UrQMD calculations of two-pion HBT correlations in central Pb-Pb collisions at sqrt{s_NN}=2.76 TeV, Q. Li, Huzhou Teachers College, P. R. China − Two-pion Hanbury-Brown-Twiss (HBT) correlations for central Pb-Pb collisions at the Large-Hadron-Collider (LHC) energy of sqrt{s_NN}=2.76 TeV are investigated for the first time with the microscopic transport model UrQMD (Ultra-relativistic Quantum Molecular Dynamics).  The transverse momentum dependence of the Pratt-Bertsch HBT radii is extracted from a three dimensional Gaussian fit to the correlator in the longitudinal co-moving system (LCMS).  Qualitative agreement with the ALICE data is obtained, however R_out is over predicted by nearly 50%. The LHC results are also compared to data from the STAR experiment at RHIC.  For both energies we find that the calculated R_O/R_S ratio is always larger than data, indicating that the emission in the UrQMD cascade calculations is less explosive than observed in the data.