Attribution-NonCommercial-NoDerivatives 4.0 International. ©2012 CERN  for the benefit of the CMS Collaboration. Published by Elsevier B.V. Open access under CC BY-NC-ND licenseExcepto si se señala otra cosa, la licencia del ítem se describe como Attribution-NonCommercial-NoDerivatives 4.0 International. ©2012 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V. Open access under CC BY-NC-ND license