624 research outputs found
A dynamical model of surrogate reactions
A new dynamical model is developed to describe the whole process of surrogate
reactions; transfer of several nucleons at an initial stage, thermal
equilibration of residues leading to washing out of shell effects and decay of
populated compound nuclei are treated in a unified framework. Multi-dimensional
Langevin equations are employed to describe time-evolution of collective
coordinates with a time-dependent potential energy surface corresponding to
different stages of surrogate reactions. The new model is capable of
calculating spin distributions of the compound nuclei, one of the most
important quantity in the surrogate technique. Furthermore, various observables
of surrogate reactions can be calculated, e.g., energy and angular distribution
of ejectile, and mass distributions of fission fragments. These features are
important to assess validity of the proposed model itself, to understand
mechanisms of the surrogate reactions and to determine unknown parameters of
the model. It is found that spin distributions of compound nuclei produced in
O+U O+U and O+U
O+U reactions are equivalent and much less than
10, therefore satisfy conditions proposed by Chiba and Iwamoto (PRC 81,
044604(2010)) if they are used as a pair in the surrogate ratio method.Comment: 17 pages, 5 figure
Vitrification of a monatomic 2D simple liquid
A monatomic simple liquid in two dimensions, where atoms interact
isotropically through the Lennard-Jones-Gauss potential [M. Engel and H.-R.
Trebin, Phys. Rev. Lett. 98, 225505 (2007)], is vitrified by the use of a rapid
cooling technique in a molecular dynamics simulation. Transformation to a
crystalline state is investigated at various temperatures and the
time-temperature-transformation (TTT) curve is determined. It is found that the
transformation time to a crystalline state is the shortest at a temerature 14%
below the melting temperature Tm and that at temperatures below Tv = 0.6 Tm the
transformation time is much longer than the available CPU time. This indicates
that a long-lived glassy state is realized for T < Tv.Comment: 5pages,5figures,accepted for publication in CEJ
Hall-conductivity sign change and fluctuations in amorphous NbGe films
The sign change in the Hall conductivity has been studied in thin amorphous
NbGe0.3) films. By changing the film thickness it is
shown that the field at which the sign reversal occurs shifts to lower values
(from above to below the mean-field transition field ) with increasing
film thickness. This effect can be understood in terms of a competition between
a positive normal and a negative fluctuation contribution to the Hall
conductivity.Comment: 5 pages, 4 figures, to appear in Phys. Rev.
Higgs Boson Mass in Low Scale Gauge Mediation Models
We consider low scale gauge mediation models with a very light gravitino
m_{3/2}~16 eV, in the light of recent experimental hints on the Higgs boson
mass. The light gravitino is very interesting since there is no gravitino
over-production problem, but it seems difficult to explain the Higgs boson mass
of ~125 GeV. This is because of the conflict between the light gravitino mass
and heavy SUSY particle masses needed for producing the relatively heavy Higgs
boson mass. We consider two possible extensions in this paper: a singlet
extension of the Higgs sector, and strongly coupled gauge mediation. We show
that there is a large parameter space, in both scenarios, where the Higgs boson
mass of ~125 GeV is explained without any conflict with such a very light
gravitino.Comment: 23 pages, 5 figure
Testing new physics with the electron g-2
We argue that the anomalous magnetic moment of the electron (a_e) can be used
to probe new physics. We show that the present bound on new-physics
contributions to a_e is 8*10^-13, but the sensitivity can be improved by about
an order of magnitude with new measurements of a_e and more refined
determinations of alpha in atomic-physics experiments. Tests on new-physics
effects in a_e can play a crucial role in the interpretation of the observed
discrepancy in the anomalous magnetic moment of the muon (a_mu). In a large
class of models, new contributions to magnetic moments scale with the square of
lepton masses and thus the anomaly in a_mu suggests a new-physics effect in a_e
of (0.7 +- 0.2)*10^-13. We also present examples of new-physics theories in
which this scaling is violated and larger effects in a_e are expected. In such
