8,105 research outputs found
Geoneutrinos in Borexino
This paper describes the Borexino detector and the high-radiopurity studies
and tests that are integral part of the Borexino technology and development.
The application of Borexino to the detection and studies of geoneutrinos is
discussed.Comment: Conference: Neutrino Geophysics Honolulu, Hawaii December 14-16, 200
Damping by slow relaxing rare earth impurities in Ni80Fe20
Doping NiFe by heavy rare earth atoms alters the magnetic relaxation
properties of this material drastically. We show that this effect can be well
explained by the slow relaxing impurity mechanism. This process is a
consequence of the anisotropy of the on site exchange interaction between the
4f magnetic moments and the conduction band. As expected from this model the
magnitude of the damping effect scales with the anisotropy of the exchange
interaction and increases by an order of magnitude at low temperatures. In
addition our measurements allow us to determine the relaxation time of the 4f
electrons as a function of temperature
Anisotropy effects on the magnetic excitations of a ferromagnetic monolayer below and above the Curie temperature
The field-driven reorientation transition of an anisotropic ferromagnetic
monolayer is studied within the context of a finite-temperature Green's
function theory. The equilibrium state and the field dependence of the magnon
energy gap are calculated for static magnetic field applied in plane
along an easy or a hard axis. In the latter case, the in-plane reorientation of
the magnetization is shown to be continuous at T=0, in agreement with free spin
wave theory, and discontinuous at finite temperature , in contrast with
the prediction of mean field theory. The discontinuity in the orientation angle
creates a jump in the magnon energy gap, and it is the reason why, for ,
the energy does not go to zero at the reorientation field. Above the Curie
temperature , the magnon energy gap vanishes for H=0 both in the
easy and in the hard case. As is increased, the gap is found to increase
almost linearly with , but with different slopes depending on the field
orientation. In particular, the slope is smaller when is along the hard
axis. Such a magnetic anisotropy of the spin-wave energies is shown to persist
well above ().Comment: Final version accepted for publication in Physical Review B (with
three figures
Applications of aerospace technology to petroleum extraction and reservoir engineering
Through contacts with the petroleum industry, the petroleum service industry, universities and government agencies, important petroleum extraction problems were identified. For each problem, areas of aerospace technology that might aid in its solution were also identified, where possible. Some of the problems were selected for further consideration. Work on these problems led to the formulation of specific concepts as candidate for development. Each concept is addressed to the solution of specific extraction problems and makes use of specific areas of aerospace technology
Structural and magnetic dynamics of a laser induced phase transition in FeRh
We use time-resolved x-ray diffraction and magnetic optical Kerr effect to
study the laser induced antiferromagnetic to ferromagnetic phase transition in
FeRh. The structural response is given by the nucleation of independent
ferromagnetic domains (\tau_1 ~ 30ps). This is significantly faster than the
magnetic response (\tau_2 ~ 60ps) given by the subsequent domain realignment.
X-ray diffraction shows that the two phases co-exist on short time-scales and
that the phase transition is limited by the speed of sound. A nucleation model
describing both the structural and magnetic dynamics is presented.Comment: 5 pages, 3 figures - changed to reflect version accepted for PR
What's Interesting About Strangeness Production? - An Overview of Recent Results
In this paper I highlight a few selected topics on strange particle
production in heavy-ion collisions. By studying the yield and spectra of
strange particles we hope to gain understanding of the conditions reached in,
and the ensuing dynamics of, the systems produced when ultra-relativistic
heavy-ions are collided.Comment: 17 Pages, 18 figures, Hot Quarks 2004 Proceeding
Identified particles in Au+Au collisions at sqrt{s_NN} = 200 GeV
The yields of identified particles have been measured at RHIC for Au+Au
collisions at sqrt{s_NN} = 200 GeV using the PHOBOS spectrometer. The ratios of
antiparticle to particle yields near mid-rapidity are presented. The first
measurements of the invariant yields of charged pions, kaons and protons at
very low transverse momenta are also shown.Comment: 4 pages, 4 figures, Contribution to Quark Matter 2002, Nantes,
France, July 200
Elliptic Flow in Au+Au Collisions at RHIC
Elliptic flow is an interesting probe of the dynamical evolution of the dense
system formed in the ultrarelativistic heavy ion collisions at the Relativistic
Heavy Ion Collider (RHIC). The elliptic flow dependences on transverse
momentum, centrality, and pseudorapidity were measured using data collected by
the PHOBOS detector, which offers a unique opportunity to study the azimuthal
anisotropies of charged particles over a wide range of pseudorapidity. These
measurements are presented, together with an overview of the analysis methods
and a discussion of the results.Comment: Presented at Hot Quarks 2004; 7 pages, 6 figure
New limits on di-nucleons decay into invisible channels
Data of the radiochemical experiment [E.L.Fireman, 1978] with 1.7 t of
KC_2H_3O_2, accumulated deep underground during ~1 yr, were reanalyzed to set
limits on di-nucleons (nn and np) decays into invisible channels
(disappearance, decay into neutrinos, etc.). The obtained lifetime bounds
tau_np > 2.1 10^25 yr and tau_nn > 4.2 10^25 yr (at 90% C.L.) are better (or
competitive) than those established in the recent experiments.Comment: 3 pages, accepted in JETP Letter
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