10-16 June 2018
Dalhousie University
America/Halifax timezone
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Enhanced $\alpha$-Transfer population of the $2^{+}_{ms}$ mixed-symmetry state in $^{52}$Ti

13 Jun 2018, 14:30
15m
SUB 224 (cap. 50) (Dalhousie University)

SUB 224 (cap. 50)

Dalhousie University

Oral (Non-Student) / Orale (non-étudiant(e)) Nuclear Physics / Physique nucléaire (DNP-DPN) W3-8 Nuclear Structure II (DNP) | Structure nucléaire II (DPN)

Speaker

Fuad A. Ali (Univerity of Guelph)

Description

The residual nucleon-nucleon interaction plays a crucial role in nuclear structure physics. In spherical even-even nuclei the quadrupole interaction leads to characteristic low-lying 2+ states of proton-neutron mixed symmetry character, decaying via M1 transitions to the proton-neutron symmetric states. We have calculated the associated M1 transition strengths in the $^{52}$Ti nucleus within the ab initio valence-space in-medium similarity renormalization group based on NN and 3N forces from chiral effective field theory. In this framework we also construct an effective valence-space M1 operator, which captures nonperturbatively many-body excitations outside the valence space. Our calculations well describe the established mixed-symmetry state in $^{52}$Ti nucleus. Thus, ab-initio calculations are able to describe fundamental low-lying collective excitaitons in nuclei.\
In order to investigate the microscopic structure of the mixedsymmetry state in $^{52}$Ti nucleus even further, we run an experiment on the $^{52}$Ti nucleus, populated via the alpha transfer reaction $^{48}$Ca($^{12}$C,$^{8}$Be)$^{52}$Ti using a $^{48}$Ca beam from the Maier-Leibnitz-Laboratory in Munich. Gamma rays of populated states were detected with the high-granularity MINIBALL array of HPGe detectors, and charged particles were detected using a highly segmented DSSD silicon detector, allowing to select the channel of interest via a multiplicity coincidence condition. In first order, $^{52}$Ti can be described as the coupling of a $^4$He nucleus to the doubly-magic $^48$Ca core. In the frame work of the interacting boson model 2 (IBM-2), Alonso $et$ $al.$[1] have shown that the population of the MS 2$^{+}_{ms}$ state is strictly forbidden. This prediction is also confirmed in our new shell model calculation using the full fp space and effective interactions. Alpha transfer spectroscopic factors were evaluated with a cluster model using the oxbash shell model code. In contrast to the theoretical predictions, we experimentally find an exceptionally strong population of the well-established $2^{+}_{ms}$ mixed-symmetry state in $^{52}$Ti relative to the population of the $2^{+}_{1}$ state. We discuss the impact of our findings to our microscopic understanding of the proton-neutron interaction and shell structure in this interesting region of the nuclear chart.
References
[1] C.E. Alonso and J.M. Arias, Phys. Rev. C 78, 017301 (2008).

Primary author

Fuad A. Ali (Univerity of Guelph)

Co-authors

Dennis Muecher (University of Guelph) V. Bildstein (Department of Physics, University of Guelph, Guelph, Ontario ) Paul Garrett (University of Guelph) Carl Svensson (University of Guelph) B. Alex Brown (Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, USA.) J. D. Holt (TRIUMF 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada) A. I Kilic (University of Guelph)

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