Friday’s arXiv posting of the paper by CDF about the multi-muon anomaly they are seeing has already generated three different conjectural explanations of what physics might be responsible for this. Undoubtedly many, many more are on the way.
We also describe model-independent physical implications of this scenario. These include the masses of anomalous and non-anomalous U(1)’s and the generic existence of a new hyperweak force under which leptons and/or quarks could be charged. We propose that such a gauge boson could be responsible for the ghost muon anomaly recently found at the Tevatron’s CDF detector.
If the Giromini et. al. explanation invoking 4 new particles is baroque, it’s hard to know what the right word is for the far more complicated constructions that are described in this paper.
This last paper is also supposed to explain the PAMELA data, and papers with other explanations of this are starting to flood hep-ph.
So far, all the explanations of the anomaly seen by CDF look suspiciously complicated, which may be one reason that many members of CDF are so skeptical about the whole thing that they were unwilling to sign on to the PRD submission. But I’m sure that many more proposals for how to explain the anomaly are being drafted at this very moment, and maybe one of them will be more convincing.
Update: Over at Tommaso Dorigo’s blog there’s a short posting about Giromini et. al., and an exchange with Nima Arkani-Hamed, who claims to have had no inside knowledge of the CDF “lepton jets” when he wrote his paper with Weiner predicting them. He also explains how the exact mechanism discussed in that paper is unlikely to explain the CDF result since their observed rate is too high for this.
Update: New Scientist has the story, emphasizing the possible relation to the work of Arkani-Hamed and Weiner:
So what could it be? As it happens, Weiner and Nima Arkani-Hamed of the Institute for Advanced Study in Princeton, New Jersey, and colleagues have developed a theory of dark matter – the enigmatic stuff thought to make up a large proportion of the universe – to explain recent observations of radiation and anti-particles from the Milky Way.
Their model posits dark matter particles that interact among themselves by exchanging “force-carrying” particles with a mass of about 1 gigaelectronvolts.
The CDF muons appear to have come from the decay of a particle with a mass of about 1 GeV. So could they be a signature of dark matter? “We are trying to figure that out,” says Weiner. “But I would be excited by the CDF data regardless.”
CDF spokesperson Jacobo Konigsberg is quoted as saying:
we haven’t ruled out a mundane explanation for this, and I want to make that very clear
Update: Then there’s Slashdot, where the hypothetical CDF particle is advertised as accounting for the Arkani-Hamed et. al. theory of dark matter.
Update: Another story, at Physics World, which has more from various people at CDF. Again, that Arkani-Hamed/Weiner “predicted a CDF–like signal”, although the problem with the rate being too low is mentioned.
Also Nature, where one learns:
Theorists are already coming up with ideas about what might be producing the excess muons. One possibility is that they stem from the decay of a heavier, yet-to-be-discovered particle — perhaps related to dark matter, an unseen material that is believed to make up some 85% of matter in the Universe.
Another idea from string theory evokes seven-dimensional ‘branes’ — theoretical surfaces that are inhabited by exotic particles manifested as strings. These higher-dimensional branes might be home to force-carrying particles that interact weakly with our three-dimensional world and create a faint, but traceable, signal in the data.
But Adam Falkowski, a theorist at CERN, Europe’s particle accelerator laboratory near Geneva, Switzerland, says that the explanations need some work, and cautions against attempting to force the data to fit into particular theories.