9,487 research outputs found

    The longitudinal and transverse distributions of the pion wavefunction from the present experimental data on the pion-photon transition form factor

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    It is noted that the low-energy behavior of the pion-photon transition form factor Fπγ(Q2)F_{\pi\gamma}(Q^2) is sensitive to the transverse distribution of the pion wavefunction, and its high-energy behavior is sensitive to the longitudinal one. Thus a careful study on Fπγ(Q2)F_{\pi\gamma}(Q^2) can provide helpful information on the pion wavefunction precisely. In this paper, we present a combined analysis of the data on Fπγ(Q2)F_{\pi\gamma}(Q^2) reported by the CELLO, the CLEO, the BABAR and the BELLE collaborations. It is performed by using the method of least squares. By using the combined measurements of BELLE and CLEO Collaborations, the pion wavefunction longitudinal and transverse behavior can be fixed to a certain degree, i.e. we obtain β[0.691,0.757]GeV\beta \in [0.691,0.757] \rm GeV and B[0.00,0.235]B \in [0.00,0.235] for Pχ290%P_{\chi^2} \geq 90\%, where β\beta and BB are two parameters of a convenient pion wavefunction model whose distribution amplitude can mimic the various longitudinal behavior under proper choice of parameters. We observe that the CELLO, CLEO and BELLE data are consistent with each other, all of which prefers the asymptotic-like distribution amplitude; while the BABAR data prefers a more broad distribution amplitude, such as the CZ-like one.Comment: 7 pages, 10 figure

    Heavy Pseudoscalar Twist-3 Distribution Amplitudes within QCD Theory in Background Fields

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    In this paper, we study the properties of the twist-3 distribution amplitude (DA) of the heavy pseudo-scalars such as ηc\eta_c, BcB_c and ηb\eta_b. New sum rules for the twist-3 DA moments \left_{\rm HP} and \left_{\rm HP} up to sixth orders and up to dimension-six condensates are deduced under the framework of the background field theory. Based on the sum rules for the twist-3 DA moments, we construct a new model for the two twist-3 DAs of the heavy pseudo-scalar with the help of the Brodsky-Huang-Lepage prescription. Furthermore, we apply them to the BcηcB_c\to\eta_c transition form factor (f+Bcηc(q2)f^{B_c\to\eta_c}_+(q^2)) within the light-cone sum rules approach, and the results are comparable with other approaches. It has been found that the twist-3 DAs ϕ3;ηcP\phi^P_{3;\eta_c} and ϕ3;ηcσ\phi^\sigma_{3;\eta_c} are important for a reliable prediction of f+Bcηc(q2)f^{B_c\to\eta_c}_+(q^2). For example, at the maximum recoil region, we have f+Bcηc(0)=0.674±0.066f^{B_c\to\eta_c}_+(0) = 0.674 \pm 0.066, in which those two twist-3 terms provide 33%\sim33\% and 22%\sim22\% contributions. Also we calculate the branching ratio of the semi-leptonic decay BcηclνB_c \to\eta_c l\nu as Br(Bcηclν)=(9.312.01+2.27)×103Br(B_c \to\eta_c l\nu) = \left( 9.31^{+2.27}_{-2.01} \right) \times 10^{-3}.Comment: 12 pages, 16 figure