740 research outputs found
K production in proton-nucleus reactions and the role of momentum-dependent potentials
The production of mesons in proton-nucleus collisions from 1.0 to 2.5
GeV is analyzed with respect to one-step nucleon-nucleon ) and
two-step -nucleon ) or pion-nucleon ) production channels on the basis of a coupled-channel transport
approach (CBUU) including the kaon final state interactions. The influence of
momentum-dependent potentials for the nucleon, hyperon and kaon in the final
state are studied as well as the importance of elastic rescattering in
the target nucleus. The transport calculations are compared to the experimental
spectra taken at LBL Berkeley, SATURNE, CELSIUS, GSI and COSY-J\"ulich.
It is found that the momentum-dependent baryon potentials effect the excitation
function of the cross section; at low bombarding energies of 1.0
GeV the attractive baryon potentials in the final state lead to a relative
enhancement of the kaon yield whereas the net repulsive potential at bombarding
energies 2 GeV causes a decrease of the cross section. Furthermore
it is pointed out, that especially the spectra at low momenta (or kinetic
energy ) allow to determine the in-medium potential almost model
independently due to a relative shift of the spectra in kinetic energy
that arises from the acceleration of the kaons when propagating out of the
nuclear medium to free space, i.e. converting potential energy to kinetic
energy of the free kaon.Comment: 11 pages, LaTeX, including 10 postscript figures, submitted to Eur.
Phys. J.
Transport analysis of K+ production in proton-nucleus reactions
The production of mesons in proton-nucleus collisions from 1.0 to 2.3
GeV is analyzed with respect to one-step nucleon-nucleon ) and
two-step -nucleon ) or pion-nucleon ) production channels on the basis of a coupled-channel transport
approach (CBUU) including the kaon final-state-interactions (FSI).
Momentum-dependent potentials for the nucleon, hyperon and kaon in the final
state are included as well as elastic rescattering in the target nucleus.
The transport calculations are compared to the experimental spectra taken
at COSY-J\"ulich. Our systematic analysis of spectra from ,
, and targets as well as their momentum
differential ratios gives a repulsive potential of MeV at
normal nuclear matter density.Comment: 7 pages, 5 figures, submitted to Eur. Phys. J.
Nonmesonic decay of the Lambda-hyperon in hypernuclei produced by p+Au collisions
The lifetime of the Lambda-hyperon for the nonmesonic decay Lambda N ---> N N
has been determined by a measurement at COSY Juelich of the delayed fission of
heavy hypernuclei produced in proton - Au collisions at T_p=1.9 GeV. It is
found that heavy hypernuclei with mass numbers A= 180 +- 5 and atomic numbers
Z= 74 +-2 fission with a lifetime
130ps +- 13ps (stat.) +- 15ps (syst.) . This value together with the results
obtained for other heavy hypernuclei in previous investigations indicates (on
the confidence level of 0.9) a violation of the phenomenological Delta I = 1/2
rule for Lambda N ---> NN transitions as known from the weak mesonic decays of
kaons and hyperons. PACS:
{13.30.-a}{Decays of baryons}
{13.75.Ev}{Hyperon-nucleon interaction}
{21.80}{Hypernuclei}
{25.80.Pw}{Hyperon-induced reactions}Comment: 3 pages, 2 Postscript figures, uses svepj.clo and svjour.cls.
submitted to European Physical Journal
The lifetime of the Lambda hyperon bound in hypernuclei produced by p+U collisions
The nonmesonic decay of the Lambda hyperon has been investigated by
observation of delayed fission from heavy hypernuclei produced in proton-U
collisions at Tp = 1.9 GeV. The lifetime of heavy hypernuclei with masses A
approximately 220 obtained in the present work, i.e.
tau = 138 +- 6 (stat.) +-m 17 (syst.) ps,
is the most accurate result for heavy hypernuclei produced in proton and
antiproton induced collisions on a U target so far.
