I am a student coming from the US to spend 2 months at CERN as a User, do I need to apply for a short-stay C-visa?

Third-country nationals not subject to short-stay C visa requirements as tourists must obtain a short-stay C visa for Switzerland when staying at CERN for a total of more than 8 days within the same calendar year and engaging in gainful occupation. Some education/training-related activities could be regarded as “gainful occupation”. This is the case when students take part in a work/production process that creates value for the institute/organization. Whether you require a visa or not will therefore depend on the exact nature of your activities at CERN.