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Has the Higgs come out of Hiding?
On Friday, researchers at the Large Hadron Collider reported data that could be the first sighting of the elusive Higgs boson.
What is the Higgs?
The Higgs boson is a particle whose existence is predicted by is the Higgs Mechanism, a theory proposed by Peter Higgs to explain why particles have mass. Gauge theory, which is the language that describes interactions between elementary particles, contains particles known as gauge bosons that transmit forces such as gravity, light and the nuclear forces. The theory predicts that these particles are massless, in contradiction to experiments that have shown that the W and Z bosons, which transmit the weak nuclear force, do in fact have mass.
Gauge theory must be modified to include a Higgs field if it is to predict massive gauge bosons. The Higgs field interacts with the other fields of the theory in a process known as spontaneous symmetry breaking, which gives mass to the W and Z bosons but leaves the photon massless.
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Fermions, such as quarks, electrons and neutrinos, also obtain mass through an interaction with the Higgs field. This is a different process known as Yukawa coupling.
The Higgs field gives rise to its own massive particle: the Higgs boson. This is the elusive particle that physicists are trying so hard to find, as it would provide strong evidence that this theory of mass generation is correct.
So, have we seen the Higgs?
Scientists have been quick to point out that the new result is not a conclusive sighting of the Higgs boson. You may well ask, how can they not know whether or not they have seen it? The short answer is that hunting the Higgs is not a straightforward process. A longer answer can be found here:
What the researchers at the LHC look for is not the Higgs boson itself, which is created and destroyed almost instantaneously in the depths of the collider, but a slight increase in the number of the particles that the Higgs decays into (mostly pairs of W bosons, Z bosons or photons). The new results report an unusual excess of particle pairs with energies in the range 120 to 145 GeV - the range of energies that pairs produced by Higgs decay are most likely to have.
Previous experiments, DZERO and CDF at the Tevatron Collider in the US also showed slight excesses in this range, although they could not be very confident in their results.
These latest results come from two experiments, ATLAS and CMS, that are operating independently at the Large Hadron Collider (LHC). The fact that two independent groups have reported the same result, and that their findings agree with previous hints of a Higgs sighting, lends weight to the argument that the result could be a genuine glimpse of the Higgs rather than a statistical fluke. However, further investigations need to be carried out to be sure. You can read more about the significance of scientific results and the necessity of repeating experiments on the hub,