Probing small neutron skin variations in isotope pairs by hyperon-antihyperon production in antiproton-nucleus interactions

We propose a new method to study the evolution of the neutron periphery between different isotopes by considering antiproton-nucleus interactions close to the production threshold of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi mathvariant="normal">Λ</a:mi><a:mover><a:mi mathvariant="normal">Λ</a:mi><a:mo>¯</a:mo></a:mover></a:mrow></a:math> and <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:msup><d:mi mathvariant="normal">Σ</d:mi><d:mo>−</d:mo></d:msup><d:mover><d:mi mathvariant="normal">Λ</d:mi><d:mo>¯</d:mo></d:mover></d:mrow></d:math> pairs. At low energies, <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:mi mathvariant="normal">Λ</g:mi><g:mover><g:mi mathvariant="normal">Λ</g:mi><g:mo>¯</g:mo></g:mover></g:mrow></g:math> pairs are produced in <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"><j:mrow><j:mover><j:mi>p</j:mi><j:mo>¯</j:mo></j:mover><j:mo>+</j:mo><j:mi>p</j:mi></j:mrow></j:math> collisions, while <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:msup><k:mi mathvariant="normal">Σ</k:mi><k:mo>−</k:mo></k:msup><k:mover><k:mi mathvariant="normal">Λ</k:mi><k:mo>¯</k:mo></k:mover></k:mrow></k:math> pairs can only be produced in <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"><n:mrow><n:mover><n:mi>p</n:mi><n:mo>¯</n:mo></n:mover><n:mo>+</n:mo><n:mi>n</n:mi></n:mrow></n:math> interactions. Within a simple geometrical picture we show that the double ratio for the production of <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"><o:mrow><o:msup><o:mi mathvariant="normal">Σ</o:mi><o:mo>−</o:mo></o:msup><o:mover><o:mi mathvariant="normal">Λ</o:mi><o:mo>¯</o:mo></o:mover></o:mrow></o:math> and <r:math xmlns:r="http://www.w3.org/1998/Math/MathML"><r:mrow><r:mi mathvariant="normal">Λ</r:mi><r:mover><r:mi mathvariant="normal">Λ</r:mi><r:mo>¯</r:mo></r:mover></r:mrow></r:math> pairs for two different isotopes are related to the variation of the neutron skin thickness between the two nuclei. Performing high statistics calculations with the Gießen Boltzmann-Uehling-Uhlenbeck (GiBUU) transport model for several isotope pairs covering a wide range of elements, we verify a strong correlation between the double ratio from the full transport simulations and the schematic model. This correlation enables us to quantify the potential of the proposed method for precise studies of neutron skin variations in isotope chains.