Title: Invariant Mass Distribution of Jet Pairs Produced in Association with a W Boson in Proton-Antiproton Collisions at sqrt{s}=1.96 TeV


We present a study of the invariant mass distribution of jet pairs produced in association with a W boson using data collected with the CDF detector which correspond to an integrated luminosity of 4.3 fb^{-1}. The observed distribution has an excess in the 120-160 GeV/c^{2} mass range which is not described by current theoretical predictions within the statistical and systematic uncertainties. In particular we will discuss the properties and the significance of this excess.