We report evidence for the simultaneous production of J/ψ and ϒ mesons in 8.1 fb^{-1} of data collected at sqrts=1.96 TeV by the D0 experiment at the Fermilab ppover ¯ Tevatron Collider. Events ...with these characteristics are expected to be produced predominantly by gluon-gluon interactions. In this analysis, we extract the effective cross section characterizing the initial parton spatial distribution, σ_{eff}=2.2±0.7(stat)±0.9(syst) mb.
The analysis of fission events following the implantation of evaporation residues produced in the fusion reaction of 50Ti and 209Bi at different bombarding energies has revealed 5 millisecond decays, ...which are attributed to the spontaneous fission of proton-evaporation channels. The average cross sections for proton evaporation are found to be ∼100 and 10 times smaller than the largest neutron-evaporation channel cross section at the same excitation energy. These results suggest that the proton evaporation channel, albeit weak, may represent a realistic alternative to synthesize new, more neutron rich super heavy nuclei.
Here, the inclusive cross section of top quark-antiquark pairs produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV is measured in the lepton+jets and dilepton decay channels. The data sample ...corresponds to 9.7 fb-1 of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Employing multivariate analysis techniques we measure the cross section in the two decay channels and we perform a combined cross section measurement. For a top quark mass of 172.5 GeV, we measure a combined inclusive top quark-antiquark pair production cross section of σ$t\bar{t}$=7.26±0.13(stat)$+0.57\atop{-0.50}$(syst) pb which is consistent with standard model predictions. We also perform a likelihood fit to the measured and predicted top quark mass dependence of the inclusive cross section, which yields a measurement of the pole mass of the top quark. The extracted value is mt=172.8±1.1(theo)$+3.3\atop{-3.1}$(exp) GeV.
We present a measurement of the fundamental parameter of the standard model, the weak mixing angle sin2θℓeff which determines the relative strength of weak and electromagnetic interactions, in ...pp¯→Z/γ*→e+e- events at a center of mass energy of 1.96 TeV, using data corresponding to 9.7 fb-1 of integrated luminosity collected by the D0 detector at the Fermilab Tevatron. The effective weak mixing angle is extracted from the forward-backward charge asymmetry as a function of the invariant mass around the Z boson pole. The measured value of sin2θℓeff=0.23147±0.00047 is the most precise measurement from light quark interactions to date, with a precision close to the best LEP and SLD results.
High-precision calculations of the ground-state binding energy of beryllium-like molybdenum (
Z
= 42) have been performed. The applied approach combines rigorous quantum-electrodynamic (QED) ...consideration up to the second order of the perturbation theory within the Furry picture and account of correlation effects of the third and higher orders within the Breit approximation. Mixing of similar configurations of identical symmetry due to electron–electron interaction effects is considered using the QED perturbation theory for quasi-degenerate levels. The most accurate up-to-date theoretical predictions for the binding energy are obtained.
—
The review presents the experiments performed with the KEDR detector at the
collider VEPP-4M in the energy range of
= 1.84–3.88 GeV. The cross section of
annihilation to hadrons was measured at 22 ...points of this range and the search for narrow resonances was conducted below 3.1 GeV. The masses of
and
mesons were measured with a record accuracy better than
; their partial and total widths were determined. Measurements of the tau lepton mass and masses of charged and neutral
mesons were performed with high precision. The measurements of the
parameters are discussed, and attention is drawn to some inconsistency of the procedure employed by the Particle Data Group for determining its parameters.
Isotope shifts of
and
levels and corresponding transitions in helium-like highly charged ions are calculated with high precision. The total value of the isotope shift is determined mainly by the sum ...of the field and mass shifts. The field shift is calculated by using the Dirac–Fock–Sturm method taking into account interaction of configurations. Quantum-electrodynamic corrections to this contribution are taken into account approximately by using the corresponding one-electron expressions. The mass shift is calculated both within the framework of the Breit approximation and by taking into account quantum-electrodynamic contributions that become substantial for heavy ions. In the case of thorium and uranium ions, corrections due to nuclear polarization and deformation are taken into account additionally.
Subcellular targeting of opsins in optogenetics provides new possibilities for studying the function of nerve cells. One of the widely used motifs for central targeting of opsins is the motif of the ...potential-dependent potassium channel Kv2.1. In our study, ChR2-Venus-Kv2.1 construct was expressed in the layer 2/3 pyramidal neurons of murine cerebral cortex by means of in utero electroporation. We found that, although the majority of neurons expressing ChR2-Venus-Kv2.1 demonstrated mainly central localization of fluorescence, limited to the soma, proximal dendrites, and axon, a considerable quantity of neurons remarkably exhibited disrupted targeting, i.e., fluorescent protein distributed far beyond the soma and proximal parts of all processes. We hypothesized that the observed mislocalization might have been caused by overexpression of the construct. It was found that a decrease in the plasmid concentration during the in utero electroporation from 1 to 0.35 μg/μl resulted in almost complete disappearance of the neurons that had altered targeting. Moreover, we found a pronounced correlation between the absolute brightness of the somatic fluorescence and the visible length of the apical dendrite, which also provides evidence that indeed overexpression might be the reason for the mislocalization of ChR2-Venus-Kv2.1 construct. Thus, the possibility of disruption of central targeting of ChR2 by the potassium channel Kv2.1 motif should be taken into account when using this construct in optogenetic experiments when somatic localization of the opsin is necessary. Lowering plasmid concentration during transfection procedure could be a solution for the above problem.
PDF
