Interaction of the Θ with the Nuclear Medium

The discovery of the Θ resonance opens the possibility of forming exotic Θ hypernuclei, which, like in the case of negative strangeness, could provide complementary information on the structure and properties of the pentaquark to that obtained from elementary reactions. In Ref. 2, a schematic model for quark-pair interaction with nucleons was used to describe the Θ, which suggested that Θ hypernuclei, stable against strong decay, might exist. Later, in Ref. 3, the Θ selfenergy in the nuclei is calculated, based on the ΘKN interaction. The results show a selfenergy too weak to bind the Θ in nuclei. In this talk, we present some selected results from Ref. 4. There, we redo the calculations of Ref. 3 modifying some of the assumptions. The results are similar to those of Ref. 3 and a quite small potential is obtained from this source. Additionally, we consider other new selfenergy pieces related to the coupling of the Θ resonance to a baryon and two mesons under certain assumptions. We find that the in-medium renormalization of the two meson cloud of the Θ could lead to a sizable attraction, enough to produce bound and narrow Θ states in nuclei. The coupling of the Θ to two mesons and a nucleon is studied using