Improving estimates of the number of fake leptons and other mis-reconstructed objects in hadron collider events: BoB's your UNCLE. (Previously "The Matrix Method Reloaded")

Abstract

We consider current and alternative approaches to setting limits on new physics signals having backgrounds from misidentified objects; for example jets misidentified as leptons, b-jets or photons. Many ATLAS and CMS analyses have used a heuristic matrix method for estimating the background contribution from such sources. We demonstrate that the matrix method suffers from statistical shortcomings that can adversely affect its ability to set robust limits. A rigorous alternative method is discussed, and is seen to produce fake rate estimates and limits with better qualities, but is found to be too costly to use. Having investigated the nature of the approximations used to derive the matrix method, we propose a third strategy that is seen to marry the speed of the matrix method to the performance and physicality of the more rigorous approach.

v1 :11 pages, 5 figures. v2: title change requested by referee, and other corrections/clarifications found during review. v3: final tweaks suggested during review + move from revtex to jhep style

References in corpus (11)

• Search for direct production of charginos, neutralinos and sleptons in final states with two leptons and missing transverse momentum in pp collisions at sqrt(s) = 8 TeV with the ATLAS detector
• Search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in $\sqrt{s}=$ 8 TeV pp collisions with the ATLAS detector
• Search for direct top-squark pair production in final states with two leptons in pp collisions at sqrt(s)=8TeV with the ATLAS detector
• Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV
• Search for strong production of supersymmetric particles in final states with missing transverse momentum and at least three b-jets at $\sqrt{s}=$ 8 TeV proton-proton collisions with the ATLAS detector
• Search for direct top squark pair production in events with a Z boson, b-jets and missing transverse momentum in sqrt(s)=8 TeV pp collisions with the ATLAS detector
• A search for ttbar resonances in lepton+jets events with highly boosted top quarks collected in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector
• Measurement of the $t\bar{t}$ production cross-section as a function of jet multiplicity and jet transverse momentum in 7 TeV proton-proton collisions with the ATLAS detector
• Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 20 fb${}^{-1}$ of $\sqrt{s}$=8 TeV proton-proton collision data with the ATLAS detector
• Search for microscopic black holes and string balls in final states with leptons and jets with the ATLAS detector at sqrt(s) = 8 TeV
• Limit setting procedures and theoretical uncertainties in Higgs boson searches

Cited by in corpus (7)

• Search for direct production of electroweakinos in final states with one lepton, missing transverse momentum and a Higgs boson decaying into two $b$-jets in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for triboson $W^{\pm }{W}^{\pm }{W}^{\mp }$ production in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector
• Tools for estimating fake/non-prompt lepton backgrounds with the ATLAS detector at the LHC
• Investigating the Quantum Properties of Jets and the Search for a Supersymmetric Top Quark Partner with the ATLAS Detector
• A search for an unexpected asymmetry in the production of $e^{+}{\mu }^{-}$ and $e^{-}{\mu }^{+}$ pairs in proton-proton collisions recorded by the ATLAS detector at $\sqrt{s}=13$ TeV
• Search for charged-lepton flavor violation in the production and decay of top quarks using trilepton final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• Reformulation of a likelihood approach to fake-lepton estimation in the framework of Bayesian inference