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

TL;DR

This paper investigates inclusive production of a Z boson in association with heavy quarks as a stepping stone to Higgs production with bottom quarks. It contrasts four-flavor and five-flavor formalisms for Higgs+bb production, arguing that the five-flavor bb->h approach better handles collinear logarithms and can be computed to NNLO, while warning about reliability for very heavy Higgs. It systematically catalogs contributing processes to Z+heavy-quark production, including Z coupling to heavy quarks and processes where the Z couples to light quarks, and quantifies their impact at the Tevatron and LHC. The authors advocate inclusive heavy-quark tagging and provide cross-section estimates (NNLO for bb->Z and cc->Z, plus LO/NLO for other channels), highlighting the scale dependence and the need for higher-order calculations to reduce uncertainties. Overall, the work establishes a framework for using Z+heavy-quark production as a feasibility study and informs strategies for Higgs searches in association with bottom quarks.

Abstract

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 b -> h, and that it is valid for all Higgs masses of interest at both the Fermilab Tevatron and the CERN Large Hadron Collider.

Figures (8)

• Figure 1: $\sigma(\tilde{b}\bar{\tilde{b}}\to h)/\sigma(gg\to hb\bar{b})$ vs. $m_h$ at the Tevatron and the LHC, using MRST2001 LO parton distribution functions Martin:2001es, $m_b=4.7$ GeV, and $\mu_F$ ($=\mu_R$) $=m_h/4$.
• Figure 2: $-t\,d\sigma/dt$ vs. $\sqrt{-t}/m_h$ for $gb\to hb$ at the Tevatron and the LHC. The factorization scale for $b\bar{b}\to h$ should be chosen near the end of the collinear plateau.
• Figure 3: $\sigma(\tilde{b}\bar{\tilde{b}}\to h)/\sigma(gg\to hb\bar{b})$ vs. $m_h$ at the Tevatron and the LHC, using MRST2001 LO parton distribution functions Martin:2001es, $m_b=4.7$ GeV, and $\mu_F$ ($=\mu_R$) determined from the end of the collinear plateau in Fig. \ref{['f:plateau']} (listed in Table \ref{['t:scale']}).
• Figure 4: Feynman diagram for $Q\bar{Q}\to Z$ ($Q=c,b$). The presence of heavy quarks in the final state is implied by the initial-state heavy quarks.
• Figure 5: Feynman diagrams for $q\bar{q}\to ZQ\overline Q$, where the $Z$ couples to the light quarks.