Double parton interactions as a background to associated HW production at the Tevatron

TL;DR

The paper addresses the DP W+jets background to associated HW production with H→bb at the Tevatron. It combines Pythia8-based simulation of HW and DP W+jets with realistic detector smearing and b-tagging, quantifying DP as a non-negligible background and demonstrating substantial overlap in kinematics. A set of angular and jet-pT–based variables is proposed and used to train an Artificial Neural Network that significantly suppresses DP relative to HW, improving the signal-to-background ratio by factors up to ~2.7 depending on Higgs mass and chosen signal efficiency. The study provides a practical method to mitigate DP backgrounds in HW searches and informs Higgs analyses that rely on the HW channel.

Abstract

In this paper we study events with W+jets final state, produced in double parton (DP) interactions, as a background to the associated Higgs boson (H) and W production, with H->bbar decay, at the Tevatron. We have found that the event yield from the DP background can be quite sizable, which necessitates a choice of selection criteria to separate the HW and DP production processes. We suggest a set of variables sensitive to the kinematics of DP and HW events. We show that these variables, being used as an input to the artificial neural network, allow one to significantly improve a sensitivity to the Higgs boson production.

Figures (11)

• Figure 1: A possible diagram for $W+b\bar{b}$ production due to DP scattering.
• Figure 2: The differential cross sections in the dijet mass $M_{jj}$ bins for signal $HW$ and background DP events including the jet $p_T$ resolution. On the left plot, dotted and dash-dotted red lines correspond to $HW$ events with $m(H)=115$ and $150$ GeV,respectively, while the full black line shows the total background from all the DP $W$+dijet channels. The right plot shows contributions from main parton scattering subprocesses composing the total DP background.
• Figure 3: The differential cross sections in the dijet mass bins for signal $HW$ and background DP events including the jet $p_T$ resolution and requirement of the two jet $b$-tagging (See also description in the caption to figure \ref{['fig:XS_hw_sm']}).
• Figure 4: The differential cross sections in the dijet mass bins for signal $HW$ and background DP events including the jet $p_T$ resolution and the combined jet $b$-tagging efficiency (see also the main text and the caption to figure \ref{['fig:XS_hw_sm']}).
• Figure 5: The ratio of $HW$ signal to DP background event yields with the combined $b$-tagging (see the main text).