Search for Lepton-Flavor Violating Decays B^{+}→K^{+}μ^{±}e^{∓}.

Area of Science:

• High Energy Physics
• Particle Physics
• Standard Model Physics

Background:

• Lepton flavor is conserved in the Standard Model.
• Searches for lepton flavor violation provide sensitive probes of new physics beyond the Standard Model.
• The B+ meson decays offer a promising channel to search for such violations.

Purpose of the Study:

• To search for the lepton-flavor violating decays B+ -> K+ mu-+ e-+.
• To set new upper limits on the branching fractions of these decays.
• To constrain new physics models by improving existing limits.

Main Methods:

• Analysis of proton-proton collision data collected by the LHCb experiment.
• Data collected at center-of-mass energies of 7 and 8 TeV.
• Integrated luminosity of 3 fb^-1.

Main Results:

• No significant signal was observed for the B+ -> K+ mu-+ e-+ decays.
• Upper limits were set on the branching fractions: B(B+ -> K+ mu- e+) < 7.0(9.5)x10^-9 and B(B+ -> K+ mu+ e-) < 6.4(8.8)x10^-9 at 90%(95%) confidence level.
• These results improve the previous best limits by over an order of magnitude.

Conclusions:

• The search places stringent constraints on lepton flavor violation in B+ decays.
• The results disfavor certain new physics scenarios that predict observable rates for these decays.
• Further data or more sensitive experiments may be needed to probe even smaller branching fractions.