Here's a quick fix to get Minecraft running on the beta version of OS X 10.11! Minecraft does not work by opening the application by clicking the icon.
1. Go to java.oracle.com, and download Java SE 8 Update 45.
2. Open the terminal on your Mac, and type:
java -d64 -jar /Applications/Minecraft.app/Contents/Resources/Java/Bootstrap.jarMinecraft should now work for you!