656 research outputs found
Roper Excitation in Alpha-Proton Scattering
We study the Roper excitation in the reaction. We consider
all processes which may be relevant in the Roper excitation region, namely,
Roper excitation in the target, Roper excitation in the projectile, and double
excitation processes. The theoretical investigation shows that the
Roper excitation in the proton target mediated by an isoscalar exchange is the
dominant mechanism in the process. We determine an effective isoscalar
interaction by means of which the experimental cross section is well
reproduced. This should be useful to make predictions in related reactions and
is a first step to construct eventually a microscopic
transition potential, for which the present reaction does not offer enough
information.Comment: Latex 17 pages; figures available by request; Phys. Rev. C in prin
Neutrino masses and mixing parameters in a left-right model with mirror fermions
In this work we consider a left-right model containing mirror fermions with
gauge group SU(3). The model has several free parameters which here we have
calculated by using the recent values for the squared-neutrino mass
differences. Lower bound for the mirror vacuum expectation value helped us to
obtain crude estimations for some of these parameters. Also we estimate the
order of magnitude of the masses of the standard and mirror neutrinos.Comment: 13 pages, version submitted to European Physical Journal
Coherent pion production in neutrino nucleus collision in the 1 GeV region
We calculate cross sections for coherent pion production in nuclei induced by
neutrinos and antineutrinos of the electron and muon type. The analogies and
differences between this process and the related ones of coherent pion
production induced by photons, or the (p,n) and reactions are
discussed. The process is one of the several ones occurring for intermediate
energy neutrinos, to be considered when detecting atmospheric neutrinos. For
this purpose the results shown here can be easily extrapolated to other
energies and other nuclei.Comment: 13 pages, LaTex, 8 post-script figures available at
[email protected]
Projectile and target-Roper excitation in the p (d, d')X reaction
In this paper we compare a model that contains the mechanisms of
excitation in the projectile and Roper excitation in the target with
experimental data from two (d, d') experiments on a proton target. The
agreement of the theory with the experiment is fair for the data taken at T_d =
2.3 GeV. The excitation in the projectile is predicted close to the
observed energy with the correct width. The theory, however, underpredicts by
about 40% the cross sections measured at T_d = 1.6 GeV at angles where the
cross section has fallen by about two orders of magnitude. The analysis done
here allows to extract an approximate strength for the excitation of the Roper
[N^*(1440)] excitation and a qualitative agreement with the theoretical
predictions is also found.Comment: 8 ps figure
Superconducting density of states at the border of an amorphous thin film grown by focused-ion-beam
We present very low temperature Scanning Tunneling Microscopy and
Spectroscopy (STM/S) measurements of a W based amorphous thin film grown with
focused-ion-beam. In particular, we address the superconducting properties
close to the border, where the thickness of the superconducting film decreases,
and the Au substrate emerges. When approaching the Au substrate, the
superconducting tunneling conductance strongly increases around the Fermi
level, and the quasiparticle peaks do not significantly change its position.
Under magnetic fields, the vortex lattice is observed, with vortices positioned
very close to the Au substrate.Comment: To appear in Journal of Physics: Conference serie
Ground states and formal duality relations in the Gaussian core model
We study dimensional trends in ground states for soft-matter systems.
Specifically, using a high-dimensional version of Parrinello-Rahman dynamics,
we investigate the behavior of the Gaussian core model in up to eight
dimensions. The results include unexpected geometric structures, with
surprising anisotropy as well as formal duality relations. These duality
relations suggest that the Gaussian core model possesses unexplored symmetries,
and they have implications for a broad range of soft-core potentials.Comment: 7 pages, 1 figure, appeared in Physical Review E (http://pre.aps.org
Incompressible flow in porous media with fractional diffusion
In this paper we study the heat transfer with a general fractional diffusion
term of an incompressible fluid in a porous medium governed by Darcy's law. We
show formation of singularities with infinite energy and for finite energy we
obtain existence and uniqueness results of strong solutions for the
sub-critical and critical cases. We prove global existence of weak solutions
for different cases. Moreover, we obtain the decay of the solution in ,
for any , and the asymptotic behavior is shown. Finally, we prove the
existence of an attractor in a weak sense and, for the sub-critical dissipative
case with , we obtain the existence of the global attractor
for the solutions in the space for any
Roper excitation in reactions
We calculate differential cross sections and the spin transfer coefficient
in the reaction for proton
bombarding energies from 1 to 10 GeV and invariant masses spanning
the region of the N(1440) Roper resonance. Two processes --
excitation in the -particle and Roper excitation in the proton -- are
included in an effective reaction model which was shown previously to reproduce
existing inclusive spectra. The present calculations demonstrate that these two
contributions can be clearly distinguished via , even under kinematic
conditions where cross sections alone exhibit no clear peak structure due to
the excitation of the Roper.Comment: 12 pages, 11 ps figures, Late
Review of magnetic nanostructures grown by focused electron beam induced deposition (FEBID)
We review the current status of the use of focused electron beam induced deposition (FEBID) for the growth of magnetic nanostructures. This technique relies on the local dissociation of a precursor gas by means of an electron beam. The most promising results have been obtained using the Co₂(CO)₈ precursor, where the Co content in the grown nanodeposited material can be tailored up to more than 95%. Functional behaviour of these Co nanodeposits has been observed in applications such as arrays of magnetic dots for information storage and catalytic growth, magnetic tips for scanning probe microscopes, nano-Hall sensors for bead detection, nano-actuated magnetomechanical systems and nanowires for domain-wall manipulation. The review also covers interesting results observed in Fe-based and alloyed nanodeposits. Advantages and disadvantages of FEBID for the growth of magnetic nanostructures are discussed in the article as well as possible future directions in this field.Financial support by several projects is acknowledged: MAT2014-51982-C2-1-R, MAT2014-51982-C2-2-R and MAT2015-69725-REDT from MINECO (including FEDER funding), CELINA COST Action CM1301, Aragón Regional Government through project E26, FP7 Marie Curie Fellowship 3DMAGNANOW, EPSRC Early Career Fellowship EP/M008517/1 and Winton Fellowship
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