The Collider Detector at Fermilab collected a unique sample of jets originating from bottom-quark fragmentation ($b$-jets) by selecting online proton-antiproton ($p\overline{p}$) collisions with a vertex displaced from the $p\overline{p}$ interaction point, consistent with the decay of a bottom-quark hadron. This data set, collected at a center-of-mass energy of 1.96 TeV, and corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$, is used to measure the $Z$-boson production cross section times branching ratio into $b\overline{b}$. The number of $Z\to b\overline{b}$ events is determined by fitting the dijet-mass distribution, while constraining the dominant $b$-jet background, originating from QCD multijet events, with data. The result, $\sigma (p\overline{p}\to Z)\times \mathcal{B}(Z\to b\overline{b})=1.11\pm 0.08(\mathrm{stat})\pm 0.14(\mathrm{syst})\mathrm{nb}$, is the most precise measurement of this process, and is consistent with the standard-model prediction. The data set is also used to search for Higgs-boson production. No significant signal is expected in our data and the first upper limit on the cross section for the inclusive $p\overline{p}\to H\to b\overline{b}$ process at $\sqrt{s}=1.96\mathrm{TeV}$ is set, corresponding to 33 times the expected standard-model cross section, or $\sigma =40.6\mathrm{pb}$, at the 95% confidence level.

• Received 5 July 2018

DOI:https://doi.org/10.1103/PhysRevD.98.072002

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Published by the American Physical Society