Mass and Lifetime at LHCb

The B c a meson is the ground state of the meson family formed by two different heavy flavor quarks, the anti-b quark and the c quark. The mass of the B c meson has been estimated theoretically to be in a range of 6.2-6.4 GeV/c [2]. Recently unquenched lattice QCD [3] gave the most accurate prediction of M(B c ) = 6278(6)(4) MeV/c , where the first error is statistical, and the second is systematic. The b̄c mesons are open-flavored and the excited states below the BD threshold can decay only through the electromagnetic or hadronic interactions into the ground state, B c , which can decay only weakly and has a relatively long lifetime. The estimated B c lifetime is in a range of 0.4-0.8 ps [2]. At present, the best prediction is given by QCD sum rules [4]: τ(B c ) = 0.48 ± 0.05 ps. Since the b̄c mesons carry two different heavy flavor quarks, their production [2] is more difficult than that of the heavy quarkonia. Including the contributions from the excited states, the cross section of the B c meson at LHC was estimated [5] to be at a level of 1 μb, and is one order higher than that at Tevatron. This means that O(10) B c mesons can be anticipated with 1 fb −1