Erice, September, 2017,

• Double beta (bb) decay neutrinoless double beta (0nbb) decay NME the specialties of 96Zr/ 96Nb for b and bb decay • Mass measurements using the JYFLTRAP ion trap • Results and the issue of the axial vector coupling gA

• Proposal for a m-capture experiment at RCNP to “measure” gA

b

2nbb-decay 0nbb-decay

allowed in Standard Model (ΔL=0) observed experimentally NME can be measured (charge-exchange) no dependence on n mass low-q phenomenon (qtr ~ 0.01 fm-1 )

forbidden in Standard Model (ΔL=2) not observed yet NME only calculated n has Majorana mass high-q phenomenon (qtr ~ 0.5 fm-1 )

eA Z N A Z N e( , ) ( 2, 2) 2 2n A Z N A Z N e( , ) ( 2, 2) 2

1. 48Ca 7. 130Te 2. 150Nd 8. 136Xe

3. 96Zr 9. 124Sn 4. 100Mo 10. 76Ge 5. 82Se 11. 110Pd 6. 116Cd

the b-b- decay candidates with Q-value > 2 MeV

bb

b

EC

(Z, N)

(Z+1, N-1)

(Z+2, N-2)

(even-even)

(even-even)

(odd-odd) 0+

0+

never 0+

bb b

(Z,N) (Z+1, N-1)

(Z+2, N-2)

(even-even)

(even-even)

(odd-odd)

0+

0+

6+ b

48Ca 96Zr

the b-b- decay candidates with Q-value > 2 MeV

1. 48Ca 7. 130Te 2. 150Nd 8. 136Xe

3. 96Zr 9. 124Sn 4. 100Mo 10. 76Ge 5. 82Se 11. 110Pd 6. 116Cd

2nbb decay:

0nbb decay: 2

34 2

13-body

)

2

( , A ei i

i

g U mG Q Z NME

1

2

2410T y

∝ Q5 calculated within models effective Majorana

n mass, mbb

4

allowed (GT)5-body

)

2

( , AgG Q Z NME

∝ Q11 from charge exchange reactions

favorable: 1. high Q-value 2. large Z

The calculated 0nbb decay NME via different models differ by more than a factor of 2-3 ( i.e. half-life 4-9)

P.Vogel, J. Phys. G, NPP39, 2012

• (i) measure Q-value for 96Zr 96Nb single b-decay by precision mass measurement and

(ii) measure the single b-decay rate

(iii) ft-value

• determine the 96Zr 4-fold forbidden

b-decay NME and confront with theory

• confront with same theories aimed at calculating 0nbb-decay NME for the same nucleus!!

natural p unnatural p

Suh

on

en

PLB

2

62

20

05

Idea for 96Zr

2 19

1/2T (2.3 0.2) 10 ynbb NEMO-3: 19

1/2T (0.94 0.32) 10 y geo-chem:

) ) )1 1 1

2

1/2 1/2 1/2T T T

nbb b

) 19

1/2T 1.6 0.9 10 yb

can this difference be reconciled ? yes, if single b competes with bb decay

two conflicting half-lives:

0+ 6+ 6-fold non-unique (unobservably long) 0+ 5+ 4-fold unique (possible) 0+ 4+ 4-fold non-unique (no phase space)

1/2

bT

19

1/2T 2.6 10 yb

expected

experiment

pred. (QRPA) 19

1/2T 24 10 yb

u

AT Q g M

21 13 2 4

1/2( ) ( )

b

b

0

Wieser, PRC64,2001, Barabash, JPG-NPP22, 1996 Heiskanen, JPG3,2007

Q-value uM 4

b T Q M m2 2

0 1 5 0

1/2( )

nbb n

bb bb

1

2

3

1 2 3

h

h

T1/2=23h

2

1/2T nbb 5+

ω- ≈ 1 kHz,

≈ 1 MHz

Homogeneous magnetic field + static electric field provides 3D confinement results in three eigenmotions:

1. Magnetron motion ω- 2. Reduced cyclotron motion ω+ 3. Axial motion ωz

z0

r0

ring

electrode

end cap

Ide

al P

en

nin

g t

rap

Bc

q

m

Figures from Eronen EPJA 48-2012

purification & isobar separation by buffer-gas cooling technique

mass measurement via cyclotron frequency, p < 10-7 mbar.

A/q = 96

ΔB/B = 8.18 × 10-12 /min

Ion source (on-line or off-line )

He

flow

Cyclotron beam

Off-line measurements

On-line measurements

Note IGISOL produces on-line : 96Zr ----- from target material 96Nb ----- (p,n) charge-ex reaction 96Mo----- from havar® separator foil

mother & daughter ions are produced at

IGISOL at the same time

off-line ion source

57% enriched 96Zr target

target (on-line) ion source

10MeV proton beam

Excite ion eigenmotion by a dipolar or a quadrupolar electric

field with a corresponding frequency (n– or nc)

excitation of ion of interest with nc causes

collisional cooling of this species in the presence of the buffer gas

(purification trap: R > 500/1 )

