Measurement of the track finding efficiency

This note presents a measurement of the track finding efficiency for long tracks in the 2010 and 2011 data. The efficiency is measured using a tag-and-probe technique with $J/\psi$. decays. The overall efficiency depends on the momentum spectrum of the tracks and the track multiplicy of the event. The efficiency ratio between data and simulation is given in a $p–\eta$. phase space, which can be used by other analyses to correct the simulation and assign a systematic uncertainty. For the momentum spectrum of the $J/\psi$. decay products the overall efficiency ratio is measured to be 99.4 $\pm$ 0.7 % for 2010 data and 100.9 $\pm$ 0.6 % for 2011 data.