Published 4 July 2012 by

Particle physics Nobel laureates are prepared to receive the Higgs in Lindau

Five minutes before the morning session we see three Nobel laureates – Tini Veltman, Carlo Rubbia and David Gross – moving around eachother next to the stand, preparing their laptops for the presentations, later displayed on the huge screens of Lindau Auditorium. Rubbia seems angry with the others because they are using his Mac connector. Veltman, however, is very calm, has just removed his dark glasses and is wondering what are those other people doing there, waiting for his turn to open the session, and Gross moves slowly away, while the lights fall on stage.

In a theatrical gesture, Tini pulls out a newspaper from the stand and lifts up, "Ladies and gentlemen, the Higgs has not made its appearance in the newspapers today," in clear reference to the rumors that CERN will announce tomorrow at 9am – at a televised conference which broadcasted through internet to all the corners of the world – the exciting discovery of the Higgs particle. Tini Veltman describing the Standard Model of Particle PhysicsThen, for half an hour, Veltman masterfully exposes the structure and content of the standard model of particle physics, with a look at the historical development of high energy physics accelerators all the way to the current Large Hadron Collider at CERN, which produces the collisions between protons that can lead to the discovery not only of the Higgs, but of the whole electroweak symmetry breaking sector. The audience feels the thrill of living a special moment in the history of particle physics. Veltman nevertheless insists that "the discovery of the Higgs is a disaster, as it closes the door of the standard model," since it completes it. It is true that discovering the Higgs, and nothing but the Higgs, could end the search for the fundamental constituents of matter. Fortunately – Veltman reminds us – we still have to understand the family problem, i.e. why are there three doublets of quarks and leptons, what determines their couplings and masses, and what significance does this have for the evolution of the universe and the cosmological constant? With this Veltman concludes, and a roar of applause filles the room. He looks satisfied.

Shortly after, Rubbia goes up to stage, clearly unhappy to be the salami in a sandwich of theorists, and when the projector gets stuck in his first slide he spits: "I hate these electronic gadgets." The rest of his talk is devoted to discussing neutrino experiments past, present and future, a world unto itself, with many graphs and few details – he does not describe the physics of neutrino oscillations – to end up convinced that there are more than three neutrinos, maybe four – to accommodate the LSND and MiniBooNE experiments – or five or six, who knows? naturally they must be sterile,otherwise you would have seen them in the Z0 boson decay width. Rubbia gives a number of one electron volt for the mass for the fourth neutrino, which might, according to him, be the dark matter in the universe. He then shows the Daya Bay experiments in China, which recently have been able to measure the third mixing angle larger than zero, which opens the door to the possibility of CP violation in the leptonic sector, a complete novelty if confirmed! It seems that at the end he is also pleased with his talk.

Carlo Rubbia surrounded by students after his talk

Gross finally stepped in with a beautiful start because, according to him, the average historical dates, (1900 +1925) / 2 = 1912.5, leads to this very day as the centenary of quantum mechanics. Masterfully managed to convince us that "quantum mechanics is the most successful of all descriptions of nature, since it not only works and makes predictions that are tested reliably with the experiment to the fourteenth decimal place, but it is also difficult to modify without destroying it." Moreover, quantum mechanics works in a spectacular range of energies and distances, from the universe as a whole, down to five orders of magnitude smaller than the atomic nucleus; from the description of elementary particles to semi- and superconducting materials with 10^23 atoms. Its more counterintuitive properties such as entanglement are used to understand from the evaporation of black holes to quantum cryptography, and possibly, in the not too distant future, also quantum computing. Right after this he described the Higgs and the physics beyond the standard model, introducing supersymmetry "as a rotation in a superspace of anticommuting dimensions," a beautiful description, no doubt. He posed himself a rhetorical question "why have we not seen supersymmetric particles yet?" to which he answers "as in the electroweak theory, supersymmetry is broken at low energies", of course. Gross is convinced that a light Higgs, as alleged to have been already discovered at the LHC at CERN, is but the window to a new realm, with a whole zoo of new particles. And what if its not? Well, after all, "supersymmetric models are not beautiful", the real gem is in string theory. Gross has little time to describe it in depth, but I am surprised at his statement that "string theory is not as revolutionary as we thought," since the recently discovered dualities suggest that the different string theories are equivalent to a quantum theory fields without gravity, where space-time appears as an emergent phenomenon. The trouble is that we don’t have the Hamiltonian and we don’t know what symmetries set the dynamics. He thus finishes his talk addressing the students "you are fortunate to be living very exciting times, because we know nothing in physics and all is yet to be discovered". Bravo! There’s nothing like a good injection of optimism.