  Background: In our recent experiment, $^9$Be+p at 5.67A MeV, the breakup
decay rates to the 3 configurations, $\alpha$+$\alpha$+n, $^8$Be$^*$+n and
$^5$He+$^4$He of $^9$Be, were observed and quantified, in a full kinematics
approach. Unfolding step by step the accessibility to the above configurations,
it will require similar studies at lower and higher energies as well as the
interpretation of the data in a theoretical framework. Purpose: Investigate the
breakup decay rate of $^9$Be+p at 2.72A MeV, where the $\alpha$+$\alpha$+n
configuration is mainly accessible. Compare and interpret data at 2.72A MeV and
5.67A MeV into a 4-body CDCC formalism; Point out and discuss couplings to
continuum. Methods: Our experimental method includes an exclusive breakup
measurement in a full kinematic approach of $^9$Be incident on a proton target
at 2.72A MeV, together with elastic scattering and other reaction channels
measurements under the same experimental conditions. The interpretation of the
data at 2.72A MeV and 5.67A MeV is considered in a 4-body CDCC approach, using
the Transformed Harmonic Oscillator method for the 3-body projectile. Results:
An elastic scattering angular distribution at 2.72A MeV is measured, which
compares very well with CDCC calculations, indicating a strong coupling to
continuum. At the same energy, the measured breakup and total reaction cross
sections present good agreement with the calculated values. Further on, the
elastic scattering and breakup cross section data at 5.67A MeV are found in
very good agreement with the CDCC calculations. The present results support
further our 3-body model for the structure of $^9$Be, validating relevant
radiative reaction rates obtained previously.
