Measurements of the Absolute Branching Fraction of the Semileptonic Decay ${\mathbf{\Xi }}^{-}\to \mathbf{\Lambda }{\mathbf{e}}^{-}{\bar{\nu }}_{\mathbf{e}}$ and the Axial Charge of the ${\mathbf{\Xi }}^{-}$

Abstract

Using $(10087\pm 44)\times 10^6$ $J/\psi$ events collected with the BESIII detector, we study the semileptonic decay ${\Xi }^{-}\to \Lambda e^{-}{\bar{\nu }}_e$ for the first time at an electron-positron collider. The absolute branching fraction is determined for the first time to be $(3.60\pm 0.40_{\mathrm{stat}}\pm 0.10_{\mathrm{syst}})\times 10^{-4}$, which is 3.9 standard deviations below the world average. In addition, using an 11-dimensional angular analysis, the axial-vector to vector coupling $g_{av}$ is determined to be $0.18\pm 0.07_{\mathrm{stat}}\pm 0.02_{\mathrm{syst}}$. These results are used to test various SU(3)-flavour effective models. Under the SU(3)-flavour symmetry limit, the axial charge is found to be $g_A^H=0.22\pm 0.08_{\mathrm{stat}}\pm 0.02_{\mathrm{syst}}$. Despite using only 5\% of the statistics of previous experiments, this analysis achieves a comparable precision for the axial charge.

10 pages, 4 figures

References in corpus (9)

• STCF Conceptual Design Report: Volume 1 -- Physics & Detector
• Number of $J/\psi$ events at BESIII
• Weak phases and CP-symmetry tests in sequential decays of entangled double-strange baryons
• Octet-baryon axial-vector charges and SU(3)-breaking effects in the semileptonic hyperon decays
• Axial charges of octet and decuplet baryons
• Octet baryon isovector charges from $N_f=2+1$ lattice QCD
• The potential of $\Lambda$ and ${\Xi }^{-}$ studies with PANDA at FAIR
• Semileptonic decays of spin-entangled baryon-antibaryon pairs
• Investigations on the flavor-dependent axial charges of the octet baryons