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Register a new userOn mass polarization effect in three-body systems
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We evaluate the mass polarization term of the kinetic-energy operator for different three-body nuclear $AAB$ systems by employing the method of Faddeev equations in configuration space. For a three-boson system this term is determined by the difference of the doubled binding energy of the $AB$ subsystem $2E_{2}$ and the three-body binding energy $E_{3}(V_{AA}=0)$ when the interaction between the identical particles is omitted. In this case: $leftvert E_{3}(V_{AA}=0)rightvert >2leftvert E_{2}rightvert$. In the case of a system complicated by isospins(spins), such as the kaonic clusters $ K^{-}K^{-}p$ and $ppK^{-}$, the similar evaluation impossible. For these systems it is found that $leftvert E_{3}(V_{AA}=0)rightvert <2leftvert E_{2}rightvert$. A model with an $AB$ potential averaged over spin(isospin) variables transforms the later case to the first one. The mass polarization effect calculated within this model is essential for the kaonic clusters. Besides we have obtained the relation $|E_3|le |2E_2|$ for the binding energy of the kaonic clusters.
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We show that the contributions of three-quasiparticle interactions to normal Fermi systems at low energies and temperatures are suppressed by n_q/n compared to two-body interactions, where n_q is the density of excited or added quasiparticles and n is the ground-state density. For finite Fermi systems, three-quasiparticle contributions are suppressed by the corresponding ratio of particle numbers N_q/N. This is illustrated for polarons in strongly interacting spin-polarized Fermi gases and for valence neutrons in neutron-rich calcium isotopes.
A charge-symmetry-breaking nucleon-nucleon force due to the up-down quark mass difference is evaluated in the quark cluster model. It is applied to the shell-model calculation for the isovector mass shifts of isospin multiplets and the isospin-mixing matrix elements in 1s0d-shell nuclei. We find that the contribution of the quark mass difference effect is large and agrees with experiment. This contribution may explain the Okamoto-Nolen-Schiffer anomaly, alternatively to the meson-mixing contribution, which is recently predicted to be reduced by the large off-shell correction.
The kaonic clusters $K^{-}K^{-}p$ and $ppK^{-}$ are described based on the configuration space Faddeev equations for $AAB$ system. The $AB$ interaction is given by isospin-dependent potentials. For this isospin model, we show that the relation $leftvert E_{3}(V_{AA}=0)rightvert~<~2leftvert E_{2}rightvert$ is satisfied when $E_{2}$ is the binding energy of the $AB$ subsystem and $E_{3}(V_{AA}=0)$ is the three-body binding energy when interaction between identical particles is omitted, $V_{AA}=0$. For the $NN{bar K}$ system, taking into account weak attraction of $NN$ interaction the relation leads to the evaluation $|E_3|le 2|E_2|$. The isospinless model for the kaonic clusters based on the isospin averaged $N{bar K}$ potential demonstrates the opposite relation $leftvert E_{3}(V_{AA}=0)rightvert~>~2leftvert E_{2}rightvert$. The isospin given charge formalism is presented for $NN{bar K}$ cluster. This formalism is related to isospin model by unitary transformation of the isospin basis. An interpretation of the particle representation for $NN{bar K}$ system is proposed.
The non-symmetrized hyperspherical harmonics method for a three-body system, composed by two particles having equal masses, but different from the mass of the third particle, is reviewed and applied to the $^3$H, $^3$He nuclei and $^3_{Lambda}$H hyper-nucleus, seen respectively as $nnp$, $ppn$ and $NNLambda$ three-body systems. The convergence of the method is first tested in order to estimate its accuracy. Then, the difference of binding energy between $^3$H and $^3$He due to the difference of the proton and the neutron masses is studied using several central spin-independent and spin-dependent potentials. Finally, the $^3_{Lambda}$H hypernucleus binding energy is calculated using different $NN$ and $Lambda N$ potential models. The results have been compared with those present in the literature, finding a very nice agreement.
Recently, many efforts are being put in studying three-hadron systems made of mesons and baryons and interesting results are being found. In this talk, I summarize the main features of the formalism used to study such three hadron systems with strangeness $S=-1,0$ within a framework built on the basis of unitary chiral theories and solution of the Faddeev equations. In particular, I present the results obtained for the $pibar{K}N$, $Kbar{K}N$ and $KKbar{K}$ systems and their respective coupled channels. In the first case, we find four $Sigma$s and two $Lambda$s with spin-parity $J^P=1/2^+$, in the 1500-1800 MeV region, as two meson-one baryon s-wave resonances. In the second case, a $1/2^+$ $N^*$ around 1900 MeV is found. For the last one a kaon close to 1420 MeV is formed, which can be identified with K(1460).
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