Particle-, Nuclear- and Atomic-Physics Aspects of Rare ... · Intro 0νECEC decays 115In Decay...

Intro 0νECEC decays 115In Decay

Particle-, Nuclear- and Atomic-Physics Aspects ofRare Weak Decays of Nuclei

Jouni Suhonen

Department of PhysicsUniversity of Jyväskylä

NCNP 2011 - XIIth Nordic Conference on Nuclear Physics,Stockholm, Sweden, 13-17 June, 2011

Contents:

Intro: 0νββ Decays

Resonant 0νECEC Decays

Rare Beta Decays

Jouni Suhonen (JYFL, Finland) NCNP 2011 1 / 27


INTRO: Neutrino Properties from Experiments

Neutrino Properties from Oscillation Experiments:

From solar, atmospheric, accelerator and reactor-neutrino data (Su-perKamiokande, SNO, KamLAND, etc.):

Squared mass differences ∆m2 of neutrinos

Matrix elements of the neutrino mixing matrix ⇔ flavor eigenstates interms of mass eigenstates: νe → νi → νµ → νj → νe → νk → νµ · · ·

Complementary Experiments:

Tritium beta decay (absolute neutrino mass),KATRIN

Double beta decay (nature, absolute mass andhierarchy of neutrinos)



Double Beta Decay (Isobars A = 76)

-75.0

-70.0

-65.0

-60.0

30 31 32 33 34 35 36

Mas

sex

cess

[MeV

]

Z

A=75

Zn

Ga

Ge

AsSe

Br

Kr

-75.0

-70.0

-65.0

-60.0

30 31 32 33 34 35 36

Mas

sex

cess

[MeV

]

Z

A=76

Zn

Ga

GeAs

Se

Br

Kr



Two-Neutrino Double Beta Decay

Nucleus half-life (years) experiments48Ca 4.2 · 1019 laboratory76Ge 1.42 · 1021 laboratory82Se 9 · 1019 laboratory, geochemical96Zr 2.1 · 1019 laboratory, geochemical

100Mo 8.0 · 1018 laboratory116Cd 3.3 · 1019 laboratory128Te 2.5 · 1024 geochemical130Te 9 · 1020 geochemical150Nd 7.0 · 1018 laboratory238U 2.0 · 1021 radio-chemical

1020 years =10000000000× age of the UNIVERSE

n n

p p

(Z,N-2)

(Z,N-2)

INTERMEDIATE STATES

INITIAL NUCLEUS

FINAL NUCLEUS

e1-

1

e2-

2



Two-Neutrino Double Beta Decay of 76Ge

76Ge 76As 76Se

0+

0+

2-

(1+)

(1+)

(1+)(1-)?(3-)?(1+)(4-)(3-)

Virtual transition

2 - -

The decay goes

through 1+ virtual

states



Neutrinoless Double Beta Decay0νββ Decay is Able to:

Reveal if the neutrino is a Majorana particle

Probe the neutrino effective mass〈mν〉 =

P

j=light λCPj |Uej|

2mj

Probe the degenerate or inverted masshierarchies (next-generation experiments!)

Probe possibly the CP phases (nuclear matrixelements are critical!)

(νe) ν1

(νµ) ν2

(ντ ) ν3}

∆m2

atm

}∆m2⊙

Normal hierarchy

ν3

ν1

ν2

}

∆m2

atm

}∆m2⊙

Inverted hierarchy

∆m2⊙ = 7.67+0.16

−0.19 × 10−5 eV2

∆m2atm = 2.39+0.11

−0.08 × 10−3 eV2

[Global 3ν oscillation analysis (2008)]

MASS MODE:T1/2 ∝ 〈mν〉

2

n n

p p

(Z,N-2)

(Z,N-2)

INTERMEDIATE STATES

INITIAL NUCLEUS

FINAL NUCLEUS

e1-

e2-

L=2

helicities

helicities

m =0



Neutrinoless Double Beta Decay of 76Ge

76Ge 76As 76Se

0+

0+

2-

(1+)

(1+)

(1+)(1-)?(3-)?(1+)(4-)(3-)Virtual transition

0 - -

The decay goes

through all Jπ virtual

states



About Experiments

UNDERGROUNDLABORATORIES

protect fromCOSMIC RAYS

and their secondaryparticles

Canfranc (Spain)Kamioka (Japan)Boulby (England)Gran Sasso (Italy)

Pyhäsalmi (Finland)Baksan (Ukraine)

Modane (France-Italy)Sudbury (Canada)



