Search for Single Production of Vector-like Quarks Coupling to Light Generations in $4.64~ifb$ of Data at $sqrt{s}=7$~TeV

This analysis presents a search for singly-produced vector-like quarks (VLQs) coupling to light quark generations in events with a $W$ or $Z$ boson produced in association with two or more high transverse momentum jets. The vector boson produced in the VLQ decay is reconstructed in the $W\to\ell\nu$ or $Z\to\ell\ell$ modes, where $\ell$ is an electron or a muon. In 4.64~$\ifb$ of data taken in 2011 by the ATLAS experiment at a centre-of-mass energy of 7~TeV, no evidence of VLQs is observed above the expected background. A fit to the distribution of the invariant mass of the system composed of the vector boson and the highest transverse momentum jet is used to set limits on the heavy quark production cross section times branching ratio, and mass bounds are obtained for different couplings. For coupling equal to $v/m_Q$, 95\% CL lower limits on the VLQ mass are determined to be $m_{Q}>1120\gev$ and $m_{Q}>1420\gev$ for VLQs of charge -1/3 and 5/3 in the $W\to\ell\nu$ channel, and $m_{Q}>1080\gev$ for a VLQ of charge 2/3 in the $Z\to\ell\ell$ channel.