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Register a new userThe K d -> Lambda(1405) n reaction with the DAFNE set up and the $bar{K}NN$ system revisited
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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.
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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 real and imaginary parts of the bar K^0 d scattering length are extracted from the bar K^0 d mass spectrum obtained from the reaction pp to d bar K^0 K^+ measured recently at the Cooler Synchrotron COSY at Julich. We extract a new limit on the K^- d scattering length, namely Im a le 1.3 fm and |Re a| le 1.3 fm. The limit for the imaginary part of the K^- d scattering length is supported by data on the total K^- d cross sections.
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.
The photo-induced $K^*$ vector meson production is investigated for the study of the $Lambda(1405)$ resonance. This reaction is particularly suited to the isolation of the second pole in the $Lambda(1405)$ region which couples dominantly to the $bar K N$ channel. We obtain the mass distribution of the $Lambda(1405)$ which peaks at 1420 MeV, and differs from the nominal one. Combined with several other reactions, like the $pi^- p to K^0 pi Sigma$ which favours the first pole, this detailed study will reveal a novel structure of the $Lambda(1405)$ state.
We have performed an exclusive measurement of the $K^{-}+! ~^{3}{rm He} to Lambda pn$ reaction at an incident kaon momentum of $1 {rm GeV}/c$.In the $Lambda p$ invariant mass spectrum, a clear peak was observed below the mass threshold of $bar{K}!+!N!+!N$, as a signal of the kaonic nuclear bound state, $bar{K}NN$.The binding energy, decay width, and $S$-wave Gaussian reaction form-factor of this state were observed to be $B_{K} = 42pm3({rm stat.})^{+3}_{-4}({rm syst.}) {rm MeV}$, $Gamma_{K} = 100pm7({rm stat.})^{+19}_{-9}({rm syst.}) {rm MeV}$, and $Q_{K} = 383pm11({rm stat.})^{+4}_{-1}({rm syst.}) {rm MeV}/c$, respectively. The total production cross-section of $bar{K}NN$, determined by its $Lambda p$ decay mode, was $sigma^{tot}_{K} cdot BR_{Lambda p} = 9.3pm0.8({rm stat.})^{+1.4}_{-1.0}({rm syst.}) mu{rm b}$.We estimated the branching ratio of the $bar{K}NN$ state to the $Lambda p$ and $Sigma^{0}p$ decay modes as $BR_{Lambda p}/BR_{Sigma^{0}p} sim 1.7$, by assuming that the physical processes leading to the $Sigma N!N$ final states are analogous to those of $Lambda pn$.
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