# Strong absorption of hadrons with hidden and open strangeness in nuclear matter

## TL;DR

This study reports the first experimental observation of K- and  absorption in nuclear matter, revealing significant in-medium effects and strong coupling between  mesons and K- in nuclear environments.

## Contribution

It provides the first experimental evidence of  and K- absorption in nuclear matter and demonstrates the strong coupling between  mesons and K- in the nuclear medium.

## Key findings

- Larger K- absorption in heavier nuclei.
- Similar /K- ratios in different reactions.
- Indication of strong N in-medium coupling.

## Abstract

We present the first observation of K- and \phi absorption within nuclear matter by means of \pi- -induced reactions on C and W targets at an incident beam momentum of 1.7 GeV/c studied with HADES at SIS18/GSI. The double ratio (K-/K+)W / (K-/K+)C is found to be 0.319 \pm 0.009(stat)+0.014-0.012 (syst) indicating a larger absorption of K- in heavier targets as compared to lighter ones. The measured \phi/K- ratios in \pi-+C and \pi^- +W reactions within the HADES acceptance are found to be equal to $0.55 \pm 0.03(stat)+0.06-0.07$ (syst) and to $0.63 \pm 0.05(stat)-0.11+0.11$ (syst), respectively. The similar ratios measured in the two different reactions demonstrate for the first time experimentally that the dynamics of the \phi meson in nuclear medium is strongly coupled to the K- dynamics. The large difference in the \phi production off C and W nuclei is discussed in terms of a strong \phiN in-medium coupling.