Absorption of phi mesons in near-threshold proton-nucleus reactions

摘要

In the framework of the nuclear spectral function approach for incoherentprimary proton--nucleon and secondary pion--nucleon production processes westudy the inclusive $\phi$ meson production in the interaction of 2.83 GeVprotons with nuclei. In particular, the A-dependences of the absolute andrelative $\phi$ meson yields are investigated within the different scenariosfor its in-medium width as well as for the cross section ratio $\sigma_{pn \topn{\phi}}/{\sigma_{pp \to pp{\phi}}}$. Our model calculations take into accountthe acceptance window of the ANKE facility used in a recent experimentperformed at COSY. They show that the pion--nucleon production channelcontributes distinctly to the $\phi$ creation in heavy nuclei in the chosenkinematics and, hence, has to be taken into consideration on close examinationof the dependences of the phi meson yields on the target mass number with theaim to get information on its width in the medium. They also demonstrate thatthe experimentally unknown ratio $\sigma_{pn \to pn{\phi}}/{\sigma_{pp \topp{\phi}}}$ has a weak effect on the A-dependence of the relative $\phi$ mesonproduction cross section at incident energy of present interest, whereas it isfound to be appreciably sensitive to the phi in-medium width, which means thatthis relative observable can indeed be useful to help determine the above widthfrom the direct comparison the results of our calculations with the future datafrom the respective ANKE-at-COSY experiment.