Extracts from the Internet


Strange meson

The SELEX collaboration at Fermilab has discovered a new elementary particle, DsJ+(2632), consisting of an s-quark and a c- antiquark. The meson with a mass of 2632 MeV was produced in proton-antiproton collisions at the Tevatron accelerator and identified from the products of its decay, which involves two (D0K+ and D+seta) production channels. The particle has an unexpected property in that although its lifetime before it decays is three times smaller than the theoretical value, its decay rate to eta mesons is six times higher than predicted by calculations - implying that some aspects of the complex dynamics of strong interaction may be left out of account. To clarify the cause of this discrepancy, further experimental and theoretical research is needed. An international collaboration that includes Russian physicists from the Institute for High Energy Physics, Institute of Experimental and Theoretical Physics, and the St Petersburg Institute of Nuclear Physics carried out the experiment. Source: hep-ex/0406045

Observing the spin of a single electron

A magnetic resonance force microscope (MRFM) capable of detecting the spin of a single electron has been constructed at an IBM laboratory. Basically, the MRFM consists of a microscopic silicon lever to which a submicron ferromagnetic particle is attached. An alternating magnetic field causes the lever to vibrate mechanically. The sample under study was brought to a distance of about 50 mkm from the lever. The spin magnetic moment of an unpaired electron in the sample exerted a perturbing force (of about 10-18 N) on the lever, leading to a shift in the lever's vibration frequency. The researchers used a laser interferometer to detect the vibrations. To enhance the effect, the system was brought to resonance by making the Larmor frequency of the electron under study equal to that of the lever's vibrations. Whereas with previous microscopes only ensembles of many electrons could be studied, the new microscope has enough sensitivity to detect single electron spins. Source: quant-ph/0312139

Five-photon quantum correlation

Five photons were put into the so-called entangled state at the University of Science and Technology in China for the first time. Although the entangled state of four particles has been obtained successfully earlier, it is only starting from five particles that the quantum error correction algorithm necessary for quantum computing can be implemented. To put five photons into the entangled state, a complicated experimental technique was developed which involves the nonlinear transformations of a laser beam passing through a crystal. The experiment was carried out by first separately entangling two photon pairs and then adding the fifth photon and putting all the photons together into a unified entangled state. Source: Nature 430 54 (2004)

Focusing sound in a phononic crystal

The term phononic crystals refers to composite materials that can cut out certain frequencies from the spectrum of a sound signal passing through them. This property is explained by the interference of the sound wave. J Page and colleagues in Canada have created a phononic crystal which has a negative index of refraction for ultrasound and is capable of focusing a sound wave. The new phononic crystal is a 3D array of tungsten carbide balls immersed in water. At a certain frequency of the sound, the diverging wave emitted by a small source on one side of the crystal is refocused on the other side of it. A negative index of refraction has already been observed in photonic crystals, which operate on electromagnetic waves. Source: Phys. Rev. Lett. 93 024301 (2004)

Polarized particles in a cyclotron

D Pritchard and his colleagues at MIT established that molecular ions possessing an electric dipole moment have a somewhat different cyclotron revolution frequency from unpolarized ions. The shift in the frequency is due to the fact that the ends of a dipole have different cyclotron frequencies. For the ion CO+, for example, the relative frequency shift is 1/109. Previous cyclotron studies have neglected this effect. The effect may prove useful for measuring dipole moments, for determining the quantum states of molecules, and possibly also for testing CPT- symmetry and searching for an electrical dipole moment in the electron. Source: Nature 430 58 (2004)

Focusing laser radiation

A new laser radiation intensity record, 0.85x1022 Watt cm-2, has been set at Michigan University. This intensity was achieved by focusing the beam from the titanium-sapphire HERCULES laser to a spot about 0.8 mkm is size. The authors used adaptive optics to correct for wave front deformation. Before being focused by a parabolic mirror, the beam reflected from another - deformable- mirror, thereby improving the wave packet shape. Source: http://physicsweb.org/

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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.

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