Charm-baryon semileptonic decays and the strange ${\Lambda }^{\ast }$ resonances: New insights from lattice QCD

Abstract

Understanding the properties of the strange ${\Lambda }^{\ast }$ baryon resonances is a long-standing and fascinating problem. ${\Lambda }_c$ charm-baryon semileptonic weak decays to these resonances are highly sensitive to their internal structure and can be used to test theoretical models. We have performed the first lattice-QCD computation of the form factors governing ${\Lambda }_c$ semileptonic decays to a ${\Lambda }^{\ast }$ resonance: the ${\Lambda }^{\ast }(1520)$, which has negative parity and spin $3/2$. Here we present the resulting Standard-Model predictions of the ${\Lambda }_c\to {\Lambda }^{\ast }(1520){\ell }^{+}{\nu }_{\ell }$ differential and integrated decay rates as well as angular observables. Furthermore, by combining the recent BESIII measurement of the ${\Lambda }_c\to X{e}^{+}{\nu }_e$ inclusive semipositronic branching fraction [Phys. Rev. Lett. 121, 251801 (2018)] with lattice-QCD predictions of the ${\Lambda }_c\to \Lambda e^{+}{\nu }_e$, ${\Lambda }_c\to n{e}^{+}{\nu }_e$, and ${\Lambda }_c\to {\Lambda }^{\ast }(1520)e^{+}{\nu }_e$ decay rates, we obtain an upper limit on the sum of the branching fractions to all other semipositronic final states. In particular, this upper limit constrains the ${\Lambda }_c\to {\Lambda }^{\ast }(1405)e^{+}{\nu }_e$ branching fraction to be very small, which may be another hint for a molecular structure of the ${\Lambda }^{\ast }(1405)$.

arXiv comment6 pages, 1 figure

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Cited by in corpus (8)

• Two-pole nature of the $\Lambda (1405)$ from lattice QCD
• Lattice QCD study of $\pi \Sigma -\bar{K}N$ scattering and the $\Lambda (1405)$ resonance
• ${\Lambda }_c\to {\Lambda }^{\ast }(1520)$ form factors from lattice QCD and improved analysis of the ${\Lambda }_b\to {\Lambda }^{\ast }(1520)$ and ${\Lambda }_b\to {\Lambda }_c^{\ast }(2595,2625)$ form factors
• Study of the Semileptonic Decay ${\Lambda }_c^{+}\to \Lambda e^{+}{\nu }_e$
• First Observation of the Semileptonic Decay ${\Lambda }_c^{+}\to p{K}^{-}{e}^{+}{\nu }_e$
• Pole trajectories of the $\Lambda (1405)$ helps establish its dynamical nature
• ${\Xi }_c\to \Xi$ form factors from lattice QCD with domain-wall quarks: A new piece in the puzzle of ${\Xi }_c^0$ decay rates
• Evidence for the semileptonic decays ${\Lambda }_c^{+}\to {\Sigma }^{\pm }{\pi }^{\mp }{e}^{+}{\nu }_e$