introduction shell evolution along ni isotopic chain, towards 78 ni. focus on 74 ni existing data....

Shell evolution in exotic Ni isotopes

T. Marchi11th INTERNATIONAL SPRING SEMINAR ON NUCLEAR PHYSICS

SHELL MODEL AND NUCLEAR STRUCTURE: achievements of the past two decades Ischia, May 12 – 16 2014

Shell evolution in exotic Ni isotopes

T. Marchi

Introduction

• Shell evolution along Ni isotopic chain, towards 78Ni.

Focus on 74Ni• Existing data.• Intermediate energy Coulomb excitation (NSCL 09031):

Exotic Beam production; Experimental setup; Data analysis and B(E2)↑ extraction; Comparison with SM calculations.

Conclusion and Outlook

11th INTERNATIONAL SPRING SEMINAR ON NUCLEAR PHYSICSSHELL MODEL AND NUCLEAR STRUCTURE: achievements of the past two decades

Ischia, May 12 – 16 2014

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[N. Shimizu et al, Progr. Theo. Exp. Phys (2012) 01A205 ]

Introduction

T. Marchi 11th INTERNATIONAL SPRING SEMINAR ON NUCLEAR PHYSICS Ischia, May 12 – 16 2014

[N. Shimizu et al, Progr. Theo. Exp. Phys (2012) 01A205 ]

Introduction


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Motivation:1-Study the evolution of nuclear Shells far from stability, towards 78Ni.2-Test model space and interactions far from stability.

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Shell Evolution

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104

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501] Proton ESPE for Ni isotopes

[K. Sieja and F. Nowacki, Phys Rev C 85, 051301]

Neutron ESPE for N=50 isotones and for Ni isotopes

See also: H. L. Crawford, PRL 110, 242701 (2013) on Fe/Cr isotopes. “twin experiment”. And S. M. Lenzi, PRC 82, 054301 (2010)

Introduction


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74Ni Existing data – 74Co β-decay


Existing data - proton scattering(p,p’) extracted from proton inelastic scattering cross section using distorted wave theory. (ECIS97 code)

[N. Aoi et al, Phys. Lett. B 602, 302 (2010)][B. Pritychenko et al, At. Dat. And Nucl. Dat. Tab. 98, 4 (2012) 798]

Assuming comparable deformation lengths also for the neutron rich part of the chain: (p,p’) C B(E2) = 1270(380) e2fm4

N=46


74Ni

Radioactive ion beam production

86Kr34+ @ 140 AMeV74Ni ≈ 0.7 pps

dp/p = 3%9Be 399 mg/cm2


74Ni

Experimental setup

Object scintillator

Secondary target position

197Au 640 mg/cm2

S800 Analysis line

S800 Spectrometer

Focal Plane detectors

CAESAR array


74Ni

The S800 spectrometer and the CAESAR array

CAESAR array

CAESAR array + S800 spectrometer


74Ni

Beam Tagging and Particle Identification

Focal plane PID Beam Tagging

Runs without target


74Ni

Data analysis: particle and gamma ray time gates

Energy-time gamma-rays gate:


74NiImpact parameter selection:

Two main issues


Beam contaminationUngated PID

Gated PID

Background modeling

74Ni

EPAX: 76Cu 1p-1n K.O. : σ = 29 mb NK.O. =18±9 Ng = 9 ±5

E (keV)

E (keV)

Event by event analysis and gamma-ray spectra

Fit: GEANT4 +exponential bkg

[A. Winther and K. Alder, Nucl. Phys. A319, 518 (1979)]

= 148+50-52 mb B(E2; 0+ -> 2+) = 642+216

-226 e2 fm4


74Ni

Ng = 99 ± 28

The B(E2; 0+ →2+) value obtained in the intermediate energy Coulomb excitation provides new important information for the understanding of the Ni isotopic chain towards the 78Ni doubly magic nucleus.1-The collectivity enhancement suggested by the (p,p’) experiment seems quenched when using purely electromagnetic probes;2-The obtained values can be used to benchmark the Model Space and Interactions used for Shell Model Calculations far from stability.

