Studies of Gamow-Teller transitions using Weak and Strong - PowerPoint PPT Presentation

Studies of Gamow-Teller transitions using Weak and Strong Interactions High-resolution Spectroscopy & Tensor Interaction @ Nakanoshima, Osaka Nov. 16 – Nov. 19, 2015 Yoshitaka FUJITA RCNP, Osaka Univ.

Neptune = Neptune driving Waves weak interaction   decay Powerful Waves = strong interaction)  Charge-Exchange Reaction

Gamow-Teller transition ｓ Mediated by  operator: both S &W int. has this Op .  S = -1, 0, +1 and  T = -1, 0, +1 (  L = 0, no change in radial w.f. )  no change in spatial w.f. Accordingly, transitions among j > and j < configurations j >  j > , j <  j < , j >  j < example f 7/2  f 7/2 , f 5/2  f 5/2 , f 7/2  f 5/2 Note that Spin and Isospin are unique quantum numbers in atomic nuclei !  GT transitions are sensitive to Nuclear Structure !  GT transitions in each nucleus are UNIQUE !

**Basic common understanding of  -decay and Charge-Exchange reaction  decays : Absolute B (GT) values, but usually the study is limited to low-lying states (p,n), ( 3 He,t) reaction at 0 o : Relative B (GT) values, but Highly Excited States ** Both are important for the study of GT transitions!

 -decay & Nuclear Reaction  2 1   -decay GT tra. rate = ( GT ) f B t K 1 / 2 B (GT) : reduced GT transition strength  (matrix element) 2 = |<f|  |i>| 2 *Nuclear (CE) reaction rate (cross-section) = reaction mechanism x operator =(matrix element) 2 x structure *At intermediate energies (100 < E in < 500 MeV) d  /d  ( q =0) : proportional to B (GT)

Simulation of  -decay spectrum f-factor (normalied) 1.2 5000 Counts + 50 Cr( 3 He,t) 50 Mn g.s.(IAS),0 + 1 0.651,1 4000 E=140 MeV/nucleon o 0.8 θ =0 3000 + + 2.441,1 3.392,1 Q EC =8.152 MeV 0.6 2000 0.4 1000 0.2 0 0 0 1 2 3 4 5 6 5 0 Mn (MeV) x in E 5000 β intensity (relative) + β -decay: 50 Fe --> 50 Mn g.s.(IAS),0 + 0.651,1 4000 *expected spectrum assuming isospin symmetry 3000 + + 2.441,1 3.392,1 Q EC =8.152 MeV 2000 1000 0 0 1 2 3 4 5 6 5 0 Mn (MeV) x in E Y.F, B.R, W.G, PPNP, 66 (2011) 549

Comparison of (p, n) and ( 3 He,t) ０ o spectra 58 Ni( p , n ) 58 Cu Counts E p = 160 MeV IAS J. Rapaport et al. 58 Ni( 3 He, t ) 58 Cu NPA (‘83) E = 140 MeV/u GTR Y. Fujita et al., GT EPJ A 13 (’02) 411. H. Fujita et al., PRC 75 (’07) 034310 0 2 4 6 8 10 12 14 Excitation Energy (MeV)

( 3 He,t) CE Reactions @ RCNP (Osaka) θ lab = 0 ° (3He,t) CE reaction Stable Target 3He WS course (beam line) Commissioning: 2000 triton T. Wakasa, K. Hatanaka, Y. Fujita, 3 He G.P.A. Berg, H. Fujimura, H. Fujita, M. Itoh, J. Kamiya, T. Kawabata et al., N.I.M. A 482 (2002) 79.

Matching Techniques Y. Fujita et al., N.I.M. B 126 (1997) 274. H. Fujita et al., N.I.M. A 484 (2002) 17. a) b) c) Focal plane Magnetic Spectrometer Target 0 + Δ p - Δ p - Δ p + Δ p 0 Angular dispersion Lateral dispersion Achromatic beam matching matching transportation  E ～  E ～ 200 keV 35 keV  sc ～ 5mrad 3 He beam for 140MeV/u Horiz. angle resolution  sc > 15mrad

RCNP, Osaka Univ.  E=30 keV Dispersion Matching Techniques were applied!  E=150 keV Y. Fujita et al, NIM B 126 (1997) 274. H. Fujita et al, NiM A 484 (2002) 17.

