Observation of associated production of a $Z$ boson with a $D$ meson in the~forward region

Abstract

A search for associated production of a $Z$ boson with an open charm meson is presented using a data sample, corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-‘}$ of proton--proton collisions at a centre-of-mass energy of 7\,TeV, collected by the LHCb experiment. %% Seven candidate events for associated production of a $Z$ boson with a $D^0$ meson and four candidate events for a $Z$ boson with a $D^{+}$ meson are observed with a combined significance of 5.1standard deviations. The production cross-sections in the forward region are measured to be $$\ddot{I}{ƒ}_{Z\to \hat{I}{¼}^{+}\hat{I}{¼}^{-},D^0}=2.50\pm 1.12\pm 0.22pb$$ $$\ddot{I}{ƒ}_{Z\to \hat{I}{¼}^{+}\hat{I}{¼}^{-},D^{+}}=0.44\pm 0.23\pm 0.03pb,$$ where the first uncertainty is statistical and the second systematic.

18 pages, 2 figures