Measurement of the helicity fractions of $W$ bosons in $t\bar{t}$ production in dilepton channel at CDF

We present a measurement of the helicity fractions of $W$ bosons in the $t\bar{t}$ candidate events selected from final states where both $W$ bosons are decaying leptonically. The analysis is based on 5 fb$^{-1}$ of data collected by the CDF detector at the Fermilab Tevatron in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV. The helicity fractions are determined by a comparison of the cos$\theta*$ distribution between the momentum of the charged lepton in the $W$ boson rest frame and the $W$ momentum in top-quark rest frame with templates corresponding to left-handed, right-handed and longitudinally polarized fractions exclusively. This is the first measurement of the $W$ boson helicity fractions in the dilepton channel using kinematic reconstruction at CDF.