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Register a new user$phi$ meson transparency in nuclei from $phi N$ resonant interactions
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We investigate the $phi$ meson nuclear transparency using some recent theoretical developments on the $phi$ in medium self-energy. The inclusion of direct resonant $phi N$-scattering and the kaon decay mechanisms leads to a $phi$ width much larger than in most previous theoretical approaches. The model has been confronted with photoproduction data from CLAS and LEPS and the recent proton induced $phi$ production from COSY finding an overall good agreement. The results support the need of a quite large direct $phi N$-scattering contribution to the self-energy.
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The $phi$-meson properties in cold nuclear matter are investigated by implementing resonant $phi N$ interactions as described in effective approaches including the unitarization of scattering amplitudes. Several $N^*$-like states are dynamically generated in these models around $2$ GeV, in the vicinity of the $phi N$ threshold. We find that both these states and the non-resonant part of the amplitude contribute sizably to the $phi$ collisional self-energy at finite nuclear density. These contributions are of a similar strength as the widely studied medium effects from the $bar K K$ cloud. Depending on model details (position of the resonances and strength of the coupling to $phi N$) we report a $phi$ broadening up to about $40$-$50$ MeV, to be added to the $phitobar K K$ in-medium decay width, and an attractive optical potential at threshold up to about $35$ MeV at normal matter density. The $phi$ spectral function develops a double peak structure as a consequence of the mixing of resonance-hole modes with the $phi$ quasi-particle peak. The former results point in the direction of making up for missing absorption as reported in $phi$ nuclear production experiments.
Nuclear production experiments report missing absorption processes of the in-medium phi meson. Contributions arising from the K-bar K cloud have already been widely studied, and therefore we investigate the phi-meson properties in cold nuclear matter with the additional inclusion of resonant phi N interactions. Two models are considered which dynamically generate N*-like states close to the phi N threshold. We find that these states, together with the non-resonant part of the amplitude, contribute to the phi self-energy with the same order of magnitude as the K-bar K effects. At non-vanishing nuclear density, both models lead to an additional in-medium broadening of the phi, up to around 50 MeV. Furthermore, at least one of the models is compatible with a mass shift to lower energies of up to 35 MeV at threshold and normal matter density. Finally, a double-peak structure appears in the spectral function due to the mixing of resonance-hole modes with the $phi$ quasi-particle peak. These results converge into the direction of the experimental findings.
Based on A Multi-Phase Transport model, the elliptic flow $v_{2}$ of $phi$ mesons which is reconstructed from $K^{+}K^{-}$ at the Relativistic Heavy Ion Collider (RHIC) energy has been studied. The results show that reconstructed $v_{2}$ of $phi$ meson can keep the earlier information before $phi$ decays and it seems to obey the number of constituent quark scaling as other mesons and baryons. This result indicates that the $phi$ $v_2$ mostly reflects the parton level collectivity developed during the early stage of the collisions and the strange and light up/down quarks have similar collectivity properties before the hadronization.
Using a relativistic effective Lagrangian at the hadronic level, near-threshold $omega$ and $phi$ meson productions in proton proton ($pp$) collisions, $p p to p p omega/phi$, are studied within the distorted wave Born approximation. Both initial and final state $pp$ interactions are included. In addition to total cross section data, both $omega$ and $phi$ angular distribution data are used to constrain further the model parameters. For the $p p to p p omega$ reaction we consider two different possibilities: with and without the inclusion of nucleon resonances. The nucleon resonances are included in a way to be consistent with the $pi^- p to omega n$ reaction. It is shown that the inclusion of nucleon resonances can describe the data better overall than without their inclusion. However, the SATURNE data in the range of excess energies $Q < 31$ MeV are still underestimated by about a factor of two. As for the $p p to p p phi$ reaction it is found that the presently limited available data from DISTO can be reproduced by four sets of values for the vector and tensor $phi NN$ coupling constants. Further measurements of the energy dependence of the total cross section near threshold energies should help to constrain better the $phi NN$ coupling constant.
We investigate the reactions p n -> d omega and p n -> d phi close to the corresponding thresholds. The S-wave amplitudes are calculated within the framework of the two-step model which is described by a triangle graph with pi, rho and omega mesons in the intermediate state. The cross sections of the reactions p n -> d omega and p n -> d phi are predicted to be significantly larger than the cross sections of the corresponding reactions p p -> p p omega and p p -> p p phi at the same values of the c.m. excess energy Q. The ratio of the yields of phi to omega is found to be (30 +/- 7) x 10^-3.
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