Search for Lepton-Universality Violation in B^{+}→K^{+}ℓ^{+}ℓ^{-} Decays.

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• The Standard Model of particle physics predicts a specific ratio for beauty quark decays.
• Deviations from these predictions could indicate the presence of new fundamental particles or forces.
• Previous measurements have shown tensions with Standard Model predictions.

Purpose of the Study:

• To precisely measure the ratio of branching fractions for B+ decays to K+μ+μ- and K+e+e-.
• To test lepton universality in B+ decays.
• To search for evidence of New Physics beyond the Standard Model.

Main Methods:

• Utilized 5.0 fb^-1 of proton-proton collision data from the LHCb experiment at 7, 8, and 13 TeV.
• Analyzed B+ meson decays into K+ lepton pairs.
• Measured the ratio R_K = Γ(B+→K+μ+μ-)/Γ(B+→K+e+e-) in the dilepton mass-squared range 1.1 < q^2 < 6.0 GeV^2/c^4.

Main Results:

• The measured ratio is R_K = 0.846 ± 0.054 (stat) ± 0.016 (syst).
• This result represents the most precise measurement of R_K to date.
• The measurement deviates from the Standard Model prediction by 2.5 standard deviations.

Conclusions:

• The precise measurement of R_K provides important data for testing lepton universality.
• The observed deviation from the Standard Model warrants further investigation.
• This result may hint at the existence of new physics phenomena.