You can count about 3,000 people for each of the ATLAS and CMS experiments. See respectively here and here for the two collaborations.
The two other LHC collaborations (LHCb and ALICE) are much smaller. Then of course, you may want to include the theorists working on these topics. However, even with them, we are probably still way below 10,000 people.
You can count about 3,000 people for each of the ATLAS and CMS experiments. See respectively here and here for the two collaborations.
The two other LHC collaborations (LHCb and ALICE) are much smaller. Then of course, you may want to include the theorists working on these topics. However, even with them, we are probably still way below 10,000 people.