The HEP theory community is atwitter over a BBC News story LHC results put supersymmetry theory ‘on the spot’ that reports from the Lepton-Photon 2011 conference in Mumbai, where more null results relevant to supersymmetry were reported. According to the story:
Results from the Large Hadron Collider (LHC) have all but killed the simplest version of an enticing theory of sub-atomic physics.
Researchers failed to find evidence of so-called “supersymmetric” particles, which many physicists had hoped would plug holes in the current theory.
Theorists working in the field have told BBC News that they may have to come up with a completely new idea.
Joe Lykken, an organizer of the SUSY11 conference about to start at Fermilab, is getting worried:
“There’s a certain amount of worry that’s creeping into our discussions,” he told BBC News.
The worry is that the basic idea of supersymmetry might be wrong.
“It’s a beautiful idea. It explains dark matter, it explains the Higgs boson, it explains some aspects of cosmology; but that doesn’t mean it’s right.
“It could be that this whole framework has some fundamental flaws and we have to start over again and figure out a new direction,” he said.
On Twitter, there’s Carlo Rovelli gloating here, Matt Strassler (here and here) and Lisa Randall (here) claiming all is not lost. In an exchange here, Strassler notes that he’s fighting to prevent the risk of “no money for your research”. It’s unclear if he’s referring to funding for the LHC experiments or for SUSY theory. There is a real long-term danger to HEP experimental funding once the public realizes that they’re not getting the extra dimensions some have promised them, but the time to fight that risk was the many years during which hype about the LHC was rampant.
Both Strassler and Kane now seem to attach great importance to the point that, in some SUSY variants, gluino mass bounds are lower than the 1 TeV of the most popular models, more like 500 GeV. Kane goes so far as to claim that the gluino will be found, at masses below 1 TeV:
The current limit on gluino masses is not above 500 GeV. Whether the squarks are indeed so heavy is not the issue, the point is that if they are the limits on gluino masses are smaller than is often stated. I and others expect this decay to tops and bottoms is the signature by which gluinos will be found, with masses well below a TeV.
Presumably LHC searches are underway for signatures of gluinos in this mass range in these versions of SUSY. I’d be very curious to hear what the status of those searches is. If they come up negative, will SUSY proponents finally give up? New results relevant to SUSY are appearing rapidly, see the latest from CMS here and here.
For some historical perspective, something I ran across recently was a 1993 New York Times report 315 Physicists Report Failure In Search for Supersymmetry, which described null results from early days of the Tevatron. One very funny thing about the article is that much of its emphasis was on the unwieldy nature of the CDF detector, with its $65 million budget and huge number of 315 physicists.
Update: SUSY11 opens tomorrow with a talk by Murayama that incorporates the BBC News story and describes evidence against superpartners as “impressive, worrisome, but not quite there yet”. No indication of when it will get there. The title of the talk: Why do SUSY in 2011?
Update: Quite interesting reading is Michael Peskin’s summary talk at Lepton Photon. On the topic of this posting, he writes:
Before the start of LHC, I expected early discovery of supersymmetry in the jets+MET signature. Many other theorists also had this belief. But, it was not correct.
and he explains why this was (large amount of fine-tuning required if superpartner masses are even as large as 1 TeV). He also explains possible ways to construct SUSY models that evade current experimental bounds while keeping superpartner masses relevant to the fine-tuning problem from getting much too large.
This week at CERN there’s a workshop on Implications of LHC results for TeV-scale physics, which should have many interesting talks.
Update: Yet another technical talk about the state of SUSY searches that begins by reproducing the BBC story is today’s talk at CERN by John Ellis. Ellis gives an overview of SUSY fits. The regions identified by these (pre-LHC) as the most likely place for SUSY to show up have in many cases now been ruled out. With the latest LHC data, the “most likely” region moves out to higher and higher masses, with less and less of a good fit. Ellis concludes:
LHC data putting pressure on popular models.
It is not time to desperate yet… but maybe it is time for depression already.”