Being away from the scene where the top HEP physicists are discussing does make me a less-than-well-informed source, but it also yields some advantages. No, I am not talking of the blue waters of Elafonisos (see right), of the fish dinners on tables planted on the sand of a beach, or of the siestas "Greek style" which lasts from about three in the afternoon to about 6.30 in the evening.
I am talking instead of the advantage of having time to think, for once. And to have a global look at where high-energy physics is going in the next decade. The crazy schedule that experiments have forced upon themselves in order to produce as many high-quality results as possible in time for ICHEP left all of us little time to think during the last few months, and those in Paris are still immersed in the same turmoil. Let us instead take a step back and observe HEP from a distance.
After the completion of the picture of elementary fermions with the discovery of the top quark and the verification of the existence of the tau neutrino, many of us had great hopes for the future. The Higgs boson was the next target, sure, but most of my colleagues felt that besides that particle fantastic new riches were going to be at arm's reach very quickly, with the soon-to-come Run II of the Tevatron and the LHC coming thereafter.
The line of reasoning is simple: the standard model is an effective theory -of this everybody is certain. It only can be valid at the energy regime at which we are testing particle physics today; it cannot be valid at much higher energies. It does not include gravity (and we all think a honest-to-God theory of everything should do that), it does not "explain" things as we see them, but just allows us to calculate reactions and rates.
Our deeply-rooted Illuminism demands that there be something else in store for us, an apocalypse (I am studying Greek, and so I was reminded recently that "apocalypse" means "revelation")! A revelation of why the masses of fermions are so different from one another, why electroweak symmetry is broken, why neutrinos mix and what causes them to do that. And the place where this something else should reveal itself is... around the corner! It was around the corner ten years ago, it surely is there now!
There was a hint that we did get, just before the last ten years of draught. The observation that neutrinos mixed among themselves was taken as an appetizer of a twelve-entrees dinner to come. Was it true ? So far, not true. After the appetizer, we have been starving. The Tevatron experiments, Belle, Babar, and a host of other apparata have provided a wealth of new knowledge about the inner workings of the standard model, the details of quantum chromodynamics, etcetera. But nothing was found beyond the picture we had drawn, and which we already knew all too well. We are as much in the dark about what exists outside as we were ten years ago. One is reminded of that old sentence, "Consistency requires to be as ignorant as you were a year ago"...
Is it going to be supersymmetry ? Or new generations of matter ? New vector bosons, gravitons, extra dimensions ? Or still more unexpected things ? For many, the hope of a new golden age of particle physics similar to that of the late fifties of last century seemed almost a certainty ten years ago. Is it right to nourish the same enthusiasm today ? Is insisting with that enthusiasm the right thing to do with the large number of students pressing from below to do fundamental physics today ?
We keep repeating to ourselves that the LHC is a discovery machine, and that if something is there, ATLAS and CMS will find it. I cannot object to this reasoning -the LHC is a unbelievable project, the most technologically complex endeavour that humanity has produced. But I do not see why new physics had to hide in the corner of phase space where the Tevatron and the other machines could not reach it yet. The LHC is great, but this does not prove it will discover anything: it is simply a non sequitur!
These ten years have seen us exploring large chunks of the parameter space of dozens of new physics models, in vain. I may be a pessimist, but I have the feeling that the LHC will only repeat the play, at a bigger scale.
I have bet 1000 dollars four years ago that we would not see any hint of Supersymmetry at the LHC. The original bet was targeting 2010 and 10 inverse femtobarns of collisions as the year and conditions for a payoff, one way or the other. Now with the delays of the machine, we are still forced to wait. According to tentative schedules of running and shutdowns at CERN, the 10 inverse femtobarns of analyzed data that we took as the basis of a conclusive deadline to assess the bet are not going to be collected before 2013. But the bet still stands, and alas, I am as convinced as I was four years ago that the next ten years will be the apocalypse of our short-sightedness.
Will I be happy if I eventually cash my bet ? Of course not! If you know the gambling game of Blackjack, you understand that the 1000 bucks were placed as an "insurance bet". But I do not see a ten coming after the ace.