Search for the decays B_{(s)};{0} --> e;{+} micro;{-} and B_{(s)};{0} --> e;{+} e;{-} in CDF run II

Area of Science:

• Particle Physics
• High-Energy Physics
• Standard Model Physics

Background:

• The Standard Model (SM) of particle physics successfully describes fundamental particles and their interactions.
• Rare B meson decays offer a unique window to probe for physics beyond the Standard Model.
• Lepton flavor violation and flavor-changing neutral currents are highly suppressed in the SM, making their observation a sign of new physics.

Purpose of the Study:

• To search for lepton flavor violating (LFV) decays B_{s}^{0} \to e^{+} \mu^{-} and B^{0} \to e^{+} \mu^{-}.
• To search for flavor-changing neutral-current (FCNC) decays B_{s}^{0} \to e^{+} e^{-} and B^{0} \to e^{+} e^{-}.
• To set upper limits on the branching ratios of these rare decays and derive constraints on new physics models, such as leptoquarks.

Main Methods:

• Analysis of 2 fb^{-1} of integrated luminosity data from pp collisions at \sqrt{s} = 1.96 TeV.
• Utilized the upgraded Collider Detector (CDF II) at the Fermilab Tevatron.
• Employed Bayesian statistical methods to set upper limits at the 90% credibility level.

Main Results:

• The observed number of candidate events for all searched decays was consistent with background expectations.
• Established Bayesian upper limits on branching ratios: B(B_{s}^{0} \to e^{+} \mu^{-}) < 2.0 \times 10^{-7}, B(B^{0} \to e^{+} \mu^{-}) < 6.4 \times 10^{-8}, B(B_{s}^{0} \to e^{+} e^{-}) < 2.8 \times 10^{-7}, and B(B^{0} \to e^{+} e^{-}) < 8.3 \times 10^{-8}.
• Derived lower bounds on Pati-Salam leptoquark masses: M_{LQ}(B_{s}^{0} \to e^{+} \mu^{-}) > 47.8 TeV/c^{2} and M_{LQ}(B^{0} \to e^{+} \mu^{-}) > 59.3 TeV/c^{2} at 90% credibility.

Conclusions:

• The absence of signals for LFV and FCNC decays in B mesons provides stringent constraints on extensions to the Standard Model.
• The derived limits place significant restrictions on the parameter space of leptoquark models.
• This search contributes to the ongoing effort to uncover new physics phenomena at high energy scales.