PACS: {13.30.-a}{Decays of baryons} {13.75.Ev}{Hyperon-nucleon interaction}
{21.80}{Hypernuclei} {25.80.Pw}{Hyperon-induced reactions}Comment: 16 pages, 4 Postscript figures, uses file appolb.cls (included),
submitted to Acta Physica Polonica B, http://th-www.if.uj.edu.pl/act
On the Delta I = 1/2 rule in the Lambda N ----> N N reaction
It is shown that the mass dependence of the -lifetime in heavy
hypernuclei is sensitive to the ratio of neutron-induced to proton-induced
non-mesonic decay rates R_n/R_p. A comparison of the experimental mass
dependence of the lifetimes with the calculated ones for different values of
R_n/R_p leads to the conclusion that this ratio is larger than 2 on the
confidence level of 0.75. This suggests that the phenomenological I=1/2
rule might be violated for the nonmesonic decay of the -hyperon.Comment: 3 pages, 2 figures, to be published in European Physical Journal
Perbaikan Sistem Produksi Minyak Angin Aromatherapy Melalui Lean Manufacturing Di PT. Us, Jawa Barat
The pharmaceutical industry is facing increased competition, cost pressures and the need to improve the performance of its manufacturing operations. Lean manufacturing offer methods, tools and heuristic program for increasing productivity in manufacturing. PT. US in West Java, Indonesia can improve company performance with implementing Lean manufacturing. This study aims to improve productivity by identifying and balancing work and researching the causes of long cycle time with value stream mapping. This research resulted in a decrease cycle time of 538.96 seconds to 445.68 seconds, a decrease of 14 personnel, operating expenses decreased man power Rp.18, 2 million per month, and reduce the lead time of 14.5 days to 11.5 days
Nonmesonic decay of the Lambda hyperon in nuclear matter - implications on the weak Lambda-N interaction
The lifetime of the Lambda hyperon in heavy hypernuclei as measured by the
COSY-13 Collaboration in proton - Au, Bi and U collisions has been analysed to
yield tau(Lambda) = (145 +- 11) ps. This value for tau(Lambda) is compatible
with the lifetime extracted from antiproton annihilation on Bi and U targets,
however, much more accurate. We find that the dependence of the lifetime
tau(Lambda) on the mass of hypernuclei indicates a violation of the
phenomenological Delta I = 1/2 rule known from the weak mesonic decays of
strange particles. PACS: {13.30.-a}{Decays of baryons}
{13.75.Ev}{Hyperon-nucleon interaction} {21.80}{Hypernuclei}
{25.80.Pw}{Hyperon-induced reactions}Comment: 21 pages, 11 PostScript figures, EPJA in prin
Maui Mesosphere and Lower Thermosphere (Maui MALT) Observations of the Evolution of Kelvin-Helmholtz Billows Formed Near 86 km Altitude
Small-scale (less than 15 km horizontal wavelength) structures known as ripples have been seen in OH airglow images for nearly 30 years. The structures have been attributed to either convective or dynamical instabilities; the latter are mainly due to large wind shears, while the former are produced by superadiabatic temperature gradients. Dynamical instabilities produce Kelvin-Helmholtz (KH) billows, which have been known for many years. However, models and laboratory experiments suggest that these billows often spawn a secondary instability that is convective in nature. While laboratory investigations see evidence of such structures, the evolution of these instabilities in the atmosphere has not been well documented. The Maui Mesosphere and Lower Thermosphere (Maui MALT) Observatory, located on Mt. Haleakala, is instrumented with a Na wind/temperature lidar that can detect dynamic or convective instabilities with 1 km vertical resolution over the altitude region from about 85 to 100 km. The observatory also includes a fast OH airglow camera, sensitive to emissions coming from approximately 82 to 92 km altitude, which obtains images every 3 s at sufficient resolution and signal to noise to see the ripples. On 15 July 2002, ripples were observed moving at an angle to their phase fronts. After a few minutes, structures appeared to form approximately perpendicular to the main ripple phase fronts. The lidar data showed that a region of dynamical instability existed from approximately 85.5 to 87 km and that the direction of the wind shear in this region was consistent with the phase fronts of the ripple features. The motion of the ripples themselves was consistent with the wind velocity at 85.9 km. Thus in this case the observed ripple motion was the advection of KH billows by the wind. The perpendicular structures were seen to be associated with the KH billows: they formed at the time when the atmosphere briefly became convectively unstable within the region where the KH billows most likely formed. Because of this and because the ripples were oriented approximately perpendicular to and moved with the billows, we speculate that they are the secondary instabilities predicted by models of KH evolution. The primary and perpendicular features were seen to decay into unstructured regions suggestive of turbulence. While the formation and decay time appear consistent with models, the horizontal wavelength of the perpendicular structures seems to be larger than models predict for the secondary instability features
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