Probing the strong interaction between charm hadrons and charged particles with femtoscopy measurements with ALICE

TL;DR

The study tackles the problem of constraining strong interactions between charm hadrons and light hadrons at nucleon-scale distances using femtoscopy. It measures the two-particle correlation function $C(k^{*})$ for charm–light systems in pp collisions at $\\sqrt{s}=13$ TeV (Run 2) and $\\sqrt{s}=13.6$ TeV (Run 3), relating it to the source function $S(\vec{r}^{*})$ and the relative wave function $\psi(\vec{r}^{*},\vec{k}^{*})$ via $C(k^{*})=\int d^{3}r^{*} S(\vec{r}^{*}) \, |\psi(\vec{r}^{*},\vec{k}^{*})|^{2}$. The analysis decomposes the $\Lambda_{c}^{+}$--p signal into non-prompt, feed-down, and prompt direct components and compares results to models including Coulomb and strong interactions. Key findings from Run 2 include D$^{+}$--p indicating a shallow $I=0$ attraction with no bound state, and D--$\pi$/$D^{*}$--$\pi$ scattering lengths near zero with tension in $I=1/2$. Run 3 provides a decomposed $\Lambda_{c}^{+}$--p correlation that favors a shallow attractive strong interaction at $1\sigma$, with implications for the existence of charmed hypernuclei and guidance for future ALICE upgrades (ITS2 and ALICE~3) and higher-statistics studies in open-charm systems.

Abstract

Studies of strong interactions between hadrons provide a valuable opportunity to test Quantum Chromodynamics at nucleon-scale distances. The femtoscopy technique has proven to be an effective tool for studying interactions between unstable hadrons by measuring the correlation function of hadron pairs in momentum space. While several measurements of the strong interactions between light and strange hadrons have been conducted using this technique, studies of charm hadrons have been limited. These studies can shed light on the formation of exotic charm states or, in the case of baryons, nuclei with charm content. In these proceedings, measurements of the strong interaction between charm hadrons and light-flavor hadrons using the femtoscopy technique are presented. The final results on the correlation functions and residual strong interactions between $\rm D$ mesons and light hadrons measured in pp collisions at $\sqrt{s} = 13$ TeV are discussed. Additionally, new studies of correlations between $Λ_{\rm c}^+$ and protons in pp collisions at $\sqrt{s} = 13.6$ TeV, utilizing the new data samples collected from LHC Run 3, are presented.

Figures (2)

• Figure 1: Left: Constraints on the scattering length in the $\rm I=0$ channel for the $\rm D^{+}$--p correlation function in pp collisions at $\sqrt{s}=13$ TeV. The band shows the uncertainty due to the source size determination ALICE:2022enj. Right: Extracted scattering parameters for the $\rm D$--$\pi$ system compared to various theoretical predictions. The results indicate vanishing scattering lengths within uncertainties, with a significant tension in the $\rm I=1/2$ channel ALICE:2024bhk.
• Figure 2: Correlation function of $\Lambda_{\rm c}^{+}$--p pairs in pp collisions at $\sqrt{s}=13.6$ TeV: left, decomposition into different sources; right, comparison with theoretical models of the strong interaction.