分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We introduce a generic algorithm to determine the time delays and spacecraft (S/C) positions to compose any time-delay interferometry (TDI) channel in the dynamical case and evaluate its sensitivity by using a full numerical method. We select 11 second-generation TDI channels constructed from four approaches and investigate their gravitational wave responses, noise levels, and averaged sensitivities under a numerical LISA orbit. The sensitivities of selected channels are various especially for frequencies lower than 20 mHz. The optimal channel A$_2$ (or equivalently E$_2$) combined from second-generation Michelson TDI channels (X$_1$, X$_2$, and X$_3$) achieves the best sensitivity among the channels, while the Sagnac $\alpha_1$ channel shows the worse sensitivity. Multiple channels show better sensitivities at some characteristic frequencies compared to the fiducial X$_1$ channel. The joint $\mathrm{A_2+E_2+T_2}$ observation not only enhances the sensitivity of the X$_1$ channel by a factor of $\sqrt{2}$ to 2 but also improves the capacity of sky coverage.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： The two-loop QCD radiative corrections to the Bc meson leptonic decay rate are calculated in the framework of NRQCD factorization formalism. Two types of master integrals appearing in the calculation are obtained analytically for the first time. We get the short-distance coefficient of the leading matrix element to order α2s by matching the full perturbative QCD calculation results to the corresponding NRQCD ones. The result in this work helps the evaluation of the Bc leptonic decay constant, as well as the Cabibbo-Kobayashi-Maskawa matrix element |Vcb|, to the full next-to-next-to-leading order degree of accuracy.
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