LHC discovers the proton’s big “ego”

[n2doc]

The TOTEM experiment at the LHC has just confirmed that, at high energy, protons behave as if they were becoming larger. In more technical terms, their total cross-section—a parameter linked to the proton-proton interaction probability—increases with energy. This phenomenon, expected from previous measurements performed at much lower energy, has now been confirmed for the first time at the LHC’s unprecedented energy.

A composite particle like the proton is a complex system that in no way resembles a static Lego construction: sub-components move inside and interactions keep the whole thing together, but in a very dynamic way. This partly explains why even the very common proton can still be hiding secrets about its nature, decades after its discovery.

One way of studying the inner properties of protons is to observe how they interact with each other, which, in technical terms, implies calculating the total cross-section of the proton-proton interactions. Early measurements at the CERN ISR surprisingly showed that the cross-section increases when the energy increases. This was then confirmed by the CERN SppS Collider and the Tevatron. But this is the first time that the trend has been confirmed at the highest energy, that of the LHC.

“TOTEM’s result of (98 ± 3) mbarn for the total cross-section confirms that, even at the so far unexplored energy of the LHC, the proton behaves as if it were becoming larger,” says Karsten Eggert, spokesperson of the TOTEM collaboration.
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http://www.rdmag.com/News/2011/09/General-Science-Physics-LHC-discovers-the-protons-big-ego/

[ChairmanAgnostic]

1. my god, it's like Sarah!

The closer she gets to a similar particle (say, Michelle) the bigger and bigger her ego gets, and the more bizarre it (she?) acts!

[Permanut]

3. Wrong...

You're not thinking of the proton, you're thinking of the moron.

[ChairmanAgnostic]

5. Damn. You are correct.

[Warpy]

2. Add energy, the component parts vibrate faster

giving the appearance of larger size, perhaps?

Those old science text drawings of a round proton being orbited by a much smaller round electron in a perfectly circular orbit for hydrogen were so incredibly inadequate to explain what's really going on there.

[DetlefK]

4. They don't get bigger, they get more reactive. And here's why:

The "cross-section" of a particle does not refer to its size (although it's measured in the same unit as area), but to its reactivity.

The phenomenon described above is known as "running coupling-constant".

For example:
The proton is covered by an electric field, composed of photons. Each photon can split up into a virtual electron-positron-pair. Those pairs arrange as dipoles and those dipoles provide an additional electric field, shielding the proton and weakening its outside interaction. Only at very high energies particles are fast enough to get that close to each other, to penetrate the dipole-hull. And that's why the electromagnetic interaction gets stronger with higher particle-energy.

[Permanut]

6. That's okay as far as it goes...

but the reactivity is also affected by the proximity of any clingon/crouton pairs in the vicinity.

[DetlefK]

7. AFAIK they have a repulsive interaction

Have you ever heard a klingon ordering croutons? Neither have I.

[Permanut]

8. Excellent point...

I forgot that part.