Search for the lepton-flavor-violating decays B(s)0→e(±)μ(∓) and B0→e(±)μ(∓)

Area of Science:

• High Energy Physics
• Particle Physics
• Beyond Standard Model Physics

Background:

• Lepton flavor violation (LFV) is a key indicator of new physics beyond the Standard Model.
• Searches for LFV decays of B-mesons provide sensitive probes of new particles and interactions.
• Previous experiments have set limits on LFV decays such as B(s)0→e(±)μ(∓) and B0→e(±)μ(∓).

Purpose of the Study:

• To search for the lepton-flavor-violating decays B(s)0→e(±)μ(∓) and B0→e(±)μ(∓).
• To set new upper limits on the branching fractions of these rare decays.
• To constrain the masses of hypothetical Pati-Salam leptoquarks.

Main Methods:

• Analysis of a data sample corresponding to an integrated luminosity of 1.0 fb(-1) of proton-proton collisions at √s=7 TeV.
• Utilizing the LHCb detector to identify and reconstruct B(s)0 and B0 meson decays.
• Statistical analysis to compare observed candidates with background expectations and set upper limits.

Main Results:

• The observed number of candidate events for both B(s)0→e(±)μ(∓) and B0→e(±)μ(∓) decays is consistent with background.
• Upper limits on branching fractions are set at B(B(s)0→e(±)μ(∓))<1.1(1.4)×10(-8) and B(B0→e(±)μ(∓))<2.8(3.7)×10(-9) at 90% (95%) confidence level.
• These limits are approximately a factor of 20 lower than those from previous experiments.

Conclusions:

• The stringent new limits significantly improve upon previous measurements for these LFV decays.
• The results place strong constraints on new physics scenarios, particularly those involving leptoquarks.
• Lower bounds on Pati-Salam leptoquark masses are established at M(LQ)(B(s)0→e(±)μ(∓))>101 TeV/c(2) and M(LQ)(B0→e(±)μ(∓))>126 TeV/c(2) at 95% C.L., a factor of 2 higher than previous bounds.