Beta decay of the exotic T z = -2 nuclei 48 Fe, 52 Ni and 56 Zn - - PowerPoint PPT Presentation

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Beta decay of the exotic T z = -2 nuclei 48 Fe, 52 Ni and 56 Zn - - PowerPoint PPT Presentation

Nov 04, 2022 674 likes •970 views

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 Radioactive nucleus -decay spectroscopy of T Z = -1 and T Z = -2

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 1

Beta decay of the exotic Tz = -2 nuclei 48Fe, 52Ni and 56Zn

Sonja Orrigo

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 2

Outline

Beta decay experiments

  • β-decay spectroscopy of TZ = -1 and TZ = -2

proton-rich nuclei (B. Rubio’s talk)

  • Focus on the study of TZ = -2 nuclei (GANIL experiment)
  • Details of the data analysis (differences in comparison to the TZ = -1 case)
  • Experimental results on the exotic 48Fe, 52Ni and 56Zn nuclei

3He

Stable Target t

(3He,t)

β+ ν Radioactive nucleus

Charge-exchange (CE) experiments

  • β-decay and CE experiments are complementary
  • For each nucleus studied via β-decay there is

already the corresponding CE experiment

  • The CE exps. are performed at RCNP Osaka

(Y. Fushita, H. Fujita, E. Ganioğlu)

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 3

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)

st t t st

In the present case (T=2):

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 4

The T = 2 case

GANIL RCNP

  • CE experiments at RCNP Osaka

(3He,t) @ 140 AMeV and ϑ = 0°

56Fe: H. Fujita et al., PRC 88, 054329 (2013) 52Cr: Y. Fujita et al., PPNP 66, 549 (2011) 48Ti: E. Ganioğlu et. al, in preparation

  • β-decay esperiments at GANIL

S.E.A. Orrigo, B. Rubio et al.,

56Zn: PRL 112, 222501 (2014) 52Ni, 48Fe: in preparation

β-delayed gamma-proton decay

  • The T = 1 case
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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 5

58Ni26+ (74.5 AMeV) + natNi @ GANIL

Ni target (natural) Incoming 58Ni26+ V1

ı

V2

ı

V3

ı

Brho1 Brho2 Slits Slits wedge Wien Filter DETECTORS

Cyclotrons CSS1 and CSS2

74.5 MeV / nucleon

3.7 emA intensity 200 μm thick

LISE 3 spectrometer

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 6

58Ni26+ (74.5 AMeV) + natNi @ GANIL

Ni target (natural) Incoming 58Ni26+ V1

ı

V2

ı

V3

ı

Brho1 Brho2 Slits Slits wedge Wien Filter DETECTORS

Cyclotrons CSS1 and CSS2

74.5 MeV / nucleon

3.7 emA intensity 200 μm thick

LISE 3 spectrometer

300 5

DSSSD detector Implantation and decay (β, p)  16 strips X and 16 strips Y  300 mm thick  3 mm pitch

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 7

58Ni26+ (74.5 AMeV) + natNi @ GANIL

Ni target (natural) Incoming 58Ni26+ V1

ı

V2

ı

V3

ı

Brho1 Brho2 Slits Slits wedge Wien Filter DETECTORS

Cyclotrons CSS1 and CSS2

74.5 MeV / nucleon

3.7 emA intensity 200 μm thick

LISE 3 spectrometer

300 5

DSSSD detector Implantation and decay (β, p)  16 strips X and 16 strips Y  300 mm thick  3 mm pitch

4 EXOGAM clovers for gamma detection

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 8

New results on TZ = -2 nuclei

Beyond the f7/2-shell the production is more difficult: ~ 2 imp/min for 56Zn

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 9

Expected β decay of TZ = -2 nuclei

In the TZ = -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 TZ = -1 nuclei, where only g emission happens

Z AXN

TZ = -2 T = 2 T = 2 T = 1/2 β-delayed p emission IAS

Sp

T = 1 β+

Z-1 AYN+1

TZ = -1

Z-2 A-1KN+1

TZ = -1/2 β-delayed g emission

It is important to measure both!

