2,749 research outputs found
Search for energetic cosmic axions utilizing terrestrial/celestial magnetic fields
Orbiting -detectors combined with the magnetic field of the Earth or
the Sun can work parasitically as cosmic axion telescopes. The relatively short
field lengths allow the axion-to-photon conversion to be coherent for
eV, if the axion kinetic energy is above
keV (Earth's field), or, MeV (Sun's field), allowing thus to search
for axions from annihilations, from supernova explosions, etc. With a
detector angular resolution of , a more efficient sky survey for
energetic cosmic axions passing {\it through the Sun} can be performed. Axions
or other axion-like particles might be created by the interaction of the cosmic
radiation with the Sun, similarly to the axion searches in accelerator beam
dump experiments; the enormous cosmic energy combined with the built-in
coherent Primakoff effect might provide a sensitive detection scheme, being out
of reach with accelerators. The axion signal will be an excess in -rays
coming either from a specific celestial place behind the Sun, e.g. the Galactic
Center, or, from any other direction in the sky being associated with a violent
astrophysical event, e.g. a supernova. Earth bound detectors are also of
potential interest. The axion scenario also applies to other stars or binary
systems in the Universe, in particular to those with superstrong magnetic
fields.Comment: 9 pages, LaTeX, small changes in text and bibliograph
Four-electron shell structures and an interacting two-electron system in carbon nanotube quantum dots
Low-temperature transport measurements have been carried out on single-wall
carbon nanotube quantum dots in a weakly coupled regime in magnetic fields up
to 8 Tesla. Four-electron shell filling was observed, and the magnetic field
evolution of each Coulomb peak was investigated, in which magnetic field
induced spin flip and resulting spin polarization were observed. Excitation
spectroscopy measurements have revealed Zeeman splitting of single particle
states for one electron in the shell, and demonstrated singlet and triplet
states with direct observation of the exchange splitting at zero-magnetic field
for two electrons in the shell, the simplest example of the Hund's rule. The
latter indicates the direct analogy to an artificial He atom.Comment: 4 pages, 3 figures, submitted to Physical Review Letter
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