Performing precision mass determination via

cyclotron frequency nc measurement

1 B2

c

q

mn

p

Cyclotron frequency nc determination

done by TOF-ICR technique

nc

at nc ion acquires extra energy shorter time of flight

nrf- nc [MHz]

FWHM = 1 / T rf ωc= 2π νc

r =n

c daughter

nc mother

Frequency ratio

Off resonance

Off resonance

On resonance

On resonance

The measured cyclotron frequency of 96Zr and 96Nb by

Ramsey excitation pattern 25-750-25 ms (on-off-on)

3356.097 0.086 keVQbb

(7.1 keV higher than AME2012)

The measured single b- and b-b- decay Q-values of the A=96 triplet

M. Alanssari et al., PRL 116 (2016) 072501

19

1/2 2

24(QRPA) 10 yr

A

Tg

19

1/2 2

11(SM) 10 yr

A

Tg

Important side effect:

single b decay depends on 2n/0nbb decay depends on

2g

A4

gA

A measurements of single b decay gives experimental handle on the quenching of gA

The muon capture and gA in weak decays

The amazing muon

mm

m

m p

2 51 3

3

1(1 ) (2,196981(2) sec) ( 10 )

192

FG m

5 21,16637(2) 10FG GeV

There has not been any other elementary particle so „successful“ in advancing our knowledge in so many different areas of physics.

Production:

(26ns)

(2.2 s) e

p A X

em

m

pm n

m n n

Eproton ~ 500 MeV

Surface muons: produced from stopped (usually negative) pions at end of target

p p m

n

Em ~ 4.1 MeV qm ~ 30 MeV/c

Life-time:

)m 105.6583745 24 m MeV

Muonium: m + e an exotic hydrogen I ~ 13.6 eV

S (l=0) P (l=1) F (l=3)D (l=2) G (l=4)n

L(nd-2p)

K(np-1s)

M(nf-3d)

N(ng-4f)

1

2

3

4

56

prompt Lyman a-series of atomic m-capture

followed by delayed nucl. capture

( . ) .

~ ( ) ~

~ . .

1 5 1

1 8 6 1

2 2 4 54 10

10 1000 10 10

0 9 1 0

cap total decay

decay

total

Q

s s

ns s

Q

m

Huff-factor

captured by

the nucleus

neutrino

• the neutrino takes most of the energy

• EX(nucl) < 10 – 20 MeV

Motivations • m-cap features momentum transfers similar to 0nbb decay (qtr ~0.5fm

-1 ~100MeV/c)

• m-cap processes to 1 states in A(m-,n)B may be compared with charge-ex reactions of (n,p) type.

• m-cap may give access to gA quenching issue

However • only the 0n-channel (~5%) is most relevant for 0nbb decay • level scheme of final odd-odd nucleus is extremely!! poorly known

The issue of gA queching

56Fe(m,nm)56Mn, (0 n)

56Fe(d,2He)56Mn

Example: Compare transition strength in m-cap and (d,2He) charge-ex

The issue of gA queching 32S(m,nm)32P, (0 n)

32S(d,2He)32P

1H

(d,2

He)

n

32S(d,2He)32P

g.s

.(1+).

78(2

+)

0

10

20

30

-2 0 2 4 6 8 10

40

01

2-dσ

d/σ

)rs/b

mV

ek0

5(/Ed = 183 keV

0o≤ σ lab < 1

o

4710

(1+)

4205

(1+)

1149

(1+)

Ex [MeV]

0+

0

1149.4

512.7

78.1

14.3 d

0+

1+

2+

1+

512.7 keV

78.1 keV

636.6 keV (50%) 1071.3 keV (43%)

Qb = 1710 keV

m-capture

(d,2He)

Example: Compare transition strength in m-cap and (d,2He) charge-ex

The issue of gA queching

24Mg(m,nm)24Na, (0 n)

24Mg(d,2He)24Na

Example: Compare transition strength in m-cap and (d,2He) charge-ex

Schematics of set-up

0 1 2 3stop C C C Cm

target can be used for solids and gas

# of mstop = 8 – 25 x 103 with 20 – 30 MeV/c

C0

g

m--beam

C2

C1target

C3

C0

Clover array

Clover array

C0

g

m--beam

C2

C1target

C3

C0

Clover array

Clover array

1770

1405

Schematics of set-up muon beam line facility

“MuSIC” + “CAGRA” at RCNP Osaka

CAGRA = Clover Array Gamma RAy spectrometer MuSIC = MUon Science Innovative muon beam Channel

The issue of gA queching

But: things are a bit more complicated

there is a pseudo-scalar coupling effective in m-capture with a constant gP ( also badly known !!) What is this ????

Inside the nucleus the muon can decay back into a virtual pion (lots of energy available!!), and the pion generates a final state imprinting it with the parity of the pion. (P(p) = 1)

The effect depends on how many protons there are. 24Mg 12 protons 32S 16 protons 56Fe 26 protons

Conclusion • Precision mass measurement:

96Zr golden case for testing NME’s of 0nbb decay

gives handle on gA for a unique forbidden decay

• m-capture

maybe the only viable tool to study weak response at

high momentum transfer (0nbb decay) and to fix the

gA problem by comparing with (d,2He)