Slow relaxation dynamics of clogs in a vibrated granular silo

We thank Luis F. Urrea for technical help and Bul- bul Chakraborty for fruitful discussions. This work was funded by Ministerio de Economia y Competitividad (Spain) through Projects No. FIS2014-57325 and No. FIS2017-84631 MINECO/AEI/FEDER, UE Project. B.G. also thanks Aso- ciacion de Amigos de la Universidad de Navarra for a grant.