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.
The moisture-sensitive plastic fiber consists of poly-methylmethacrylate doped with phenol-red dye. The propagation loss of this fiber at around 530 nm increases with increasing water vapor in air, and hence it operates as an excellent humidity sensor with a fast response time. This fiber can also be used for optically detecting moisture equivalent in the soil.
Amorphous silica aerogels doped with Al 3+ ions (SADAs) were prepared by the sol-gel route and supercritical drying. The visible luminescence of SADAs was measured and compared with that of porous silicon (PS), pure silica aerogels (PSAs) and silica xerogels doped with Al 3+ ions (SXDAs). The effect of annealing on the luminescence intensity of SADAs was investigated. Results show that (1) the luminescent intensity of as-prepared SADAs is much higher than that of as-prepared PSAs and SXDAs after annealing at 300 • C; (2) after annealing at 500 • C, the visible luminescence of SADAs is further substantially enhanced and becomes much higher than that of PS. However, for PSAs and SXDAs after annealing at 500 • C the luminescent intensity is still kept at a very low value in comparison with that of SADAs. The strong visible luminescence appearing in SADAs is ascribed to significant amounts of the twofold coordinated Si (the Si(II) 0 (neutral) centre) in SADAs.
As a new nonlinear optical material, Fast Red ITR organic crystal has been grown in the form of crystal fibers from the melt. This crystal has a wide optical transparency range from 340 nm to near infrared and large birefringence. The second- and third-harmonic generations of a Nd: glass laser have been observed in this Fast Red ITR crystal fiber.
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