Kaon-deuteron femtoscopy from unitarized chiral interactions

We have performed a theoretical study of the correlation functions of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mi>K</a:mi> <a:mo>−</a:mo> </a:msup> <a:mi>d</a:mi> </a:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msup> <c:mi>K</c:mi> <c:mo>+</c:mo> </c:msup> <c:mi>d</c:mi> </c:math> pairs and compared them with those provided by the ALICE Collaboration from Pb-Pb collisions and also from high-multiplicity p-p collisions in the case of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msup> <e:mi>K</e:mi> <e:mo>+</e:mo> </e:msup> <e:mi>d</e:mi> </e:math> . In addition to implementing the effect of the Coulomb force, the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:msup> <g:mi>K</g:mi> <g:mo>−</g:mo> </g:msup> <g:mi>d</g:mi> </g:math> and <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:msup> <i:mi>K</i:mi> <i:mo>+</i:mo> </i:msup> <i:mi>d</i:mi> </i:math> wave functions are derived from the corresponding strong scattering amplitudes that are built employing a unitarized chiral model for the elementary <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msup> <k:mi>K</k:mi> <k:mo>−</k:mo> </k:msup> <k:mi>N</k:mi> </k:math> and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:msup> <m:mi>K</m:mi> <m:mo>+</m:mo> </m:msup> <m:mi>N</m:mi> </m:math> interactions. We present results for the impulse approximation, which accounts for single-scattering processes of the kaon with the nucleons of the deuteron, as well as for the solution of the Faddeev equations in the so-called fixed center approximation, which includes multiple rescattering effects. The <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:msup> <o:mi>K</o:mi> <o:mo>−</o:mo> </o:msup> <o:mi>d</o:mi> </o:math> correlation function is shown to be very sensitive to both the size of the source and the relative momentum of the interacting pair, with large deviations from the Coulomb baseline and sizable multistep scattering contributions, effects that are tied to a <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:mover accent="true"> <q:mi>K</q:mi> <q:mo stretchy="false">¯</q:mo> </q:mover> <q:mi>N</q:mi> </q:math> strong interaction that is dominated by the influence of the subthreshold resonance <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"> <u:mi mathvariant="normal">Λ</u:mi> <u:mo stretchy="false">(</u:mo> <u:mn>1405</u:mn> <u:mo stretchy="false">)</u:mo> </u:math> . In contrast, the <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"> <z:msup> <z:mi>K</z:mi> <z:mo>+</z:mo> </z:msup> <z:mi>d</z:mi> </z:math> correlation function only differs appreciably from the Coulomb one for relatively small sources, reflecting the mildly repulsive and elastic behavior of the <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline"> <bb:mi>K</bb:mi> <bb:mi>N</bb:mi> </bb:math> strong force. The calculated correlation functions are found to nicely reproduce the experimental data of the ALICE Collaboration. Our study serves to reinforce the validity of the theoretical models employed and demonstrates the value of femtoscopy as a powerful tool for probing hadronic interactions involving strangeness.