Connection ： Charge Exchange &  decay ** 0 + & 1 + relationship of g.s. 0 +  1 + 0 + & 1 + relationship log ft in A=58 Nuclei 58 Cu 4.8 (in real energy space) 58 Ni 62 Ni 1 + 5.2 1 + 62 Ni 68 Ga 5.2 68 Zn 78 Br (p,n)-type 1 + 4.8 78 Se 104 Rh 0 + 4.3 , IAS 1 + 104 Ru 1 + 118 Sb 4.5 118 Sn 58 Cu 120 Sb 4.5  -decay Tz=0 120 Sn 136 La 0 + 4.6 QEC=8.56 136 Ba (stable) 140 Pr 4.4 58 Ni 140 Ce 178 Ta 4.7 Tz=+1 178 Hf

***Isospin Symmetry an important idea to see the connection of decays and excitations caused by Strong, EM and Weak interactions ! There are many cases that the “operators” are the same in transitions caused by “strong,” “EM” and “weak” int.

T=1/2 Isospin Symmetry Koelner Dom Koeln, Germany (157m high)

T =1/2 Mirror Nuclei : Structures & Transitions (p,n)-type V  (e,e')  -decay  -d ecay M1 M1 M1 GT  -decay ( 3 He,t)   V  V  (Z+1,N) (Z,N+1) Tz=+1/2 Tz=-1/2 GT + Fermi 27 27 13 Al 14 14 Si 13

Symmetry in A=27 System d KN J 2 B G q 0 T d 2 J π 2 J π 3 + 2.98 2.88 3 + 5 + 2.74 5 + 2.65 7 + 2.21 7 + 2.17 3 + 3 + 1.01 0.98  decay ( 3 He, t ) Good proportionality g.s. g.s. 5 + 5 + between both B(GT)s ! 27 27 13 Al 14 14 Si 13 T z =1/2 T z =-1/2

Analogous relationship: A=9, 13 system 15.06 3/2 - 14.66 T =3/2 9 Li 9 C log ft =5.3 log ft =5.3 13 B 13 O log ft =4.1 log ft =4.0 g.s. 3/2 - T =1/2  9 Be 9 B 13 C 13 N log ft =3.7 All of them are T z =+3/2 T z = +1/2 T z = -1/2 T z = -3/2 analogous ! *Small isospin asymmetry can be seen for T z =+3/2  +1/2 and T z =-1/2  -3/2 GT transitions.

T=1 Isospin Symmetry Byodoin-temple, Uji, Kyoto

T=1 Isospin Symmetry GT GT 26 14 Si 12 26 26 12 Mg 14 13 Al 13 T z = +1 T z = 0 T z = -1

Tz=+1  0  -1 Symmetry  + direction  - direction (n,p)-type (p,n)-type [e-capture]

Super-Byodoin 平等院 T=2 Isospin Symmetry GT GT  + -decay CE-reaction 52 Ni 52 Cr 52 Mn 52 Fe 52 Co

Isospin Structure of T=2 system Talk by S. Orrigo: 48 Fe, 52 Ni, 56 Zn  decay

**GT transitions in each nucleus are UNIQUE ! - pf -shell nuclei -

rp -process Path 58 Zn (T=1 system) Z 54 Ni 58 Ni 50 Fe 54 Fe N=Z line 46 Cr 50 Co 42 Ti 46 Ti 42 Ca N

