Mass calibration of distant SPT galaxy clusters through expanded weak
  lensing follow-up observations with HST, VLT & Gemini-South
  Expanding from previous work we present weak lensing measurements for a total
sample of 30 distant ($z_\mathrm{median}=0.93$) massive galaxy clusters from
the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) Survey, measuring galaxy
shapes in Hubble Space Telescope (HST) Advanced Camera for Surveys images. We
remove cluster members and preferentially select $z\gtrsim 1.4$ background
galaxies via $V-I$ colour, employing deep photometry from VLT/FORS2 and
Gemini-South/GMOS. We apply revised calibrations for the weak lensing shape
measurements and the source redshift distribution to estimate the cluster
masses. In combination with earlier Magellan/Megacam results for
lower-redshifts clusters we infer refined constraints on the scaling relation
between the SZ detection significance and the cluster mass, in particular
regarding its redshift evolution. The mass scale inferred from the weak lensing
data is lower by a factor $0.76^{+0.10}_{-0.14}$ (at our pivot redshift
$z=0.6$) compared to what would be needed to reconcile a flat Planck
$\nu\Lambda$CDM cosmology (in which the sum of the neutrino masses is a free
parameter) with the observed SPT-SZ cluster counts. In order to sensitively
test the level of (dis-)agreement between SPT clusters and Planck, further
expanded weak lensing follow-up samples are needed.