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 10

β-decay ↔ Implant correlations

The time difference between implants and β-decay events give us the Half-life T1/2 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

 Good correlations

Random Correlations

This will result in:  Random correlations

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 11

The background subtraction procedure

It is important to remove the background due to random correlations in both DSSSD and g spectra (a) Initial energy spectrum (1st time cut) (b) Background energy spectrum (2nd time cut) (c) BG-free energy (subtraction of previous ones) DSSSD spectra

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 12

The background subtraction procedure

It is important to remove the background due to random correlations in both DSSSD and g spectra (a) Initial energy spectrum (1st time cut) (b) Background energy spectrum (2nd time cut) (c) BG-free energy (subtraction of previous ones) Gamma spectra

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 13

New results for 48Fe: the DSSSD spectrum

b-delayed protons b

48Fe → 48Mn* + β+ 48Mn* → 47Cr + p Z AXN

TZ = -2 T = 2 T = 2 T = 1/2 p emission IAS

Sp

T = 1 β+

Z-1 AYN+1

TZ = -1

Z-2 A-1KN+1

TZ = -1/2 g emission

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 14

48Fe: the DSSSD spectrum

  • C. Dossat et al., NPA 792, 18 (2007)

We improved the energy resolution in comparison to a previous experiment

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 15

48Fe: comparison of DSSSD and CE spectra

The preliminary comparison looks promising!

  • E. Ganioğlu et al., in preparation

Ela Ganioğlu’s talk

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 16

48Fe: the half-life T1/2

48Fe → 48Mn* + β+ 48Mn* → 47Cr + p

b-delayed protons b

Gating on the β-delayed protons:

Z AXN

TZ = -2 T = 2 T = 2 T = 1/2 p emission IAS

Sp

T = 1 β+

Z-1 AYN+1

TZ = -1

Z-2 A-1KN+1

TZ = -1/2 g emission

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 17

48Fe: the gamma spectrum

48Fe → 48Mn* + β+ 48Mn* → 48Mn + g Z AXN

TZ = -2 T = 2 T = 2 T = 1/2 p emission IAS

Sp

T = 1 β+

Z-1 AYN+1

TZ = -1

Z-2 A-1KN+1

TZ = -1/2 g emission

b-delayed gammas

DSSSD spectrum gated on the 98 keV g ray

47Cr* + p

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 18

The decay scheme of

48Fe

13% 87%

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 19

52Ni → 52Co* + β+ 52Co* → 51Fe + p

New results for 52Ni: the DSSSD spectrum

b-delayed protons b

Z AXN

TZ = -2 T = 2 T = 2 T = 1/2 p emission IAS

Sp

T = 1 β+

Z-1 AYN+1

TZ = -1

Z-2 A-1KN+1

TZ = -1/2 g emission

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 20

52Ni: the DSSSD spectrum

We improved statistics and energy resolution in comparison to a previous experiment

  • C. Dossat et al., NPA 792, 18 (2007)
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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 21

52Ni: 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)

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 22

52Ni: the half-life T1/2

Z AXN

TZ = -2 T = 2 T = 2 T = 1/2 p emission IAS

Sp

T = 1 β+

Z-1 AYN+1

TZ = -1

Z-2 A-1KN+1

TZ = -1/2 g emission

52Ni → 52Co* + β+ 52Co* → 51Fe + p

Gating on the β-delayed protons:

b-delayed protons b

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 23

52Ni: the gamma spectrum

52Ni → 52Co* + β+ 52Co* → 52Co + g Z AXN

TZ = -2 T = 2 T = 2 T = 1/2 p emission IAS

Sp

T = 1 β+

Z-1 AYN+1

TZ = -1

Z-2 A-1KN+1

TZ = -1/2 g emission

b-delayed gammas

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 24

The decay scheme of

52Ni

25% 75%

The analysis is in progress, we will get soon the β-decay strengths

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 25

The decay scheme of

56Zn

First observation of β-delayed gamma-proton decay in the fp-shell g p β+

S.E.A. Orrigo et al., Phys. Rev. Lett. 112, 222501 (2014)

44% 56%

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 26

56Zn: β-decay strengths

S.E.A. Orrigo et al., Phys. Rev. Lett. 112, 222501 (2014)

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 27

Summary and outlooks

We have studied the β decay of the TZ = -2, 48Fe, 52Ni and 56Zn proton rich-nuclei at GANIL  New decay schemes have been determined  The corresponding B(F), B(GT) values have been determined (in progress for 52Ni) β+ decay  (3He,t) : nice mirror symmetry, helps in the understanding 56Zn: 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) 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

  • f B(GT) in proton-rich nuclei

 Importance of detecting the g rays also for p-rich nuclei  It is expected to be important in heavier nuclei

g p β+

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Sonja Orrigo HST 2015, Osaka, Japan 19/11/2015 28

The E556a Collaboration

Thank you for your attention!