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Why the Higgs boson is important

Real CMS proton-proton collision events in which 4 high energy electrons (green lines and red towers) are observed. The event shows characteristics expected from the decay of a Higgs boson but is also consistent with background Standard Model physics processes. (Image: CERN)

Two recent experiments (ATLAS - A Toroidal Lhc ApparatuS, and CMS - Compact Muon Solenoid) have independently found indications that the Higgs boson may exist (with a mass of about 125 GeV/c2, or roughly 133 times the mass of a hydrogen atom). Although these indications are at about the 2 sigma level of certainty (5 sigma levels are required to claim a discovery), the experimental results suggest that the existence and properties of the Higgs boson should be pinned down during 2012, if all goes well.

Why is finding the Higgs boson so important to the future of high energy physics? The Standard Model (SM) explains the existence of massive particles by the Higgs mechanism, in which a spontaneously broken symmetry associated with a scalar field (the Higgs field) results in the appearance of mass. The quantum of the Higgs field is the Higgs boson. It is the last particle predicted by the SM that has still to be discovered experimentally.

Lisa Randall is the Baird Professor of Theoretical Physics at Harvard University. She has received multiple awards and honorary degrees while pursuing the furthest boundaries of fundamental physics. Randall's most recent book, Knocking on Heaven's Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World, contains a chapter on the Higgs mechanism and boson, and several more on the application and potential of the Large Hadron Collider.

AAAS MemberCentral had the opportunity to talk with Randall about the CERN results and the Higgs boson.

AAASMC: Why is determining the existence (or lack thereof) of the Higgs Boson such an important question that it has attracted the professional efforts of thousands of scientists?
Lisa Randall:
We understand the Standard Model of particle physics that tells us about matter's most basic elements and interactions (as observed so far) extremely well. But, as I describe in Knocking on Heaven's Door, the story of physics has to do with advancing in scales. We know the Standard Model works at the energies we've so far observed--it's been extremely well tested--but we don't know what underlies it. This is particularly acute for the Standard Model because it assumes elementary particles can have masses. But consistency of our theory tells us that those masses can only arise as a consequence of something called the Higgs mechanism.

If particles had masses from the get-go, the predictions for their interactions at high energy would be nonsense.

(Detecting) the Higgs boson would be, first of all, an experimental verification that the Higgs mechanism is correct. It would also tell us something about what underlying theory was responsible for distributing "charge" in the vacuum in the first place.

AAASMC: Assuming the Higgs Boson is confirmed to exist, will this put the Standard Model on a firmer foundation? Will the adjustable parameters of the SM decrease in number or in range?
Lisa Randall:
We will indeed understand the basis for the Standard Model better. We will still be left with questions about particular mass values, for example, but we will know the context in which to try to solve these problems.

AAASMC: If there is no Higgs Boson, is the Standard Model dead? If the Higgs Boson does exist, are we left only with the Standard Model as a viable theoretical framework?
Lisa Randall:
The Higgs boson with the particular properties that are currently assumed is a consequence of one particular implementation of the Higgs mechanism. Other implementations have other experimental evidence. And, until we rule those out, we can't rule out the Higgs mechanism, even if the particular model that predicts a standard Higgs boson is ruled out.

AAASMC: Does the Higgs Boson itself have mass? That is, does it interact with the Higgs field in such a way that it is a massive particle?
Lisa Randall:
It does indeed have mass and it is indeed a consequence of its interactions with the Higgs field. Nice question.

AAASMC: Do we have any idea how Higgs Mechanism mediated mass might couple into (generate) general relativistic space-time curvature?
Lisa Randall:
The same way all other masses do. Once the Higgs mechanism is in place, particles act like they have mass.

AAASMC: What is the difference between the Higgs Field as an omnipresent background field and the classical notion of 'an ether'?
Lisa Randall:
An ether is supposed to be some actual substance. It would pick out a particular reference frame for example (that in which it isn't moving). The Higgs field isn't an actual thing. It is more like a charge. It is a property of empty space--space that is empty of any material matter.

AAASMC: Why was the Higgs Boson nicknamed the 'God' particle?
Lisa Randall:
Leon Lederman named it that in his book. The Higgs mechanism is important, but so are a lot of other aspects of physics, science, and the world. We can leave religion out of it!

More information:

Lisa Randall recently spoke at a recent AAAS Dialogue on Science, Ethics and Religion Program discussion on what science can explain.

At the 2011 Annual Meeting, Lisa Randall presented on the latest thinking on String Theory, Higgs Boson

Representative Image Caption
Real CMS proton-proton collision events in which 4 high energy electrons (green lines and red towers) are observed. The event shows characteristics expected from the decay of a Higgs boson but is also consistent with background Standard Model physics processes. (Image: CERN)
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