  The magnetic dynamic structure factor of the one-dimensional S = 1/2 chain
system BaCu2(Si0.5Ge0.5)2O7 is studied in a wide range of energy transfers and
temperatures. Contrary to previous erroneous reports [T. Masuda et al., Phys.
Rev. Lett. 93, 077206 (2004)], the scaling properties observed in the range
0.5-25 meV are found to be fully consistent with expectations for a Luttinger
spin liquid. At higher energies, a breakdown of scaling laws is observed and
attributed to lattice effects. The results are complementary to those found in
literature for other S = 1/2-chain compounds, such as KCuF3 and Cu-benzoate.