Resultsp n

LNPS pf p, f5/2, g9/2 d5/2 [1]

Vlow_k f7/2, p3/2 p, f5/2, g9/2,d5/2 [2]

A3DA pf g9/2d5/2 [3]

[1] K. Sieja, F. Nowacki, Phys Rev C 85, 051301(R) (2012) K. Sieja, F. Nowacki, arXiv:1201.0373v1 (2012) S. M. Lenzi et al, Phys Rev C 82, 054301 (2010)[2] L. Coraggio, PRC 89, 024319 (2014) L. Coraggio et al., Prog. Part. Nucl. Phys 62, 135 (2009)[3] N. Shimizu et al., Progr Theor Exp. Phys, 01A205 (2012) Y. Tsunoda et al., PRC 89, 031301(R) (2014)


Discussion and outlookInelastic scattering data compared to Coulex results allow to disentangle the proton/neutron excitation matrix elements. For the 74Ni isotope, their difference could be an indication of the relative proton/neutron cores polarization leading to different deformation. A higher degree of accuracy is needed to constrain the B(E2) error bar and provide quantitative Mn/Mp ratio information.


Exp 2.4±0.8

LNPS 1.8

Discussion and outlookInelastic scattering data compared to Coulex results allow to disentangle the proton/neutron excitation matrix elements. For the 74Ni isotope, their difference could be an indication of the relative proton/neutron cores polarization leading to different deformation. A higher degree of accuracy is needed to constrain the B(E2) error bar and provide quantitative Mn/Mp ratio information.


Exp 2.4±0.8

LNPS 1.8

Outlook:

72Ni and 76Ni become key nuclei to understand the evolution of collectivity along the Ni chain. 76Ni still represents a challenge in terms of RIB production.Two different experiments are under analysis:-68 – 70 - 72Ni (p,p’) inelastic scattering at NSCL (GRETINA) – NSCL E12016-74Ni Coulex at RIKEN with higher beam intensity (~150 counts in the 2+ peak).

Collaboration

T. Marchi,1, 2 G. De Angelis,1 J.J. Valiente-Dobón,1 V. Bader3, T. Baugher,3 D. Bazin,3 J. Berryman,3 A. Bonaccorso,4 R. Clark,5 L. Coraggio,6 E. L. Crawford,5 M. Doncel,7

E. Farnea,8 A. Gade,3 A. Gadea,9 A. Gargano,6 T. Glasmacher,3 A. Gottardo,1, 2 F. Gramegna,1 N. Itaco,10,6 P.R. John,8,2 R. Kumar,11 S. M. Lenzi,8,2 S. Lunardi,8,2 S. McDaniel,3 C. Michelagnoli,8,2 D. Mengoni,8,2 V. Modamio,1 D.R. Napoli,1

B. Quintana,12 A. Ratkiewicz,3 F. Recchia,8,2 E. Sahin,1 R. Stroberg,3

D. Weisshaar,3 K. Wimmer,3 and R. Winkler3

1INFN Legnaro National Laboratories, Legnaro (Pd), Italy2Department of Physics, Padua University, Padua, Italy3National Superconducting Cyclotron Laboratory , Michigan State University, East Lansing, Michigan, USA4INFN Sezione di Pisa, Pisa, Italy5Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA6INFN Sezione di Napoli, Napoli, Italy7Ionizing Radiations Laboratory, University of Salamanca, Spain8INFN Sezione di Padova, Padova, Italy9CSIC-IFIC, Valencia, Spain10Dipartimento di Fisica, Università “Federico II”, Napoli, Italy11Deenbandhu Chhoturam University of Science and Technology, Haryana, 131039 India12Grupo de Fisica Nuclear, Universidade de Salamanca, Spain

Thank you!

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[T. Otsuka, A. Schwenk, Nucl Phys News 22-4 (2012) 12]


introduction shell evolution along ni isotopic chain, towards 78 ni. focus on 74 ni existing data....

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