Sagrada Familia et al.

I have not reported much from CERN in May because I was away most of the time. Last week I was enjoying my holidays in Barcelona. One of the numerous tourist attractions there is a cool science museum with a planetarium, physics toys, dinosaur skeletons, gaudy fish and octopussies. What kids seemed to like the most, however, was a temporary exhibition of particle physicists in their natural habitat who were attracted to that place by the conference Planck'08. On the photo you can see the exhibits observed by an intrigued American tourist. The physicists are kept behind a provisional fence so that tourists do not feed them (scientists in general require a carefully selected diet of coffee and cookies).

Planck is an annual European meeting centered around model building beyond the Standard Model. It usually gives a fair overview of what's new in the field. A short glance at the program reveals that there is not much. I could often hear this unpleasant sound of an empty barrel being scraped. Nevertheless, there were a few noteworthy talks too. Amusingly, most of the theoretical developments these days happens in the queer corner of particle physics. For more than 30 years particle physics was focused on very well motivated extensions of the Standard Model, which didn't get us very far. The recent trend, prompted by Howard Georgi's joke, is to play with perfectly unmotivated models instead. The hope is that shooting at random will prove, if not more successful, at least more fun. Thus, there's much a do about unparticles and its close relatives - the hidden valley models. A new member of the family proposed by Markus Luty is called quirks. This is an extension of the Standard Model with a hidden sector being a QCD-like confining theory. Unlike the ordinary QCD where some light quarks are much lighter than the QCD scale ~1 GeV, that hidden sector has a small (much less than TeV) confinement scale but heavy (more than TeV) quarks. The resulting phenomenology is weird. In QCD, two quarks flying apart form a string in between them whose energy density soon becomes large enough to pull new quarks out of the vacuum. For quirks this is not the case, so that a string between two quirks does not break and may stretch to macroscopic sizes. Markus is currently investigating the collider signals of his quirky scenario.

Besides that, I would mention Gia Dvali who keeps pushing his huge-number-of-degrees-of-freedom solution to the hierarchy problem, Riccardo Rattazzi who made some progress in understanding of the conformal field theories of the Luty-Okui type, and John Terning who explores the AdS/CFT approach to unparticles and hidden valley. Yet the overall impression is that theorists are regrouping their forces while waiting for the LHC. The real game will begin in a year or so.