Test of Lepton Universality in b→sℓ^{+}ℓ^{-} Decays

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• Lepton universality is a key prediction of the Standard Model, stating that fundamental particles like muons and electrons should behave identically in certain interactions.
• Deviations from lepton universality in B meson decays could indicate the presence of new physics beyond the Standard Model.
• Previous experiments have hinted at potential discrepancies, motivating further precise measurements.

Purpose of the Study:

• To perform the first simultaneous test of muon-electron universality in B+→K+ℓ+ℓ− and B0→K*0ℓ+ℓ− decays.
• To measure lepton universality in two distinct ranges of the dilepton invariant-mass squared (q²).
• To compare experimental results with Standard Model predictions to search for new physics phenomena.

Main Methods:

• Utilized data from proton-proton collisions collected by the LHCb detector between 2011 and 2018.
• Analyzed a large dataset corresponding to an integrated luminosity of 9 fb⁻¹.
• Performed precise measurements of branching ratios and angular observables for the specified B meson decays.

Main Results:

• Presented four lepton universality measurements, each being either novel for its q² interval or an improvement on previous LHCb results.
• Observed consistency between the measured ratios of decay rates involving muons and electrons.
• All measurements were found to be compatible with the Standard Model predictions within experimental uncertainties.

Conclusions:

• The first simultaneous test of muon-electron universality in these B meson decays shows agreement with the Standard Model.
• No evidence for new physics beyond the Standard Model was found in this analysis.
• These precise measurements contribute to the ongoing effort to test the Standard Model with high-precision data from flavor physics.