The study of W γ production at DØ: Anomalous coupling limits and the radiation amplitude zero
Pawloski, Gregory J.
Padley, B. Paul
Doctor of Philosophy
W γ production is analyzed in the electron and muon decay channels with approximately 1 fb –1 of data from pp collisions that were produced at a center-of-mass energy of [special characters omitted] = 1.96 TeV and that were collected by the D∅ detector at the Fermilab Tevatron collider. The inclusive p p → ℓνγ cross section is measured in both channels and is found to be consistent with the Standard Model expectation of 2.08 ± 0.05 PDF pb for events with a photon E T > 11 GeV , Δ R ℓγ > 0.7, and ℓνγ transverse mass greater than 90 GeV . The observed cross section is measured to be 2.05 ± 0.18 stat ± 0.10 sys ± 0.13 lumi pb and 1.72 ± 0.19 stat ± 0.15 sys ± 0.10 lumi pb for the electron and muon channels respectively. The photon E T spectrum is examined for indications of anomalous WW γ couplings. No evidence is found, and the following one-dimensional limits are set at a 95% confidence level: –0.18 The observed charge-signed photon-lepton rapidity difference is consistent with the Standard Model prediction and is indicative of the theoretically expected radiation amplitude zero. The distribution exhibits a bimodal structure which is expected from the destructive interference, with the unimodal hypothesis being ruled out at the 94% confidence level.
Particle physics; Pure sciences; Anomalous coupling; Radiation amplitude; W bosons