Beta decay of the exotic T z = -2 nuclei 48 Fe, 52 Ni and 56 Zn Sonja Orrigo Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 1
Outline Beta decay experiments ν Radioactive nucleus β -decay spectroscopy of T Z = -1 and T Z = -2 proton-rich nuclei (B. Rubio’s talk) β + Focus on the study of T Z = -2 nuclei (GANIL experiment) Details of the data analysis (differences in comparison to the T Z = -1 case) Experimental results on the exotic 48 Fe , 52 Ni and 56 Zn nuclei Charge-exchange (CE) experiments β -decay and CE experiments are complementary For each nucleus studied via β -decay there is Stable Target already the corresponding CE experiment t ( 3 He,t) 3 He The CE exps. are performed at RCNP Osaka (Y. Fushita, H. Fujita, E. Ganioğlu ) Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 2
Complementarity of β decay and CE reactions Under the assumption of isospin symmetry , mirror Fermi and Gamow Teller transitions are expected to have the same strength β decay gives access to the absolute B(F) and B(GT) values The Charge Exchange cross section is proportional to B(F) and B(GT) Y. Fujita, B. Rubio, W. Gelletly, Progress in Particle and Nuclear Physics 66, 549 (2011) In the present case (T=2): st st t t Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 3
The T = 2 case β -decay esperiments at GANIL β -delayed gamma-proton decay S.E.A. Orrigo, B. Rubio et al., 56 Zn: PRL 112, 222501 (2014) 52 Ni, 48 Fe: in preparation GANIL RCNP CE experiments at RCNP Osaka ( 3 He,t) @ 140 AMeV and ϑ = 0 ° 56 Fe: H. Fujita et al., PRC 88, 054329 (2013) 52 Cr: Y. Fujita et al., PPNP 66, 549 (2011) The T = 1 case 48 Ti: E. Ganioğlu et. al, in preparation Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 4
58 Ni 26+ (74.5 AMeV) + nat Ni @ GANIL 74.5 MeV / nucleon 3.7 e m A intensity Incoming 58 Ni 26+ LISE 3 spectrometer Cyclotrons Ni target ı V 1 Brho1 CSS1 and (natural) wedge Slits CSS2 200 μ m thick Brho2 ı V 2 Slits Wien Filter V 3 ı DETECTORS Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 5
58 Ni 26+ (74.5 AMeV) + nat Ni @ GANIL 74.5 MeV / nucleon 3.7 e m A intensity Incoming 58 Ni 26+ LISE 3 spectrometer Cyclotrons Ni target ı V 1 Brho1 CSS1 and (natural) wedge Slits CSS2 200 μ m thick Brho2 ı V 2 Slits Wien Filter V 3 ı DETECTORS DSSSD detector Implantation and decay ( β , p) 16 strips X and 16 strips Y 300 m m thick 3 mm pitch 5 300 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 6
58 Ni 26+ (74.5 AMeV) + nat Ni @ GANIL 4 EXOGAM clovers 74.5 MeV / nucleon for gamma detection 3.7 e m A intensity Incoming 58 Ni 26+ LISE 3 spectrometer Cyclotrons Ni target ı V 1 Brho1 CSS1 and (natural) wedge Slits CSS2 200 μ m thick Brho2 ı V 2 Slits Wien Filter V 3 ı DETECTORS DSSSD detector Implantation and decay ( β , p) 16 strips X and 16 strips Y 300 m m thick 3 mm pitch 5 300 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 7
New results on T Z = -2 nuclei Beyond the f 7/2 -shell the production is more difficult: ~ 2 imp/min for 56 Zn Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 8
Expected β decay of T Z = -2 nuclei In the T Z = -2 proton-rich nuclei the decay is expected to proceed mostly by proton emission However the p-decay of the T = 2 Isobaric Analogue State (IAS) is usually isospin-forbidden, making possible the gamma emission in competition This situation is very different from the case of T Z = -1 nuclei, where only g emission happens T = 2 β + A X N Z β -delayed T = 1 T Z = -2 p emission T = 2 IAS It is important β -delayed g emission to measure T = 1/2 S p both! A-1 K N+1 Z-2 T Z = -1/2 A Y N+1 Z-1 T Z = -1 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 9
β -decay ↔ Implant correlations The time difference between implants and β -decay events give us the Half-life T 1/2 Each decay is correlated with all the implants happening in the same pixel of the DSSSD (statistical correlation) decay decay decay decay decay decay decay decay decay decay This will result in: Good correlations Random correlations Random Correlations Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 10
The background subtraction procedure DSSSD spectra It is important to remove the background due to random correlations in both DSSSD and g spectra (a) Initial energy spectrum (1 st time cut) (b) Background energy spectrum (2 nd time cut) (c) BG-free energy (subtraction of previous ones) Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 11
