First observation of forward $Z \to b\overline{b}$ production in $pp$ collisions at $\sqrt{s}$ = 8 TeV

The decay $Z boverline{b}$ is reconstructed in $pp$ collision data, corresponding to 2fb$^{−1}$ of integrated luminosity, collected by the LHCb experiment at a centre-of-mass energy of $sqrt{s}$ = 8 TeV. The product of the $Z$ production cross-section and the $Z boverline{b}$ branching fraction is measured for candidates in the fiducial region defined by two particle-level $b$-quark jets with pseudorapidities in the range $2.2 20 GeV$ and dijet invariant mass in the range $45 u003c m_{jj} u003c 165 GeV$. From a signal yield of $5462 pm 763 Z boverline{b}$ events, where the uncertainty is statistical, a production cross-section times branching fraction of $332 pm 46 pm 59 $ pb is obtained, where the first uncertainty is statistical and the second systematic. The measured significance of the signal yield is 6.0 standard deviations. This measurement represents the first observation of the $Z boverline{b}$ production in the forward region of $pp$ collisions.