58 Ni Talk: B. Rubio N 54 Fe 50 Cr 46 Ti rp -process path nuclei 42 Ca N=Z line ( T = 1 symmetry) Z

14 54 Ni  -decay x (MeV) measurement Energy Resolution : 21 keV 12 ο E E = 140 MeV/u, θ = 0 •at GSI (FRS facility) 10 54 Co •RISING 0+ 3 He,t) 54 Ni (stopped beam campaign) 8  + decay 54 Fe( Q =8.800 6 S p =4.35 4 Measurement of delayed-  is important ! 2 0.937, 1 + g.s. IAS IAS 0 1000 800 600 400 200 0 Counts

GSI RISING set up Active Beam Stopper Campaign July-August, 2007

( 3 He,t), RCNP Osaka, T. Adachi et al. Talk: B. Rubio Newly observed ! Corresponding Transitions were observed  decay, GSI, Rising 2007 in a wide E x range ! F. Molina et al., PRC 91, 014301 (‘15)

42 Ca( 3 He,t) 42 Sc in 2 scales B(GT) = 2.2 (from mirror  decay) B(F)=2 80% of the total B(GT) strength is concentrated in the excitation of the 0.611 MeV state.

GT states B(F)=N-Z in A=42-54 Peak heights are T z =0 nuclei proportional to B(GT) values Y. Fujita et al. PRL 2014 PRC 2015 T. Adachi et al. PRC 2006 Y. Fujita et al. PRL 2005 T. Adachi et al. PRC 2012

SM Configurations of GT transitions 28 20   particle-hole configuration + IV-type int. = REPULSIVE

Role of Residual Int. (repulsive) Single particle-hole 1p-1h strength strength strength distribution Graphical solution of the Ex RPA dispersive eigen-equation positive = repulsive Ex p-h configuration + IV excitation collective = repulsive strength (GR) Collective excitation strength formed by the repulsive residual interaction Ex

Role of Residual Int. (repulsive) 1p-1h strength strength Collective excitation formed by the repulsive residual interaction Ex Ex collective strength (GR) strength Ex

42 Ca( 3 He,t) 42 Sc in 2 scales B(GT) = 2.2 (from mirror  decay)

SM Configurations of GT transitions 28 20    -p -  -p configurations particle-hole configurations sensitive to IS pairing int. + IV-type excitation (  )  attractive  repulsive (spin-triplet, IS int. is stronger than spin-singlet, IV int.) by Engel, Bertsch, Macchiavelli

SM Configurations of GT transitions 28 20   particle-particle int. (attractive) particle-hole int. (repulsive) (IS p-n int. is attractive) Isoscalar interaction Overwhelming the repulsive nature of  int. ! can play Important roles !

QRPA-cal. GT-strength (with IS-int.) Bai, Sagawa, Colo et al., PRC 90 (2014) 054335 42 Ca 42 Ca  42 Sc (Q-value)

QRPA cal. including IS int. Bai, Sagawa, Colo et al., PRC 90 (2014) 054335 Configurations are in phase! Low-energy collective GT excitation ! (collectivity is from IS p-n int. !)

Role of Residual Int. (attractive) strength Collective excitation formed by the attractive IS residual interaction Ex 42 Ca( 3 He,t) 42 Sc Ex collective strength strength (GR) Ex

42Ca  42Sc: Shell Model Cal.: Transition Matrix Elements SM cal: M. Honma 1 + 1 Matrix Elements are in-phase !

42 Ca( 3 He,t) 42 Sc in 2 scales GT IAS Low-energy collective GT excitation ! B(GT) = 2.2 (collectivity is from IS p-n int. !) Low Energy Super GT state Suggestion in  p-pRPA calculation (K. Yoshida) Precursory soft mode of the IS pairing condensation ! Phys. Rev. C 90 , 031303(R) (2014). Y. Fujita, et al., PRL 112, 112502 (2014). PRC 91, 064316 (2015).

Super-allowed GT transitions in  decay (smaller log ft  larger B(GT)) GT Fermi 5 0 10 log ft 6 He, 0 +  6 Li, 1 + log ft = 2.9 Super-allowed 18 Ne, 0 +  18 F, 1 + log ft = 3.1 GT transitions 42 Ti, 0 +  42 Sc, 1 + log ft = 3.2