# Measurement of $\sigma(b \bar{b})$ with inclusive final states

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## Abstract

A measurement of the cross section for the production of $b\bar{b}$ pairs based on $b$ inclusive final states is presented using LHCb data collected from $pp$ collisions at $\sqrt s$= 7 TeV in 2010, corresponding to an integrated luminosity of $\sim$18 pb$^{-1}$. The inclusive $b\bar{b}$ sample is selected on the basis of decay vertices displaced from the primary interaction. The measurement has been performed in a region of pseudorapidity 2.5 $<\eta<$ 4.0 and transverse momentum $p_{\rm T}$ $> 5$ GeV of the $b$ hadron candidate. The selected sample is a mixture of $b\bar{b}$ and $c\bar{c}$ events with a negligible contamination of light quarks, a measurement of the cross section for the production of $c\bar{c}$ can therefore be performed simultaneously. The results are $\sigma^{b\bar{b}} = 7.7\pm0.12 \rm{(stat)}\pm0.84 \rm{(syst)} \mu$b and $\sigma^{c\bar{c}} = 104.6\pm2.7 \rm{(stat)}\pm11.4 \rm{(syst)} \mu$b, inside the kinematic range defined above.

## Figures and captions

 $\Delta\phi$ between the $b\bar{b}$ quark pairs: distributions are shown at the very first {\sc Pythia} production step (continuous red line) and at the last step before hadronization (dotted black line). The distribution for the $b$ hadron pairs is shown in the yellow filled histogram. Fig1.eps [11 KiB] HiDef png [207 KiB] Thumbnail [177 KiB] *.C file Difference in azimuthal angles of the two $b$ hadrons for {\sc Pythia} at the LO approximation (black line) and {\sc Powheg} at the NLO approximation (blue filled histogram) in the $b\bar{b}$-inclusive events. Fig2.eps [7 KiB] HiDef png [158 KiB] Thumbnail [132 KiB] *.C file Resolution in (a) $\phi$ and (b) $\theta$ for the seed measured as described in the text for events with one $b$ hadron and one reconstructed seed. Fig3a.eps [9 KiB] HiDef png [171 KiB] Thumbnail [158 KiB] *.C file Fig3b.eps [9 KiB] HiDef png [177 KiB] Thumbnail [157 KiB] *.C file Distribution of $\Delta \phi$ of a seed pair before (black line) and after (red histogram) the merging procedure. Fig4.eps [14 KiB] HiDef png [199 KiB] Thumbnail [168 KiB] *.C file (a) Correlations in $\eta$ between the $B^{0} \rightarrow D^{-} \pi^{+}$ decay, and the seed reconstructed with the particles originating from the signal $B^{0}$. (b) Correlations in $\eta$ between the $B^{0} \rightarrow D^{-} \pi^{+}$ decay and the seed reconstructed without the particles originating from the signal $B^{0}$. Fig5a.eps [49 KiB] HiDef png [320 KiB] Thumbnail [204 KiB] *.C file Fig5b.eps [53 KiB] HiDef png [449 KiB] Thumbnail [311 KiB] *.C file Comparison of the transverse momentum of the seed before and after calibration (red histogram and black points respectively), and with true $b$ hadrons (yellow filled histogram), in the fiducial region of the measurement. Distributions are normalized to unity. Fig6.eps [877 KiB] HiDef png [455 KiB] Thumbnail [190 KiB] *.C file Distributions of (a) $\Delta\phi$ and (b) $p_{\rm T}$ of the seeds. Data (black dots), $b\bar{b}$ (yellow light histogram), $c\bar{c}$ (blue dark histogram). Expected contributions of $b\bar{b}$ and $c\bar{c}$ are subsequently added. Fig7a.eps [13 KiB] HiDef png [197 KiB] Thumbnail [179 KiB] *.C file Fig7b.eps [13 KiB] HiDef png [194 KiB] Thumbnail [176 KiB] *.C file Response of the BDTG (defined in the text) for data (black dots) fitted with shapes evaluated from simulated $b\bar{b}$ (red dotted line) and $c\bar{c}$ (green dashed line) events. The fit result is indicated by the solid blue line. Fig8.eps [888 KiB] HiDef png [506 KiB] Thumbnail [217 KiB] *.C file Animated gif made out of all figures. CONF-2013-002.gif Thumbnail

## Tables and captions

 Requirements on the tracks to form two- or three-track seeds. Table_1.pdf [31 KiB] HiDef png [72 KiB] Thumbnail [34 KiB] tex code Requirements on the reconstructed secondary vertices of two or three tracks. The seed $p_{\rm T}$ is defined as the sum of the four-momenta of constituent tracks. DOCA indicates the distance of closest approach between two tracks. Table_2.pdf [40 KiB] HiDef png [46 KiB] Thumbnail [22 KiB] tex code Sources of systematic uncertainties. Table_3.pdf [31 KiB] HiDef png [107 KiB] Thumbnail [50 KiB] tex code

Created on 19 October 2019.