VcbV_{cb} from the semileptonic decay B→DℓνˉℓB\to D \ell \bar{\nu}_{\ell} and the properties of the DD meson distribution amplitude

The improved QCD light-cone sum rule (LCSR) provides an effective way to deal with the heavy-to-light transition form factors (TFFs). Firstly, we adopt the improved LCSR approach to deal with the $B\to D$ TFF $f^{+}(q^2)$ up to twist-4 accuracy. Due to the elimination of the most uncertain twist-3 contribution and the large suppression of the twist-4 contribution, the obtained LCSR shall provide us a good platform for testing the $D$-meson leading-twist DA. For the purpose, we suggest a new model for the $D$-meson leading-twist DA ($\phi_{3D}$), whose longitudinal behavior is dominantly determined by a parameter $B$. Moreover, we find its second Gegenbauer moment $a^D_2\sim B$. Varying $B$ within certain region, one can conveniently mimic the $D$-meson DA behavior suggested in the literature. Inversely, by comparing the estimations with the experimental data on the $D$-meson involved processes, one can get a possible range for the parameter $B$ and a determined behavior for the $D$-meson DA. Secondly, we discuss the $B\to D$ TFF at the maximum recoil region and present a detailed comparison of it with the pQCD estimation and the experimental measurements. Thirdly, by applying the LCSR on $f^{+}(q^2)$, we study the CKM matrix element \Vcb together with its uncertainties by adopting two types of processes, i.e. the $B^0/\bar{B}^0$-type and the $B^{\pm}$-type. It is noted that a smaller $B \precsim 0.20$ shows a better agreement with the experimental value on \Vcb. For example, for the case of $B=0.00$, we obtain $|V_{cb}|(B^0/\bar{B}^0-{\rm type})=(41.28 {^{+5.68}_{-4.82}} {^{+1.13}_{-1.16}}) \times 10^{-3}$ and $|V_{cb}|(B^{\pm}-{\rm type})=(40.44 {^{+5.56}_{-4.72}} {^{+0.98}_{-1.00}}) \times 10^{-3}$, whose first (second) uncertainty comes from the squared average of the mentioned theoretical (experimental) uncertainties.Comment: 13 pages, 10 figures. Reference updated and discussion improved. To be published in Nucl.Phys.

Wind-induced vibration and equivalent wind load of double-layer cylindrical latticed shells

Previous studies have not comprehensively revealed the wind effects on the double-layer cylindrical latticed shell (DCLS). In the paper, the code considering cross spectra of wind and cross terms of modes is programmed and verified. All the nodes and elements are selected to study the characteristics of wind pressure and response spectra. Studies show that wind pressure energy at the top of the shell is higher than that at the windward or leeward side. The most unfavorable wind direction and the dangerous area is 90° and the middle top, not 120° and the end area as stated in the previous documents. Different orders of mode are excited in various responses, and the resonant component should not be ignored. Higher turbulence at the flow separation area leads to stronger structural amplification on wind effects and different ESWL distributions for various targets. The type of target of should be properly chosen according to the concerned structural performance. Under high wind velocity, structural material and geometric nonlinearities make the dynamic equilibrium positions of the shell jump with time

3,3′-Diazenediyldiphthalic acid dihydrate

In the crystal structure of the title compound, C16H10N2O8·2H2O, the organic mol­ecule is located on a centre of symmetry. The two benzene rings are parallel, but not coplanar, as indicated by N=N—C—C torsion angles involving the azo group of 12.1 (5) and −168.2 (3)°. The organic mol­ecule and the water mol­ecule are linked by O—H⋯O hydrogen bonds, forming a three-dimensional network