Recent Progress in Λc+ Decays

Studying Λc+ decays provides important and complementary information to help understand the effects of non-perturbative quantum chromodynamics. Recently, many interesting results about Λc+ decays have been reported thanks to the high luminosity in Belle and dedicated operation at the Λc+ pair production threshold in BESIII. This paper reviews the recent progress in experimental measurements, containing sections about the hadronic weak decay, semileptonic decay, and decay asymmetry parameters and CP violation.

Observation of the Singly Cabibbo Suppressed Decay Λ_{c}^{+}→nπ^{+}

The singly Cabibbo-suppressed decay Λ_{c}^{+}→nπ^{+} is observed for the first time with a statistical significance of 7.3σ by using 3.9  fb^{-1} of e^{+}e^{-} collision data collected at center-of-mass energies between 4.612 and 4.699 GeV with the BESIII detector at BEPCII. The branching fraction of Λ_{c}^{+}→nπ^{+} is measured to be (6.6±1.2_{stat}±0.4_{syst})×10^{-4}. By taking the upper limit of branching fractions of Λ_{c}^{+}→pπ^{0} from the Belle experiment, the ratio of branching fractions between Λ_{c}^{+}→nπ^{+} and Λ_{c}^{+}→pπ^{0} is calculated to be larger than 7.2 at the 90% confidence level, which disagrees with most predictions of the available phenomenological models. In addition, the branching fractions of the Cabibbo-favored decays Λ_{c}^{+}→Λπ^{+} and Λ_{c}^{+}→Σ^{0}π^{+} are measured to be (1.31±0.08_{stat}±0.05_{syst})×10^{-2} and (1.22±0.08_{stat}±0.07_{syst})×10^{-2}, respectively, which are consistent with previous results.

Study of the standard model with weak decays of charmed hadrons at BESIII

A comprehensive review of weak decays of charmed hadrons (D 0/ +, [Formula: see text] and [Formula: see text]) based on analyses of the threshold data from e + e - annihilation in the BESIII experiment is presented. Current experimental challenges and successes in understanding decays of the charmed hadrons are discussed. Precise calibrations of quantum chromodynamics and tests of the standard model are provided by measurements of purely leptonic and semi-leptonic decays of charmed hadrons, and lepton universality is probed in purely leptonic decays of charmed mesons to three generations of leptons. Quantum correlations in threshold data samples provide access to strong phases in the neutral D meson decays and probe the decay dynamics of the charmed Λ c baryon. Charm physics studies with near-threshold production of charmed particle pairs are unique to BESIII, and provide many important opportunities and challenges.