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Simple cesium atoms can they beat the LHC?
:: 10 May, 2009
Can we test some predictions of the theory of superstrings or theories unifying the electroweak force and strong nuclear force without going through the LHC, the observation of cosmic rays or the Planck satellite? Yes, according to a group of researchers at the University of Nevada in Reno.
The cost of the LHC is several billion. Test of physics beyond the standard model requires indeed build giant detectors and to collisionner beams of protons accelerated to speeds approaching that of light. It is the only way to achieve very high energies, when the collisions between the quarks composing the proton. In full operation, 14 TeV will be available to hope to create new particles predicted by models that are extensions of the standard model.
Of these, certain classes of string theories and GUT, the Grand Unification theories combining electroweak force and strong nuclear force, predicting the existence of a fifth force carried by generalizations of bosons of weak interactions vectors of model standard. These interactions are carried by charged W bosons and a neutral Z boson.
Generalizations of the standard model introducing additional bosons that participate in weak interactions between quarks and leptons, and that is why they are called Z 'and W'. Their masses are not known but experiments in accelerators indicate that they should be rather cumbersome to have so far escaped detection. Remarkably, they could be sufficiently light to be produced at LHC.
Andrei Derevianko, a professor at the University of Nevada in Reno, just to beat the LHC in the field of hunting boson Z 'with the help of his colleagues and of measures on atomic transitions of simple atoms of cesium, does requiring no expensive laboratory equipment and bulky. The key to achieve this tour of force: the violation of the equality of the weak interactions ...
Violation of parity in the disintegration of the nucleus of cobalt 60. The electron is emitted preferentially in the opposite direction to the spin of the nucleus. Looking at the image in a mirror, the spin changes direction (it is a pseudovector) and the electron is emitted preferentially in the direction of spin of the nucleus.
Cesium: a laboratory alone
Predicted in 1956 by Tsung-Dao Lee and Cheng Ning Yang, it was observed in 1957 by Chien-Shiung Wu, who unfortunately was overlooked for the award of the Nobel Prize in physics.
The violation of parity is not difficult to understand. When we consider an experiment with her image in a mirror, it should also be so changed in the Universe. It speaks of symmetry P. Otherwise we speak of violation of parity.
In the experiment of Wu, one atom of radioactive cobalt (60 Co) is not disintegrating in the same way, emitting electrons as its kinetic moment is in one way or another, corresponding to its image in a mirror. The type of disintegration is beta, it involves weak interactions.
At the level of atoms, specifically the levels of very fine energy electrons orbiting around nuclei, with the transitions of the emission of photons can also present the phenomenon of violations of the parity. It is this time the influence of quarks of nucleons of the core electrons on the electronic layer.
Quarks exchange indeed Z bosons with these electrons and since the 1980s, we can do experiments on the violation of parity in atomic physics induced by the weak nuclear forces. The cesium atom is particularly appropriate for this kind of experience.
Derevianko and his colleagues were able to exploit the results of more precise experiments with the 55 electrons of the cesium atom. They also and above all made use of new techniques and calculations of the growing power computers to predict the effects of violations of parity even thinner due to the hypothetical boson Z 'introduced by certain classes of GUT theories and superstrings.
Remarkably accurate, the new results do not reveal any violations of the standard model predictions. This result may seem disappointing but it is not completely because researchers now know that the boson Z ', if it exists, must have a mass greater than a new terminal, which the needle in some theoretical directions.
Tags: cesium atoms , LHC , Planck satellite , University of Nevada , ,
