The top quark as a calibration tool at the LHC

Thanks to the large top quark pair production cross section and the relatively low background at the LHC, $t\bar{t}$ events can be used for calibration at ATLAS and CMS. Assuming the Standard Model prediction $BR(t\rightarrow bW)$=1 to be true, the heavy flavour content of $t\bar{t}$ events is well predicted, which allows to calibrate and measure the efficiency of $b$-tagging algorithms directly from the data with a precision of about 5\%. The light ($b$-) jet energy scale can also be extracted from $t\bar{t}$ events at the 1\% level using $W$ (and top) hadronic decays.