Luis J. Boya. PHOTO: Manuel Castells

Luis J. Boya, Full Professor emeritus of Theoretical Physics at the University of Zaragoza and president of the Academy of Exact, Physical, Chemical and Natural Sciences of Zaragoza, gave a lecture at seminar organized by the group of research 'Science, Reason and Faith' of the University of Navarra. His talk was on"The current status of the standard particle model : Superluminal neutrinos? Traces of the Higgs boson?".

The standard particle model was established around 1975. What is its current status ?

More than 30 years have passed since then and we have no experimental data against model. On the contrary: there are numerous confirmations and it gives very precise experimental results. Nevertheless, it is unsatisfactory from a theoretical point of view because it leaves many questions unanswered.

Many resources are currently being employed to experimentally test the hypothesis of the "Higgs particle", whose existence seems to be about to be confirmed. What implications would this have for modern physics?

I met Peter Higgs in Edinburgh in 1970. He was a relativistic physicist; when he developed the first model (1964), he was actually looking for something else: a way to spontaneously break the gauge symmetry, which is the mathematical formalization that allows the three forces of microphysics to be described quantitatively. His model was perfectly compatible with gauge invariance: if the symmetry is exact, the carrier should have zero mass, but there was clear evidence that the weak interactions were short-range and if they had a carrier, it would be massive. Higgs' model solved this 'mystery', for according to him the first scalar particle - which today bears his surname- plays an intermediate role, and the weak force carriers are made to acquire mass, from agreement with experiments (W and Z mesons).

The first person to use the Higgs mechanism to make a concrete model of weak interactions was Steven Weinberg. In 1967 he proposed a theory that unified the electromagnetic theory with that of weak interactions, taking into account that the latter are short-range. Therefore, scientists have been hoping to find the Higgs particle ever since. It is interesting and satisfying that the latest experiments at CERN are pointing to such a particle subject.

The theory makes reference letter to the visible subject , which makes up only 4% of the universe. What about the dark subject ?

It is worth distinguishing the particle problems - which have their Philosophy, their technique, their quantum mechanism... - from those concerning cosmology and astronomy, for although these also concern the observable world, they constitute another subject domain.

The Higgs particle theory was devised to account for questions of the microcosm: as such, it is essential to explain why the weak interaction is broken even though there is no prediction regarding its mass. Today we have only indirect hints that the mass may be of the order of 124 to 126 GeV (a unit equal to one billion electron volts).

The dark subject is a term created for astronomical and cosmological problems. The total mass of visible galaxies can be calculated by translating the visible light into mass and taking into account the rotational velocity of the galaxy. It is assumed that there is a dark subject which is not observed optically, but gravitationally, indicating a disagreement between the visible subject and the galaxy's heavy mass. This is the phenomenon of the dark subject .

The "Higgs particle" is also called the "God particle". How does it relate to the discussion science-faith?

Lederman, an American physicist, award Nobel, gave it that name purely for marketing purposes. I know of no scientists who have questioned the existence of God because of the existence of the particle. Whether the "Higgs particle" exists or not, science will go one way and theology another. For my part, I maintain the idea that they are separate domains, but both are necessary for a global understanding of the world.