Measuring the hydrostatic mass bias in galaxy clusters by combining
  Sunyaev-Zel'dovich and CMB lensing data
  The cosmological parameters prefered by the cosmic microwave background (CMB)
primary anisotropies predict many more galaxy clusters than those that have
been detected via the thermal Sunyaev-Zeldovich (tSZ) effect. This tension has
attracted considerable attention since it could be evidence of physics beyond
the simplest $\Lambda$CDM model. However, an accurate and robust calibration of
the mass-observable relation for clusters is necessary for the comparison,
which has been proven difficult to obtain so far. Here, we present new
contraints on the mass-pressure relation by combining tSZ and CMB lensing
measurements about optically-selected clusters. Consequently, our galaxy
cluster sample is independent from the data employed to derive cosmological
constrains. We estimate an average hydrostatic mass bias of $b = 0.26 \pm
0.07$, with no significant mass nor redshift evolution. This value greatly
reduces the tension between the predictions of $\Lambda$CDM and the observed
abundance of tSZ clusters while being in agreement with recent estimations from
tSZ clustering. On the other hand, our value for $b$ is higher than the
predictions from hydro-dynamical simulations. This suggests the existence of
mechanisms driving large departures from hydrostatic equilibrium and that are
not included in state-of-the-art simulations, and/or unaccounted systematic
errors such as biases in the cluster catalogue due to the optical selection.
