  Measurements of charged-particle fragmentation functions of jets produced in
ultra-relativistic nuclear collisions can provide insight into the modification
of parton showers in the hot, dense medium created in the collisions. ATLAS has
measured jets in $\sqrt{s_{NN}} = 2.76$ TeV Pb+Pb collisions at the LHC using a
data set recorded in 2011 with an integrated luminosity of 0.14 nb$^{-1}$. Jets
were reconstructed using the anti-$k_{t}$ algorithm with distance parameter
values $R$ = 0.2, 0.3, and 0.4. Distributions of charged-particle transverse
momentum and longitudinal momentum fraction are reported for seven bins in
collision centrality for $R=0.4$ jets with $p_{{T}}^{\mathrm{jet}}> 100$ GeV.
Commensurate minimum $p_{\mathrm{T}}$ values are used for the other radii.
Ratios of fragment distributions in each centrality bin to those measured in
the most peripheral bin are presented. These ratios show a reduction of
fragment yield in central collisions relative to peripheral collisions at
intermediate $z$ values, $0.04 \lesssim z \lesssim 0.2$ and an enhancement in
fragment yield for $z \lesssim 0.04$. A smaller, less significant enhancement
is observed at large $z$ and large $p_{\mathrm{T}}$ in central collisions.