The background subtraction procedure Gamma spectra It is important to remove the background due to random correlations in both DSSSD and g spectra (a) Initial energy spectrum (1 st time cut) (b) Background energy spectrum (2 nd time cut) (c) BG-free energy (subtraction of previous ones) Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 12
New results for 48 Fe: the DSSSD spectrum b 48 Fe → 48 Mn* + β + b -delayed protons 48 Mn* → 47 Cr + p T = 2 β + A X N Z T = 1 T Z = -2 p emission IAS T = 2 g emission T = 1/2 S p A-1 K N+1 Z-2 T Z = -1/2 A Y N+1 Z-1 T Z = -1 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 13
48 Fe: the DSSSD spectrum We improved the energy resolution in comparison to a previous experiment C. Dossat et al., NPA 792, 18 (2007) Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 14
48 Fe: comparison of DSSSD and CE spectra The preliminary comparison looks promising! Ela Ganioğlu’s talk Sonja Orrigo HST 2015, Osaka, Japan E. Ganioğlu et al., in preparation 19/11/2015 15
48 Fe: the half-life T 1/2 b 48 Fe → 48 Mn* + β + b -delayed protons 48 Mn* → 47 Cr + p T = 2 β + A X N Z T = 1 T Z = -2 p emission IAS T = 2 Gating on the β -delayed protons: g emission T = 1/2 S p A-1 K N+1 Z-2 T Z = -1/2 A Y N+1 Z-1 T Z = -1 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 16
48 Fe: the gamma spectrum b -delayed gammas 48 Fe → 48 Mn* + β + 48 Mn* → 48 Mn + g T = 2 β + A X N Z T = 1 T Z = -2 p emission 47 Cr* + p IAS T = 2 DSSSD spectrum gated on the 98 keV g ray g emission T = 1/2 S p A-1 K N+1 Z-2 T Z = -1/2 A Y N+1 Z-1 T Z = -1 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 17
The decay scheme of 48 Fe 13% 87% Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 18
New results for 52 Ni: the DSSSD spectrum b -delayed protons b 52 Ni → 52 Co* + β + 52 Co* → 51 Fe + p T = 2 β + A X N Z T = 1 T Z = -2 p emission IAS T = 2 g emission T = 1/2 S p A-1 K N+1 Z-2 T Z = -1/2 A Y N+1 Z-1 T Z = -1 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 19
52 Ni: the DSSSD spectrum We improved statistics and energy resolution in comparison to a previous experiment C. Dossat et al., NPA 792, 18 (2007) Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 20
52 Ni: comparison of DSSSD and CE spectra Good isospin symmetry: All the dominant transition are observed in both spectra Y. Fujita, B. Rubio, W. Gelletly, PPNP 66, 549 (2011) Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 21
52 Ni: the half-life T 1/2 b -delayed protons b 52 Ni → 52 Co* + β + 52 Co* → 51 Fe + p T = 2 β + A X N Z T = 1 T Z = -2 p emission IAS T = 2 Gating on the β -delayed protons: g emission T = 1/2 S p A-1 K N+1 Z-2 T Z = -1/2 A Y N+1 Z-1 T Z = -1 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 22
52 Ni: the gamma spectrum 52 Ni → 52 Co* + β + b -delayed gammas 52 Co* → 52 Co + g T = 2 β + A X N Z T = 1 T Z = -2 p emission IAS T = 2 g emission T = 1/2 S p A-1 K N+1 Z-2 T Z = -1/2 A Y N+1 Z-1 T Z = -1 Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 23
The decay scheme of 52 Ni 25% 75% The analysis is in progress, we will get soon the β -decay strengths Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 24
The decay scheme of 44% 56% 56 Zn First observation of β -delayed gamma-proton decay in the fp -shell β + g p S.E.A. Orrigo et al., Phys. Rev. Lett. 112, 222501 (2014) Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 25
56 Zn: β -decay strengths S.E.A. Orrigo et al., Phys. Rev. Lett. 112, 222501 (2014) Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 26
Summary and outlooks We have studied the β decay of the T Z = -2, 48 Fe, 52 Ni and 56 Zn proton rich-nuclei at GANIL New decay schemes have been determined The corresponding B(F), B(GT) values have been determined (in progress for 52 Ni) β + decay ( 3 He,t) : nice mirror symmetry, helps in the understanding 56 Zn: Isobaric Analogue State Evidence for fragmentation due to strong isospin mixing of 33(10)% Nuclear structure is responsible for the competition of the proton and g decays Shell Model calculations (A. Poves) β + We have observed the β -delayed gamma-proton decay for the first time in the fp -shell in 3 branches This exotic decay affects the conventional determination g of B(GT) in proton-rich nuclei p Importance of detecting the g rays also for p-rich nuclei It is expected to be important in heavier nuclei Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 27
The E556a Collaboration Thank you for your attention! Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 28
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