Observation of B_{c}^{+}→D^{0}K^{+} Decays.

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doi:10.1103/physrevlett.118.111803

Abstract

Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb^{-1}, recorded by the LHCb detector at center-of-mass energies of 7 and 8TeV, the B_{c}^{+}→D^{0}K^{+} decay is observed with a statistical significance of 5.1 standard deviations. By normalizing to B^{+}→D[over ¯]^{0}π^{+} decays, a measurement of the branching fraction multiplied by the production rates for B_{c}^{+} relative to B^{+} mesons in the LHCb acceptance is obtained, R_{D^{0}K}=(f_{c}/f_{u})×B(B_{c}^{+}→D^{0}K^{+})=(9.3_{-2.5}^{+2.8}±0.6)×10^{-7}, where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first B_{c}^{+} decay of this nature to be observed.

Highlights

The Bþc meson is the only ground-state meson consisting of two heavy quarks of different flavor, namely a band a c quark
The expected branching fraction for this decay is a factor jVub=Vcbj2 ≈ 0.007 lower than the favored b → c and color-allowed Bþc → J=ψπþ decay [4,5], placing this mode at the limit of sensitivity with current LHCb data. This expectation may be enhanced by penguin and weak annihilation amplitudes, which will be more pronounced in the Bþc → DðÃÞ0Kþ mode [see Fig. 1(b) and 1(c)]
This motivates a search for the Bþc → DðÃÞ0Kþ and Bþc → DðÃÞ0πþ decays, as the branching fraction estimates in the literature vary considerably [6,7,8]

Summary

Introduction

The Bþc meson is the only ground-state meson consisting of two heavy quarks of different flavor, namely a band a c quark. Since the ratio of production rates for Bþc and Bþ mesons within the LHCb acceptance, fc=fu, is unknown, the measured observables are where h is π or K and BðBþc → DðÃÞ0hþÞ represents the corresponding branching fraction. The four observables are measured with a simultaneous fit to the D0πþ and D0Kþ invariant mass distributions.

Results

Conclusion