you can watch the xbox briefing here if you missed it earlier, or just want to rewatch the event
watch the gamescom Xbox Briefing live on Tuesday, August 12 at 5 am PDT / 8 am EDT. immediately after the Briefing, there will be live playthroughs of games like Sunset Overdrive, Forza Horizon 2, Halo: The Master Chief Collection and "big surprises".
if you are looking for more of a text-based live blog, @majornelson will be tweeting all week long. thee will also be event updates on Xbox Wire "which will be previewing nearly every Xbox game at the show throughout the week."