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D. Melikhov 《Physics letters. [Part B]》1996,380(3-4)
Quark model results for the B → π, decays are analysed, making use of the dispersion formulation of the model: The form factors at q2 > 0 are expressed as relativistic invariant double spectral representation over invariant masses of the initial and final mesons through their light-cone wave functions. The dependence of the results on the quark model parameters is studied. For various versions of the quark model the ranges
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, and ΓL/ΓT = 0.7 ± 0.08 are found. The effects of the constituent quark transition form factor are briefly discussed. 相似文献
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We argue that the amplitude does not vanish in the limit of zero quark masses. This represents a new kind of violation of the classical equation of motion for the axial current and should be interpreted as the axial anomaly for bound states. The anomaly emerges in spite of the fact that the one loop integrals are ultraviolet finite as guaranteed by the finite size of bound-state wave functions. As a result, the amplitude behaves like approximately 1/p(2) in the limit of a large momentum p of the current. The observed effect requires the modification of the classical equation of motion of the axial-vector current by nonlocal operators. 相似文献
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The Fokker Planck equation was used to analyze the probability of the appearance of radionuclide impulses of any type. Distribution
functions for the stationary state and conditions when different factors influence the impulse amplitude and duration are
presented. A high degree of correlation was obtained between our results and an analysis of distribution functions of radioactivity
and seismic noises in certain regions in Europe and Japan found in the literature. This presents a contribution to the further
explanation of the mechanism of radioactivity changes in the near ground layers of air. 相似文献
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R.L. Hadimani P.A. BartlettY. Melikhov J.E. SnyderD.C. Jiles 《Journal of magnetism and magnetic materials》2011,323(5):532-534
Gd5(SixGe1−x)4, known for its giant magnetocaloric effect, also exhibits a colossal strain of the order of 10,000 ppm for a single crystal near its coupled first-order magnetic-structural phase transition, which occurs near room temperature for the compositions 0.41≤x≤0.575. Such colossal strain can be utilised for both magnetic sensor and actuator applications. In this study, various measurements have been carried out on strain as a function of magnetic field strength and as a function of temperature on single crystal Gd5Si2Ge2 (x=0.5), and polycrystalline Gd5Si1.95Ge2.05 (x=0.487) and Gd5Si2.09Ge1.91 (x=0.52). Additionally a giant magnetostriction/thermally induced strain of the order of 1800 ppm in polycrystalline Gd5Si2.09Ge1.91 was observed at its first order phase transition on varying temperature using a Peltier cell without the use of bulky equipment such as cryostat or superconducting magnet. 相似文献
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The procedure of extracting the ground-state parameters from vacuum-to-vacuum and vacuum-to-hadron correlators within the
method of sum rules is considered. The emphasis is laid on the crucial ingredient of this method—the effective continuum threshold.
A new algorithm to fix this quantity is proposed and tested. First, a quantum-mechanical potential model which provides the
only possibility to probe the reliability and the actual accuracy of this method is used as a study case. In this model, our
algorithm is shown to lead to a remarkable improvement of the accuracy of the extracted ground-state parameters compared to
the standard procedures adopted in the method and used in all previous applications of dispersive sum rules in QCD. As a next
step, it is demonstrated that the procedures of extracting the ground-state decay constant in the potential model and in QCD
are quantitatively very close to each other. Therefore, the application of the proposed algorithm in QCD promises a considerable
increase of the accuracy of the extracted hadron parameters. 相似文献