Roles of scalar mesons in charmless $\Lambda_b$ decays

TL;DR

This paper investigates the role of scalar mesons in charmless $ ext{Lambda}_b$ decays, providing predictions for branching ratios and comparing them with experimental data, highlighting the first evidence of scalar meson production in these decays.

Contribution

It offers the first theoretical predictions for scalar meson contributions in $ ext{Lambda}_b$ decays and compares them with recent experimental results.

Findings

Predicted branching ratios for $ ext{Lambda}_b$ decays involving scalar mesons.

Comparison of predictions with LHCb experimental data.

Evidence for scalar meson production in anti-triplet $b$-baryon decays.

Abstract

We first study the charmless two-body $\Lambda_b$ decays with the scalar mesons as the final states and predict that ${\cal B}(\Lambda_b\to \Lambda f_0(980,1500))=(2.9\pm 0.7,12.4\pm 3.8)\times 10^{-6}$ and ${\cal B}(\Lambda_b\to p K^{*-}_0(800,1430))=(1.9\pm 0.5,14.1\pm 4.5)\times 10^{-6}$. With the resonant $f_0(980,1500)\to (\pi^+\pi^-,K^+K^-)$ and $K^{*-}_0\to \bar K^0 \pi^-$ decays, we then obtain ${\cal B}(\Lambda_b\to \Lambda (\pi^+\pi^-,K^+K^-))=(4.2\pm 1.0,3.5\pm0.7)\times 10^{-6}$ and ${\cal B}(\Lambda_b\to p\bar K^0 \pi^-)=(10.4\pm2.9)\times 10^{-6}$, in comparison with the data of $(4.6\pm 1.9,15.9\pm2.6)\times 10^{-6}$ and $(12.6\pm 4.0)\times 10^{-6}$ from LHCb, respectively. Our results for $\Lambda_b\to \Lambda\pi^+\pi^-$ and $\Lambda_b\to p\bar K^0 \pi^-$ would be regarded as the first evidences of the scalar meson productions in the anti-triplet $b$-baryon decays. The smaller predicted value of ${\cal B}(\Lambda_b\to \Lambda K^+K^-)$ indicates the existences of other resonant contributions to the decay, such as $\Lambda_b\to K^-(N^{*+}\to)\Lambda K^+$.