The news coming out of CERN in recent weeks has been hard to miss. At first, there was a dripfeed of gossip which turned into a firehose of ‘Higgsteria’. Finally, last Wednesday, CERN announced that it had found a new particle that is “consistent with the long-sought Higgs boson”.
Note the phrasing. CERN has been careful not to claim that the new particle is the Higgs, only that it could be.
But if not the Higgs, what else might it be?
Today, Ian Low at Argonne National Laboratory in Illinois and a couple of buddies comb through the data in an attempt to throw some light on this question. Their conclusion is that the data is consistent with at least two other particles that are not the standard Higgs boson.
Particle identification is not always an easy task. Physicists use a theory known as the Standard Model of particle physics to predict how particles should behave. In 1964, Peter Higgs and others used this theory to predict the existence of the Higgs particle. They said it should be heavy and that it should exist only fleetingly before decaying into various other particles.
In fact, its existence is so fleeting that the only way of spotting the Higgs is to look for the signature of particles that it produces, such as pairs of photons or pairs of other heavy particles called Z bosons.
The trouble is that this signature is not unique, at least not given the amount of data that CERN has so far collected.
Low and co say that given various assumptions about the data, there are several theoretical possibilities. One of these is that the data shows the Higgs boson as predicted by the Standard Model.
But another equally likely option is that the data is evidence of a more exotic theory in which the Higgs boson exists in several different forms. So the new particle might be one of these, examples of these are a generic Higgs doublet or a triplet imposter.
A final option is based on the idea that particles can exist in mixtures. So the new data does not show the Higgs but a mixture of it and some other particle.
Low and co analyse the data and come to the following conclusion. “A generic Higgs doublet and a triplet imposter give equally good ﬁts to the measured event rates.”
In particular, they say that the predicted signatures of the Higgs boson and the triplet imposter are both within one sigma of the measured value. And by one measure, the CERN data even favours the triplet imposter.
However, Low and co are quick to add that the Standard Model prediction is a slightly better fit overall.
The message here is that the data at this stage is far from conclusive and could support the existence of any of these three particles.
So now there is much to do to clarify exactly what it is that CERN has found.
As Low and co point out: “This is only the beginning of a challenging program of “Higgs Identiﬁcation”.
Let the Higgsteria continue.
Ref: Have We Observed the Higgs (Imposter)? arxiv.org/abs/1207.1093