Search for rare SM processes in the MET+b-jets signature at CDF

TL;DR

This paper discusses advanced techniques to identify rare Standard Model processes involving MET and b-jets at CDF, improving sensitivity for Higgs and new physics searches by effectively rejecting backgrounds.

Contribution

It introduces data-driven and multivariate methods to suppress backgrounds, enabling more sensitive searches for rare SM processes in the MET+b-jets signature at CDF.

Findings

Successful rejection of QCD multi-jet background.

Evidence for electroweak single top production.

Measurement of top pair production cross-section.

Abstract

The missing transverse energy (MET) plus b-jets signature is very promising for searches for the Higgs boson or new physics. Indeed, MET naturally arises from unidentified particles such as neutrinos, neutralinos, gravitons, etc., and b-quarks are the main decay products of a low mass Higgs boson as well as of several exotic particles. The main challenge is to identify and reject the numerous standard model (SM) backgrounds that mimic this signature. This is especially so for QCD multi-jet production, a large background due to mis-measurement (rather than undetectable particles). We present state-of-the-art data-driven and multivariate techniques to characterize and reject this instrumental background. These techniques make analyses in this signature as sensitive as those using lepton identification and allow probing for rare SM processes. We describe searches for electroweak single top production, a part of the observation of single top by CDF, and for a low mass SM Higgs boson, one of the most sensitive among low mass Higgs searches at CDF. We also present a measurement of the top pair cross-section in this signature, and discuss other analyses and future prospects.