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New particle discovered - probably Higgs Boson

Wednesday, 04 July 2012

A proton-proton collision event in the CMS experiment producing two high-energy photons (red towers). Credit: CERN

The long and complicated journey to detect the Higgs boson, which started with one small step about 25 years ago, might finally have reached its goal. This was reported by LHC particle accelerator scientists today at the European Laboratory for Particle Physics, CERN, near Geneva.

The Higgs boson is the final building block that has been missing from the "Standard Model," which describes the structure of matter in the universe. The Higgs boson combines two forces of nature and shows that they are, in fact, different aspects of a more fundamental force. The particle is also responsible for the existence of mass in the elementary particles.

Weizmann Institute scientists have been prominent participants in this research from its onset. Prof. Giora Mikenberg was for many years head of the research group that searched for the Higgs boson in CERN's OPAL experiment. He was then leader of the ATLAS Muon Project – one of the two experiments that eventually revealed the particle. Prof. Ehud Duchovni heads the Weizmann Institute team that examines other key questions at CERN. Prof. Eilam Gross is currently the ATLAS Higgs physics group convener. In the Weizmann team three scientific "generations" are represented: Mikenberg was Duchovni's supervisor, who was, in turn, Gross's supervisor.

Gross: "This is the biggest day of my life. I have been searching for the Higgs since I was a student in the 1980's. Even after 25 years, it still came as a surprise. No matter what you call it – we are no longer searching for the Higgs but measuring its properties. Though I believed it would be found, I never dreamed it would happen while I was holding a senior position in the global research team."

Most of us experience the world as a diverse and complex place. But the physicists among us are not content with visible reality. They are striving to get to the bottom of that reality and to see whether it is, as they think, based on the absolute simplicity displayed by the early universe. They expect to observe a range of particles that are different "ensembles" of a handful of elementary particles. The scientists are hoping to see a unification of the four fundamental forces of nature that act on these particles (the weak force responsible for radioactivity, electromagnetic force, the strong force responsible for the existence of protons and neutrons, and gravitation).

The first step in the journey to unify the forces was completed with the almost certain discovery of the Higgs particle: The union of two elementary forces – the electromagnetic and weak force, to become the electroweak force.

One aspect of the Higgs boson, named after the Scottish physicist Peter Higgs, manifests itself in the giving of mass to the weak force carriers – the "W" and "Z" particles. (The electromagnetic force carrier, the photon, remains massless.)