Charge Radius of Neutron-Deficient <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ni</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>54</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math> and Symmetry Energy Constraints Using the Difference in Mirror Pair Charge Radii
Skyy Pineda, Kristian König, D. Rossi, B. A. Brown, Anthony Incorvati, Jeremy Lantis, K. Minamisono, W. Nörtershäuser, J. Piekarewicz, Robert Powel, F. Sommer
Abstract
The nuclear root-mean-square charge radius of $^{54}\mathrm{Ni}$ was determined with collinear laser spectroscopy to be $R(^{54}\mathrm{Ni})=3.737(3)\text{ }\text{ }\mathrm{fm}$. In conjunction with the known radius of the mirror nucleus $^{54}\mathrm{Fe}$, the difference of the charge radii was extracted as $\mathrm{\ensuremath{\Delta}}{R}_{\mathrm{ch}}=0.049(4)\text{ }\text{ }\mathrm{fm}$. Based on the correlation between $\mathrm{\ensuremath{\Delta}}{R}_{\mathrm{ch}}$ and the slope of the symmetry energy at nuclear saturation density ($L$), we deduced $21\ensuremath{\le}L\ensuremath{\le}88\text{ }\text{ }\mathrm{MeV}$. The present result is consistent with the $L$ from the binary neutron star merger GW170817, favoring a soft neutron matter EOS, and barely consistent with the PREX-2 result within $1\ensuremath{\sigma}$ error bands. Our result indicates the neutron-skin thickness of $^{48}\mathrm{Ca}$ as 0.15--0.21 fm.