tokens: This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.000010.SV. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. We are grateful to Antonio Garufi for many discussions and for sharing his infrared polarization images. We thank Sebastian Stammler for insightful discussions on the effect of the CO snowline on dust and for showing us the results of his simulations in advance of publication. We thank the anonymous referee for the helpful comments. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The fits have been carried out on the computing facilities of the Computational Center for Particle and Astrophysics (C2PAP) as part of the approved project “Dust evolution in protoplanetary disks”. M.T. and L.T. are grateful for the experienced support by F. Beaujean (C2PAP). This work was partly supported by the Italian Ministero dell’Istruzione, Università e Ricerca through the grant Progetti Premiali 2012 – iALMA (CUP C52I13000140001).
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