D. Frekers. Novel approaches to the nuclear physics of bb-decay: INT chargex reactions, mass-measurements,m-capture

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1 D. Frekers Novel approaches to the nuclear physics of bb-decay: chargex reactions, mass-measurements,m-capture b n n INT b GT? Gentle Touch: q tr = 0 l = 0 dσ dσ hω excitation σ n n

2 Where do we stand in bb decay when putting together the pieces of the puzzle? 1. General features 2. Chargex-reactions ( 3 He,t) & (d, 2 He) perfect for 2nbb NME s 3. Chargex-reactions limited for 0nbb NME s (here: 2 states and nuclear wave function) 4. Mass measurements 0nbb NME 96 Zr is a golden case (PRL116, Feb-2016) 96 Zr (b ) 96 4u Nb, and g A 5. Muon capture projects starting (MuSIC) a high-q transfer phenomenon!! gives handle on g A quenching

3 -1- General features (2nbb / 0nbb decay)

4 4 2 2 C GF g n A (2 n ) 2 ( b b ) 7 C DGT F ( ) cos( ) M f( Q) 8 2! 2n 4 (2 n ) g A DGT G (Q,Z) M 2 q tr ~ 0.01 fm 1 accessible thru charge-ex reaction

5 M ( 2n ) DGT = = (f) (i) 0g.s. s kt k 1m 1m s kt 0 k k k g.s. 1 (f) + m 2 Q bb(0 g.s.) + E(1 m )- E0 å å m m å ( + ) ( -) m M GT M GT E m å to remember: 1. 2 sequential & allowed b -decays of Gamow-Teller type 2. 1, 2, 3,... forbidden decays negligible 3. Fermi transitions do no contribute (because of different isospin-multiplets) Can be determined via chargeexchange reactions in the (n,p) and (p,n) direction ( e.g. (d, 2 He) or ( 3 He,t) )

6 0n 0n (Q,Z) ( b b ) A! 2 æ ( 0 ) g ö n ç V ( 0n) DGT ç DF èg A ø G = G g M - ç M m 2 n e Majorana-n! 2 q tr ~ 0.5 fm 1!! NOT accessible thru charge-ex reaction

7 The situation of the Nuclear Matrix Elemets for neutrinoless bb decay P. Vogel, J. Phys. G, NPP39, g A

8 -2- Charge-exchange reactions GT-part (2nbb decay)

9 Charge-exchange reactions DE/E ~ 5 x10-5 ~ 25 kev at 420 MeV ( 3 He)

10 76 Ge N-Z=10 Resolution is the key!!!

11 almost 70!! resolved single states up to 5 MeV identified as GT 1+ transitions!!!

12 ~ 70!! single states up to 5 MeV!!! the other leg???? anti-correlation???? (BGT + ): 76 Se(d, 2 He) 76 As MeV is the anti-correlation a property of deformation?? 76Ge moderately oblate/ prolate (b 2 ~ 0.1) (DE = 120 kev) 76Se oblate (b 2 ~ 0.2)

13 ~ 70!! single states up to 5 MeV!!!???? anti-correlation???? the other leg (BGT + ): 76 Se(d, 2 He) 76 As MeV (DE = 120 kev) anti-correlation a property of deformation?? 76Ge moderately oblate/ prolate (b 2 ~ 0.1) 76Se oblate (b 2 ~ 0.2)

14 a surprise: low-e part of NME makes up ~100% of total 2nbb-ME 2nbb (given by T 1/2 = 1.4 x yr) no need for GT giant resonance contribution

15 Nuclear matrix elements and deformation 76 Ge: b ~ Se : b ~ 0.2 reduction of the NME due to deformation is theoretically confirmed but expm lly it seems to manifests itself (in 2nbb decay) by a lack of correlation between the two different B(GT) legs, rather than a reduction of individual strength From: T. R. Rodriguez, et al, PRL105 (2010)

16 100 Mo 2nbb T 1/2 N-Z=16 = 6.9 x yr has the largest NME (NME ~ 0.24/MeV)

17 HERE: almost the entire low-e GT strength is concentrated in the g.s. 100 Mo entire low-energy GT strength is concentrated in a SINGLE STATE and with b logft known M n (g.s.) M (total) 2n 2 DGT DGT No need for GT giant resonance

18 136 Xe 2nbb T 1/2 = 2.2 x yr has the smallest NME question: why so stable!!! (lives 300 times longer than 100 Mo)

19 (2 ) 136Xe

20 What s the size of the NME? n =. T yr ( 2n ) -1 DGT MeV M. all signs positive > m ( + ) - 2 GT ( -» ) m GT B 10 B ( + ) - 3 m» B GT 10!!!!

