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Using a data sample corresponding to an integrated luminosity of 2.93 fb −1 recorded by the BESIII detector at a center-of-mass energy of 3.773 GeV, we present an analysis of the decays D 0 →π − π 0 e þ ν e and D þ → π − π þ e þ ν e. By performing a partial wave analysis, the π þ π − S-wave contribution to D þ → π − π þ e þ ν e is observed to be ð25.7 AE 1.6 AE 1.1Þ% with a statistical significance greater than 10σ, besides the dominant P-wave contribution. This is the first observation of the S-wave contribution. We measure the branching fractions BðD 0 →ρ − e þ ν e Þ¼ð1.445AE0.058AE0.039Þ×10 −3 , BðD þ →ρ 0 e þ ν e Þ¼ ð1.860AE0.070AE0.061Þ×10 −3 , and B(D þ →f 0 ð500Þe þ ν e ;f 0 ð500Þ→π þ π −)¼ð6.30AE0.43AE0.32Þ×10 −4. An upper limit of B(D þ → f 0 ð980Þe þ ν e ; f 0 ð980Þ → π þ π −) < 2.8 × 10 −5 is set at the 90% confidence level. We also obtain the hadronic form factor ratios of D → ρe þ ν e at q 2 ¼ 0 assuming the single-pole dominance parametrization: r V ¼ f½Vð0Þ=½A 1 ð0Þg ¼ 1.695 AE 0.083 AE 0.051, r 2 ¼ f½A 2 ð0Þ=½A 1 ð0Þg ¼ 0.845 AE 0.056 AE 0.039.

The form factors parameterizing the weak D and D s transitions to light pseudoscalar and vector mesons are calculated in the framework of the relativistic quark model based on the quasipotential approach. The special attention is paid to the systematic account of the relativistic effects including transformation of the meson wave function from the rest to moving reference frame and contributions of the intermediate negative-energy states. The form factors are expressed through the overlap integrals of the meson wave functions, which are taken from previous studies of meson spectroscopy. They are calculated in the whole range of the transferred momentum q 2 . Convenient parameterization of the form factors which accurately reproduces numerical results is given. The obtained values of the form factors and their ratios at q 2 = 0 agree well with the ones extracted form the experimental data. On the basis of these form factors and helicity formalism, differential and total semileptonic decay rates of D and D s mesons as well as different asymmetries and polarization parameters are calculated. The detailed comparison of the obtained results with other theoretical calculations and experimental data is given.

Based on a sample of 1.31 × 10 9 J=ψ events collected with the BESIII detector, the matrix elements for the decays η 0 → ηπ þ π − and η 0 → ηπ 0 π 0 are determined using 351,016 η 0 → ðη → γγÞπ þ π − and 56,249 η 0 → ðη → γγÞπ 0 π 0 events with background levels less than 1%. Two commonly used representations are used to describe the Dalitz plot density. We find that an assumption of a linear amplitude does not describe the data well. A small deviation of the obtained matrix elements between η 0 → ηπ þ π − and η 0 → ηπ 0 π 0 is probably caused by the mass difference between charged and neutral pions or radiative corrections. No cusp structure in η 0 → ηπ 0 π 0 is observed.

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Analysis of D+ -> (K)over-bar(0)e(+)nu(e) and D+ -> pi(0)e(+)nu(e) semileptonic decays Haddadi, Zahra; Kalantar-Nayestanaki, Nasser; Kavatsyuk, Myroslav; Löhner, Herbert; Messchendorp, Johannes; Tiemens, M.; BESIII Collaboration Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Haddadi, Z., Kalantar-Nayestanaki, N., Kavatsyuk, M., Löhner, H., Messchendorp, J. G., Tiemens, M., & BESIII Collaboration (2017). Analysis of D+ -> (K)over-bar(0)e(+)nu(e) and D+ -> pi(0)e(+)nu(e) semileptonic decays. Physical Review D, 96(1), [012002]. DOI: 10.1103/PhysRevD.96.012002 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum.