BESIII recently reported the study of the Cabibbo-favored Semileptonic (SL) decay Λ_c⁺->Λe⁺ν_e[Phys. Rev. Lett. 129, 231803 (2022)], with the largest Λ_cthreshold data sets collected at the center-of-mass energy region between 4.6 GeV and 4.7 GeV.

The study ofΛ_cSL decays provides valuable information about weak and strong interactions in baryons containing a heavy quark. In particular, the SL decayΛ_c⁺->Λe⁺ν_ewhich is the dominant component inΛ_cSL decays, is the most interesting to measure. Its decay rate depends on the weak quark mixing Cabibbo-Kobayashi-Maskawa (CKM) matrix element |Vcs| and strong interaction effects parameterized by form factors describing the hadronic transition between the initial and the final baryons. Measurement of |Vcs| viaΛ_c⁺->Λe⁺ν_eis an important consistency test for the standard model (SM) and a probe for new physics beyond the SM. Motivated by the measurements of the absolute branching fractions (BFs) forΛ_c⁺->Λe⁺ν_eandΛ_c⁺->Λμ⁺ν_μby BESIII experiment, the first calculation of the BFs forΛ_c⁺->Λl⁺ν_lfrom the lattice quantum chromodynamics (LQCD) are available in 2017. The LQCD also investigated the internal dynamics and predicted the form factors and differential decay rates inΛ_c⁺->Λe⁺ν_edecay, followed by a series of other LQCD calculations in this sector. These theoretical works are important for understanding the decay mechanism in SL decays in the charmed baryon sector. However, there is no direct experimental data for testing and calibrating these calculations.

Using the 4.5/fb Λ_cthreshold data sets collected with BESIII detector,we report an updated measurement of the absolute BF forΛ_c⁺->Λe⁺ν_eto be(3.56±0.11±0.07)%, which improvesprecision of the world average value more than threefold. Combing BF ofΛ_c⁺->Λe⁺ν_emeasured in this work,Λ_c⁺life timeand the q²-integrated rate predicted by LQCD, we determine |Vcs|=0.936±0.017±0.025, which is in consistent with |Vcs|=0.939±0.038 measured inD->Kl⁺ν_ldecays within one standard deviation.Furthermore, by analyzing the dynamics ofΛ_c⁺->Λe⁺ν_e, we measure the decay form factors for the first time. Figures 1 and 2 show comparisons of the form factors and the differential decay rate between measurements in this work and that in LQCD calculations. It is noted that the dependences of measuredFFs show different kinematic behavior compared to those predicted from LQCD calculations. In particular, discrepancies can be seen at high q²-region for f_⊥(q²) and g_⊥(q²), as well as at low q²-region for f₊(q^2). For f₊(q²) and f_⊥(q²), our measurement tends to have steeper slope than those from LQCD calculations, while on the contrary for g₊(q²) and g_⊥(q²). The corresponding comparison on differential decay rates, shown in Figure 2, gives fair agreement throughout the q²region.