  Molecular line surveys are among the main tools to probe the structure and
physical conditions in protoplanetary disks (PPDs), the birthplace of planets.
The large radial and vertical temperature as well as density gradients in these
PPDs lead to a complex chemical composition, making chemistry an important step
to understand the variety of planetary systems. We aimed to study the chemical
content of the protoplanetary disk surrounding GG Tau A, a well-known triple T
Tauri system. We used NOEMA with the new correlator PolyFix to observe
rotational lines at 2.6 to 4 mm from a few dozen molecules. We analysed the
data with a radiative transfer code to derive molecular densities and the
abundance relative to $^{13}$CO, which we compare to those of the TMC1 cloud
and LkCa15 disk. We report the first detection of CCS in PPDs. We also
marginally detect OCS and find 16 other molecules in the GG Tauri outer disk.
Ten of them had been found previously, while seven others ($^{13}$CN,
N$_2$H$^+$, HNC, DNC, HC$_3$N, CCS, and C$^{34}$S) are new detections in this
disk. The analysis confirms that sulphur chemistry is not yet properly
understood. The D/H ratio, derived from DCO$^{+}$/HCO$^{+}$, DCN/HCN, and
DNC/HNC ratios, points towards a low temperature chemistry. The detection of
the rare species CCS confirms that GG Tau is a good laboratory to study the
protoplanetary disk chemistry, thanks to its large disk size and mass.
