Inclusive production of a Higgs or $Z$ boson in association with heavy quarks

We calculate the cross section for the production of a $Z$ boson in association with heavy quarks. We suggest that this cross section can be measured using an inclusive heavy-quark tagging technique. This could be used as a feasibility study for the search for a Higgs boson produced in association with bottom quarks. We argue that the best formalism for calculating that cross section is based on the leading-order process $b\overline{b}\to h$, and that it is valid for all Higgs masses of interest at both the Fermilab Tevatron and the CERN Large Hadron Collider.

Figure 1

$\sigma (\tilde{b}\overline{\tilde{b}}\to h)/\sigma (gg\to hb\overline{b})$ vs $m_h$ at the Tevatron and the LHC, using MRST2001 LO parton distribution functions [43], $m_b=4.7\mathrm{GeV}$, and ${\mu }_F$ ($={\mu }_R$) $=m_h/4$.

Figure 2

$-td\sigma /dt$ vs $\sqrt{-t}/m_h$ for $gb\to hb$ at the Tevatron and the LHC. The factorization scale for $b\overline{b}\to h$ should be chosen near the end of the collinear plateau.

Figure 3

$\sigma (\tilde{b}\overline{\tilde{b}}\to h)/\sigma (gg\to hb\overline{b})$ vs $m_h$ at the Tevatron and the LHC, using MRST2001 LO parton distribution functions [43], $m_b=4.7\mathrm{GeV}$, and ${\mu }_F$ ($={\mu }_R$) determined from the end of the collinear plateau in Fig. 2 (listed in Table ).

Figure 4

Feynman diagram for $Q\overline{Q}\to Z$ ($Q=c,b$). The presence of heavy quarks in the final state is implied by the initial-state heavy quarks.

Figure 5

Feynman diagrams for $q\overline{q}\to ZQ\overline{Q}$, where the $Z$ couples to the light quarks.

Figure 6

Feynman diagrams for $qQ\to ZqQ$, where the $Z$ couples to the light quarks

Figure 7

Factorization-scale dependence of $b\overline{b}\to Z$ at LO, NLO, and NNLO at the Tevatron and the LHC. Only processes in which the $Z$ couples to the heavy quarks are included. Also shown is $gg\to Zb\overline{b}$ at LO, using $m_b=4.7\mathrm{GeV}$. We use the LO, NLO, and NNLO parton distribution functions MRST2001 LO [43] and MRST2002 [35].

Figure 8

Same as Fig. 7, but for $c\overline{c}\to Z$. For $gg\to Zc\overline{c}$, we use $m_c=1.4\mathrm{GeV}$.