Why is the top quark a "Unique" opportunity to study a raw quark?

[Ludovic]

The wikipedia page on the top quark says that:

The Standard Model determines the top quark’s mean lifetime to be roughly 5×10−25 s. This is about a twentieth of the timescale for strong interactions, and therefore it does not form hadrons, giving physicists a unique opportunity to study a “bare” quark (all other quarks hadronize, meaning that they combine with other quarks to form hadrons and can only be observed as such).

Okay. It’s clear that once they were able to study a top quark in the small amount of time that it exists, they were able to study a “bare” quark. But why can’t the same techniques used to study the top quark in the short time it exists also be used to study the other quarks in that same short time period before they hadronize and therefore also study the other quarks when they are “bare”?

[Karen_Lingel]

I haven’t been a particle physicist for quite some time, but the simple explanation is you cannot study quarks at all until they “do” something. (It’s not like you have a powerful microscope where you can just watch them zip around!) Top quarks decay while they are “bare”, and that decay gives you information. Whereas other types of quarks hadronize first, then decay, so you get “unbare” quark information from that.

[Senegoid]

Studying bare naked quarks sounds skeevy.

[Stranger_On_A_Train]

The top quart has the greatest mass (172.76 ± 0.3 [GeV/c²) of all quarks; hence, it’s effects are more observable, and it s only decay is into a W⁺ boson and a bottom quark, so its effects are statistically distinguisable from other quark decays and interactions.

Stranger

[Chronos]

Those two particles are always called “t” and “b”, but the old names were “truth” and “beauty”, instead of “top” and “bottom”. So (as observed probably by either Feynman or Gell-Mann) particle physicists used to be looking for naked beauty, and now instead look for bare bottoms.

[MikeS]

The techniques physicists use to study particles are pretty ham-handed: we smash stuff together and look at the wreckage. That’s really all that we can do. There’s a lot of work that goes into smashing the stuff together harder, and making sure that we know the properties of all of the wreckage, but we can’t take a video of a particle collision and slow it down or pause it or rewind it or anything like that. We effectively get a picture of “before” and “after” and that’s it.

So the reason that the top quark is unique is that it rarely turns into a jet of hadrons between the “before” and “after” pictures; it decays into a small number of other particles first. All the other quarks live long enough that they hadronize, making a big mess of wreckage that’s harder to understand.

[Stranger_On_A_Train]

@MikeS

The techniques physicists use to study particles are pretty ham-handed: we smash stuff together and look at the wreckage. That’s really all that we can do. There’s a lot of work that goes into smashing the stuff together harder, and making sure that we know the properties of all of the wreckage, but we can’t take a video of a particle collision and slow it down or pause it or rewind it or anything like that. We effectively get a picture of “before” and “after” and that’s it.

The analogy I’ve made that seems to illustrate the difficulty to people is that it is like doing geological analysis of rocks by catapulting the at one another across the Grand Canyon and then taking a series of snapshots of the rare impact, using the color and shape of the debris to try to determine the composition. It is a tedious business of compiling information through many, many collisions to make educated guesses about the type of rock and its structure.

Stranger

[mixdenny]

The top quark is right there on top of the steaming heap, right?

[Peter_Morris]

@Senegoid

Studying bare naked quarks sounds skeevy.

Only the bottoms