Electron-electron interaction at decreasing kFlk_Fl

The contribution of the electron-electron interaction to conductivity is analyzed step by step in gated GaAs/InGaAs/GaAs heterostructures with different starting disorder. We demonstrate that the diffusion theory works down to $k_F l\simeq 1.5-2$, where $k_F$ is the Fermi quasimomentum, $l$ is the mean free paths. It is shown that the e-e interaction gives smaller contribution to the conductivity than the interference independent of the starting disorder and its role rapidly decreases with $k_Fl$ decrease.Comment: 5 pages, 6 figure

Low-sulfide platinum-palladium deposits of the Paleoproterozoic Fedorova-Pana Layered Complex, Kola Region, Russia

Several deposits of low-sulfide Pt–Pd ores have been discovered in recent decades in the Paleoproterozoic Fedorova–Pana Layered Complex located in the Kola Region (Murmansk Oblast) of Russia. The deposits are divided into two types: reef-style, associated with the layered central portions of intrusions, and contact-style, localized in the lower parts of intrusions near the contact with the Archean basement. The Kievey and the North Kamennik deposits represent the first ore type and are confined to the North PGE Reef located 600–800 m above the base of the West Pana Intrusion. The reef is associated with a horizon of cyclically interlayered orthopyroxenite, gabbronorite and anorthosite. The average contents of Au, Pt and Pd in the Kievey ore are 0.15, 0.53 and 3.32 ppm, respectively. The North Kamennik deposit has similar contents of noble metals. The Fedorova Tundra deposit belongs to the second ore type and has been explored in two sites in the lower part of the Fedorova intrusion. Mineralization is mainly associated mainly with taxitic or varied-textured gabbronorites, forming a matrix of intrusive breccia with fragments of barren orthopyroxenite. The ores contain an average of 0.08 ppm Au, 0.29 ppm Pt and 1.20 ppm Pd. In terms of PGE resources, the Fedorova Tundra is the largest deposit in Europe, hosting more than 300 tons of noble metals

Measurement of the ratio of the leptonic widths Γee/Γμμ\Gamma_{ee}/\Gamma_{\mu\mu} for the J/ψJ/\psi meson

The ratio of the electron and muon widths of the $J/\psi$ meson has been measured using direct $J/\psi$ decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result $\Gamma_{ee}(J/\psi)/\Gamma_{\mu\mu}(J/\psi)=1.0022\pm0.0044\pm0.0048\ (0.65\%)$is in good agreement with the lepton universality. The experience collected during this analysis will be used for a$J/\psi$ lepton width determination with up to 1% accuracy.Comment: 5 pages, 6 figures, 2 table

Study of the nature of high-magnesian xenoliths of the Gabbro-10 massif, Monchegorsk Complex, the Kola Region

The results of studying geology, petrography and geochemistry of chlorite-amphibole rocks and fine-grained metagabbro in the Gabbro-10 massif have been presented. Chlorite-amphibole rocks are found as large fragments of irregular shape. They have a porphyraceous texture, a schistose structure and are enriched in magnesium and chromium (19 and 0.3 wt % respectively) concerning the metagabbro prevailing in the massif. According to the classification and variation diagrams of main elements, as well as to the diagrams of the trace-element composition normalized to primitive mantle, the chlorite-amphibole rocks are metamorphosed xenoliths of melanocratic norites of the Nyud-Poaz massif. Fine-grained metagabbros, on the other hand, occur in the form of numerous angular fragments concentrated near the lower contact of the intrusion. These massive rocks of the blastogabbroic texture are less enriched in magnesium and chromium (8 and 0.02 wt % respectively) and correspond to the composition of mesocratic gabbronorites. According to the spectra of trace elements normalized to the primitive mantle, fine-grained metagabbro, with pronounced negative Nb-Ta & Zr-Hf anomalies and positive Sr & Eu anomalies, corresponds to the rocks of the marginal zones of the NKT and Nude-Poaz massifs. However, the greatest similarity is established between these rocks and the schistose gabbroids of the marginal zone of the Gabbro-10 massif. Thus, the fragments of fine-grained metagabbro are possibly autoliths of the intrusion. Collectively, the obtained data have indicated the late intrusion of the Gabbro-10 massif following the crystallization of the Nude-Poaz rocks, and the presence of autoliths of its own marginal zone in the massif points at several magmatic impulses during its formation