models the value of a_e is correlated with specific predictions for processes
with violation of lepton number or lepton universality, and with the electric
dipole moment of the electron.Comment: 34 pages, 7 figures. Minor changes and references adde
Search for lepton-flavor-violating decays at Belle
We have searched for neutrinoless lepton decays into and ,
where stands for an electron or muon, and for a vector meson
(, , , or ), using 543 fb
of data collected with the Belle detector at the KEKB asymmetric-energy
collider. No excess of signal events over the expected background has
been observed, and we set upper limits on the branching fractions in the range
at the 90% confidence level. These upper limits
include the first results for the mode as well as new limits that
are significantly more restrictive than our previous results for the , , and modes.Comment: 7 pages, 16 figure
Liver cancer risk, coffee, and hepatitis C virus infection: a nested caseâcontrol study in Japan
We examined hepatocellular carcinoma mortality in relation to coffee consumption and anti-hepatitis C virus (HCV) antibody seropositivity in a nested caseâcontrol study involving 96 cases. The multivariate-adjusted odds ratios (95% confidence interval) for daily coffee drinkers vs non-drinkers were 0.49 (0.25â0.96), 0.31 (0.11â0.85), and 0.75 (0.29â1.92) in all cases, in HCV-positive and in HCV-negative individuals, respectively
Immunity status of adults and children against poliomyelitis virus type 1 strains CHAT and Sabin (LSc-2ab) in Germany
<p>Abstract</p> <p>Background</p> <p>In October 2007, the working group CEN/TC 216 of the European Committee for standardisation suggested that the Sabin oral poliovirus vaccine type 1 strain (LSc-2ab) presently used for virucidal tests should be replaced by another attenuated vaccine poliovirus type 1 strain, CHAT. Both strains were historically used as oral vaccines, but the Sabin type 1 strain was acknowledged to be more attenuated. In Germany, vaccination against poliomyelitis was introduced in 1962 using the oral polio vaccine (OPV) containing Sabin strain LSc-2ab. The vaccination schedule was changed from OPV to an inactivated polio vaccine (IPV) containing wild polio virus type 1 strain Mahoney in 1998. In the present study, we assessed potential differences in neutralising antibody titres to Sabin and CHAT in persons with a history of either OPV, IPV, or OPV with IPV booster.</p> <p>Methods</p> <p>Neutralisation poliovirus antibodies against CHAT and Sabin 1 were measured in sera of 41 adults vaccinated with OPV. Additionally, sera from 28 children less than 10 years of age and immunised with IPV only were analysed. The neutralisation assay against poliovirus was performed according to WHO guidelines.</p> <p>Results</p> <p>The neutralisation activity against CHAT in adults with OPV vaccination history was significantly lower than against Sabin poliovirus type 1 strains (Wilcoxon signed-rank test P < 0.025). In eight sera, the antibody titres measured against CHAT were less than 8, although the titre against Sabin 1 varied between 8 and 64. Following IPV booster, anti-CHAT antibodies increased rapidly in sera of CHAT-negative adults with OPV history. Sera from children with IPV history neutralised CHAT and Sabin 1 strains equally.</p> <p>Conclusion</p> <p>The lack of neutralising antibodies against the CHAT strain in persons vaccinated with OPV might be associated with an increased risk of reinfection with the CHAT polio virus type 1, and this implies a putative risk of transmission of the virus to polio-free communities. We strongly suggest that laboratory workers who were immunised with OPV receive a booster vaccination with IPV before handling CHAT in the laboratory.</p
Detailed α-decay study of 180Tl
International audienceA detailed -decay spectroscopy study of has been performed at ISOLDE (CERN). -selective ionization by the Resonance Ionization Laser Ion Source (RILIS) coupled to mass separation provided a high-purity beam of . Fine-structure decays to excited levels in the daughter were identified and an -decay scheme of was constructed based on an analysis of - and -- coincidences. Multipolarities of several -ray transitions deexciting levels in were determined. Based on the analysis of reduced -decay widths, it was found that all decays are hindered, which signifies a change of configuration between the parent and all daughter states
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