Hints of an unexpected new particle could be confirmed within days
Unfortunately, this sort of linkbait headline has become typical for Scientific American (which is one of the reasons I haven't subscribed for years). As has already been pointed out in these comments, the Standard Model is already believed to be incomplete by particle physicists, and discovering a new particle in this general energy regime is exactly what everyone has been hoping for for a couple of decades now. Yes, such a new particle is not included in the Standard Model--because there hasn't been any experimental evidence for one. If this discovery pans out, particle physicists will finally be able to start model building again the way it was done when the SM itself was built: based on good experimental data.