Measurement of correlated $b\overline{b}$ production in $p\overline{p}$ collisions at $\sqrt{s}=1960\mathrm{GeV}$

We present a measurement of the correlated $b\overline{b}$ production cross section. The data used in this analysis were taken with the upgraded CDF detector (CDF II) at the Fermilab Tevatron collider, and correspond to an integrated luminosity of $742{\mathrm{pb}}^{-1}$. We utilize muon pairs with invariant mass $5\le m_{\mu \mu }\le 80\mathrm{GeV}/c^2$ produced by $b\overline{b}$ double semileptonic decays. For muons with $p_T\ge 3\mathrm{GeV}/c$ and $|\eta |\le 0.7$, that are produced by $b$ and $\overline{b}$ quarks with $p_T\ge 2\mathrm{GeV}/c$ and $|y|\le 1.3$, we measure ${\sigma }_{b\to \mu ,\overline{b}\to \mu }=1549\pm 133\mathrm{pb}$. We compare this result with theoretical predictions and previous measurements. We also report the measurement of ${\sigma }_{c\to \mu ,\overline{c}\to \mu }$, a by-product of the study of the background to $b\overline{b}$ production.

Figure 1

Impact parameter distributions of muons coming from $b$- and $c$-hadron decays (simulation) and of prompt muons (data). Distributions are normalized to unit area.

Figure 2

Distribution of the invariant mass of muon pairs in the ${\rm Y}$ region. The prompt template in Fig. 1 is derived using muons with invariant mass between 9.28 and $9.6\mathrm{GeV}/c^2$. The background is sideband subtracted using dimuons with invariant mass between 9.04 and $9.2\mathrm{GeV}/c^2$ and between 9.64 and $9.8\mathrm{GeV}/c^2$.

Figure 3

Projections of the two-dimensional impact parameter distributions of some components used to fit the dimuon data (see text).

Figure 4

Two-dimensional impact parameter distributions of muon pairs (a) before and (b) after cosmic removal.

Figure 5

Invariant mass spectrum of the muon pairs used in this study.

Figure 6

The projection of the two-dimensional impact parameter distribution of muon pairs onto one of the two axes is compared to the fit result (histogram).

Figure 7

Distribution of the pulls—(data-fit)/$\sqrt{\mathrm{fit}}$—of the fit listed in Table 1 for the impact parameter bins with at least 10 entries. The solid line represents a fit of the pull distribution to a Gaussian function. The fit returns an average of $0.04\pm 0.10$ and $\sigma =1.06\pm 0.09$.

Figure 8

Invariant mass distribution of CMUP muon pairs with a randomly chosen muon that (a) satisfies or (b) fails the ${\chi }^2<9$ requirement.

Figure 9

Simulated impact parameter distributions of pion and kaon tracks from (a) $b$- and (b) $c$-quark decays are compared to those of muons from semileptonic decays with the same kinematical requirements.

Figure 10

Transverse momentum distributions in the data ($•$) and simulation ($\circ$) for muon pairs arising from (left) $b\overline{b}$ and (right) $c\overline{c}$ production. Distributions are normalized to unit area.

Figure 11

Transverse momentum distribution of (left) prompt muons in the data and (right) muons from $b$- or $c$-hadron decays in the simulation. Simulated distributions are normalized to unit area.

Figure 12

Distributions of the opening azimuthal angle between two muons from (left) $b\overline{b}$ and (right) $c\overline{c}$ production in the data ($•$) and simulation ($\circ$). Distributions are normalized to unit area.

Figure 13

Distribution of the invariant mass of the prompt dimuon component as determined by the fit to the muon impact parameter. The solid line represents a fit to the distribution that returns $9899\pm 142$ ${\rm Y}(1S)$ candidates, whereas the same fit to the data in Fig. 2 yields $9952\pm 122$ candidates.

Figure 14

Distributions of the invariant mass of muon pairs from (left) $b\overline{b}$ and (right) $c\overline{c}$ production in the data ($•$) and simulation ($\circ$). Distributions are normalized to unit area.

Figure 15

Invariant mass distribution of CMUP muons paired with a displaced track (a) with or (b) without a CMUP stub. Lines represent the fits described in the text.

Figure 16

Invariant mass distribution of CMUP muons paired with other CMUP muons in the event (a) with or (b) without a L1 CMU primitive. In order to derive the efficiency from the numbers of $J/\psi$ candidates in plots (a) and (b), the histogram in (a) has an entry for each CMUP leg. Solid lines represent the fits described in the text.

Figure 17

Invariant mass distribution of CMUP muon pairs in which a first randomly chosen muon (a) passes or (b) fails the SVXII requirements. Solid lines represent the fits described in the text.

Figure 18

Invariant mass distribution of CMUP muon pairs in which a first randomly chosen muon track satisfies the SVXII requirements and the second muon track (a) passes or (b) fails the SVXII requirements. Solid lines represent the fits described in the text.

Figure 19

Distribution of the event vertex along the beam line in the data ($•$) and in the heavy flavor simulation (histogram).

Figure 20

Distribution of ratio of the energy carried by all $B$ hadrons to that of the parent $b$ quarks. The data are OPAL measurements at the $Z$ pole [59], while the herwig distribution is obtained with the parameter tuning listed in Table 9.

Figure 21

Distribution of ratio of the momentum carried by $D^{*}$ mesons to that of the parent $c$ quarks. The data are BELLE measurements [54], while the herwig distribution is obtained with the parameter tuning listed in Table 9.

Figure 22

Distributions of (a) $m_{D^{*\pm }}-m_{D^0}$ and (b) the invariant mass of $D^0$ candidates (the solid line represents the fit described in the text).

Figure 23

Invariant mass distribution of $D^0$ candidates with (left) a kaon or (right) a pion leg identified as a CMUP muon. Solid lines represent the fits described in the text.

Figure 24

Invariant mass distribution of $D^0$ candidates with (left) a kaon or (right) a pion leg identified as a CMUP muon. Top (bottom) plots require muons passing (failing) the ${\chi }^2<9$ cut. Solid lines represent the fits described in the text.

Figure 25

Transverse momentum distributions of (left) kaons and (right) pions from $D^0$ decays ($\circ$) are compared to those of tracks ($•$) arising from simulated $b$-hadron decays.

Figure 26

Fake muon probability as a function of the (left) kaon and (right) pion transverse momentum.