Measurements of the ratio of W and Z production and the W boson decay width at CDF.

摘要

We present a new method of measuring the ratio of W and Z production and decay (R) at the CDF experiment. We analyze 307 pb -1 of proton-antiproton collisions at the Fermilab Tevatron center-of-mass energy of 1.96 TeV.;A single sample containing both W and Z boson candidates is selected by requiring at least one high-energy electron in an event with low hadronic activity. We estimate that less than one percent of our sample is made up of background events after a cut on the recoil energy. A maximum likelihood fit is performed on the missing transverse energy spectrum of the events to determine the relative rates of W and Z production in the common sample. This ratio is defined as: R=sW ˙Br&parl0;W→ℓn&parr0; sZ˙BrZ→ ℓℓ= sWsZ GW→ ℓnG W1 BrZ→ℓℓ .;We have obtained the first result using this method for the electron channel. R=10.55+0.09stat +/-0.12syst We then extract the Branching Ratio of W → ℓnu using the Branching Ratio of Z → ℓ+ℓ - measured at LEP and a theoretical value for the ratio of the cross sections. BrW→ℓn =R˙sZ sWBr Z→ℓ+ℓ- =0.1054+/-0.0016 .;We also obtain an indirect measurement of the W width of GtotW = 2148 +/- 32 MeV. This width gives us information about all the possible decays of the W boson. The W width also constrains the sum of the CKM elements involved in W decays. We find the following value for Vcs, the least constrained element: |Vcs| = 1.008 +/- 0.029.