Physics Today seems to have decided to deal with Sabine Hossenfelder’s criticism of a future collider by publishing the least credible possible response: a column by Gordon Kane arguing that string theory predicts new particles of just the right mass to be likely beyond the LHC reach, but accessible to a higher-energy proton-proton machine.
In the column, we learn that:
In recent years there has been progress in understanding those [string theory] models. They predict or describe the Higgs boson mass. We can now study the masses that new particles have in such models to get guidance for what colliders to build. The models generically have some observable superpartners with masses between about 1500 GeV and 5000 GeV. The lower third or so of this range will be observable at the upgraded LHC. The full range and beyond can be covered at proposed colliders. The full range might be covered at a proton–proton collider with only two to three times the energy of the LHC. One important lesson from studying such models is that we should not have expected to find superpartners at the LHC with masses below about 1500 GeV.
Kane has a long history with this kind of thing at Physics Today, publishing there back in 1997 much the same sort of argument, in an article entitled String Theory is Testable, Even Supertestable. According to the Kane of 1997, a generic “prediction of string models” was a gluino at around 250 GeV, just beyond the Tevatron limits of the time. Thirteen years later, Physics Today had him back, publishing an article entitled String theory and the real world. I don’t have the time to do a full search, but, by 2011 after the first LHC results came in, Kane had a string theory prediction of a gluino mass at 600 GeV, or “well below a TeV”.
As better LHC results have come in, each time Kane has issued a new “string theory prediction” that the mass is a bit higher, just about to appear at the next round of LHC results. The last version of this I had seen (see here), was from 2017 and predicted “that gluinos will have masses of about 1.5 TeV”. This is already disconfirmed and out of date, with Kane now telling us “between about 1500 GeV and 5000 GeV.”
For some other evidence of how Kane deals with the problem of having predictions falsified, one can compare the 2000 and 2013 versions of his popular book on SUSY, an exercise I went through here.
At this point, the argument that we need a new collider because “string theory predictions” say that it will see gluinos has zero credibility. I don’t know of any other theorist besides Kane who believes such a thing. That Physics Today is publishing this is just mystifying. Perhaps a collider skeptic there has come up with this as a clever way to back the Hossenfelder side of the argument.
There are some other odd things in the piece, one that stuck out for me was this bizarre claim about recent history:
We now know that if Fermilab and the US Department of Energy had taken the Higgs physics more seriously, the Tevatron would have discovered the Higgs boson years before the Large Hadron Collider did.
I see Will Kinney has more about this on Twitter.