We derive an improved prescription for the merging of matrix elements with parton showers, extending the CKKW approach. A flavour-dependent phase space separation criterion is proposed. We show that this new method preserves the logarithmic accuracy of the shower, and that the original proposal can be derived from it. One of the main requirements for the method is a truncated shower algorithm. We outline the corresponding Monte Carlo procedures and apply the new prescription to QCD jet production in e + e − collisions and Drell-Yan lepton pair production. Explicit colour information from matrix elements obtained through colour sampling is incorporated in the merging and the influence of different prescriptions to assign colours in the large N C limit is studied. We assess the systematic uncertainties of the new method.
We developed a compact synchrotron X-ray topography system equipped with a demountable Si channel-cut crystal monochromator with an energy range of 5-20 keV at beamline 09A in SAGA Light Source (SAGA-LS) to enable switching between a white X-ray beam and a monochromatic X-ray beam. The position of incidence of the X-ray beam on the sample is kept constant because the beam-path difference, which is caused by inserting the monochromator and by tuning the X-ray energy, is adjusted automatically. Two possible applications of this system are proposed: (1) the observation of dislocations in a thick Si rod by white X-ray topography, and (2) a comparative study of X-ray images of defects and strain in a 4H-SiC wafer captured using white and monochromatic X-ray beams.
X-ray magnetic circular dichroism spectra have been measured from dilute Ru alloys of Co at the Ru K edge, evidencing the induced magnetization on Ru in contact with ferromagnetic Co. This was made possible using circularly polarized probing beams of approximately 22 keV in energy obtained from a germanium Laue-reflection phase retarder at a synchrotron source. The Ru dichroism is quite small with a main peak of −3 ϫ 10 −4 in flipping ratio at about 6 eV above the K absorption edge. The spectrum has a very similar profile to the one of the Co K-edge dichroism. Ab initio calculations indicate that the Ru dichroism is generated by the p-orbital magnetic moment on the core-hole site, which is induced through the p-d hybridization between Co and Ru.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.