  A recent neutrino experiment at Daya Bay gives superior data of the
distribution of the prompt energy. In this paper, the energy distribution
presented in the experiment is simulated by applying a Gaussian-like packet to
the neutrino wave function received by the detector. We find that the wave
packet of neutrinos is expanded during the propagation. As a result, the mixing
angle $\theta_{13}$ is more difficult to be measured than $\theta_{12}$ and
$\theta_{23}$ in long baseline experiments.
  Some other propagation properties, such as the time evaluation of the
survival probability, the neutrino oscillation and the $CP$ violation, are also
studied with the employment of the coherent state method. When the Gaussian
packet width increases, the amplitude of the neutrino oscillation decreases,
whereas the oscillation period increases gradually.
