Strong-interaction effect measurements in sigma hyperonic atoms of W and Pb

Strong-interaction effects have been observed in the x-ray spectra of atoms formed with ${\mathrm{\Sigma }}^{\mathrm{-}}$ hyperons in W and Pb. The spectra were analyzed for energy shifts and broadenings and for yield reductions of the final x-ray transitions before absorption of the ${\mathrm{\Sigma }}^{\mathrm{-}}$ by the nucleus. The results for the 10l→9k transitions of ${\mathrm{\Sigma }}^{\mathrm{-}}$ hyperonic atoms averaged over fine structure components are ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$: ɛ(9k)=214±60 eV, Γ(9k)=18±149 eV, Γ(10l)=2±2 eV; ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$: ɛ(9k)=422±56 eV, Γ(9k)=428±158 eV, Γ(10l)=17±3 eV, where the strong interaction shift ɛ=${\mathit{E}}_{\mathit{m}}$-${\mathit{E}}_{\mathit{c}}$, ${\mathit{E}}_{\mathit{m}}$ is the measured transition energy, and ${\mathit{E}}_{\mathit{c}}$ is the transition energy calculated assuming no strong interaction and Γ is the Lorentzian broadening. A four-parameter optical potential representing an effective spin-independent ${\mathrm{\Sigma }}^{\mathrm{-}}$-nuclear hadronic interaction was fitted by these results in combination with previous data from lower-Z nuclei.