14,906 research outputs found
Single spin-torque vortex oscillator using combined bottom-up approach and e-beam lithography
A combined bottom-up assembly of electrodeposited nanowires and electron beam
lithography technique has been developed to investigate the spin transfer
torque and microwave emission on specially designed nanowires containing a
single Co/Cu/Co pseudo spin valve. Microwave signals have been obtained even at
zero magnetic field. Interestingly, high frequency vs. magnetic field
tunability was demonstrated, in the range 0.4 - 2 MHz/Oe, depending on the
orientation of the applied magnetic field relative to the magnetic layers of
the pseudo spin valve. The frequency values and the emitted signal frequency as
a function of the external magnetic field are in good quantitative agreement
with the analytical vortex model as well as with micromagnetic simulations.Comment: 9 pages, 4 figure
Processo agroindustrial: elaboração de chips de macaxeira.
bitstream/item/28108/1/com.tec.222.pdfDisponível também on-line
A Monte-Carlo generator for statistical hadronization in high energy e+e- collisions
We present a Monte-Carlo implementation of the Statistical Hadronization
Model in e+e- collisions. The physical scheme is based on the statistical
hadronization of massive clusters produced by the event generator Herwig within
the microcanonical ensemble. We present a preliminary comparison of several
observables with measurements in e+e- collisions at the Z peak. Although a fine
tuning of the model parameters is not carried out, a general good agreement
between its predictions and data is found.Comment: 19 pages, 28 figures, 6 tables. v2: added sections on comparison
between the Statistical Hadronization Model and the Cluster Model and on the
interplay between Herwig cluster splitting algorithm and Statistical
Hadronization Model predictions. Fixed typos and references added. Version
accepted for publication in EPJ
On the absorption and production cross sections of and
We have computed the isospin and spin averaged cross sections of the
processes and , which are crucial in the
determination of the abundances of and in heavy ion collisions.
Improving previous calculations, we have considered several mechanisms which
were missing, such as the exchange of axial and vector resonances (,
, , etc...) and also other processes such as and . We find that
some of these mechanisms give important contributions to the cross section. Our
results also suggest that, in a hadron gas, production might be more
important than its absorption
production and absorption in a hot hadron gas
We calculate the time evolution of the abundance in the hot hadron
gas produced in the late stage of heavy ion collisions. We use effective field
Lagrangians to obtain the production and dissociation cross sections of
. In this evaluation we include diagrams involving the anomalous
couplings and and also the
couplings of the with charged and mesons. With these new
terms the interaction cross sections are much larger than those found
in previous works. Using these cross sections as input in rate equations, we
conclude that during the expansion and cooling of the hadronic gas, the number
of , originally produced at the end of the mixed QGP/hadron gas phase,
is reduced by a factor of 4.Comment: 8 pages, 4 figure
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