Azimuthal decorrelation in $t\bar{t}$ production at hadron colliders
  We present a new observable, $\Delta \phi$, an azimuthal angle difference between $t$ and $\bar{t}$ quarks in $t\bar{t}$ pair production, at hadron colliders as an interesting probe of the radiative quantum chromodynamics process as well as a high-order correction in the high-mass regime. This variable also enables good discrimination on some new physics models that may explain the forward-backward charge asymmetry of $t\bar{t}$ production measured at the Tevatron. With a reliable estimation of the dataset obtained up to 2011 at the Tevatron and Large Hadron Collider, we present an opportunity for testing the standard model as well as searching new physics models with the $\Delta \phi$ observable. 
Suyong Choi and Hyun Su Lee
hep-ph hep-ex