Measurement of the absolute branching fraction for Λc+→Λμ+νμ

We report the first measurement of the absolute branching fraction for Λc+→Λμ+νμ. This measurement is based on a sample of e+e− annihilation data produced at a center-of-mass energy s=4.6 GeV, collected with the BESIII detector at the BEPCII storage rings. The sample corresponds to an integrated luminosity of 567 pb−1. The branching fraction is determined to be B(Λc+→Λμ+νμ)=(3.49±0.46(stat)±0.27(syst))%. In addition, we calculate the ratio B(Λc+→Λμ+νμ)/B(Λc+→Λe+νe) to be 0.96±0.16(stat)±0.04(syst)

Study of D+ →k-π+e+νe

We present an analysis of the decay D+→K-π+e+νe based on data collected by the BESIII experiment at the ψ(3770) resonance. Using a nearly background-free sample of 18262 events, we measure the branching fraction B(D+→K-π+e+νe)=(3.77±0.03±0.08)%. For 0.8<mKπ<1.0 GeV/c2, the partial branching fraction is B(D+→K-π+e+νe)[0.8,1.0]=(3.39±0.03±0.08)%. A partial wave analysis shows that the dominant K̄∗(892)0 component is accompanied by an S-wave contribution accounting for (6.05±0.22±0.18)% of the total rate and that other components are negligible. The parameters of the K̄∗(892)0 resonance and of the form factors based on the spectroscopic pole dominance predictions are also measured. We also present a measurement of the K̄∗(892)0 helicity basis form factors in a model-independent way

Improved measurement of the absolute branching fraction of D+ → K0µ+νµ

By analyzing 2.93 fb-1 of data collected at √s = 3.773 GeV with the BESIII detector, we measure the absolute branching fraction B(D+ → K 0µ+νµ) = (8.72 ±0.07stat. ±0.18sys.) %, which is consistent with previous measurements within uncertainties but with significantly improved precision. Combining the Particle Data Group values of B(D0 → K-µ+νµ), B(D+ → K 0e+νe), and the lifetimes of the D0 and D+ mesons with the value of B(D+ → K 0µ+νµ) measured in this work, we determine the following ratios of partial widths: Γ(D0 → K-µ+νµ)/Γ(D+ → K 0µ+νµ) = 0.963 ± 0.044 and Γ(D+ → K 0µ+νµ)/Γ(D+ → K 0e+νe) = 0.988±0.033. mechanisms with better accuracy. In addition, the improved B(D+ → K 0µ+νµ) can also be used to precisely determine the form factor f K+ (0) and the quark mixing matrix element |Vcs| from D semileptonic decays. Previous measurements of B(D+ → K 0µ+νµ) come from MARKIII, FOCUS and BESII. In this paper, by analyzing 2.93 fb-1 of data collected at the centerof- mass energy of √s = 3.773 GeV by the BESIII detector, we determine the absolute branching fraction of D+ → K 0µ+νµ. Throughout the paper, charge conjugation is implied

Amplitude Analysis of the Decays η′ →π+π-π0 and η′ →π0π0π0

Based on a sample of 1.31×109 J/ψ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays η′→π+π-π0 and η′→π0π0π0 is performed. A significant P-wave contribution from η′→ρ±π is observed for the first time in η′→π+π-π0. The branching fraction is determined to be B(η′→ρ±π)=(7.44±0.60±1.26±1.84)×10-4, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant S-wave component, there is a significant σ meson component. The branching fractions of the combined S-wave components are determined to be B(η′→π+π-π0)S=(37.63±0.77±2.22±4.48)×10-4 and B(η′→π0π0π0)=(35.22±0.82±2.54)×10-4, respectively. The latter one is consistent with previous BESIII measurements