Experimental constraints on the $\omega$-nucleus real potential

TL;DR

This study investigates the potential of the $$-nucleus interaction by searching for bound states in photon-induced reactions, finding evidence for a weakly attractive potential much shallower than some theoretical models predict.

Contribution

It provides experimental constraints on the real part of the $$-nucleus potential, showing it is weakly attractive and much shallower than previously predicted by some theories.

Findings

No structures indicating bound $$-nucleus states were observed.

The measured potential depth is approximately -15 MeV, with large uncertainties.

Results suggest the $$-nucleus interaction is weaker than some theoretical predictions.

Abstract

In a search for $\omega$ mesic states, the production of $\omega$-mesons in coincidence with forward going protons has been studied in photon induced reactions on $^{12}$C for incident photon energies of 1250 - 3100 MeV. The $\pi^0 \gamma$ pairs from decays of bound or quasi-free $\omega$-mesons have been measured with the CBELSA/TAPS detector system in coincidence with protons registered in the MiniTAPS forward array. Structures in the total energy distribution of the $\pi^0 \gamma$ pairs, which would indicate the population and decay of bound $\omega~^{11}$B states, are not observed. The $\pi^0 \gamma$ cross section of 0.3 nb/MeV/sr observed in the bound state energy regime between -100 and 0 MeV may be accounted for by yield leaking into the bound state regime because of the large in-medium width of the $\omega$-meson. A comparison of the measured total energy distribution with calculations suggests the real part $V_0$ of the $\omega~^{11}$B potential to be small and only weakly attractive with $V_0(\rho=\rho_0) = -15\pm$ 35(stat) $\pm$20(syst) MeV in contrast to some theoretical predictions of attractive potentials with a depth of 100 - 150 MeV.