Associated Production of a Z Boson and a Single Heavy-Quark Jet

TL;DR

The paper provides a comprehensive NLO study of Z boson production in association with a single heavy-quark jet, focusing on the gQ→ZQ channel calculated in the ACOT scheme with mQ=0 and supplemented by LO treatments of qq¯→ZQ¯Q and Zj/gq→Zq to build the inclusive Z+heavy-quark-jet cross section. It details the calculation framework (dipole subtraction), jet definitions, and the handling of multi-jet final states, and it analyzes scale and PDF uncertainties, as well as mistag backgrounds from Zj. The results quantify the relative sizes of Zb and Zc channels at the Tevatron and LHC, assess the impact of fake ZQ from light-jet mistags, and provide cross sections and kinematic distributions to support SM background modeling and potential constraints on heavy-quark PDFs. Overall, the work demonstrates that ZQ production, especially at the LHC, can serve both as a background control tool and as a probe of heavy-quark parton distribution functions relevant to Higgs and new-physics searches.

Abstract

The leading-order process for the production of a Z boson and a heavy-quark jet at hadron colliders is gQ -> ZQ (Q=c,b). We calculate this cross section at next-to-leading order at the Tevatron and the LHC, and compare it with other sources of ZQ events. This process is a background to new physics, and can be used to measure the heavy-quark distribution function.

Figures (9)

• Figure 1: Associated production of a $Z$ boson and a single high-$p_T$ heavy quark ($Q=c,b$).
• Figure 2: Representative Feynman diagrams for $q\bar{q}\to ZQ\overline Q$. The $Z$ boson may be radiated off (a) the initial-state quarks or (b) the final-state quarks.
• Figure 3: Representative Feynman diagrams for $Zj$ production via (a) $gq\to Zq$ and (b) $q\bar{q}\to Zg$.
• Figure 4: Cross section for $gb\to Zb$ at the Tevatron vs. the renormalization scale (solid curves) and factorization scale (dashed curves). The ratio of the cross section at scale $\mu$ to the cross section at scale $\mu=M_Z$ is plotted vs. the ratio of the scales. The next-to-leading-order (NLO) inclusive cross section (bold) is less sensitive to the scales than the leading-order (LO) cross section (regular).
• Figure 5: Same as Fig. \ref{['fig:mudep_tevb']}, but at the LHC.