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The detailed analysis is presented of an event which is interpreted as the mesonic cascade decay of a double hyperfragment produced by the capture of a E~ hyperon on a light emulsion nucleus. The most likely interprétations of the double hyperfragment are those in terms of either ^^Be'» or ^^Be".

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The existence of the H particle, the dihyperon predicted by Jaffe, would bring into question the existence of double hypernuclei. We review the two double hypernucleus events published in the literature. We include an independent report, hitherto unpublished, which was made on the ΛΛ 10 Be event in 1963 and clarifies the salient features of the event; this report reaffirms its published interpretation. We have made a simple calculation of the energy spectrum for Ξ - hyperons produced with K - beams in past emulsion experiments, with a result which accounts adequately for the paucity of reported double hypernucleus events. We outline a hybrid emulsion experiment that would locate Ξ - hyperon interactions efficiently and could thereby greatly improve our knowledge of double hypernuclei.

During a systematic scan for interactions of 1. 3-and 1. 5-GeV/c K" mesons 1 in emulsions irradiated in the separated K' meson beam at CERN, 2 an event has been found which is interpreted as the production and subsequent mesonic cascade decay of a double hyper fragment. A photomicrograph and explanatory schematic drawing of the event are given in Fig. 1, AS" hyperon (track 1) emitted from the interaction of a K~ meson of momentum 1. 5 GeV/c (star A) comes to rest and is absorbed at B. A double hyperfragment (track 6) and another charged particle (track 5) are observed to come from star B. The double hyperfragment decays at C into a n~ meson (track 7), a singly charged particle (track 8), and an ordinary hyperfragment (track 9). This hyperfragment decays at D into a n~ meson (track 10) and three other charged particles (tracks 11, 12, and 13). The results of the measurements of the angles of emission and ranges of all the charged particles involved in these processes are summarized in Table I. All reasonable interpretations of this event, other than that of a H~ hyperon capture at B leading to the emission of a double hyperfragment, have been considered and discarded. 3 The ordinary hyperfragment was analyzed using only the kinematics of its decay, whereas the possible identities and decay schemes of the double hyperfragment were assigned from a study of both the production and decay processes. In particular, the Coulomb barrier argument was used to establish the fact that the H" hyperon capture occurred on a light nucleus (C,N, O) of the emulsion. The final results of this analysis are summarized in Table II.From a comparison of the binding energy B^A of the two A 0 hyperons in double hyperfragments with Bj^ for ordinary hyperfragments, one can expect to obtain information not only on the 29

We investigate the optical properties of a three-dimensional metamaterial nanotip that has a pyramidal shape. The nanotip itself is made of a large number of densely packed metallic nanospheres. In analogy to the emergence of a continuous energy band in a crystal, the strong coupling among neighboring nanospheres forces them to act collectively and allows the observation of a broad plasmonic band. The largely increased degrees of freedom within the metamaterial nanotip allow to sustain a great variety of different localized eigenmodes. In this contribution, we systematically reveal their peculiar polarization state and show that they allow for light localization in various well-defined spatial domains.

We report a phenomenon of focusing a radially polarized beam from the visible range by a silver film with no hole on the optical axis and double-sided concentric corrugations. The axes of symmetry of grooves and the illuminating beam coincide. An Ag lens of 100 nm thickness, five grooves, of which the outermost has 5 microm diameter, at lambda=400 nm transmits 22% of electric energy and focuses light into a 0.2lambda2 spot area at a focal length close to 2lambda, while at lambda=500 nm the results are 11%, 0.16lambda2 and lambda, respectively. This Ag lens focuses without contribution of evanescent waves a far-field source into a far-field spot. The nanolens acts like a refractive optical system of high numerical aperture close to unity.

A photonic crystal fiber made of fused silica glass and infiltrated with nitrobenzene (C 6 H 5 NO 2 ) was proposed as a new nonlinear medium for supercontinuum generation (SG). The guiding properties of the fiber structure were studied numerically, including estimation of the effective refractive index, attenuation, and dispersion of the fundamental mode. Based on the obtained results, three optimized structures were selected and tested numerically for SG. With numerical simulations of nonlinear propagation, we demonstrated the feasibility of spectrally broad and coherent SG in the proposed structures. For the first we obtained a supercontinuum (SC) in the range of 0.8-1.8 µm, for the second in the range of 0.8-2.1 µm, and for the third 1.3-2.3 µm. The pulse energy was in the range of 0.06-0.5 nJ while the pulse duration was 90 fs or 120 fs. For all structures an SC was formed in the first centimeter of the light propagation and conveniently allowed to assume short segments of the fibers. The proposed fibers are good candidates for all-fiber SC sources constituting an attractive alternative to glass-core fibers, since the nonlinearity of nitrobenzene is significantly higher than that of silica. The proposed solution may lead to new low-cost all-fiber optical systems for SG.