Feynman diagram calculations are considerably simpler in the framework of Weyl-Van der Waerden spinors than in the standard formalism. We collect the basic formulae and illustrate the method by a few examples. We study pion pair decay in considerable detail and find that the long-standing ambiguity in determining the ratio of axial vector to vector structure term that hampered pion radiative decay can be resolved in the pair decay. 相似文献
The distribution of the azimuthal angle between the planes formed by the two highest energy jets and the two lowest energy jets in four-jet events of e+e− annihilation, depends characteristically on the triple-gluon vertex. 相似文献
This article gives an overview of the main experimental tests of perturbative QCD performed at LEP. It covers the following topics: determination of αs from event shapes, tests of flavour independence of αs, studies of heavy quark mass effects, differences between quark and gluon jet fragmentation and study of the triple gluon vertex. To cite this article: D. Duchesneau et al., C. R. Physique 3 (2002) 1211–1222.相似文献
We calculate heavy (MH2/s) and light (ML2/s) jet masses up toO(αs2) in perturbative Quantum Chromodynamics (QCD). The sensitivity of these quantities to radiative corrections, quark masses, fragmentation effects as well as their infrared stability properties, are investigated and compared to those exhibited by other jet measures. A comparison with recent Mark II data is also presented. 相似文献
Employing global SU(2)WI symmetry and γW3 mixing we derive a lagrangian for vector-boson self-interactions whose strength may considerably differ from the ones required by the standard model; the neutral-current structure and the mass relationship of the standard model remain intact, however. Numerical results for the cross section for e+e− → W+W− are presented. 相似文献
We present a multiplicity distribution which is a solution to the stochastic branching equation proposed by Giovannini. This solution is more commonly known as generalized multiplicities distribution (GMD) and has already been successfully applied to bothpp andp
collisions. It assumes that shapes and energy dependence of distributions are basically determined by hard parton scattering and subsequent branching. We apply GMD to the recente+e– data by Tasso Collaboration. 相似文献
The features of the low-lying spectrum and the complete set of quantum numbers of each of the low-lying states of a (e+e+e−e−) system have been deduced based on symmetry. 相似文献
Higgsino production in e+e− reactions is considered in the simplest model where the higgsino is the lightest supersymmetric particle. The supersymmetric version of the Wilczek mechanism seems to be the best way to detect higgsinos and photinos in the LEP energy range. 相似文献
We present a new class of observables which distinguish events containing two or three hadron jets from those containing a larger number. These observables, which essentially measure the coplanary of events, are calculable in QCD perturbation theory. Their use should allow the mechanism of decay to be determined. 相似文献
On the basis of perturbative QCD and relativistic quark model we calculate relativistic and bound state corrections in the production processes of a pair of \(\mathcal{P}\)-wave charmonium states. Relativistic factors in the production amplitude are taken into account connected with the relative motion of heavy quarks and the transformation law of the bound-state wave function to the reference frame of the moving \(\mathcal{P}\)-wave mesons. Relativistic corrections to the quark bound-state wave functions in the rest frame are considered by means of the Breit-like potential. It turns out that the examined effects change essentially nonrelativistic results of the cross section for the reaction e+ + e? → hc + χcJ at the center-of-mass energy √s = 10.6 GeV. 相似文献
The radiative decay of the chargedπ-mesonπ→e+ν+γ is calculated using dispersion relation techniques. It is assumed that the weak interaction producing the decay has a V-A structure. The decay through the vector variant has been reinvestigated and found to be different from the result ofVaks andIoffe. The theoretical prediction of this paper is in agreement with a preliminary experiment recently performed at CERN. 相似文献
The thrust distribution ine+e–-annihilation is analysed in perturbative QCD. Proper account is taken of multiple emission of gluons. Scaling holds for this quantity in the sense that its energy dependence comes only through the change in the QCD effective coupling. It thus provides an ideal means to determine the value of the QCD mass scale experimentally. From the data atW=91 GeV by the ALEPH collaboration at LEP, we obtain
. 相似文献
We calculate the total and differential cross sections for the process e+e−→W+W− including the effects of the extra Z-boson coming from the E8⊗E8 superstring. It is pointed out that the observation of the total and differential cross sections can determine the relative sign of the Weinberg angle τw and the mixing angle τe between Z'0 and Z E. 相似文献
The production of the σ(500) meson in γγ→π0π0 is studied. In particular, the KLOE data collected during the DAΦNE run at
are appropriate to this purpose because of the strong reduction of kaon backgrounds.
PACS 12.39.-x 相似文献