2,690 research outputs found
Heavy Hyperon--Antihyperon Production
Based on the experience from the production of anti-Lambda Lambda and
anti-Sigma Sigma pairs at LEAR (experiment PS185) it is suggested to continue
the investigations towards the heavier antihyperon--hyperon pairs anti-Xi Xi
and anti-Omega Omega in view of: (1) the production dynamics of the heavier
antihyperon--hyperon out of the anti-p p annihilation (2) a comparison of the
(3s 3anti-s quark system) anti-Omega Omega to the (3 (anti-s s)) 3 phi meson
production, where both systems have similar masses (3.345 and 3.057,
respectively) and identical valence quark content. A systematic study of the
antihyperon--hyperon production with increasing strangeness content is
interesting for the following reasons: The anti-Omega Omega production is the
creation of two spin 3/2 objects out of the two spin 1/2 anti-p p particles.
Results of the PS185 experiments prove a clear dominance of the spin triplet
anti-s s dissociation. In the Omega anti-Omega the three s-quarks (three anti-s
quarks) are aligned to spin 3/2 each. If the three anti-s s pairs are now all
in spin triplet configurations when created out of the gluonic interaction they
should have spin parity quantum number as 3^- as long as Omega anti-Omega is
created with relative L=0 angular momentum. The comparison of the Omega
anti-Omega baryon pair to the phi phi phi three meson production (where the
three anti-s s quark pairs might not but can be produced without relative
correlation) would provide a unique determination of the intermediate matter
state. Measurements of excitation functions and polarization transfers should
be used to examine these gluon rich anti-p p --> anti-Omega Omega and anti-p p
--> phi phi phi reaction channels. Such experiments should be performed at the
PANDA detector at the FAIR facility of the GSI.Comment: 4 pages, 2 figures, Presented at LEAP05: International Conference on
Low Energy Antiproton Physics, Bonn - Juelich, Germany, May 16-22, 200
The accuracy of interpreting key psychiatric terms by ad hoc interpreters at a South African psychiatric hospital
Objective: This study examined the competence and accuracy of ad hoc interpreters in interpreting key psychiatric terms at a South African psychiatric hospital.Method: Nine individuals were asked to translate key psychiatric terms from English to Xhosa. These translations were then back-translated by independent translators, who do not have knowledge of psychiatric terminology. These back-translations were then compared with the original English. Results: It was clear that not all the participants were fully competent in English. None had formal training in interpreting or psychiatric terminology. Not all of the participants were familiar with the psychiatric concepts that clinicians use and they often made mistakes while interpreting. Conclusion: The competency levels of interpreters are unsatisfactory to ensure the optimal delivery of mental health care. It is clear that there is a need for trained interpreters in South Africa, as the continuous use of untrained interpreters compromises the effectiveness of mental health care and could lead to adverse health outcomes.Keywords: Translation; Cultural Diversity; South Africa; Health Care Quality; Access and EvaluationAfrican Journal of Psychiatry • November 2013, 16(6
Stagnation and Infall of Dense Clumps in the Stellar Wind of tau Scorpii
Observations of the B0.2V star tau Scorpii have revealed unusual stellar wind
characteristics: red-shifted absorption in the far-ultraviolet O VI resonance
doublet up to +250 km/s, and extremely hard X-ray emission implying gas at
temperatures in excess of 10^7 K. We describe a phenomenological model to
explain these properties. We assume the wind of tau Sco consists of two
components: ambient gas in which denser clumps are embedded. The clumps are
optically thick in the UV resonance lines primarily responsible for
accelerating the ambient wind. The reduced acceleration causes the clumps to
slow and even infall, all the while being confined by the ram pressure of the
outflowing ambient wind. We calculate detailed trajectories of the clumps in
the ambient stellar wind, accounting for a line radiation driving force and the
momentum deposited by the ambient wind in the form of drag. We show these
clumps will fall back towards the star with velocities of several hundred
km/sec for a broad range of initial conditions. The infalling clumps produce
X-ray emitting plasmas with temperatures in excess of (1-6)x10^7 K in bow
shocks at their leading edge. The infalling material explains the peculiar
red-shifted absorption wings seen in the O VI doublet. The required mass loss
in clumps is 3% - 30% ofthe total mass loss rate. The model developed here can
be generally applied to line-driven outflows with clumps or density
irregularities. (Abstract Abridged)Comment: To appear in the ApJ (1 May 2000). 24 pages, including 6 embedded
figure
Existence of orbital polarons in ferromagnetic insulating LaSrMnO (0.110.14) evidenced by giant phonon softening
We present an inelastic light scattering study of single crystalline
(LaPr)SrMnO (, and
,). A giant softening up to 20 - 30 cm of the
Mn-O breathing mode has been observed only for the ferromagnetic insulating
(FMI) samples () upon cooling below the Curie
temperature. With increasing Pr-doping the giant softening is gradually
suppressed. This is attributed to a coupling of the breathing mode to orbital
polarons which are present in the FMI phase.Comment: 4 pages, 5 figure
Theory of anomalous magnon softening in ferromagnetic manganites
In metallic manganites with low Curie temperatures, a peculiar softening of
the magnon spectrum close to the magnetic zone boundary has experimentally been
observed. Here we present a theory of the renormalization of the magnetic
excitation spectrum in colossal magnetoresistance compounds. The theory is
based on the modulation of magnetic exchange bonds by the orbital degree of
freedom of double-degenerate e_g electrons. The model considered is an
orbitally degenerate double-exchange system coupled to Jahn-Teller active
phonons which we treat in the limit of strong onsite repulsions. Charge and
coupled orbital-lattice fluctuations are identified as the main origin of the
unusual softening of the magnetic spectrum
Strong and Electromagnetic Decays of Two New Baryons
Two recently discovered excited charm baryons are studied within the
framework of Heavy Hadron Chiral Perturbation Theory. We interpret these new
baryons which lie 308 \MeV and 340 \MeV above the as
members of a P-wave spin doublet. Differential and total decay rates for their
double pion transitions down to the ground state are calculated.
