| We present an analysis of W/Z+gamma events produced in p¯p collisions at the Fermilab Tevatron, with s = 1.8 TeV. Our primary research interest is W/ Z+gamma production with W/Z bosons decaying hadronically, although we also study the properties of W/Z+gamma production with the bosons decaying leptonically. The p¯p → W/Z+gamma process allows us to test the validity of electroweak theory and the gauge couplings for gammaW and gammaZ. In addition, the study is a prelude to a Higgs boson search in similar channels ( p¯p → WH, ZH).;The data are selected using a high transverse momentum photon trigger (photon pt > 23 GeV/c). The final event sample contains two jets (corrected Et > 15 GeV, |eta d| < 2.4), as well as the high pt photon. There are 9605 2 jet + gamma candidates in 90 pb-1 of Run 1b data. The dijet mass spectrum from the data shows no obvious W/Z → 2 jets signal.;The W/Z+gamma production with W/Z → 2 jets is obscured by large QCD backgrounds. Two dominant QCD production processes are 2 jets + gamma and 3 jets with one jet faking a photon. The shape of their resulting dijet mass distribution fits well to an exponential: dNdmjj = A * exp(- b * mjj).;The signal for p¯p → W/ Z+gamma with W/Z → 2 jets has been simulated in detail using Standard Model predictions. The Monte Carlo generator consists of three parts: the parton level calculation based on leading order matrix elements, the parton shower generator HERWIG, and a simulation of the CDF detector. The Standard Model cross section for sigma( p¯p → Wgamma) x BR( W → jj) is 6.35 pb and for sigma( p¯p → Zgamma) x BR( Z → jj) is 6.52 pb. These numbers are calculated with respect to parton level cuts of pt(gamma) > 15 GeV/c with no cuts on the quark momenta. The shape of the dijet mass distribution for the Monte Carlo signal fits well to a double Gaussian: dNdmjj = A * (exp(0.5 * (( mjj - 88.52)/12.12)2) + 0.094 * exp(-0.5 * ((mjj - 97.88)/30.50)2).;The limit on the cross section for p¯p → W/Z+gamma is obtained by comparing the shape of the dijet mass distribution from the data, with the combination of the dijet mass distributions from the QCD background (exponential) and from the Monte Carlo signal (double Gaussian). The 95% confidence limit on the cross section for p¯p → W/Z+gamma, with W/Z → 2 jets, is calculated to be <81 pb, with a most probable fit value of 19+25-19 pb (1sigma error). This is consistent with the production cross section of 12.9 pb predicted from the Standard Model. |
