Observation of B_c Mesons in p-bar p Collisions at sqrt{s} = 1.8 TeV

TL;DR

This paper reports the first observation of B_c mesons in proton-antiproton collisions at 1.8 TeV, measuring their mass, lifetime, and production rate using the CDF detector at Fermilab.

Contribution

The study provides the first experimental evidence of B_c mesons, including their mass, lifetime, and production cross section ratio, using semileptonic decay channels at Tevatron energies.

Findings

Observed 20.4 B_c events with high significance.

Measured B_c mass as 6.40 GeV/c^2 with uncertainties.

Determined B_c lifetime as approximately 0.46 ps.

Abstract

We report the observation of bottom-charmed mesons B_c in 1.8 TeV p-bar p collisions using the CDF detector at the Fermilab Tevatron. The B_c mesons were found through their semileptonic decays, B_c -> J/psi lepton X. A fit to the J/psi lepton mass distribution yielded 20.4 +6.2 -5.5 events from B_c mesons. A test of the null hypothesis, i.e. an attempt to fit the data with background alone, was rejected at the level of 4.8 standard deviations. By studying the quality of the fit as a function of the assumed B_c mass, we determined M(B_c) = 6.40 +- 0.39 +- 0.13 GeV/c^2. From the distribution of trilepton intersection points in the plane transverse to the beam direction we measured the B_c lifetime to be tau(B_c) = 0.46 +0.18 -0.16 +- 0.03 ps. We also measured the ratio of production cross section times branching fraction for B_c -> J/psi lepton neutrino relative to that for B+ -> J/psi K to be: 0.132 +0.041 -0.037 (stat) +- 0.031 (syst) +0.032 -0.020 (lifetime)