Experiments Searching for 0νββ Decays:

Major Running Experiments:

Heidelberg–Moscow (76Ge) (ceased, claim of detection but resultstill controversial)

NEMO3 (76Ge 82Se 96Zr 100Mo 116Cd . . . ) running in Modane

Cuoricino (128,130Te) running in Gran Sasso

Future Experiments:

SUPERNEMO (82Se 100Mo. . . ), GERDA (76Ge), MAJORANA (76Ge),CAMEOII,III (116Cd), CUORE (128,130Te), MOON (100Mo), EXO (136Xe),COBRA (70Zn 106,114,116Cd 128,130Te), ZORRO (96Zr)

These are in 100 − 1000 kg scale and cost about 100000000 EURO/$each!



Topic I

Resonant 0νECEC Decays



Two-Neutrino Double Electron Capture

p

n

(Z − 2, N)

(Z − 2, N)

p

n

e−bound

νe

e−bound

νe

H H ′

Final nucleus (Z − 2, N + 2)

Initial nucleus (Z, N)



Neutrinoless Double Electron Capture

Radiative 0νECEC

p

n

(Z − 2, N)

(Z − 2, N)

p

n

e−bound

e−bound

H H ′

Final nucleus (Z − 2, N + 2)


γ

νe = ν̄e

Resonant 0νECEC

p

n

(Z − 2, N)

(Z − 2, N)

p

n

e−bound

e−bound

H H ′

Final nucleus (Z − 2, N + 2)∗


νe = ν̄e



Resonant 0νECEC Decay of 106Cd

10646Pd60

0+gs

2+1

511.86 keV

2+2

1128.0 keV0+

1

1133.7 keV4+1229.2 keV

0+2766.26 keV

XK XK

1+1

10647Ag59

0+1

10648Cd58R0νECEC

0νβ+β+, 0νβ+EC

0νβ+EC Q = 2770(7) keV

Qβ− = 202 keV



Half-life Estimate for 106Cd

Decay width of the two-hole state: Γ = 10.24 eV

1024

1025

1026

1027

1028

1029

1030

1031H

alf-life

(yr)

100 101 102 103

x (eV)

〈mν〉 = 1.0 eV

〈mν〉 = 0.3 eV

〈mν〉 = 0.05 eV

T1/2 = ln 2 (x/Γ)2+1/4gECEC[MECEC]2〈mν〉2

Γ, x = |Q− E| (degeneracy parameter)



Resonant 0νECEC Decay of 112Sn

11248Cd64

0+1

2+1

617.516 keV

0+4

1924.3 keV

XK XK

1+1

11249In63

0+1

11250Sn620νECEC

Q = 1919.82(16) keV

Qβ− = 658 keV



Half-Life Estimate for 112Sn

Γ = few tens of eV ; MECEC0ν = 4.76 (unitless NME)

Q value measured in JYFLTRAP (S Rahaman, V.-V. Elomaa, T. Eronen, J. Hakala, A.

Jokinen, A. Kankainen, J. Rissanen, J. Suhonen, C. Weber, and J. Äystö, Phys. Rev. Lett. 103 (2009)

042501)

Q− E = −4.5 keV for KK capture= 18.2 keV for KL capture= 40.9 keV for LL capture

Hence:

T1/2 >5.9 × 1029

(〈mν〉[eV])2years

Conclusion: Decay rate much suppressed by the rather largedegeneracy parameter Q− E



Resonant 0νECEC Decay of 74Se

7432Ge42

0+1

2+1

595.88 keV

2+2

1204.31 keV

XL XL

2−17433As41

0+1

7434Se400νECEC

Q = 1209.171(49) keV

Qβ− = 1353.1 keV



Half-Life Estimate for 74Se

Γ = few tens of eV ; MECEC0ν < 0.0160 (unitless NME)

Q value measured in JYFLTRAP (V.S. Kolhinen, V.-V. Elomaa, T. Eronen, J. Hakala,

A. Jokinen, M. Kortelainen, J. Suhonen and J. Äystö, Phys. Lett. B 684 (2010) 17)

Q− E = 2.23 keV for LL capture (most favorable)

Hence:

T1/2 ≈5× 1043


Conclusion: Decay rate much suppressed both by the rather largedegeneracy parameter Q− E and the very small NMEfor the 2+

f final state. The same occurs for the 2νβ−β− decay(see M. Aunola and J. Suhonen, Nucl. Phys. A 602 (1996) 133)



Resonant 0νECEC Decay of 136Ce

13656Ba80

0+1

2+1

818.50 keV

0+4

2390.20 keV

XK XK 1+1

13657La79

0+1

13658Ce780νECEC

Q = 2378.53(27) keV

Qβ− = 460 keV



Half-Life Estimate for 136Ce

Γ = 13.81 eV ; MECEC = 0.250 (unitless NME)

Q value measured in JYFLTRAP(V.S. Kolhinen, T. Eronen, D. Gorelov, J.

