Radiative corrections to Zb{\bar b} production

TL;DR

This work provides the first NLO QCD corrections to p p̄ → Z b b̄ in the massless b-quark limit, implemented in the MCFM Monte Carlo framework to yield IR-safe predictions that include Z decays and experimental cuts. It details the Born, real, and virtual components, employing Catani–Seymour dipole subtraction and full matrix elements to achieve finite results. The study finds large radiative corrections, particularly from gg initial states, which significantly increase the Zbb background in the Higgs search channel ZH at the Tevatron, and it shows notable shape changes in the m_bb distribution. Consequently, the potential Higgs signal in ZH could be more challenging to observe than previously estimated, highlighting the importance of detector effects and data-driven background normalization for accurate assessments.

Abstract

We report on QCD radiative corrections to the process, p\bar{p} to Zb\bar{b} in the approximation in which the b-quark is considered massless. The implementation of this process in the general purpose Monte Carlo program MCFM is discussed in some detail. These results are used to investigate backgrounds to Higgs boson production in the ZH channel. We investigate the Higgs mass range (100 GeV < m_H < 130 GeV) for the Tevatron running at sqrt{s}=2 TeV.

Figures (7)

• Figure 1: Representative diagrams contributing to $Zb{\bar{b}}$ production at lowest order. A complete gauge-invariant set of diagrams is included in the actual calculation.
• Figure 2: Lowest order predictions showing the validity of the zero mass approximation
• Figure 3: The $b \bar{b}$ mass distribution in $b \bar{b}$ + missing energy events with the renormalization and factorization scale $\mu=100{\;\rm GeV}$.
• Figure 4: The $b \bar{b}$ mass distribution in $b \bar{b}$ + missing energy events with the renormalization and factorization scale $\mu=20{\;\rm GeV}$.
• Figure 5: The scale dependence of the $Zb{\bar{b}}$ result at both leading and next-to-leading order, with $94<m_{b{\bar{b}}}<126$ GeV, appropriate for $M_H =110$ GeV with $\Delta=11$ GeV.