A study of four- and six-body reactions in π+ andK + p interactions at 250 GeV/c

Data on the reactions (K ⁺/π⁺)p→(K ⁺/π⁺)pπ⁺π^- and (K ⁺/π⁺)p→(K ⁺/π⁺)p2π⁺2π^-, obtained with the European Hybrid Spectrometer, are presented and compared with data at lower energies. The contribution of beam and target diffractive dissociation and double Pomeron exchange, and porperties of these reactions are discussed.     

高能诱发核反应中粒子产生的相对信息熵

在本实验中，引用了一个新的特征量，相对信息熵Ｒ，研究了能量为１４．６，６０，２００ＡＧｅＶ的氧离子和２００ＡＧｅＶ的硫离子诱发核反应的产生粒子多重数分布．在目前的能区中，Ｒ近似地能量无关．Ｒ对快度窗口大小依赖的饱和性，揭示了中心区的熵集中产生．实验结果与Ｌｕｎｄ模型的ＦＲＩＴＩＯＦ模拟计算的预言一致．     

Coherent production ofρ − mesons in charged current antineutrino-neon interactions in BEBC

Coherent production ofρ ^? mesons in charged current antineutrino interactions on neon nuclei is studied in the BEBC bubble chamber exposed to the CERN SPS wide band beam. The cross section is measured to be (95±25)·10^?40 cm² per neon nucleus, averaged over the beam energy spectrum. The distributions of kinematical variables and the absolute value of the cross section are in agreement with theoretical predictions based on the CVC hypothesis and the vector meson dominance model.     

A precise determination of the electroweak mixing angle from semileptonic neutrino scattering

The cross-section ratio of neutral-current and charged-current semileptonic interactions of muon-neutrinos on isoscalar nuclei has been measured with the result:R ^v =0.3093±0.0031 for hadronic energy larger than 4 GeV. From this ratio we determined the electroweak mixing angle sin² θ _W , wherem _c is the charm-quark mass in GeV/c². Comparison with direct measurements ofm _w andm _z determines the radiative shift of the intermediate boson mass Δr=0.077±0.025(exp.)±0.038(syst.), in agreement with the prediction. Assuming the validity of the electroweak standard theory we determined ?=0.990?0.013(m _c ?1.5)±0.009(exp.)±0.003(theor.).     

Search for a low mass CP-odd Higgs boson in $\mathrm{e^+e^-}$ collisions with the OPAL detector at LEP2

We have analysed the data collected by OPAL at centre-of-mass energies between 189 and 209 GeV searching for Higgs boson candidates from the process followed by the decay of where is the CP-odd Higgs boson. The search is done in the region where the mass, , is below the production threshold for , and the CP-even Higgs boson mass is within the range 45-86 GeV/c ² . In this kinematic range, the decay of may be dominant and previous Higgs boson searches have very small sensitivities. This search can be interpreted within any model that predicts the existence of at least one scalar and one pseudoscalar Higgs boson. No excess of events is observed above the expected Standard Model backgrounds. Model-independent limits on the cross-section for the process are derived assuming 100% decays of the into and 100% decays of the into each of the following final states: , , , , and . The results are also interpreted in the CP-conserving no-mixing MSSM scenario, where the region and is excluded. Received: 13 March 2002 / Published online: 26 February 2003     

Synthesis of a Novel Conjugate of Dibenzoyldiazomethane and Polyamide Containing N-Methylimidazoles

A novel conjugate of dibenzoyldiazomethane and polyamide containing N-methylimidazoles was synthesized by a chloroform reaction and a DCC/HOBT coupling reaction.     

A measurement of the photon structure function F 2γ at an average Q 2 of 12 GeV2/ c 4

The hadronic photon structure functionF ₂ ^γ has been measured in theQ ² range from 4 to 30 GeV²/c ⁴ and down tox values of order 0.001, using data taken with the DELPHI detector at LEP between 1991 and 1993. A comparison is made with severalF ₂ ^γ parameterizations with special emphasis on their lowx behaviour. A result on theQ ² evolution ofF ₂ ^γ is presented.     

X射线荧光基本参数法测定焊锡中的锡和铅

本文在无标样的情况下,用X射线荧光基本参数法测定了焊锡中的锡和铅的含量。     

高阶奇异积分的Hadamard主值

应用Ｅｕｌｅｒ径向微分算子:Ｄ＝ｚｌ＋…＋ｚｎ研究复ｎ维超球面Ｂ＝{ζ∈Ｃｎ|ζ＝(ζ１,…,ζｎ),|ζ１|２＋…＋|ζｎ|２＝１}上两类高阶奇异积分的Ｈａｄａｍａｒｄ主值．本文得到置换和合成公式并讨论了它们的拓广以及在偏微分奇异积分方程上的应用．     

Possible dibaryon states produced in4He-proton interactions

In the hydrogen bubble chamber study of the⁴Hep→dppn reaction at incident alpha 8.6 GeV/c momentum the structures in the two-proton effective mass distribution are observed at 2,035±15 MeV and 2,137±15 MeV. Possible nature of the effect is discussed.