W/Z+jets Background Determination in the ATLAS ICHEP SUSY Notes Dan Tovey University of Sheffield 1

ATLAS ICHEP SUSY Notes 2

0-lepton Analysis 3

0-lepton Analysis NO ETmiss cut With ETmiss cut 4

0-lepton Analysis 5

1-lepton Analysis 6

Monte Carlo Samples ALPGEN multi-parton ME MC with CTEQ6L1 LO PDF set 0 – 5 parton samples (0 - 4 parton excl, 5 parton inclusive) MLM matching: ETclus = 20 GeV, ΔRmatch = 0.7 Herwig + Jimmy for PS and UE Wlν and Zll (m(ll) cut) unbiased Zνν : filter requiring at least one Anti-KT(0.4) truth-jet with pT>25 GeV in |η| < 5 Low mass DY for dilepton analysis uses PYTHIA (m(ll) cut) 7

Normalisation Ultimately aim to obtain this where possible with data-aware / driven / validated techniques (see next talk) 1-lepton analysis W+jets: use control region enriched in W+jet events 30 GeV < ETmiss < 50 GeV 40 GeV < mT(l, ν) < 80 GeV Overall normalisation 2.1 ± 1.0 Apply normalisation factor to signal region with assumed 50 % total uncertainty Z+jets backgrounds normalised to cross-section Ditto W/Z+jets in 0-lepton analysis QCD jet estimate normalised in control region with ETmiss cut removed 8

Control Region No mT cut No mT cut No ETmiss cut No ETmiss cut 9

W+jets Normalisation W+jets (0-lepton analysis): normalise to NNLO prediction using FEWZ with MSTW2008 PDF set 10.45 nb k-factor = 1.20 with respect to ALPGEN LO cross-section Expect ~3% uncertainty from PDF and scale choice Luminosity uncertainty 11% 10

Z+jets Normalisation Z+jets: normalise to NNLO prediction using FEWZ with MSTW2008 PDF set Z(νν): 5.82 nb k-factor = 1.28 with respect to ALPGEN LO cross-section Z(ll): 0.79 nb (per channel, m(ll)>60 GeV) Expect ~3% uncertainty from PDF and scale choice Luminosity uncertainty 11% 11