Isospin amplitudes in $\Lambda_b^0\to J/\psi \Lambda(\Sigma^0)$ and $\Xi_b^0\to J/\psi \Xi^0(\Lambda)$ decays

TL;DR

This paper reports the first measurements of isospin amplitude ratios in b-baryon decays, providing insights into weak and strong interaction interplay and searching for physics beyond the Standard Model using LHCb data.

Contribution

It presents the first measurement of isospin amplitudes in b-baryon decays and observes the Cabibbo suppressed decay $ o$ first measurement of its amplitude ratio.

Findings

Isospin amplitude ratio $|A_1( o J/ heta o heta)$ less than 1/21.8 at 95% CL.

First observation of $ o J/ heta o heta$ decay, with a measured amplitude ratio of 0.37 ± 0.06 ± 0.02.

Abstract

Ratios of isospin amplitudes in hadron decays are a useful probe of the interplay between weak and strong interactions, and allow searches for physics beyond the Standard Model. We present the first results on isospin amplitudes in $b$-baryon decays, using data corresponding to an integrated luminosity of 8.5 fb$^{-1}$, collected with the LHCb detector in $pp$ collisions at center of mass energies of 7, 8 and 13 TeV. The isospin amplitude ratio $|A_1(\Lambda_b^0\to J/\psi \Sigma^0)/A_0(\Lambda_b^0\to J/\psi\Lambda)|$, where the subscript on $A$ indicates the final-state isospin, is measured to be less than 1/21.8 at 95\% confidence level. The Cabibbo suppressed $\Xi_b^0\to J/\psi\Lambda$ decay is observed for the first time, allowing for the measurement $|A_0(\Xi_b^0\to J/\psi\Lambda)/A_{1/2}(\Xi_b^0\to J/\psi\Xi^0)| =0.37 \pm 0.06\pm 0.02$, where the uncertainties are statistical and systematic, respectively.