1,745 research outputs found
How many electrons are needed to flip a local spin?
Considering the spin of a local magnetic atom as a quantum mechanical
operator, we illustrate the dynamics of a local spin interacting with a
ballistic electron represented by a wave packet. This approach improves the
semi-classical approximation and provides a complete quantum mechanical
understanding for spin transfer phenomena. Sending spin-polarized electrons
towards a local magnetic atom one after another, we estimate the minimum number
of electrons needed to flip a local spin.Comment: 3 figure
Tagging single muons and other long-flying relativistic charged particles by ultra-fast timing in air Cherenkov telescopes
Atmospheric air Cherenkov telescopes are successfully used for ground-based,
very high-energy (VHE) gamma ray astronomy. Triggers from the so-called single
muon and other long-flying relativistic charged particle events are an unwanted
background for the Cherenkov telescope. Because of low rate at TeV energies the
muon background is unimportant. It is much more intense for telescopes with
high photon sensitivity and low energy threshold. Below a few hundred GeV
energy, the so-called muon background becomes so intense, that it can
deteriorate the sensitivity of telescopes (the so-called muon-wall problem).
From general considerations it can be anticipated that the signature of these
particles should be a light pulse with a narrow time structure. In fact,
simulations show that the pulses from muons have a very narrow time profile
that is well below the time resolutions of nearly all currently operating
telescopes. In this report we elaborate on the time profile of Cherenkov light
from the so-called single muons and show that a telescope with ultra-fast time
response can open a new dimension allowing one to tag and to reject those
events.Comment: Accepted by Astroparticle Physic
Effects to Scalar Meson Decays of Strong Mixing between Low and High Mass Scalar Mesons
We analyze the mass spectroscopy of low and high mass scalar mesons and get
the result that the coupling strengths of the mixing between low and high mass
scalar mesons are very strong and the strengths of mixing for scalar
mesons and those of I=0 scalar mesons are almost same. Next, we analyze the
decay widths and decay ratios of these mesons and get the results that the
coupling constants for which represents the coupling of high
mass scalar meson -> two pseudoscalar mesons are almost same as the
coupling for the I=0. On the other hand, the coupling constant for
which represents the low mass scalar meson -> are far
from the coupling constant for I=0. We consider a resolution for this
discrepancy. Coupling constant for glueball -> is smaller than
the coupling . is .Comment: 15 pages, 6 figure
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