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Register a new userK^- ^3He and K^+K^- interactions in the pd -> ^3He K^+K^- reaction
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We investigate the K^- ^3He and K^+ K^- interactions in the reaction pd -> ^3He K^+ K^- near threshold and compare our model calculations with data from the MOMO experiment at COSY-Juelich. A large attractive effective K^- p amplitude would give a significant K^- ^3He final-state interaction effect which is not supported by the experimental data. We also estimate upper limits for the a_0(980) and f_0(980) contributions to the produced K^+ K^- pairs.
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The $bar{K} + N to K + Xi$ reaction is studied for center-of-momentum energies ranging from threshold to 3 GeV in an effective Lagrangian approach that includes the hyperon $s$- and $u$-channel contributions as well as a phenomenological contact amplitude. The latter accounts for the rescattering term in the scattering equation and possible short-range dynamics not included explicitly in the model. Existing data are well reproduced and three above-the-threshold resonances were found to be required to describe the data, namely, the $Lambda(1890)$, $Sigma(2030)$, and $Sigma(2250)$. For the latter resonance we have assumed the spin-parity of $J^P=5/2^-$ and a mass of 2265 MeV. The $Sigma(2030)$ resonance is crucial in achieving a good reproduction of not only the measured total and differential cross sections, but also the recoil polarization asymmetry. More precise data are required before a more definitive statement can be made about the other two resonances, in particular, about the $Sigma(2250)$ resonance that is introduced to describe a small bump structure observed in the total cross section of $K^- + p to K^+ + Xi^-$. The present analysis also reveals a peculiar behavior of the total cross section data in the threshold energy region in $K^- + p to K^+ + Xi^-$, where the $P$- and $D$-waves dominate instead of the usual $S$-wave. Predictions for the target-recoil asymmetries of the $bar{K} + N to K + Xi$ reaction are also presented.
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.
We study the production of $Xi^-$-hypernuclei, $^{12}_{Xi^{-}}$Be and $^{28}_{Xi^{-}}$Mg, via the ($K^-,K^+$) reaction within a covariant effective Lagrangian model, employing the bound $Xi^-$ and proton spinors calculated by the latest quark-meson coupling model. The present treatment yields the $0^circ$ differential cross sections for the formation of simple s-state $Xi^-$ particle-hole states peak at a beam momentum around 1.0 GeV/c with a value in excess of 1 $mu$b.
At the present work we propose a new method for studying the processes of thermodynamic equilibrium setting in the adsorbed 3He film in a porous media. By this method we have studied the thermalization of the adsorbed 3He on the silica aerogel surface at the temperature 1.5 K. The process of the thermodynamic equilibrium setting was controlled by measuring of the pressure in the experimental cell, the amplitude of the NMR signal and the time of the nuclear spin-spin and spin-lattice relaxation times of an adsorbed 3He. The thermodynamic equilibrium setting in the system adsorbed helium-3 - aerogel has the characteristic time 26 min.
Total and reaction cross sections are derived self consistently from the attenuation cross sections measured in transmission experiments at the AGS for K^+ on Li^6, C, Si and Ca in the momentum range of 500-700 MeV/c by using a V_{opt}=t_{eff}(rho)rho optical potential. Self consistency requires, for the KN in-medium t matrix, that Im t_{eff}(rho) increases linearly with the average nuclear density in excess of a threshold value of 0.088+-0.004 fm^-3. The density dependence of Re t_{eff}(rho) is studied phenomenologically, and also applying a relativistic mean field approach, by fitting the integral cross sections. The real part of the optical potential is found to be systematically less repulsive with increasing energy than expected from the free-space repulsive KN interaction. When the elastic scattering data for Li^6 and C at 715 MeV/c are included in the analysis, a tendency of Re V_{opt} to generate an attractive pocket at the nuclear surface is observed.
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