 |
RSS feeds |
|
|||||
| Issue 11, 2024 |
|
||||||
|
|
|
||||||
Extracts from the Internet | ||
Rare channel of the single top quark production1 April 2014CDF and DZero collaborations (E. Fermi National Laboratory, USA) identified events of s-channel production of a single (but not free) t-quark upon p-anti-p-collisions. These t-quarks are most often produced in t-anti-tpairs in strong interactions, while rare events of single t-quark production in the s-channel are due to weak interactions when two of the colliding quarks, from the composition of the p and anti-p, transform into a W-boson which then breaks up into anti-t- and b-quarks. The data obtained from 2001 to 2011 give 40 such events. With the precision currently attained, the measured single t-quark production cross section in the s-channel 1.36+0.37-0.32 pb agrees with the cross section 1.05 ± 0.05 pbcalculated within the Standard model. In the 1960s (before quark confinement was revealed) Ya.B. Ztl’dovich with colleagues analyzed various astrophysical and physico-chemical aspects of the hypothesis of free quark existence, see Sov. Phys. Usp. 8 702 (1966). Sources: arXiv:1402.3756 [hep-ex], www.fnal.gov Neutrino oscillations in the Terrestrial matter1 April 2014Data on the terrestrial matter effects on neutrino (ν) oscillations by the Mikheev-Smirnov-Wolfenstein mechanism were first obtained using the Super-Kamiokandedetector (Japan). The ν oscillations, i.e., the transformation of one type of ν to another, are due to the difference in their flavor and mass states. The oscillations of noninteracting ν may be caused by a time-dependent change in the phase difference of states. These are called vacuum oscillations. But νe oscillations can be amplified resonancely in interaction with charged particles in a substance (the Mikheyev – Smirnov – Wolfenstein effect). Approximately half of νe produced in nuclear reactions in the Sun reach the Earth, and the rest of νe transform on the way to νμ and ντ. Part of these νμ and ντ oscillate back to νe when passing through the Earth depth at night, which was just recorded by the Super-Kamiokande detector with confidence of 2.7σ. According to the data accumulated within 18 years of observations, at night the detector registered by 3.2 ± 1.1(stat) ± 0.5(syst) % more νe than in the daytime. In other experiments, including those with atmospheric ν, the terrestrial matter effect on neutrino oscillations has not yet been observed. Source: Phys. Rev. Lett. 112 091805 (2014) Possible registration of relic gravitational waves1 April 2014The data on the relic gravitational wave effect on the microwave background radiation anisotropy were first obtained on BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) radio telescope on the South Pole in Antarctica. An array of 512 superconducting detectors was used during three seasons of 2010-2012 to observe the celestial area of 380 sq.deg at a frequency of 150 GHz. Gravitational waves have not yet been registered straightforwardly, but BICEP2 revealed their indirect effect on relic radiation polarization. This effect showed up in the epoch of recombination when the Universe age was 380 thousand years. In the range of multipoles l = 30-150 BICEP2 registered with confidence of 5.9σ an excess of polarization B-mode which could not be caused by the effect of gravitational lensing other sources, but is rather due to gravitational waves. The determined ratio of the tensor perturbation mode to the scalar one is r = 0.20+0.07-0.05, which somewhat exceeds the upper limit obtained earlier by other telescopes. The existence of relic gravitational waves was predicted by the inflation model of the early Universe based on the idea of a rapid exponential expansion in very early cosmological epochs. Gravitational waves are generated at the inflation stage simultaneously with curvature disturbance by quantum fluctuations. The discovery of relic gravitational waves is a serious argument in favor of the inflation theory, but independent confirmation will make the results more reliable. Source: arXiv:1403.3985 [astro-ph.CO] Cobalt from supernova outburst1 April 2014The research workers of the RAS Institute of Space Research and the Max Plank Institute for Astrophysics (Germany) E.M. Churazov, R.A. Sunyaev S.A. Grebnev and their colleagues from other countries carried out observations on gamma-spectrometer SPI of the orbital observatory INTEGRAL and registered (at 847 keV) the spectral line of the decay of radioactive nuclei of 56Co produced upon the explosion of Ia type supernova SN2014J in galaxy M82. Cobalt lines have already been registered upon explosions of collapsing supernovae (for example, supernova SN 1987A), but for Ia supernova this line was observed for the first time. Ia type supernovae correspond to thermonuclear explosions of stars – white dwarfs in binary systems upon the gas flow from the companion star onto the white dwarf or upon confluence of two white dwarfs. The examination of SN 2014J using INTEGRAL was undertaken 46-63 days after the outburst. The observations confirmed the expectations of scientists that the photon yield from radioactive 56Co decay must begin at precisely this time. An estimate was obtained showing that 56Ni in the amount of about 0.7 of the solar mass was synthesized upon the explosion, and then 56Ni nuclei decayed into 56Co. Observation of the cobalt decay line is important for specification of the models of supernovae and nucleosynthesis processes in the Universe. Source: www.astronomerstelegram.org, IKI Press Service Galactic tendrils in voids1 April 2014Examining correlation of galaxies in the survey GAMA (Galaxy and Mass Assembly) M. Alpashan (the University of St. Andreas, Great Britain and the University of Western Australia) and colleagues discovered in voids a new type of large-scale structures, namely, tendrils consisting of several galaxies. Earlier, only single galaxies were observed in voids, i.e., in regions with a lowered concentration of galaxies between superclusters. The tendrils of galaxies originate at a filament and terminate at another filament or in an empty space in a void. They contain up to six galaxies and are ≈ 14 kpc long. The discovered tendrils are fairly numerous, their constituent galaxies may contain up to a quarter of the entire stellar baryon matter. The morphological tendrils differ from the filaments (giant filament-like structures containing galaxies and galactic clusters) in that they possess a much lower mean density. Plane and elongated structures in the distribution of galaxies were studied in theoretical works of Ya.B. Zel’dovich and his colleagues and were on the whole confirmed by astronomical observations. The discovered galactic tendrils represent a new, previously unknown type of large-scale structures. Source: MNRAS Lett. 440 L106 (2014) |
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. | |
|
© 1918–2024 Uspekhi Fizicheskikh Nauk Email: ufn@ufn.ru Editorial office contacts About the journal Terms and conditions |