What is the evidence for a higgs particle?

[tozhan]

Ive started to hear a lot about this 'higgs' particle recently. Any chance sum1 can explain to me what the particle is/does/comes from etc??

any help would be great.

also what are the implications of its existence??

 

[misogynisticfeminist]

the higgs particle gives mass to other particles and it is selective though, not everything interacts with the higgs. It is now used to explain the huge masses of the weak gauge bosons or just any particle which suddenly has cetain unaccounted mass.

Uhh, to say where the higgs particle comes from is like asking where muons or electrons come from. Its almost like asking how the universe came about. But it you're talking about a certain decay series which has this particle decaying into something and a higgs, then I'm not too sure about that.

I myself don't know what kinda stuff will imply the existence of a higgs, probably of other particles slowing down, implying that they just gained some mass. Perhaps the experts can fill you in on this.

 

[Haelfix]

The Higgs particle is a massive excitation of a presumably scalar field. So it should in principle have decay modes, the likes of which would be detectable.

The reason we think it exists is precisely b/c the Standard Model works in every other experiment to date, and w/o a Higgs particle much of the theory would be glaringly inconsistent.

Most particle theorists feel its guarenteed to exist in some form (not necessarily the minimal theory tho), just like the top quark was.

If its not found in the next two or three set(s) of particle accelerators, all hell breaks loose so to speak and then everyone will be thoroughly confused =)

(Incidentally, in one of the most experimentally profound derivations of the standard model, using partial wave unitarity bounds as a prerequisite as well as minimality, the Higgs *must* exist)

 

[cosmoboy]

read this article
http://www.fnal.gov/pub/inquiring/questions/higgs_boson.html

 

[arivero]

As for evidence, we all hold breath until 2007 or so (except if cosmic ray films do not trap it casually). There has been some deviations at 115 GeV which could fit with a neutral higgs boson, as well as some smaller ones around 69 GeV which could fit with a charged higgs. Charged higgs appear in SUSY breaking, but not with so low energy.

 

[PhysicsFan]

Higgs physics

Brian Greene's most recent book The Fabric of the Cosmos (2004) has extensive coverage of Higgs fields. What I (a non-physicist) grasped about Higgs fields is that two key areas of theoretical interest they address are: differential masses of different types of particles; and unification of different forces of nature.

Higgs fields create barriers to the movement of other kinds of particles, with different types of particles encountering different degrees of resistance. The more resistance a type of particle encounters, the more mass it is said to have. Higgs fields have been analogized to molasses or a bunch of paparazzi photographers. As Greene explains:

"If we liken a particle's mass to a person's fame, then the Higgs ocean is like the paparazzi: those who are unknown pass through the swarming photographers with ease, but famous politicians and movie stars have to push much harder to reach their destination" (p. 263).

Greene also notes that:

"Photons pass completely unhindered through the Higgs ocean and so have no mass at all. If, to the contrary, a particle interacts significantly with the Higgs ocean, it will have a higher mass. The heaviest quark (it's called the top quark), with a mass that's about 350,000 times an electron's, interacts 350,000 times more strongly with the Higgs ocean than does an electron; it has greater difficulty accelerating through the Higgs ocean, and that's why it has a greater mass" (p. 263).

In terms of unifying the different forces, Greene discusses how photons ("messenger particles" of the electromagnetic force) and W and Z particles (particles of the weak nuclear force) were indistinguishable at one point (known as "electroweak unification"), but are now considered to be different, due to the influence of the Higgs field.

Glashow, Salam, and Weinberg "realized that before the Higgs ocean formed, not only did all the force particles have identical masses -- zero -- but the photons and W and Z particles were identical in essentially every other way as well... At high enough temperatures, therefore, temperatures that would vaporize today's Higgs-filled vacuum, there is no distinction between the weak nuclear force and the electromagnetic force... The symmetry between the electromagnetic and weak forces is not apparent today because as the universe cooled, the Higgs ocean formed, and -- this is vital -- photons and W and Z particles interact with the condensed Higgs field differently. Photons zip through the Higgs ocean... and therefore remain massless. W and Z particles... have to slog their way through, acquiring masses that are 86 and 97 times that of a proton, respectively" (excerpts from pp. 264-265).

A common term used to describe this phenomenon is "symmetry breaking."

One of Greene's former professors, Howard Georgi (whose last name, I learned from talking to someone in physics, is pronounced Georg-EYE, not Georgie, as I first thought) spearheaded an idea called "grand unification" that attempted to bring the strong nuclear force into the unification with electromagnetic and weak. According to Greene, grand unification has not yet worked out, but the physicist I talked to seemed fairly optimistic that it might still.

 

[ahrkron]

At some point in the development of the SM, things seemed to work fine, but there was a little problem: the symmetry of the model needed all particles to be massless, in contradiction with everyday life.

However, Peter Higgs (among others) found a way in which such symmetry, although present, could be "broken" to allow particles to show a mass. This "Higgs mechanism" needs the existence of a new field (plus its corresponding particle). Finding the Higgs boson would be a high point in the history of physics, since its existence was deduced from trying to preserve a symmetry of the model (sort of what happened when Pauli recognized that an apparent violation of energy conservation was reason enough to predict a new particle --the neutrino).

In a way, finding the Higgs would show us that local gauge invariance (the symmetry that such particle was invented to preserve) is more than just a "desirable feature" of our models.

Also, if the Higgs boson is discovered, we'll be able to measure its mass and other properties that will help us explore physics beyond the current model.

 

[tozhan]

thanks guys this was all great stuff

 

[nickthrop101]

it gives a reason for why their isn't a disaster as all particle shouldn't ave mass, yet this gives a reason why they do

 

[Vanadium 50]

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