Erice, September, 2017,

Transcription

1 Erice, September, 2017,

2 Double beta (bb) decay neutrinoless double beta (0nbb) decay NME the specialties of 96 Zr/ 96 Nb for b and bb decay Mass measurements using the JYFLTRAP ion trap Results and the issue of the axial vector coupling g A Proposal for a m-capture experiment at RCNP to measure g A

3 A( Z, N ) A( Z 2, N 2) 2e 2n A( Z, N ) A( Z 2, N 2) 2e allowed in Standard Model (ΔL=0) observed experimentally NME can be measured (charge-exchange) no dependence on n mass low-q phenomenon (q tr ~ 0.01 fm -1 ) e b forbidden in Standard Model (ΔL=2) not observed yet NME only calculated n has Majorana mass high-q phenomenon (q tr ~ 0.5 fm -1 ) 2nbb-decay 0nbb-decay

4 (even-even) 0 + (Z, N) EC never 0 + (Z+1, N-1) (odd-odd) b b b 0 + (Z+2, N-2) (even-even) Ca Te Nd Xe Zr Sn Mo Ge Se Pd Cd the b-b- decay candidates with Q-value > 2 MeV

5 48 Ca 96 Zr (even-even) 0 + (Z,N) b b b 6 + (Z+1, N-1) (odd-odd) b 0 + (Z+2, N-2) (even-even) Ca Te Nd Xe Zr Sn Mo Ge Se Pd Cd the b-b- decay candidates with Q-value > 2 MeV

6 2nb b decay: G Q Z 4 (, ) ga 5-body NME allowed (GT) 2 0nb b decay: T y G Q Z 3-body Q NME from charge exchange reactions (, ) ga Ueimi 2 i1 2 favorable: 1. high Q-value 2. large Z Q 5 calculated within models effective Majorana n mass, m bb

7 P.Vogel, J. Phys. G, NPP39, 2012 The calculated 0nbb decay NME via different models differ by more than a factor of 2-3 ( i.e. half-life 4-9)

8 Suhonen PLB Idea for 96 Zr (i) measure Q-value for 96 Zr 96 Nb single b-decay by precision mass measurement and (ii) measure the single b-decay rate (iii) ft-value determine the 96 Zr 4-fold forbidden b-decay NME and confront with theory natural p unnatural p confront with same theories aimed at calculating 0nbb-decay NME for the same nucleus!!

9 NEMO-3: geo-chem: two conflicting half-lives: 2 19 T nbb 1/2 ( ) 10 y 19 T ( ) 10 y 1/2 can this difference be reconciled? yes, if single b competes with bb decay 2nbb b T1/2 ) T1/2 ) T1/2 ) ) 19 expected 1/2 experiment T 1/2 pred. (QRPA) T y T b y 1/2 ( ) ( ) y b u T Q g A M 2 1/2 0 b b T1/ fold non-unique (unobservably long) fold unique (possible) fold non-unique (no phase space) T 1/2 =23h 2 T nbb 5 + 1/2 h h Q-value u M 4 0nbb b ( T1/2 ) n Q M bb mbb Wieser, PRC64,2001, Barabash, JPG-NPP22, 1996 Heiskanen, JPG3,2007

10 Ideal Penning trap Homogeneous magnetic field + static electric field provides 3D confinement results in three eigenmotions: 1. Magnetron motion ω - end cap 2. Reduced cyclotron motion ω + 3. Axial motion ω z z 0 ring electrode r0 ω - 1 khz, 1 MHz c q m B

11 Figures from Eronen EPJA Ion source (on-line or off-line ) A/q = 96 He flow Cyclotron beam ΔB/B = /min purification & isobar separation by buffer-gas cooling technique mass measurement via cyclotron frequency, p < 10-7 mbar.

