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Register a new userProduction of $phi(2170)$ and $eta(2225)$ in a kaon induced reaction
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In this work, we study the production of strange quarkoniums, the $phi(2170)$, also named $Y(2175)$, and the $eta(2225)$, via a kaon induced reaction on a proton target in an effective Lagrangian approach. The total and differential cross sections of the reactions $K^{-}prightarrow phi (2170)Lambda $ and $K^{-}prightarrow eta (2225)Lambda $ are calculated by the Reggeized $t $-channel Born term under an assumption that the $phi(2170)$ and $eta(2225)$ are $Lambdabar{Lambda}$ molecular states. At the center of mass energies of about 4.2 GeV, the total cross section for the $phi(2170)$ production is predicted to be about 1 $mu $b. The numerical results indicate that it is feasible to produce the $phi (2170)$ via kaon beam scattering at the best energy window near 4.2 GeV. The total cross section for the $eta(2225)$ production is smaller than that for the $phi(2170)$ production and it may reach an order of the magnitude of 0.1 $mu$b. The differential cross sections for both reactions at different center of mass energies are also presented. It is found that the Reggeized $t$ channel gives a considerable contribution at forward angles. As the energy increases, the contribution from the $t$-channel almost concentrates at extreme forward angles. From these theoretical predictions, the relevant experimental research is suggested, which could provide important information to clarify the internal structure and production mechanism of these two strange quarkoniums.
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The $eta$ mesic nucleus is considered to be one of the interesting exotic many body systems and has been studied since 1980s theoretically and experimentally. Recently, the formation of the $eta$ mesic nucleus in the fusion reactions of the light nuclei such as $d + d rightarrow (eta + alpha) rightarrow X$ has been proposed and the experiments have been performed by WASA-at-COSY. We develop a theoretical model to evaluate the formation rate of the $eta$ mesic nucleus in the fusion reactions and show the calculated results. We find that the $eta$ bound states could be observed in the reactions in cases with the strong attractive and small absorptive $eta$-nucleus interactions. We compare our results with existing data of the $d + d rightarrow eta + alpha$ and the $d + d rightarrow {^3 rm He} + N + pi$ reactions. We find that the analyses by our theoretical model with the existing data can provide new information on the $eta$-nucleus interaction.
We consider the reaction g+d -> pi+d in a wide energy range around and above the eta-meson photoproduction threshold at backward CM angles of the outgoing pion. Our theoretical analysis is essentially motivated by the recent measurements of the CLAS Collaboration at Jefferson Lab, where this kinematical region of the reaction has been thoroughly studied for the first time and a cusps in the energy dependence of the differential cross section in the region of Eg = 600-800 MeV has been observed. Our preliminary and qualitative analysis, based on single- and double-scattering diagrams, shows that the observed structure can be explained by the contribution of the double-scattering diagram with intermediate production of the eta meson. The effect, to a considerable extent, is formed due to the contribution of N(1535) resonance to the amplitudes of subprocesses on the nucleons.
The $eta N$ final state is isospin-selective and thus provides access to the spectrum of excited nucleons without being affected by excited $Delta$ states. To this end, the world database on eta photoproduction off the proton up to a center-of-mass energy of $Esim 2.3$ GeV is analyzed, including data on differential cross sections, and single and double polarization observables. The resonance spectrum and its properties are determined in a combined analysis of eta and pion photoproduction off the proton together with the reactions $pi Nto pi N$, $eta N$, $KLambda$ and $KSigma$. For the analysis, the so-called Julich coupled-channel framework is used, incorporating unitarity, analyticity, and effective three-body channels. Parameters tied to photoproduction and hadronic interactions are varied simultaneously. The influence of recent MAMI $T$ and $F$ asymmetry data on the eta photoproduction amplitude is discussed in detail.
The production of eta mesons in photon- and hadron-induced reactions has been revisited in view of the recent additions of high-precision data to the world data base. Based on an effective Lagrangian approach, we have performed a combined analysis of the free and quasi-free gamma N -> eta N, N N -> N N eta, and pi N -> eta N reactions. Considering spin-1/2 and -3/2 resonances, we found that a set of above-threshold resonances {S_{11}, P_{11}, P_{13}}, with fitted mass values of about M_R=1925, 2130, and 2050 MeV, respectively, and the four-star sub-threshold P_{13}(1720) resonance reproduce best all existing data for the eta production processes in the resonance-energy region considered in this work. All three above-threshold resonances found in the present analysis are essential and indispensable for the good quality of the present fits.
We study the $K^+pto pi^+KN$ reaction with kinematical condition suited to the production of the $Theta^+$ resonance. It is shown that in this reaction with the polarization experiment, a combined consideration of the strength at the peak and the angular dependence of cross section can help determine the $Theta^+$ quantum numbers.
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