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Register a new userToward establishing low-lying $Lambda$ and $Sigma$ hyperon resonances with the $bar K + d to pi + Y + N$ reaction
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A model for the $bar K d to pi Y N$ reactions with $Y=Lambda, Sigma$ is developed, aiming at establishing the low-lying $Lambda$ and $Sigma$ hyperon resonances through analyzing the forthcoming data from the J-PARC E31 experiment. The off-shell amplitudes generated from the dynamical coupled-channels (DCC) model, which was developed in Kamano et al. [Phys. Rev. C 90, 065204 (2014)], are used as input to the calculations of the elementary $bar K N to bar K N$ and $bar K N to pi Y$ subprocesses in the $bar K d to pi Y N$ reactions. It is shown that the cross sections for the J-PARC E31 experiment with a rather high incoming-$bar{K}$ momentum, $|vec p_{bar K}|= 1$ GeV, can be predicted reliably only when the input $bar K N to bar K N$ amplitudes are generated from a $bar KN$ model, such as the DCC model used in this investigation, which describes the data of the $bar K N$ reactions at energies far beyond the $bar K N$ threshold. We find that the data of the threefold differential cross section $dsigma/(dM_{piSigma}dOmega_{p_n})$ for the $K^- d to pi Sigma n$ reaction below the $bar K N$ threshold can be used to test the predictions of the resonance poles associated with $Lambda(1405)$. We also find that the momentum dependence of the threefold differential cross sections for the $K^- d to pi^- Lambda p$ reaction can be used to examine the existence of a low-lying $J^P=1/2^+$ $Sigma$ resonance with a pole mass $M_R = 1457 -i39$ MeV, which was found from analyzing the $K^-p$ reaction data within the employed DCC model.
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The $bar{K} + N to K + Xi$ reaction is studied for center-of-momentum energies ranging from threshold to 3 GeV in an effective Lagrangian approach that includes the hyperon $s$- and $u$-channel contributions as well as a phenomenological contact amplitude. The latter accounts for the rescattering term in the scattering equation and possible short-range dynamics not included explicitly in the model. Existing data are well reproduced and three above-the-threshold resonances were found to be required to describe the data, namely, the $Lambda(1890)$, $Sigma(2030)$, and $Sigma(2250)$. For the latter resonance we have assumed the spin-parity of $J^P=5/2^-$ and a mass of 2265 MeV. The $Sigma(2030)$ resonance is crucial in achieving a good reproduction of not only the measured total and differential cross sections, but also the recoil polarization asymmetry. More precise data are required before a more definitive statement can be made about the other two resonances, in particular, about the $Sigma(2250)$ resonance that is introduced to describe a small bump structure observed in the total cross section of $K^- + p to K^+ + Xi^-$. The present analysis also reveals a peculiar behavior of the total cross section data in the threshold energy region in $K^- + p to K^+ + Xi^-$, where the $P$- and $D$-waves dominate instead of the usual $S$-wave. Predictions for the target-recoil asymmetries of the $bar{K} + N to K + Xi$ reaction are also presented.
The appearance of some papers dealing with the $K^- d to pi Sigma n$ reaction, with some discrepancies in the results and a proposal to measure the reaction at forward $n$ angles at J-PARC justifies to retake the theoretical study with high precision to make accurate predictions for the experiment and extract from there the relevant physical information. We do this in the present paper showing results using the Watson approach and the truncated Faddeev approach. We argue that the Watson approach is more suitable to study the reaction because it takes into account the potential energy of the nucleons forming the deuteron, which is neglected in the truncated Faddeev approach. Predictions for the experiment are done as well as spectra with the integrated neutron angle.
The $K^{-}$ induced production of $Lambda(1405)$ in the $K^{-} d to pi Sigma n$ reaction is investigated having in mind the conditions of the DAFNE facility at Frascati. We find that the fastest kaons from the decay of the $phi$ at DAFNE are well suited to see this resonance if one selects forward going neutrons in the center of mass, which reduce the contribution of single scattering and stress the contribution of the double scattering where the signal of the resonance appears clearer. We take advantage to report briefly on a recent work in which in addition to the $bar{K}NN$ system with total spin S=0, we find a less bound state (although with equally large width) with S=1, like in the $K^{-} d$ reported in the first part.
We study the $bar K p to Y Kbar K pi$ reactions with $bar K = bar K^0, K^-$ and $Y=Sigma^0, Sigma^+, Lambda$, in the region of $Kbar K pi$ invariant masses of $1200-1550$ MeV. The strong coupling of the $f_1(1285)$ resonance to $K^* bar K$ makes the mechanism based on $K^*$ exchange very efficient to produce this resonance observed in the $Kbar K pi$ invariant mass distribution. In addition, in all the reactions one observes an associated peak at $1420$ MeV which comes from the $K^* bar K$ decay mode of the $f_1(1285)$ when the $K^*$ is placed off shell at higher invariant masses. We claim this to be the reason for the peak of the $K^* bar K$ distribution seen in the experiments which has been associated to the $f_1(1420)$ resonance.
We present calculations of the invariant mass spectra of the $Lambda$p system for the exclusive $p p to K^+ Lambda p$ reaction with the aim of studying the final state interaction between the $Lambda$-hyperon and the proton. The reaction is described within a meson exchange framework and the final state $Lambda p$ interaction is incorporated through an off-shell t-matrix for the $Lambda p to Lambda p$ scattering, constructed using the available hyperon-nucleon (YN) potentials. The cross sections are found to be sensitive to the type of YN potential used especially at the $Lambda$ and $Sigma$ production thresholds. Hence, data on this exclusive reaction, which can be used to constrain the YN potentials are desirable.
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