12 Off-line measurements On-line measurements off-line ion source 57% enriched 96 Zr target Note IGISOL produces on-line : 96 Zr from target material 96 Nb (p,n) charge-ex reaction 96 Mo----- from havar separator foil 10MeV proton beam target (on-line) ion source mother & daughter ions are produced at IGISOL at the same time

13 Excite ion eigenmotion by a dipolar or a quadrupolar electric field with a corresponding frequency (n or n c ) excitation of ion of interest with n c causes collisional cooling of this species in the presence of the buffer gas (purification trap: R > 500/1 )

14 Performing precision mass determination via cyclotron frequency n c measurement n c 1 2p q m B ω c = 2π ν c FWHM = 1 / T rf Cyclotron frequency n c determination done by TOF-ICR technique n c n rf- n c [MHz] Frequency ratio r = n c daughter n c mother at n c ion acquires extra energy shorter time of flight

15 Off resonance On resonance Off resonance On resonance

16 The measured cyclotron frequency of 96 Zr and 96 Nb by Ramsey excitation pattern ms (on-off-on)

17 Q bb kev (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)

18 T /2(QRPA) 10 yr 2 ga T (SM) 11 1/2 2 ga yr Important side effect: single b decay depends on 2n/0nbb decay depends on 2 g A4 g A A measurements of single b decay gives experimental handle on the quenching of g A

19 The muon capture and g A in weak decays

20 GF The amazing muon There has not been any other elementary particle so successful in advancing our knowledge in so many different areas of physics. Production: p A X p (26ns) m nm (2.2ms) e n e n E proton ~ 500 MeV m Surface muons: produced from stopped (usually negative) pions at end of target Life-time: p p E m ~ 4.1 MeV q m ~ 30 MeV/c m n GFmm 1 3 m (1 ) (2,196981(2) m sec) ( 10 ) 3 m 192p 5 2 1,16637(2) 10 GeV m MeV m ) Muonium: m + e an exotic hydrogen I ~ 13.6 ev

21 n neutrino S (l=0) P (l=1) D (l=2) F (l=3) K(np-1s) L(nd-2p) M(nf-3d) G (l=4) N(ng-4f) prompt Lyman a-series of atomic m-capture followed by delayed nucl. capture Q cap total decay Huff-factor 1 captured by the nucleus decay total ( 2. 2ms) ~ ( ns) ~ Q ~ s s the neutrino takes most of the energy E X (nucl) < MeV

22 Motivations m-cap features momentum transfers similar to 0nbb decay (q tr ~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 g A 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

23 The issue of g A queching 56 Fe(m,n m ) 56 Mn, (0 n) 56 Fe(d, 2 He) 56 Mn Example: Compare transition strength in m-cap and (d, 2 He) charge-ex

24 1 0 2 g.s.(1+). 78(2+) 1149 (1+) 4205 (1+) 4710 (1+) 1+ The issue of g A queching m-capture S(m,n m ) 32 P, (0 n) kev (50%) kev (43%) kev 78.1 kev d (d, 2 He) 32 S(d, 2 He) 32 P Q b = 1710 kev S(d, 2 He) 32 P Example: Compare transition strength in m-cap and (d, 2 He) charge-ex - dσ / d σ /(50 kev mb/sr ) H(d,2He) n E d = 183 kev 0 o σ lab < 1 o E x [MeV]

25 The issue of g A queching 24 Mg(m,n m ) 24 Na, (0 n) 24 Mg(d, 2 He) 24 Na Example: Compare transition strength in m-cap and (d, 2 He) charge-ex

26 Schematics of set-up C0 Clover array m--beam C1 C2 g target C3 C0 Clover array mstop C0 C1 C2 C3 # of mstop = 8 25 x 10 3 with MeV/c target can be used for solids and gas

27 Schematics of set-up muon beam line facility MuSIC + CAGRA at RCNP Osaka C0 Clover array m--beam C1 C2 g target C3 C0 Clover array 1770 CAGRA = Clover Array Gamma RAy spectrometer MuSIC = MUon Science Innovative muon beam Channel 1405

28 The issue of g A queching But: things are a bit more complicated there is a pseudo-scalar coupling effective in m-capture with a constant g P ( 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. 24 Mg 12 protons 32 S 16 protons 56 Fe 26 protons

29 Conclusion Precision mass measurement: 96 Zr golden case for testing NME s of 0nbb decay gives handle on g A 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 g A problem by comparing with (d, 2 He)

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