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Register a new userFirst observation of forward $Z rightarrow b bar{b}$ production in $pp$ collisions at $sqrt{s}=8$ TeV
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The decay $Z rightarrow b bar{b}$ is reconstructed in $pp$ collision data, corresponding to 2 fb$^{-1}$ 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 $Z rightarrow b bar{b}$ branching fraction is measured for candidates in the fiducial region defined by two particle-level $b$-quark jets with pseudorapidities in the range $2.2 < eta < 4.2$, with transverse momenta $p_{T}>20$ GeV and dijet invariant mass in the range $45 < m_{jj} < 165$ GeV. From a signal yield of $5462 pm 763$ $Z rightarrow b bar{b}$ 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 $Z rightarrow b bar{b}$ production in the forward region of $pp$ collisions.
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