A question of spin for the new boson

Physicists speaking today at the Moriond conference in La Thuile, Italy, have announced that the new particle discovered at CERN last year is looking more and more like a Higgs boson. However, more analysis is still required before a definitive statement can be made. The keys to a positive identification of the particle are a detailed analysis of its quantum properties and the way that it interacts with other particles. Since the announcement last July, much more data has been analysed, and these properties are becoming clearer.

Take the property of spin. If this particle is a Higgs, its spin must be zero. If its spin is not zero, then it is something different, possibly linked to the way gravity works. All the analysis conducted so far strongly indicate spin-zero, but is not yet able to rule out other possibilities.

"Until we have a clearer picture of the new particle’s interactions with other particles, and can confidently tie down its spin," said CERN Research Director Sergio Bertolucci, "then the particle will remain Higgs-like. Dropping the ‘like’ could come soon, but that will not be the end of the story."

Even then, the work will be far from over.  If the new particle is a Higgs, it could be the Higgs as predicted in the 1960s, which would complete the Standard Model of particle physics, or it could be a more exotic particle that would lead us beyond the Standard Model. The stakes are high. The Standard Model accounts for all the visible matter in the Universe, including the stuff that we are made of, but it does not account for the 96% of the Universe that is invisible to us - the dark universe. Finding out what kind of Higgs it is will require more data to further tie down the particle's interactions with other particles, and that will take several years to resolve.