Probe New Physics in Leptonic Bc Decays at CERN LHC

With respect to large samples of Bc mesons expected to be produced at CERN Large Hadron Collider(LHC) and the large branching ratios Br(Bc → τ ν̄) and Br(Bc → μν̄), we suggest that Bc purely leptonic decays could offer an unique probe of the standard model and its extensions such as two Higgs doublet models and models involving supersymmetry, and also the structure of charged weak currents. PACS numbers 13.20.He 12.15.-y 12.60.Fr Email: [email protected], [email protected] Mailing address 1 Being consisted of two different heavy flavors, Bc meson is believed to offer an unique probe of both strong and weak interactions. The physics of Bc meson has stimulated much recent works on their properties, weak decays and production cross section at high energy colliders. Although Bc meson is hard to be produced, the number of Bc meson produced at LHC is estimated[1] to be 2.1 × 10 (for 100fb integrated luminosity with cuts of PT (Bc) > 20GeV, | y(Bc) |< 2.5 ). Once produced, an excited bc̄ meson will cascade down through lower energy bc̄ states via hadronic or electromagnetic transitions to the pseudoscalar ground state Bc with mass lying below the B̄D threshold, which decays weakly. The weak decays Bc → τ ν̄, μν̄ are of particular interest because of at least two reasons: • The compact size of Bc meson enhanced the importance of annihilation decays, i.e, the decay constant fBc is much larger than that of other heavy mesons. Furthermore, compared with Γ(B u → lν̄l), Γ(B c → lν̄l) is enhanced by a large factor Γ(B c → lν̄l) Γ(B− u → lν̄l) = (