Constraining QCD multijet background in the $\textit{t}$-channel single-top quark production at $\sqrt{s}=13\ TeV$

TL;DR

This paper presents a data-driven method to constrain the QCD multijet background in the measurement of the t-channel single top quark production cross section at 13 TeV, improving the precision of the Standard Model test.

Contribution

It introduces a novel data-driven technique to better estimate and constrain QCD multijet background in single top measurements at 13 TeV.

Findings

Effective reduction of QCD background uncertainty

Improved accuracy in single top cross section measurement

Method applicable to early LHC data analyses

Abstract

Precision measurement of the cross section for single top production is an important test of the Standard Model (SM). The purity of the collected data in single top events is limited by the understanding of the shape and yield of background contributions. Besides electroweak and $\rm{t\bar{t}}$ processes, QCD multijet events constitute a non-negligible background for the considered signal bq$'\rightarrow$ tq ($\textit{t}$-channel) process. The data-driven technique for constraining QCD contribution, employed in the measurement of the $\textit{t}$-channel single top-quark cross section using the very first LHC proton-proton collisions at $\sqrt{s}=13\ TeV$ with the CMS detector, is described. The dataset corresponds to an integrated luminosity of $\mathcal{L}=42\ pb^{\mathrm{-1}}$.