  [abridged] We analyzed mid-infrared high-contrast coronagraphic images of the
beta Pictoris system, taking advantage of the NEAR experiment using the
VLT/VISIR instrument. The goal of our analysis is to investigate both the
detection of the planet beta Pictoris b and of the disk features at mid-IR
wavelengths. In addition, by combining several epochs of observation, we expect
to constrain the position of the known clumps and improve our knowledge on the
dynamics of the disk. To evaluate the planet b flux contribution, we extracted
the photometry and compared it to the flux published in the literature. In
addition, we used previous data from T-ReCS and VISIR, to study the evolution
of the position of the southwest clump that was initially observed in the
planetary disk back in 2003. While we did not detect the planet b, we were able
to put constraints on the presence of circumplanetary material, ruling out the
equivalent of a Saturn-like planetary ring around the planet. The disk presents
several noticeable structures, including the known southwest clump. Using a
16-year baseline, sampled with five epochs of observations, we were able to
examine the evolution of the clump: the clump orbits in a Keplerian motion with
an sma of 56.1+-0.4 au. In addition to the known clump, the images clearly show
the presence of a second clump on the northeast side of the disk and fainter
and closer structures that are yet to be confirmed. We found correlations
between the CO clumps detected with ALMA and the mid-IR images. If the
circumplanetary material were located at the Roche radius, the maximum amount
of dust determined from the flux upper limit around beta Pictoris b would
correspond to the mass of an asteroid of 5 km in diameter. Finally, the
Keplerian motion of the southwestern clump is possibly indicative of a
yet-to-be-detected planet or signals the presence of a vortex.
