Characterizing the neutron skin of $$^{48}$$Ca through collective flow at the CERN large hadron collider

Abstract The recently developed “imaging-by-smashing” technique has emerged as a powerful approach to connect final-state collective flow phenomena in ultra-relativistic nuclear collisions with the intrinsic structure of the colliding nuclei. While most efforts have focused on constraining nuclear shape properties such as deformation and triaxiality, less attention has been given to the neutron skin, primarily in heavy nuclei such as $$^{208}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>208</mml:mn> </mml:mmultiscripts> </mml:math> Pb. In this work, a novel study of the neutron-skin thickness in $$^{48}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>48</mml:mn> </mml:mmultiscripts> </mml:math> Ca is presented, based on comparative analyses of $$^{48}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>48</mml:mn> </mml:mmultiscripts> </mml:math> Ca+ $$^{48}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>48</mml:mn> </mml:mmultiscripts> </mml:math> Ca and $$^{40}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>40</mml:mn> </mml:mmultiscripts> </mml:math> Ca+ $$^{40}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>40</mml:mn> </mml:mmultiscripts> </mml:math> Ca collisions at $$\sqrt{s_\textrm{NN}}=5.02$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:msub> <mml:mi>s</mml:mi> <mml:mtext>NN</mml:mtext> </mml:msub> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>5.02</mml:mn> </mml:mrow> </mml:math> TeV. Simulations within the AMPT framework are employed to investigate the impact of varying neutron-skin thicknesses $$\Delta r_{np}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msub> <mml:mi>r</mml:mi> <mml:mrow> <mml:mi>np</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> for $$^{48}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>48</mml:mn> </mml:mmultiscripts> </mml:math> Ca on collective flow observables, including anisotropic flow coefficients and mean transverse momentum ( $$[p_\textrm{T}]$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>[</mml:mo> <mml:msub> <mml:mi>p</mml:mi> <mml:mtext>T</mml:mtext> </mml:msub> <mml:mo>]</mml:mo> </mml:mrow> </mml:math> ) fluctuations. The triangular flow $$v_3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>v</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:math> , quadrangular flow $$v_4$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>v</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:math> , as well as the variance and skewness of $$[p_\textrm{T}]$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>[</mml:mo> <mml:msub> <mml:mi>p</mml:mi> <mml:mtext>T</mml:mtext> </mml:msub> <mml:mo>]</mml:mo> </mml:mrow> </mml:math> fluctuations, display notable sensitivity to $$\Delta r_{np}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msub> <mml:mi>r</mml:mi> <mml:mrow> <mml:mi>np</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math>