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Strange meson
1 August 2004
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
1 August 2004
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
1 August 2004
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
1 August 2004
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
1 August 2004
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
1 August 2004
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. It is compiled from a multitude of Internet sources.
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