Estimates for their radiative decay rates are also discussed. We find that the
experimentally determined characteristics of the baryons may be
simply understood in the effective theory.Comment: 16 pages with 4 figures not included but available upon request,
CALT-68-191
Experimental results on strangeness production in proton-proton collisions at COSY
The production of K+ and K- mesons in elementary proton-proton collision has
been investigated at the Cooler Synchrotron COSY in Juelich. A high quality
proton beam with low emittance and small momentum spread permitted to study the
creation of these mesons very close to the kinematical threshold. The energy
dependence of the total cross section is investigated using internal beam
facilities providing a high accuracy particle momentum determination as well as
an external non-magnetic detection setup with a large geometrical acceptance.
The determination of the four-momentum vectors for all ejectiles of each
registered event gives the complete kinematical information allowing to study
the interaction of the outgoing particles. Results on the performed studies of
the pp --> pp K+ K-, pp --> p Lambda K+ and pp --> p Sigma0 K+ reactions will
be presented and their relevance to the interpretation of heavy ion collisions
will be discussed.Comment: 8 pages, 6 figures, plenary talk at 6th International Conference On
Strange Quarks in Matter: '2001 - A Flavorspace Odyssey' (SQM2001),
Frankfurt, Germany, September 25-29, 2001, to be published in J. Phys. G:
Nucl. Part. Phy
Kaon Production and Interaction
Exclusive data on both the elementary kaon and antikaon production channels
have been taken at the cooler synchrotron COSY in proton-proton scattering. In
the kaon--hyperon production an enhancement by one order of magnitude of the
Lambda/Sigma0 ratio has been observed at excess energies below Q=13 MeV
compared to data at higher excess energies (Q>300 MeV). New results obtained at
the COSY-11 facility explore the transition region between the regime of this
low-energy Sigma0 suppression and excess energies of 60 MeV. A comparison of
the energy dependence of the Lambda and Sigma0 total cross sections exhibits
distinct qualitative differences between both hyperon production channels.
Studies of kaon-antikaon production have been motivated especially by the
ongoing discussion about the nature of the scalar resonances f0(980) and
a0(980) coupling to the K anti-K channel. For the reaction pp->ppK+K- a first
total cross section value is reported at an excess energy of Q=17 MeV, i.e.
below the phi threshold. Calculations obtained within an OBE model indicate
that the energy dependence of the available total cross section data close to
threshold is rather difficult to reconcile with the assumption of a phase-space
behaviour modified predominantly by the proton-proton final state interaction.Comment: 10 pages, 4 figures, Presented at Meson 2002: 7th International
Workshop on Meson Production, Properties and Interaction, Cracow, Poland,
24-28 May 200
Strong Decays of Strange Charmed P-Wave Mesons
Goldstone boson decays of P-wave mesons are studied within the
framework of Heavy Hadron Chiral Perturbation Theory. We first analyze the
simplest single kaon decays of these strange charmed mesons. We derive a model
independent prediction for the width of and use experimental
information on to constrain the S-wave contribution to decay.
Single and double pion decay modes are then discussed and shown to be
significantly restricted by isospin conservation. We conclude that the pion
channels may offer the best hope for detecting one strange member of an
otherwise invisible P-wave flavor multiplet.Comment: 16 pages, 2 updated figures not included but available upon request,
CALT-68-1902. (Revised estimates for error on width and for isospin
violating neutral pion decay of .
Abundances and Physical Conditions in the Warm Neutral Medium Towards mu Columbae
We present ultraviolet interstellar absorption line measurements for the
sightline towards the O9.5 V star mu Columbae obtained with the Goddard High
Resolution Spectrograph (GHRS) on board the Hubble Space Telescope. These
archival data represent the most complete GHRS interstellar absorption line
measurements for any line of sight towards an early-type star. The 3.5 km/s
resolution of the instrument allow us to accurately derive the gas-phase column
densities of many important ionic species in the diffuse warm neutral medium
using a combination of apparent column density and component fitting
techniques, and we study in detail the contamination from ionized gas along
this sightline. The low-velocity material shows gas-phase abundance patterns
similar to the warm cloud (cloud A) towards the disk star zeta Oph, while the
component at v = +20.1 km/s shows gas-phase abundances similar to those found
in warm halo clouds. We find the velocity-integrated gas-phase abundances of
Zn, P, and S relative to H along this sightline are indistinguishable from
solar system abundances. We discuss the implications of our gas-phase abundance
measurements for the composition of interstellar dust. The relative ionic
column density ratios of the intermediate velocity components show the imprint
both of elemental incorporation into grains and (photo)ionization. The
components at v = -30 and -48 km/s along this sightline likely trace shocked
gas with very low hydrogen column densities. Appendices include a new
derivation of the GHRS instrumental line spread function, and a new very
accurate determination of the total H I column along this sightline. (Abridged)Comment: Accepted for publication in the Astrophysical Journal. 80 pages
including 19 embedded figures and 12 embedded tables. Version with higher
resolution figures can be downloaded from
http://fuse.pha.jhu.edu/~howk/Papers/papers.htm
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