  The effect of event background fluctuations on charged particle jet
reconstruction in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV has been
measured with the ALICE experiment. The main sources of non-statistical
fluctuations are characterized based purely on experimental data with an
unbiased method, as well as by using single high $p_{\rm T}$ particles and
simulated jets embedded into real Pb-Pb events and reconstructed with the
anti-$k_{\rm T}$ jet finder. The influence of a low transverse momentum cut-off
on particles used in the jet reconstruction is quantified by varying the
minimum track $p_{\rm T}$ between 0.15 GeV/$c$ and 2 GeV/$c$. For embedded jets
reconstructed from charged particles with $p_{\rm T} > 0.15$ GeV/$c$, the
uncertainty in the reconstructed jet transverse momentum due to the heavy-ion
background is measured to be 11.3 GeV/$c$ (standard deviation) for the 10% most
central Pb-Pb collisions, slightly larger than the value of 11.0 GeV/$c$
measured using the unbiased method. For a higher particle transverse momentum
threshold of 2 GeV/$c$, which will generate a stronger bias towards hard
fragmentation in the jet finding process, the standard deviation of the
fluctuations in the reconstructed jet transverse momentum is reduced to 4.8-5.0
GeV/$c$ for the 10% most central events. A non-Gaussian tail of the momentum
uncertainty is observed and its impact on the reconstructed jet spectrum is
evaluated for varying particle momentum thresholds, by folding the measured
fluctuations with steeply falling spectra.
