What will the LHC discover

The excitement generated by the LHC kick-off last week is still in the air. I'm beginning to realize that soon we will k.n.o.w. Which means that it's the last moment for gambling and wild guessing. Here are my expectations. The probabilities were computed using all currently available data and elaborated Bayesian statistics.

Higgs boson. Probability 80%
Peter Higgs' kid is ugly and problematic, however his big advantage is that he does his job right. Firstly, he knows how to break electroweak symmetry in such a way that the scattering amplitudes of W and Z bosons remain unitary at high energies. Secondly, if he is not much heavier than 100 GeV, he is consistent with stringent precision tests performed by LEP and Tevatron. No one else can achieve both without complicated gymnastics. That's why Higgs is the safest bet.

Non-SM Higgs boson. Probability 50%
The Standard Model uniquely predicts the couplings of the Higgs to all fermions and gauge bosons. From experience, these couplings are very sensitive to new physics in any form.That's why a precise measurement of the Higgs production cross section and all possible decay rates may be far more exciting than the discovery itself.

New Beyond SM Particles. Probability 50%
That's what particle physics is about, isn't it ;-) Almost any extension of the Standard Model that explains electroweak symmetry breaking predicts some particles in the TeV range. So it seems a good bet that we will see some of the junk. The question is if we will be able to make sense of the pattern that will reveal...

Strong Interactions. Probability 20%
Nature has repeated this scenario all over again: interactions between fundamental constituents become strong and new collective degrees of freedom emerge. Condensed matter physicists see it everyday in their laboratories. In particle physics, the theory of quarks and gluons knowns as QCD at low energies undergoes a transition to a confining phase where it is more adequately described by mesons and baryons. It is conceivable that some of the Standard Model particles also emerge in this manner from a TeV scale strongly interacting dynamics. The problem is that we should have already seen the hints of the composite structure in low-energy precision tests, flavor physics and so on, but we see none of that. The reason why the probability for this scenario remains relatively high is our shameful ignorance of strongly interacting dynamics -- we might have easily missed something.

Dark matter. Probability 5%
All hopes lie in numerology: a stable particle with a weak-scale mass and a typical weak annihilation cross-section of order 1 picobarn would have roughly the right thermal abundance to explain the observed dark matter abundance. If this is the right track, the LHC would grab the most important discovery in the history of collider physics. But we know dozens of other plausible scenarios where the dark matter particle is either too heavy or too weakly interacting to be discovered at the LHC.

Little Higgs and friends. Probability 1%
It is a plausible possibility that the Higgs boson is a pseudo-Goldstone boson whose mass is protected from radiative corrections by approximate global symmetries, a sort of mechanism we see at work in the pion sector of QCD. Proof-of-principle models have been constructed: Little Higgs and Gauge-Higgs unification scenarios. But they are all kind of elephants on elephants...

Supersymmetry. Probability 0.1%
Supersymmetry is just behind the corner. After the LHC she will just pick another corner to hide behind. Supersymmetry will of course be seen at the LHC, just like she was seen in all previous hadron colliders. But, once the data are well understood, she will take a leave and come back into hiding where she clearly feels more comfortable. Susy aficionados should not however be worried. The field will flourish as a new, vast and exciting parameter space above 3 TeV will open for exploration. The wealth of new experimental constraints from the LHC, satellite missions, and dark matter detection experiments will make the-allowed-parameter-space plots colorful and sexy.

Dragons. Probability $e^{-S_{dragon}}$
This possibility was recently pointed out by Nima Arkani-Hamed. The laws of quantum mechanics allow anything to happen, albeit the probability may be exponentially suppressed for complicated (large entropy) objects. CERN officials maintain there is no imminent danger since the putative LHC dragons will be microscopic (small dragons have the smallest entropy, hence the largest probability to appear in particle collisions) and anyway they will quickly suffocate in the vacuum of the beam pipe. Some researchers, however, have expressed concerns that the dragons might survive, grow, burn ATLAS, kidnap ALICE and lock her in a tower. A more comprehensive study of the potential risks is underway.

Black Holes. Probability $0.1*e^{-S_{dragon}}$
Although microscopic black holes have smaller entropy than typical dragons, the advantage of the latter is that they are consistent with the established laws of physics, whereas TeV-scale black holes are not. There are many indirect arguments against TeV scale gravity, from precision tests, through flavor physics, to cosmology. Certainly, dragons are a bit safer bet.