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| Issue 11, 2024 |
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Extracts from the Internet | ||
Neutrino oscillations1 July 1998Compelling evidence for neutrino oscillation, i. e., the mutual transformation of different neutrino species, was reported at the Neutrino 98 conference in Japan based on neutrino detection experiments at the underground Super-Kamiokande facility. This latter, a huge steel tank 41m in height and 38m in diameter, is filled with pure water and has thousands of photodetectors mounted on its inner surface. Neutrinos produced by cosmic rays hitting the upper atmosphere were studied by detecting the Cerenkov radiation from electrons and muons they scatter. The existence of neutrino oscillations established from several thousands of such events implies that mass neutrino is nonzero and differs for different neutrino species. A nonzero neutrino mass is predicted by most Great Unification theories, in which the weak, electromagnetic, and strong interactions are united. While the experiment yields the difference between the electron and muon neutrino masses (0.07eV), the mass itself still remains undetermined. The oscillation phenomenon may perhaps account for the shortfall of neutrinos from the Sun. Implications of the finite neutrino mass for the formation of the universe's large-scale structure are pointed out. Source: http://www.phys.hawaii.edu:80/~jgl/nuosc_story.html Search for the magnetic monopole1 July 1998Magnetic monopoles, hypothetical magnetically charged particles, are being searched for at Fermilab in the same proton-antiproton collision data used to discover the top quark. While the monopole itself has not yet been found, a lower limit on its mass is established, which is 600 or 900 GeV depending on the spin. Source: Physics News Update, Number 375 Ultracool atoms in a quantum cavity1 July 1998A Caltech group reports a study of a single atom-single photon quantum system in a small mirror-walled cavity capable of trapping photons of certain frequencies. The atoms used were those of cesium cooled down to 20µK using a magneto-optic trap. A beam of such ultracool atoms, when combined with a very weak laser radiation, secures that only one atom and one photon are in the cavity at any given moment. Interestingly, the system's resonance curve is asymmetric with respect to the central frequency - presumably because the nature of the atom-cavity interaction changes from repulsion to attraction as the photon frequency is detuned blue or red, respectively. Source: http://publish.aps.org/FOCUS/ A bright quasar1 July 1998A new quasar was discovered by G Lewis and his colleagues using a 2.5-m Isaac Newton Telescope in Canary Islands, which is 10 times brighter than the most powerful quasars known. The quasar is about 11 billion light years from Earth (redshift is z=3.6) and its emitted energy is shared about equally between the infrared and optical+UV ranges. It is not clear if the quasar's apparent brightness is the true one or is due to a gravitational magnifying lens on the line of sight. The quasar was discovered by M Schmidt in 1963. Today, its high brightness is mostly ascribed to an accretion disk surrounding supermassive black holes located in galactic nuclei. Source: http://www.nature.com/ New class of star1 July 1998A new class of star has been discovered for the first time in several decades by a 2MASS (Two-Micron All-Sky Survey) team under Dr. J D Kirkpatrick. In all, about 20 unusual infrared sources (named L dwarfs) were found, whose spectral studies using the Keck II telescope at Hawaii showed them to be star-like objects which differ dramatically in their features from ordinary stars. In particular, the surface temperature of only 1500 to 2000 C makes the objects all but invisible in the optical range. As their masses are only 6% of the solar mass, no stable fusion process is possible in their interiors. Source: http://unisci.com/ |
The Extracts from the Internet is a section of Uspekhi Fizicheskih Nauk (Physics Uspekhi) — the monthly rewiew journal of the current state of the most topical problems in physics and in associated fields. The presented News is devoted to the fundamental discoveries of physics and astrophysics. Permanent editor is Yu.N. Eroshenko. It is compiled from a multitude of Internet sources. | |
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