QCD Background… and the Resolution Saminder Dhaliwal August 30 th 2005

Resolution!!!! Z -> e- e+ aod’s Herwig and Jimmy Resolution as a function of Energy Resolution as a function of eta Formula: (Reconstructed E – True E) / (0.1)*(sqrt [True E])

Resolution at different Energy’s

RMS and Sigma Full range of E 40GeV < E < 70GeV 50GeV < E < 70GeV 70GeV < E < 150GeV E > 150GeV Entries RMS sigma

Resolution at different eta’s -2.5 < eta < < eta < -1.5

-0.5 < eta < < eta < < eta < -0.5

1.0 < eta < < eta < < eta < 1.0

Resolution at different eta’s 2.0 < eta < < eta < 2.0

RMS (Black) and Sigma (Red) at eta

QCD background Full Production Background mimics Higgs -> TauTau signal  Two tag Jets  One Tau Jet and one electron Tau e- qqqq Higgs Begin by Filtering events to have a background with a Lead jet and Second jet with certain Pt requirements. As well as this we filter for a possible Taujet and electron.

Filter 1Filter 2Filter 3Filter 4 Lead Jet Pt Second Jet Pt eta gap Number of Electrons Filter Off 90 Filters: events generated with each filter

Electron Pt: with and without filter Lead Jet Pt > 30GeV Second Jet Pt > 15GeV eta gap > 3.0 No Filter used

Jet Pt with and without filter Jet 2Jet 1 Jet 3 Jet 4 Black = Filter OFF Green = Hard Filter (ON) Red = Soft Filter (ON)

Jet Eta with and without filter Jet 1Jet 2 Jet 3 Jet 4 Black = Filter OFF Red = Filter ON

Delta Eta Black = Filter OFF Red = Filter ON

Full Production Filter that asks for Lead Jet Pt > 30GeV, Second Jet Pt > 15GeV and eta gap > 3.0 We have at least events with filters generated daily (about 5% of events pass filter). About 40GB/day Expect about 52 electrons of which 4-5 have Pt>20GeV to be generated daily.

Results so far… Identifying electrons  “hasTrack” and Pt > 20GeV  egamma  isEM Minimizing background electrons, (while keeping optimum signal)  Isolation cut (etcone)  E/P restrictions

Identifying Electrons HasTrack  Cluster matched to track by: 1) eta and phi at origin of track are compared to eta and phi of cluster. Need 0.05 agreement in eta, 0.1 in phi and E/P < 4 2) Track extrapolated from cluster to origin, at each compartment deltaEta and deltaPhi are calculated. Required to be 0,025 and 0.05 respectively. Egamma  Differentiates between egamma object and soft electrons  Considers shape of cluster and requires certain energy thresholds

Identifying Electrons isEM  A selection tool that considers the following: ClusterEtaRange, ClusterHadronicLeakage, ClusterMiddleSampling, ClusterFirstSampling, TrackEtaRange,TrackHits A0, TrackMatchAndEoP, TrackTRT (not used now)  Stricter than egamma, looks closer at the shower shape and track to calorimeter tracking.

Identifying electrons: Pt hasTrack and Pt < 20GeV egammaisEM

Identifying electrons: eta hasTrack and Pt < 20GeV egamma isEM

Identifying Electrons No CutshasTrack & Pt > 20 GeV egammaisEM Number of electrons candidates e % of original candidates % % % Number of e- matched to Truth e Fake Rate % % % %

Minimizing Background electrons First Reduction by Etcone < 10GeV Secondly: 1.8 < E/P < 1.4 Cut selection minimizes background whilst keeping signal efficiency as high as possible. etcone cutetcone and E/P cut

Minimizing Background hasTrack & Pt > 20GeV egammaisEM etcone < 10GeV etcone<10GeV& 1.8 < E/P < 1.4 Number of electron candidates % of original candidates % % % % % Number of e- matched to Truth Fake Rate % % % % %