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Register a new userDouble-strangeness production in $Lambda pto K^+X$ reaction
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We investigate $S=-2$ production from the $Lambda pto K^+X$ reactions within the effective Lagrangian approach. The $Lambda pto K^+LambdaLambda$ and $Lambda pto K^+Xi^-p$ reactions are considered to find the lightest $S=-2$ system, which is $H$-dibaryon. We assume that the $H(2250)toLambdaLambda$, and $H(2270)toXi^-p$ decays with the intrinsic decay width of 1 MeV. According to our calculations, the total cross-sections for $Lambda pto K^+LambdaLambda$ and $Lambda pto K^+Xi^-p$ reactions were found to be of the order of a few $mu$b in the $Lambda$ beam momentum range of up to 5 GeV$/c$. Furthermore, the direct access of information regarding the interference patterns between the $H$-dibaryon and non-resonant contributions was demonstrated.
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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.
The reaction $gamma pto K^+Lambda$ has been investigated over the center-of-momentum energy, $W$, range from threshold up to 2.2 GeV in a tree-level effective Lagrangian model that incorporates most of the well-established baryon resonances with spins equal to or below 5/2. Four less well-established nucleon resonances of higher mass are also included. The fitted parameters consist, for each resonance included, of the products of the coupling strengths at the electromagnetic and strong interaction vertices and, for the less-established nucleon resonances, the total decay width. For the well-established nucleon resonances, the energy and momentum dependence of the widths is treated within a dynamical model that is normalized to give the empirical decay branching ratios on the resonance mass shells. For the less-established resonances, the total decay width is treated as a single parameter independent of the reaction kinematics. The model is used to fit recent data for the unpolarized differential cross section (CLAS), the induced hyperon polarization asymmetry, $P$ (CLAS, GRAAL, and SAPHIR), the beam spin asymmetry, $Sigma$ (LEPS), and the double polarization observables $C_x$ and $C_z$ (CLAS). Two different fits were obtained: one that incorporates SU(3) symmetry constraints on the Born contributions to the reaction amplitude and one in which these constraints are relaxed. Explicit numerical results are given only for the first fit since the two fits gave nearly identical results for the observables and the $chi^2$ per degree of freedom obtained with the second fit was only marginally better than that of the first fit ($<1%$ better). Results are presented for the fitted observables at several different energies and center-of-momentum (c.m.) frame kaon angles.
The cross sections for the reactions pp -> p Lambda^0K^+ and pn -> n Lambda^0K^+ are calculated near threshold of the final states. The theoretical ratio of the cross sections R = sigma(pn -> n Lambda^0K^+)/ sigma(pp ->pLambda^0K^+) = 3 shows the enhancement of the pn interaction with respect to the pp interaction near threshold of the strangeness production N Lambda^0K^+. Such an enhancement is caused by the contribution of the np interaction in the isospin-singlet state, which is stronger than the $pn$ interaction in the isospin-triplet state. For the confirmation of this result we calculate the cross sections for the reactions pp -> pp pi^0, pi^0 p -> Lambda^0 K^+ and pi^-p -> Lambda^0 K^0 near threshold of the final states. The theoretical cross sections agree well with the experimental data.
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.
The paper gives an overview of strangeness-production experiments at the Cooler Synchrotron COSY. Results on kaon-pair and $phi$ meson production in $pp$, $pd$ and $dd$ collisions, hyperon-production experiments and $Lambda p$ final-state interaction studies are presented as well as a search for a strangeness $S=-1$ resonance in the $Lambda p$ system.
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