Abstract
A first search for same-sign WW production via double-parton scattering is performed based on proton-proton collision data at a center-of-mass energy of 8 TeV using dimuon and electron-muon final states. The search is based on the analysis of data corresponding to an integrated luminosity of 19.7 fb−1. No significant excess of events is observed above the expected single-parton scattering yields. A 95% confidence level upper limit of 0.32 pb is set on the inclusive cross section for same-sign WW production via the double-parton scattering process. This upper limit is used to place a 95% confidence level lower limit of 12.2 mb on the effective double-parton cross section parameter, closely related to the transverse distribution of partons in the proton. This limit on the effective cross section is consistent with previous measurements as well as with Monte Carlo event generator predictions.
Highlights
Background evaluationThe majority of background events originate from processes in which one or both of the leptons, coming from leptonic decays of heavy quarks or in-flight decays of light mesons, pass the event selection criteria
This paper presents the first measurement of the double-parton scattering (DPS) process for same-sign WW events in the dilepton final sta√te using pp collision data collected by the CMS experiment at a center-of-mass energy of s = 8 TeV
These limits are estimated by fitting the shape of the boosted decision trees (BDT) discriminant, using the methodology developed by the ATLAS and CMS collaborations [59]
Summary
Background evaluationThe majority of background events originate from processes in which one or both of the leptons, coming from leptonic decays of heavy quarks or in-flight decays of light mesons, pass the event selection criteria. In the case of the electrons, overlaps of π0 → γγ decays with charged hadrons may contaminate the sample. These lepton candidates are referred to as misidentified leptons. Events containing one prompt and one misidentified lepton, referred to as prompt-misid. Events, mainly come from W+jets production and from semileptonic decays of top quarks. A method based on control samples in the data is used to estimate the contributions of misid.-misid. The lepton misidentification rates are measured using a control sample in the data that is enriched with misidentified leptons, and are parametrized as a function of the lepton pT and η
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