Speaker
Description
The evolution of the nuclear shell closure along N=28 has gathered much interest due to the observed
discrepancies between the well established shell model with SDPF-U interaction and measurements of
the half-magic 46Ar isotope.
In particular, while remarkable agreement was observed between theoretical and experimental values
of Sn, transition probabilities measured with intermediate Coulomb excitation diverge by a factor of two
from their predicted values[1, 2]. The reason behind this mismatch has been pinned down to the proton
transition matrix elements[2] and hints at an incorrect description of the sd proton space below Z=20 [3].
The experiment we proposed aimed at shedding some light on this peculiar problem by directly
probing the proton component of the wavefunction via a proton-pickup direct reaction: 46Ar(3He, d)47K
at an energy of 350 MeV.
The experiment, performed at the Spiral 1 facility in GANIL with a post-accelerated radioactive 46Ar
beam impinging on a high-density cryogenic 3He target, will assess the amount of d3/2 state relative to
the s1/2 relying on a state-of-the-art experimental setup for a precise reconstruction of the kinematics of
the reaction.
The heavy reaction fragment was identi ed by the high acceptance magnetic spectrometer, VAMOS,
while the high-granularity silicon DSSSD detector, MUGAST, allowed the measurement of the angular
distribution of the light ejectile while also performing particle identi cation. The AGATA[5] gamma-ray
tracking germanium array measured the gamma rays produced by the decay of the 47K excited states.
Experimental results will be compared with theoretical models to infer information on the proton
wavefunction of 46Ar.
References
[1] A. Gade et al., Phys. Rev. C 74, 034322 (2006)
[2] S. Calinescu et al., Phys. Rev. C 93, 044333 (2016)
[3] Z. Meisel et al., Phys. Rev. Lett. 114, 022501 (2015)
[4] M.Rejmund et al., Nucl. Inst. Meth. A 646, 184-191 (2012)
[5] S. Akkoyun et al., Nucl. Inst. Meth. A 668, 26-58 (2012)
