Study of the dependence of the top-quark mass measurement on event kinematics

We present the first data study of possible kinematic biases in the measurement of the top-quark mass based on the invariant mass of its decay products. The analysis uses a sample of $\text{t}\bar{\text{t}}$ candidate events with one electron or muon and at least four jets in the final state, collected by CMS in $\text{pp}$ collisions at $\sqrt{s}=7~\text{TeV}$ at the LHC. A total of 5174 candidate events is selected from data corresponding to an integrated luminosity of $5.0~\text{fb}^{-1}$. For each event the mass is reconstructed from a kinematic fit of the decay products to a $\text{t}\bar{\text{t}}$ hypothesis. The top-quark mass is determined simultaneously with the jet energy scale, constrained by the known mass of the $\text{W}$ boson in $\text{q}\bar{\text{q}}$ decays, in dependence of each kinematic observable. The effects observed are well reproduced by simulations based on ${\rm M{\small \text{AD}}G{\small \text{RAPH}}}$, ${\rm {\small \text{POWHEG}}}$, and ${\rm {\small \text{MC@NLO}}}$ with tunes including and excluding the effects of colour reconnection.