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

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.

13 pages, 8 figures

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• Recent Progress in QCD Condensate Evaluations and Sum Rules
• Photoproduction of the $\omega$ meson off the proton near threshold
• Remarks on nuclear matter: how an ${\omega }_0$ condensate can spike the speed of sound, and a model of $Z(3)$ baryons
• Determination of the real part of the η'-Nb optical potential
• Momentum dependence of the imaginary part of the $\omega$- and ${\eta }^{\prime }$-nucleus optical potential
• The η'-carbon potential at low meson momenta
• $\omega N$ scattering length from $\omega$ photoproduction on the proton near the threshold
• Light vector correlator in medium: Wilson coefficients up to dimension 6 operators
• Medium effects in $\Lambda K^{+}$ pair production by 2.83 GeV protons on nuclei
• Study of in-medium ${\eta }^{\prime }$ properties in the ($\gamma$, ${\eta }^{\prime }p$) reaction on nuclei
• Effect of the final state interaction of ${\eta }^{\prime }N$ on the ${\eta }^{\prime }$ photoproduction off nucleon