What is the Higgs boson?

John Ellis,theoretical physicist, answers the question "What is the Higgs boson?" in preparation for the press conference following the seminar on LHC 2012 results on the Higgs boson search, due on July 4 2012 at CERN. For more details: http://cern.ch/press/PressReleases/Releases2012/PR16.12E.html

[video also available via https://cdsweb.cern.ch/record/1458922]

What is the Higgs?

Since 1964 we've had this idea

proposed by Englert, Brout and Higgs

that empty space is like a medium

and as particles travel through this medium

some of them interact with it,

some of them don't interact with it.

The ones that do interact with this medium,

they acquire masses,

and the ones that pass through it without interacting,

those are massless particles.

Let me give you an analogy:

imagine an infinite field of snow

extending thoughout all of space,

flat, featureless, going in all directions,

maybe the middle of Siberia.

Now imagine that you're trying to cross

this field of snow.

So maybe you're a skier,

and you skim across the top,

that's like a particle that

does not interact with the Higgs field,

it does not sink into the snow, it goes very fast.

That's like a particle with no mass travelling at the speed of light.

But maybe you've only got snow shoes,

in that case you sink into the Higgs snow field,

you've got less speed that the skier,

less that the speed of light.

That's like a particle with mass, because you are

connecting, interacting, with that Higgs snow field.

And then finally if you've just got boots on,

then you you sink deeply into the snow,

you go very very slowly,

and that's like a particle with a big mass.

So, think of this Higgs field as being

like this universal field of snow.

Now, where does the Higgs boson come in?

We all know what snow is made out of, right.

It's made out of snow flakes.

In the same way this universal Higgs snow field,

is made up out of little quanta,

those quanta are like snowflakes, that's what we call the Higgs boson.

The Higgs boson has this job of giving masses

to all the other elementary particles.

If you look at the basic equations

of the Standard Model, as written on my T-shirt,

they're very symmetric, that way in which

all the different particles appear is the same.

At least on the top two lines there is nothing

to distinguish particles that have different masses for example.

But this symmetry has to be broken,

electrons are lighter than muons,

the top quark is much much heavier

than the quarks that make up everyday nuclei.

So, the top two lines, the symmetric lines,

cannot be all there is,

there has to be something to discriminate,

distinguish, between the different types of particle.

And that's the job of the Higgs boson,

that's the job of the two bottom lines.

Depending on how those different types of quark

or the electron and muon,

depending on how they connect to that Higgs field, that Higgs boson,

we believe they get different masses.

The symmetry between these particles is broken.