  The dependence of jet shapes in $t\bar{t}$ events on the $b$-quark mass and
the strong coupling is investigated. To this end, the Pythia Monte Carlo
generator is used to produce samples of $t\bar{t}$ events in $pp$ collisions at
$\sqrt{s} = 7 \ \mathrm{TeV}$, performing a scan over the values for the shower
QCD scale $\Lambda_s$ and the $b$-quark mass $m_b$. The obtained jet shapes are
compared with recently published data from the ATLAS collaboration. From fits
to the light-jet data, the Monte Carlo shower scale is determined, while the
$b$-quark mass is extracted using the $b$-jet shapes. The result for the mass
of the $b$-quark is $m_b = 4.86 ^{+0.49}_{-0.42}\ \mathrm{GeV}$.