21 A. Poves (simultaneous to our publication): NO CANCELLATION!! there is no B(GT + ) strength, except for lowest 1 + state Recall: 136 Xe is almost doubly magic!! 3x10-3 Shell model provides conclusive explanation for the deemed pathologically long half-life of 136 Xe. Expt l test: 136 Ba(d, 2 He) 136 Cs

22 -3- Charge-exchange reactions spin-dipole part (0nbb decay)

23 Charge-exchange reaction towards the 0nbb NME s Here: 2 - states via chargex reactions

24 (Poves) 35!!!

25

26 Low-energy spin-dipole (2 ) strength to test nuclear wave function for 0nbb decay NME s SD d m k N K ( M 2). d k r A q max 2 qmax f J 2 D 1/3 i 0 2 MODELS QRPA reasonable description no-core QRPA washes out shell structures forbidden in the extreme shell model FSQP semi-microscopic model, excellent description of data

27 -4- Mass measurements and 0nbb NMEs 96 Zr

28 b b decay (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 highest Q-value

29 b b decay 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 highest Q-value

30 Suhonen PLB Idea measure Q-value for 96 Zr 96 Nb single b-decay by precision mass measurement measure the single b-decay rate ft-value determine the 96 Zr 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 unnatural

31 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 expected experiment pred. (QRPA) 2nbb b T1/2 ) T1/2 ) T1/2 ) /2 ) 19 T b y T b 1/2 T b y 1/ y 19 ( ) ( ) 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

32 Results Q bb kev 7.1 kev higher than AME2012 Q b kev

33 Next: need T 1/2 of single b decay T /2(QRPA) 10 yr 2 ga T (SM) 11 1/2 2 ga T yr 19 1/2 (exp) 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 expmtl handle on the quenching of g A

34 0nbb NMEs 1. what about getting the 0nbb NMEs? 2. what about how to test the models? 3. what are the expmtl tools? P. Vogel, J. Phys. G, NPP39, 2012 investigate higher-order forbidden matrix elements of type (0 2 ; 0 3 ;... ) limited possibilities, not promising are there nuclei, where b and bb decay are in competition? YES! 48 Ca and 96 Zr can muon-nuclear physics help? YES m-capture a potentially powerful tool

35 Muon capture and 0nbb NMEs 56 Fe 24 Mg 32 S

36 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 (~10%) is relevant for 0nbb decay level scheme of final odd-odd nucleus is extremely poorly known

37 The muon capture and g A in weak decays

38 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 (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 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 ,16637(2) 10 GeV m MeV m ) Muonium: m + e an exotic hydrogen I ~ 13.6 ev

39 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

40 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

41 1 0-2 dσ d g.s.(1+). 78(2+) /( (1+) kev mb/sr 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 / σ ) H(d,2He) n E d = 183 kev 0 o σ lab < 1 o E x [MeV]

42 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

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

44 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

45 The issue of g A queching But: Hold your horses!!! 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( ) = 1) The effect depends on how many protons there are. 24 Mg 12 protons 32 S 16 protons 56 Fe 26 protons

46 Charge-ex reactions: useful tool for 2nbb decay NME s. Spin-dipole excitation via charge-ex: used for first time, low-e spin-dipole strength mirrors ground-state properties Precision mass measurement: 96 Zr is a golden case for testing 0n NME s and getting experimental handle on g A m-cap: Conclusion maybe the only viable tool to study weak response at high momentum transfer and to fix the g A problem by comparing with (d, 2 He)