Measurement of the ratio of inclusive cross sections $\sigma (p\overline{p}\to Z+b\mathrm{\text{−}}\mathrm{\text{quark jet}})/\sigma (p\overline{p}\to Z+\mathrm{\text{jet}})$ at $\sqrt{s}=1.96\mathrm{TeV}$

The ratio of the cross section for $p\overline{p}$ interactions producing a $Z$ boson and at least one $b$-quark jet to the inclusive $Z+\mathrm{\text{jet}}$ cross section is measured using $4.2{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions collected with the D0 detector at the Fermilab Tevatron collider at $\sqrt{s}=1.96\mathrm{TeV}$. The $Z\to {\ell }^{+}{\ell }^{-}$ candidate events with at least one $b$ jet are discriminated from $Z+\mathrm{\text{charm}}$ and light jet(s) events by a novel technique that exploits the properties of the tracks associated to the jet. The measured ratio is $0.0193\pm 0.0027$ for events having a jet with transverse momentum $p_T>20\mathrm{GeV}$ and pseudorapidity $|\eta |\le 2.5$, which is the most precise to date and is consistent with theoretical predictions.

Figure 1

The probability densities of the $D_{\mathrm{JLIP}}^{M_{\mathrm{SV}}}$ discriminant for $b$, $c$, and light jets passing the NN $b$ tagging requirement. Also shown is the distribution for the negative tagged (NT) jets in the data, described in the text.

Figure 2

The observed $p_T$ distribution of the leading jet in the (a) $\mu \mu$ and (b) $ee$ channel compared with the SM prediction. The uncertainties on the data points are statistical, and the prediction is normalized to the data, as described in the text.

Figure 3

The $D_{\mathrm{JLIP}}^{M_{\mathrm{SV}}}$ discriminant distribution of events in the combined sample. The distributions of the $b$, $c$, and light jets are weighted by the fractions found from the fit. Uncertainties are statistical only.