Precision measurements of the W mass:
Precision measurements of MW using leptonic decays were discussed in the talk of Glazov. Can we use rare exclusive hadronic decays of the W for the same purpose? Discussed possibilities were W->3\pi, W->\pi+\gamma, W->D+J/psi. The use of inclusive J/psi trigger makes the third mode attractive. There is a theoretical issue with the 3\pi case if we are talking about few MeV precision (soft gluon exchange between particles). A paper by Mangano and Melia has looked into this A paper by Grossman et al. has revisited the theoretical predictions []. The branching ratio is also important to measure.
Question: can the achievable precision on MW using the J/psi mode be estimated?

Four flavor vs five flavor scheme:
To improve the accuracy of PDFs there are various issues to consider. For example, are the charm distributions inside the proton below the charm mass threshold zero? Can we add the top quark to create a 6-flavor scheme? Tao Han and collaborators have recently proposed suplementing the usual PDFs with top PDFs Mangano has studied this issue and found that the best is sometimes to not add the top quark to the PDFs even at 100 TeV.

When dealing with charm and bottom quarks there are perturbative as well as non-perturbative issues to consider. One thing that was noticed for single top production by the experimentalists is that the 4 flavor scheme gives a better description of the kinematics than the 5 flavor scheme.

Additional information concerning single top production provided by Alison:

Talk by Dominic Hirschbuehl.

Talk by Rikkert Frederix.

There are some plots comparing the 4 and 5 flavour scheme predictions of the fiducial cross section.
e.g. slide 10:
That plots comes from the 8 TeV CONF note (paper in preparation): Figures 8 and 9

Summary plots have a nice (visual but not numerical) comparison of the various 'state of the art' calculations which include
the new NNLO, an NLO+NNLL and a pure NLO calculation as well:

Paper on associated H+top production and talk by Marco Zaro.

Comment: we will organize a discussion on 4-flavor vs 5-flavor scheme next week.

4F versus 5F schemes
(M Ubiali)
For a discussion on the origin of the differences between the 4F and 5F schemes it is useful to look at the talks that were given at the HF@LHC in Durham, see for instance (in order of priority)

Link to some recent papers that analyse 4F versus 5F schemes at the level of inclusive cross section

* Inclusive cross section with two b in initial state (or t at future colliders)
  • Inclusive cross section with one b in the initial state (Wb,single t)

and differential distributions

Heavy flavor and vector boson pT resummation:
Experimentalists notice a difference between CuTe and DYres in their treatment of heavy flavors. These differences affect the extraction of the W mass.
Question: can these differences be probed using higher-order fixed-order programs, to see if it is a resummation artifiact?