I don't know where you get 5.9 sigma but that might have been the confidence at the time it was discovered in 2012. Since then the LHC took a lot more data and

I don't know where you get 5.9 sigma but that might have been the confidence at the time it was discovered in 2012. Since then the LHC took a lot more data and the confidence is more like 20 sigma. That said, these days it's harder to find a paper that gives a confidence for discovery, since they are all quoting the signal strength with respect to the standard model prediction. They generally measure this within about 5%, see for example https://arxiv.org/abs/2404.05498 https://arxiv.org/abs/2404.05498