Who's song is this actually?

I was listening to "Turn It Up" by Pixie Lott and I came across songs like Use Somebody and When Love Takes Over. But these songs are performed by Kings Of Leons and David Guetta & Kelly. Then I looked up the album tracklist in Wikipedia and even there these songs were mentioned. So I wanna ask who's songs are these actually? Did any party buy the copyrights or whatever from the original owner?