1. The project wants to fill some gaps in the pheno investigation of ALPs signatures at colliders.

2. The first goal is to expand the analysis of the t tbar + MET signature that is mentioned in 1701.05379, for collider-stable ALPs. In your paper there is only a plot of how the missing transverse energy spectrum is modified by the presence of a light ALP in association with ttbar at 13 TeV but there is no translation of this modification into bounds for the coefficients that are listed in table 2 (bottom line). So the initial work could be to fill this gap and expand the analysis. I suggested we start reproducing the plot in Fig. 14 using a suitable UFO and MadGraph and then we start from there to then produce bounds for the coefficients of the linear and non-linear EFT expansions.

3. Then there is the work on the unstable ALPs of 2107.11392. A relevant question to answer in more detail would be how the presence of an off-shell axion might modify the ttbar signature at the LHC and what is the sensitivity at HL-LHC.

4. Finally, once we get from James a PDF set that is modified by the presence of axions, it would be nice to see how the pheno analysis of the ALP-photon and ALP-gluon coupling would be modified.