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Register a new userCoupling of bar K*N to the Lambda(1520)
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T. Hyodo
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We study the coupling of the Lambda(1520)= Lambda* resonance to the bar K* vector meson and nucleon. This coupling is not directly measured from the resonance decay, but is expected to be important in hyperon production reactions, in particular for the exotic Theta+ production. We compute the coupling in two different schemes, one in the chiral unitary model where the Lambda* is dominated by the quasibound state of mesons and baryons, and the other in the quark model where the resonance is a p-wave excitation in the three valence quarks. Although it is possible to construct both models such that they reproduce the bar K N and pi Sigma decays, there is a significant difference between the Lambda* bar K* N couplings in the two models. In the chiral unitary model $|g_{Lambda^*bar{K}^* N}| sim 1.5$, while in the quark model $|g_{Lambda^*bar{K}^* N}| sim 10$. The difference of the results stems from the different structure of the Lambda* in both models, and hence, an experimental determination of this coupling would shed light on the nature of the resonance.
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Differential cross sections and photon-beam asymmetries for the gamma p -> K+ Lambda(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6<cos(theta)<1. A new bump structure was found at W=2.11 GeV in the cross sections. The bump is not well reproduced by theoretical calculations introducing a nucleon resonance with J<=3/2. This result suggests that the bump might be produced by a nucleon resonance possibly with J>=5/2 or by a new reaction process, for example an interference effect with the phi photoproduction having a similar bump structure in the cross sections.
Here we give our reply to the comment by Sibirtsev et al on our paper ``Mass and K-Lambda Coupling of the N*(1535).
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.
Using a sample of $1.06times10^8 psip$ events produced in $e^+e^-$ collisions at $sqrt{s}$ = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays $klx+c.c.$ and $gklx+c.c.$. We observe two hyperons, $Xi(1690)^-$ and $Xi(1820)^-$, in the $K^-Lambda$ invariant mass distribution in the decay $klx+c.c.$ with significances of $4.9 sigma$ and $6.2 sigma$, respectively. The branching fractions of $klx+c.c.$, $ksx+c.c.$, $psiptogamma chi_{cJ}to gamma K^- Lambda bar{Xi}^+ +c.c.$ $(J=0, 1, 2)$, and $psipto Xi(1690/1820)^{-} bar{Xi}^++c.c$ with subsequent decay $Xi(1690/1820)^-to K^-Lambda$ are measured for the first time.
The newly observed $Xi(1620)^0$ by the Belle Collaboration inspires our interest in performing a systematic study on the interaction of an anti-strange meson $(bar{K}^{(*)})$ with a strange or doubly strange ground octet baryon $mathcal{B}$ ($Lambda$, $Sigma$, and $Xi$), where the spin-orbit force and the recoil correction are considered in the adopted one-boson-exchange model. Our results indicate that $Xi(1620)^0$ can be explained as a $bar{K}Lambda$ molecular state with $I(J^P)=1/2(1/2^-)$ and the intermediate force from $sigma$ exchange plays an important role. Additionally, we also predict several other possible molecular candidates, i.e., the $bar{K}Sigma$ molecular state with $I(J^P)=1/2(1/2^-)$ and the triply strange $bar{K}Xi$ molecular state with $I(J^P)=0(1/2^-)$.
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