Isospin Amplitudes in Λ_{b}^{0}→J/ψΛ(Σ^{0}) and Ξ_{b}^{0}→J/ψΞ^{0}(Λ) Decays

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• Isospin amplitude ratios in hadron decays offer insights into fundamental interactions.
• Searches for new physics phenomena often utilize deviations from the Standard Model predictions.
• B-baryon decays provide a unique laboratory for studying these interactions.

Purpose of the Study:

• To present the first measurements of isospin amplitudes in b-baryon decays.
• To constrain parameters related to the interplay of weak and strong forces.
• To search for physics beyond the Standard Model.

Main Methods:

• Analysis of proton-proton collision data collected by the LHCb detector.
• Utilizing an integrated luminosity of 8.5 fb⁻¹ at center-of-mass energies of 7, 8, and 13 TeV.
• Measurement of specific decay modes, including the observation of the Ξ_{b}^{0}→J/ψΛ decay.

Main Results:

• The isospin amplitude ratio |A_{1}(Λ_{b}^{0}→J/ψΣ^{0})/A_{0}(Λ_{b}^{0}→J/ψΛ)| was measured to be less than 1/21.8 at 95% confidence level.
• The first observation of the Cabibbo-suppressed Ξ_{b}^{0}→J/ψΛ decay was achieved.
• The ratio of isospin amplitudes for this decay was measured as |A_{0}(Ξ_{b}^{0}→J/ψΛ)/A_{1/2}(Ξ_{b}^{0}→J/ψΞ^{0})|=0.37±0.06±0.02.

Conclusions:

• These results provide crucial data for understanding the complex dynamics of weak and strong interactions in b-baryon decays.
• The observed decay and measured amplitude ratio offer new avenues for testing theoretical models and searching for new physics.
• The study highlights the sensitivity of LHCb to rare and suppressed processes.