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Register a new userTesting the origin of the $f_1(1420)$ with the $bar K p to Lambda (Sigma) Kbar K pi$ reaction
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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.
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In this talk, we investigate $Xi(1690)^-$ production from the $K^-pto K^+K^-Lambda$ reaction wit the effective Lagrangian method and consider the $s$- and $u$-channel $Sigma/Lambda$ ground states and resonances for the $Xi$-pole contributions, in addition to the $s$-channel $Lambda$, $u$-channel nucleon pole, and $t$-channel $K^-$-exchange for the $phi$-pole contributions. The $Xi$-pole includes $Xi(1320)$, $Xi(1535)$, $Xi(1690)(J^p=1/2^-)$, and $Xi(1820)(J^p=3/2^-)$. We compute the Dalitz plot density of $(d^2sigma/dM_{K^+K^-}dM_{K^-Lambda}$ at 4.2 GeV$/c$) and the total cross sections for the $K^-pto K^+K^-Lambda$. Employing the parameters from the fit, we present the cross sections for the two-body $K^-pto K^+Xi(1690)^-$ reaction near the threshold. We also demonstrate that the Dalitz plot analysis for $p_{K^-}=1.915 sim2.065$ GeV/c makes us to explore direct information for $Xi(1690)^-$ production, which can be done by future $K^-$ beam experiments.
Various model-independent aspects of the $bar{K} N to K Xi$ reaction are investigated, starting from the determination of the most general structure of the reaction amplitude for $Xi$ baryons with $J^P=frac12^pm$ and $frac32^pm$ and the observables that allow a complete determination of these amplitudes. Polarization observables are constructed in terms of spin-density matrix elements. Reflection symmetry about the reaction plane is exploited, in particular, to determine the parity of the produced $Xi$ in a model-independent way. In addition, extending the work of Biagi $mathrm{textit{et al. } [Z. Phys. C textbf{34}, 175 (1987)]}$, a way is presented of determining simultaneously the spin and parity of the ground state of $Xi$ baryon as well as those of the excited $Xi$ states.
In the present work, we investigate the hidden-strangeness production process in the $S=+1$ channel via $K^+pto K^+phi,p$, focussing on the exotic textit{pentaquark} molecular $K^*Sigma$ bound state, assigned by $P^+_s(2071,3/2^-)$. For this purpose, we employ the effective Lagrangian approach in the tree-level Born approximation. Using the experimental and theoretical inputs for the exotic state and for the ground-state hadron interactions, the numerical results show a small but obvious peak structure from $P^+_s$ with the signal-to-background ratio $approx1.7,%$, and it is enhanced in the backward-scattering region of the outgoing $K^+$ in the center-of-mass frame. We also find that the contribution from the $K^*(1680,1^-)$ meson plays an important role to reproduce the data. The proton-spin polarizations are taken into account to find a way to reduce the background. The effects of the possible $27$-plet pentaquark $Theta^{++}_{27}$ is discussed as well.
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.
We report on a theoretical study of the newly observed $Omega(2012)$ resonance in the nonleptonic weak decays of $Omega_c^0 to pi^+ bar{K}Xi^*(1530) (eta Omega) to pi^+ (bar{K}Xi)^-$ and $pi^+ (bar{K}Xipi)^-$ via final-state interactions of the $bar{K}Xi^*(1530)$ and $eta Omega$ pairs. The weak interaction part is assumed to be dominated by the charm quark decay process: $c(ss) to (s + u + bar{d})(ss)$, while the hadronization part takes place between the $sss$ cluster from the weak decay and a quark-antiquark pair with the quantum numbers $J^{PC} = 0^{++}$ of the vacuum, produces a pair of $bar{K}Xi^*(1530)$ and $eta Omega$. Accordingly, the final $bar{K}Xi^*(1530)$ and $eta Omega$ states are in pure isospin $I= 0$ combinations, and the $Omega_c^0 to pi^+ bar{K}Xi^*(1530)(eta Omega) to pi^+ (bar{K}Xi)^-$ decay is an ideal process to study the $Omega(2012)$ resonance. With the final-state interaction described in the chiral unitary approach, up to an arbitrary normalization, the invariant mass distributions of the final state are calculated, assuming that the $Omega(2012)$ resonance with spin-parity $J^P = 3/2^-$ is a dynamically generated state from the coupled channels interactions of the $bar{K}Xi^*(1530)$ and $eta Omega$ in $s$-wave and $bar{K}Xi$ in $d$-wave. We also calculate the ratio, $R^{bar{K}Xipi}_{bar{K}Xi} = {rm Br}[Omega_c^0 to pi^+ Omega(2012)^- to pi^+ (bar{K}Xi pi)^-] / {rm Br}[Omega_c^0 to pi^+ Omega(2012)^- to pi^+ (bar{K}Xi)^-$]. The proposed mechanism can provide valuable information on the nature of the $Omega(2012)$ and can in principle be tested by future experiments.
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