  The gamma Cygni supernova remnant (SNR) is a middle-aged, Sedov-phase SNR in
the Cygnus region. It is a known source of non-thermal emission at radio,
X-ray, and gamma-ray energies. Very-high energy (VHE, >100 GeV) gamma-ray
emission from gamma Cygni was first detected by the VERITAS observatory and it
has since been observed by other experiments. Observations so far indicate that
there must be a population of non-thermal particles present in the remnant
which produces the observed emission. However, it is not clear what kind of
particles (protons/ions or electrons) are accelerated in the remnant, how
efficient the acceleration is, and up to which energy particles can be
accelerated. Accurate measurements of the VHE gamma-ray spectrum are crucial to
investigate particle acceleration above TeV energies. This presentation will
focus on multi-wavelength observations of the gamma Cygni SNR and their
interpretation. We will present improved measurements of the VHE gamma-ray
emission spectrum of gamma Cygni by the High-Altitude Water Cherenkov (HAWC)
gamma-ray observatory, and use these results as well as measurements from other
instruments to model the underlying particle populations producing this
emission. HAWC's excellent sensitivity at TeV energies and above enables us to
extend spectral measurements to higher energies and better constrain the
maximum acceleration energy.