Hakala, A. Jokinen, A. Kankainen, J. Rissanen, J. Suhonen and J. Äystö, Phys. Lett. B

697 (2011) 116)

Q− E = −11.67 keV for KK capture= 19.78 keV for KL capture= 51.24 keV for LL capture

Hence:

T1/2 >2.26 × 1033


Conclusion: Decay rate much suppressed by the rather largedegeneracy parameter Q− E and the rather small NME



Topic II

115In: Beta decay with an ultra-low Qvalue



115In: Beta Decay with an Ultra-Low Q Value

First discovered by Cattadori et al. (Nucl. Phys. A 748 (2005) 333)

9/2+ 0.000

1/2− 0.336

3/2+ 0.497

1/2+ 0.000

11549In

11550Sn

T1/2 = 4.4 × 1014a

stable

4.5 h

11 ps

Suggested as a possible independent experiment to look for theneutrino mass



Experimental Results

LNGS (C.M. Cattadori et al.) first observationb = 1.18(31) × 10−6

Tpartial1/2 = 3.73(98) × 1020 a

HADES∗ b = 1.07(17) × 10−6

Tpartial1/2 = 4.1(6) × 1020 a

JYFLTRAP∗ Qβ− = 0.35(17) keV

∗ J.S.E. Wieslander, J. Suhonen, T. Eronen, M. Hult, V.-V. Elomaa, A. Jokinen, G.

Marissens, M. Misiaszek, M.T. Mustonen, S. Rahaman, C. Weber and J. Äystö, Phys.

Rev. Lett. 103 (2009) 122501.

Lowest Q value recorded so far!

Previous record: 187Re Qβ− = 2.469(4) keV 1

1M.S. Basunia, Nucl. Data Sheets 110 (2009) 999.Jouni Suhonen (JYFL, Finland) NCNP 2011 23 / 27


Theory

2nd-forbidden unique 115In(9/2+) → 115Sn(3/2+) decay

dependent on only one nuclear matrix element (NME)M

T1/2 =1

M2fK(w0,Zf ,R)

wave functions from the proton-neutron microscopicquasiparticle-phonon model (pnMQPM)

pnMQPMwas previously successfully applied to the4th-forbidden non-unique 115In(9/2+) → 115Sn(1/2+) g.s.-to-g.s.decay (log ft, half-life, electron spectrum) 2

2M.T. Mustonen and J. Suhonen, Phys. Lett. B 657 (2007) 38.Jouni Suhonen (JYFL, Finland) NCNP 2011 24 / 27


Experiments Meet Theory

0.01

0.1

1

10

100 200 300 400 500

Ha

lf-life

(1

02

0 y

)

Q-value (eV)

Beta decay of 115

In g.s. to the lowest excited state of 115

Sn

JYFLTRAPBJM

BJM = B.J. Mount, M. Redshaw and E.G. Myers, Phys. Rev. Lett. 103 (2009) 122502



Possible Sources of Discrepancy

Nuclear wave functions?

MQPM and pnMQPM take also into account the 3-qp degrees offreedom⇒ Relevant states still dominantly 1-qp states

To explain the discrepancy, the NME should be wrong by a factorof 5 or more!

Maybe the problem lies in the lepton wave functions...

Atomic effects for ultra-low Q values

electron screening (not estimated for forbidden decays)

atomic overlap (previous approximations break down)

exchange effects (contradictory results for low Q values)

final-state interactions (estimates only for tritium beta decay)



Conclusions and Outlook

Conclusions:

The 0νECEC decays of 112Sn and 136Ce are NOT OBSERVABLE due tobadly fulfilled resonance condition

The 0νECEC decay of 74Se is NOT OBSERVABLE due to badly fulfilledresonance condition and tiny NME115In decays by an ultra-low Q value −→ ATOMIC effects important

Outlook:Other resonant 0νECEC decays should be studied for their Q valuesusing the atom trap techniques, e.g. 106Cd

Much work needed to chart the magnitudes of the atomic effects in betadecays with ultra-low Q values. Only then the hunt for the elusiveneutrino mass in these decays is possible.


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