⟶0gs+ )
72 ≤ A ≤ 136
Good correlation betweenM1M1 and 0νββ NMEs!
Valid across the nuclear chartfor the nuclear shell model
Overall, study ∼ 50 transitionsseveral nuclear interactionsfor each of them
The correlation is slightly differentfor lighter nuclei:effect of energy denominator
Romeo, JM, Peña-GarayarXiv:2102.11101
32 / 37
Intermediate states of the M1M1 transition
TiCrFeZnSe
GeKrTeXeBa
0.5 1.0 1.5 2.0 2.5 3.0 3.50
2
4
6
8
M0νββ0gs+ ⟶0gs+
αM1
M1(0 D
IAS
+⟶
0 gs+)[μ
N2 ]
46 ≤ A ≤ 136
Dominant intermediate statesat lower energies for lighter nuclei,otherwise similar energies
One or few intermediate statestypically dominate the transition
When energy denominators are(artificially) removed, samecorrelation across the nuclear chart
Romeo, JM, Peña-GarayarXiv:2102.11101
48Ti82Se128Te
5.0 7.5 10.0 12.5 15.0-0.2
0
0.2
0.4
0.6
0.8
En(MeV)
Mγγ(M
1M1)
[μN2
MeV-
1 ]
33 / 37
Spin, angular momentum decomposition
The numerator NME can be decomposed into
Mss + Mll + Mls
spin, angular momentum and interference components
ss llls
T ss ll ls T ss ll ls T ss ll ls T ss ll ls T0
0.2
0.4
0.6
0.8
Mxx
'γγ[μ
N2 ] 48Ti 72Zn 78Ge 134Xe 136Ba
Spin, angular momentum termsstrikingly similar,always carry same sign
Interference termcan cancel the other twobut always much smaller
Romeo, JM, Peña-GarayarXiv:2102.11101
34 / 37
Total angular momentum decompositionThe numerator NME can be decomposed into
Mss(J ) + Mll (J ) + Mls(J )
spin, angular momentum and interference componentsand total angular momentum of the nucleons involved in the transition
sslllsT
0 1 2 3 4 5 6 7 8 9 10-0.5
0
0.5
1.0
1.5
Mxx
'γγ(
)[μ
N2 ]
Dominance of J = 0 termsfor spin and orbital contributionsjust like in 0νββ decay
Cancellation from J > 0 termsless pronounced in orbital part
Explains similar behaviour ofspin and orbital components
Romeo, JM, Peña-GarayarXiv:2102.11101
35 / 37
Experimental feasibility of γγ decay?γγ decays are very suppressed with respect to γ decaysjust like ββ decays are much slower than β decays
γγ decays have been observed recentlyin competition with γ decaysWaltz et al. Nature 526, 406 (2015), Soderstrom et al. Nat. Comm. 11, 3242 (2020)
-75
-74
-73
-72
31 32 33 34 35
76Se
76Ge
76As
76Ge double isobaric analogue state
β-β
- γ γ
Bin
din
g e
nerg
y (
MeV
)
Atomic number, Z
Outlook:
Study in detail leadingdecay channels for M1M1 decayin DIAS of ββ nuclei
Particle emission,M1, E1 decay
Experimental proposal for 48Tiby Valiente-Dobón et al.
Valiente-Dobón, Romeo et al., in prep36 / 37
Summary
Calculations of 0νββ NMEschallenge nuclear many-body methods
0νββ searches demand reliable NMEsnuclear structure measurements caninform us on their value
Double Gamow-Teller transitionsvery good correlation with 0νββ NMEspotentially accessible in chargeexchange experiments
Electromagnetic M1M1 decayof the DIAS of the initial ββ nucleusgood correlation to 0νββ NMEsfeasibility of measurements in progress
αMγ
γ(0 D
IAS
+⟶
0 gs+)[μ
N2Me
V-1 ]
TiCrFe
0
0.5
1.0
1.5
2.0
2.5
46 ≤ A ≤ 60
ZnSeGeKr
TeXeBa
1.0 1.5 2.0 2.5 3.00
0.5
1.0
1.5
2.0
2.5
M0νββ(0gs+ ⟶0gs+ )
72 ≤ A ≤ 136
37 / 37
Collaborators
L. Jokiniemi, J. P. Linares, P. Soriano
C. Peña-Garay, B. Romeo
E. A. Coello Pérez
C. Brase, A. Schwenk
N. Shimizu, K. Yako
37 / 37
Top Related