It’s official: Mumford & Sons’ sophomore release, “Babel,” has earned the biggest debut of any album this year in the United States. “Babel” sold 600,000 in its first week, according to Nielsen SoundScan, and becomes the rock quartet’s first No. 1 on the Billboard 200 albums chart. It’s also the first No. 1 for Mumford & Sons’ record label, Glassnote Records. Read more.