Absolute Measurement of Semileptonic Decay of Λc at BESIII
The BESIII Collaboration measured the absolute branching fraction of the, Λ+c→Λe +νe, decay with data set at theΛ+cΛ-c threshold (~4.6GeV). This result is essential for understanding the theoretical model of charm baryon and provides important information for future collider experiments.
The study of the weakly semileptonic decays plays an important role in probing the internal structure of particles and testing theoretical models with extremely high sensitivity, since calculatingthe weak interaction is relatively reliable. Λc is the lightest charmed baryon, and contains three quarks (c, u and d), with the c quark being the heaviestandthe u and d quarks much lighter in an isospin zero state. The distribution and dynamics of the three quarks inside the Λc need dedicated theoretical models to describe them. The relevant theoretical research, however, is very limited at present, so thisimproved measurement will provide important input for theoretical research.
The proposal to accumulate data at 4.6 GeV was approved by the BESIII collaboration in 2013, to get the high statistics, clean data sample necessary to study the decay properties of theΛc. A data sample of approximately 500pb-1 at 4.6GeV was accumulated in 2014. Using double tag and the missing energy methods, careful analysis was performed and the absolute decay branching fraction of theΛ+c→Λe + νe decay was measured for the first time, in a model-independent way. This is the first Λc result at the Beijing Spectrometer experiment since it started its first run almost 30 years ago. This result will not only help us to better understand the internal structure of Λcand the weak and strong interactions of the Standard Model, but also to reveal the sources of matter-antimatter asymmetry in the universe.