When you install Logic Studio and choose to include the GarageBand, Soundtrack Pro, and Jam Pack content, these loops are installed in /Library/Audio/Apple Loops/Apple. There will be a folder there for each collection installed:

• Apple Loops for GarageBand
• Apple Loops for Soundtrack Pro
• iLife Sound Effects
• Jam Pack 1
• Jam Pack Remix Tools
• Jam Pack Rhythm Section
• Jam Pack Symphony Orchestra
• Jam Pack World Music
  

When you install Logic Express 8, the included loop content will be installed in /Library/Audio/Apple Loops/Apple/Apple Loops for GarageBand. You may see additional folders if you have iLife, or if you have installed any additional Jam Packs.

Loops you create in Logic are saved at ~/Library/Audio/Apple Loops/User Loops/ (where "~" represents your home folder). To access these loops:

1. In the Finder, choose Go > Go to Folder from the menu.
2. Type ~/Library/Audio/Apple Loops in the "Go to the folder" field.
3. Press the Go button.

 For information about where loops in previous versions of Logic and GarageBand are stored refer to GarageBand, Logic: Where loops get installed.