Hi Stefano, The original issue that we found/fixed is that for fixed order (both LO and NLO) the rapidity distribution were not in agreement with other codes when the two beams had asymmetric energies (i.e. the hadronic cm frame was not the lab frame). Manna Laboni checked that the rapidity dstribution was actually plotted in the hadronic cm frame and not the lab frame. And she proposed one additional boost before the plotting function to fix the issue. Rikkert point out that one likely needs to implement a similar fix for aMC@(N)LO. We still need to double check that case but one can guess that it will suffer the same issue. Now when looking at how one can implement the boost for aMC@NLO. I realised that the rapidity of a frame was also used in those three functions and for the third a clear warning was set that it should be the same rapidity as the one used to boost the event. So what I mean by "corrected" is to modify the rapidity shift in "put_on_MC_mshell_in" to be consistent with the additional boost used to write the events. The situation for the two other function seems less clear to me. They also use a shift in rapidity but computed in a different way (via ybst_til_tocm rather than via ybst_til_tolab variable). So my question for you, is how can we check that those three functions are working correctly in presence of assymetric beams? (for the LHC, nothing will change actually) to be sure that the rapidity shift used in those function are fully consistent? Thanks, Olivier > On 24 Feb 2022, at 15:45, Stefano Frixione