add private T2tt diagonal samples

Notes from Ana:

We have produced three T2tt points on the top corridor, specifically: mStop = 170, 172, 173 GeV with mLSP = 1 GeV (note that the on-shell top mass is set to the default Pythia 171 GeV with natural width).

The 170 point is produced in two ways:

• stop -> chi10 + W + b, i.e. a 3-body decay
• stop -> chi10 + t*, i.e. a 2-body decay via an off-shell top (this one is tagged by "_2bd" in the filenames and in the model tag in the LHEEventInfoProduct)

The current scans use the syntax for 3-body decays due to confusion of how the off-shell top decay should be specified in Pythia 8 at the beginning of the 74X production. Unless there is evidence that this has a significant impact, the same LHE will also be used in 80X. The two versions of the mStop=170 point can be used to understand the effect of how the decay is modeled, since the effect should be most pronounced when the top is barely off-shell. In particular, in the 2-body decay scenario, analyses involving top-tagging could be more sensitive to points very near the diagonal since the invariant mass of the W and b is pushed towards 171 GeV.

The samples (in MiniAODv2) are available on cern eos: /eos/cms/store/group/phys_susy/LHE/private_samples/FSPremix74X/SMS-T2tt/