Measurements of the ratio of <italic>W</italic> and <italic>Z</italic> production and the <italic>W</italic> boson decay width at CDF.

Abstract

We present a new method of measuring the ratio of W and Z production and decay (<bold>R</bold>) at the CDF experiment. We analyze 307 pb<super> -1</super> 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: <display-math> <fd> <b>R</b>=sW &dot;Br&parl0;W&rarr;&ell;n&parr0;<de> sZ&dot;BrZ&rarr; &ell;&ell;</fen></de>= sW<de>sZ </de>GW&rarr; &ell;n</fen><de>G W</fen></de>1<de> BrZ&rarr;&ell;&ell;</fen> </de> </fd> </display-math> We have obtained the first result using this method for the electron channel. <display-math> <fd> <b>R</b>=10.55+0.09stat</fen> +/-0.12syst</fen> </fd> </display-math> We then extract the Branching Ratio of <italic>W</italic> &rarr; &ell;nu using the Branching Ratio of <italic>Z</italic> &rarr; &ell;<super>+</super>&ell;<super> -</super> measured at LEP and a theoretical value for the ratio of the cross sections. <display-math> <fd> BrW&rarr;&ell;n</fen> =<b>R</b>&dot;sZ <de>sW</de>Br Z&rarr;&ell;+&ell;-</fen> =0.1054+/-0.0016 </fd> </display-math> 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 <italic>W</italic> boson. The <italic>W</italic> width also constrains the sum of the CKM elements involved in <italic>W</italic> decays. We find the following value for <italic>V_cs</italic>, the least constrained element: |<italic>V_cs</italic>| = 1.008 +/- 0.029.