Postmortem on CDF's Wjj anomaly

CDF's Wjj anomaly was the occasion for the creation of this blog. But its failure to show up at D0 quickly led people to assume it was a mistake. Now via Jester we learn that the postmortem is almost done - papers giving the official analysis are on their way. For now, see this talk - discussion starts around slide 49, a summing up appears on slide 75.

The new austerity

First the LHC tells us that the Higgs has no properties inconsistent with the standard model, and now Planck tells us that it looks like the universe began with the simplest sort of inflation. Is it apt that this conceptual austerity is coming from Europe, as it also struggles with the new economic austerity?

A new hope for orthodoxy?

The plan was, build the LHC, observe beyond-standard-model particles, and then happily figure out the new physics. It could still happen... but for now, the LHC is just saying "Higgs".

Andrew Oh-Willeke has a post summarizing different responses to this situation, especially as it pertains to supersymmetry. For the hardbitten supersymmetry skeptic, it's confirmation of what was suspected all along. For traditional supersymmetry diehards, it's just incremental progress, excluding some more parameter space. And if you're Nima Arkani-Hamed, it means it's time to think about explaining the hierarchy problem anthropically, while retaining supersymmetry for other reasons.

Peter Woit speculates that, if no new particles show up, the future of physics could be a new dogma combining split supersymmetry with anthropic finetuning, according to which the superpartners like gluinos are out there, but at undetectably high energies. As for myself, the Shaposhnikov-Wetterich prediction of the Higgs mass impresses me - perhaps that is the future, and the anthropic Higgs will just be a fad.

Meanwhile, however, it seems that astronomy is yielding so much data, that the phenomenologists will be able to justify their work without too much of a paradigm shift. Early-universe cosmology already provides a formidable constraint on particle models. We have dark matter to account for. The "130 GeV gamma ray line" might be a direct sign of dark matter annihilation.

Now two new papers suggest to me that there is just so much data coming from astrophysics and cosmology, that it can begin to play the role that the LHC was supposed to play - as the main source of new physics data, that constrains the baroque constructions of the phenomenologists. (The LHC also constrains their work, but so long as it shows nothing but standard model, it plays only a negative role.)

First, Archidiacono et al have produced new fits of both "3+1" and "3+2" extensions of the SM's neutrino sector, to a combination of cosmological and more traditional observations. I don't know if it's the first time, but my previous impression had been that, on the one hand, you could constrain neutrino physics using cosmological data, and on the other hand, the "short base-line" observations were yielding a vexed, contradictory set of results. Apparently it's possible to aggregate everything after all.

Second, Hooper and Slatyer claim that the "low-galactic-latitude" emissions from the "Fermi Bubbles" that lie above and below the plane of the Milky Way, require some new physical mechanism, possibly dark matter annihilation. But it's coming at an order of magnitude lower than the 130 GeV line, so it would have to be some other aspect of dark-sector physics that's on display here.

Astrophysical observation has been a factor in particle physics theory for a long time now. But what I'm claiming here, is that there is now so much to explain, that the future dystopia of untested anthropic dogma as the new physics consensus may be averted, because even the builders of anthropic, split-supersymmetric models will want to account for this increasingly complex-looking dark sector.

Perhaps we can say that the two great empirical sources of fundamental new information, bearing on particle physics, are now neutrino physics and dark matter observation - with CMB observation a close third. CMB observation is entirely cosmological; dark matter is originally and mostly a matter of astronomical observation, though we are trying to directly detect it on Earth as well; and in neutrino physics, as we have seen, cosmology and traditional methods are playing an equal role.

There may be other surprises in store. I have a somewhat frivolous blog which toys with particle "numerology" of a sort which "alternative physicists" love, but which the mainstream rejects as coincidence, for its own reasons. Conceivably, patterns in the existing data, such as the particle masses, will yield a new stage of progress in physics, all by themselves. And of course, new particles may yet turn up at the LHC, in its next period of activity, starting two years from now. But my chief claim here is that, even if neither of those things happen, the wealth of data from the universe will be enough to keep theoretical physics an empirical discipline - even its anthropic and supersymmetric "sector".

Note: In a discussion of Hooper and Slatyer's paper, Lubos Motl dubs the two regions of the Fermi Bubbles "polar" and "tropical". "Polar" corresponds to high galactic latitudes, "tropical" to low galactic latitudes. The possible dark matter signal is "tropical" in origin... which fits the original theme of this blog.