The Standard Model of particle physics is currently our best description of nature, but it is well known that it cannot be complete. BSM (Beyond the Standard Model) theories often attempt to solve this problem by including new particles—most famously, supersymmetric versions of existing particles. This question will resolve as yes if, by December 31, 2025, a new, BSM particle has been discovered according to broad scientific consensus.
Note: only elementary particles will count for the purposes of this question. E.g. if a new, exotic bound state of quarks is discovered, this will not count as a new, BSM particle, even if theoretical calculations involve modifications of existing theory, in this case QCD; however, if said measurement implies the existence of a BSM particle to a stastically significant degree (5 sigma or better) and there is consensus about the status of this particle, then the question will resolve as yes.
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3.00Grad student in theoretical particle physics here: I'm strongly betting no. The only new stuff we're getting out of the LHC by 2025 is just more data that's more of the same conditions... I don't remember the LHC run schedule for the next few years off the top of my head, but if we haven't gotten enough events to start noticing something in the data by now, I highly doubt we'll get enough events by 2025 to get a 5-sigma discovery.
What would be a much more interesting bet is 1) if the LHC discovers BSM physics by the end of its lifetime in the 2030s, especially after it gets its high luminosity upgrade in 2029 and 2) if the Mu2e experiment at Fermilab is going to find indirect evidence of BSM physics - it's going to be highly, highly sensitive to a lot of BSM physics models while being able to tell us very little about the specific BSM physics it could detect. https://en.wikipedia.org/wiki/Mu2e#:~:text=Mu2e%2C%20or%20the%20Muon%2Dto,a%20number%20of%20theoretical%20models.
@BenGuthrie Definitely good points. I actually worked on some Mu2e stuff as an undergrad and have already created a market for it:
@BenGuthrie What about other experiments? For example experiments aiming for direct detection of dark matter: https://en.wikipedia.org/wiki/Stawell_Underground_Physics_Laboratory