nucleon constituents

mathman

I understand that nucleons (protons and neutrons) consist of 3 valence quarks and a sea of other stuff, virtual quark-antiquark pairs and gluons. Question: are the virtual quarks only up and down or may there be heavier quarks?

fzero

All flavors contribute because of [itex]g\leftrightarrow q\bar{q}[/itex] processes. A quick search didn't turn up any sort of canonical reference, but http://cerncourier.com/cws/article/cern/29441 explains some experimental measurements related to the strange component of the proton.

mfb

This pdg review has (predicted) parton distribution functions on page 12. Heavier quarks are suppressed, but they are present.

mathman

I would guess that it is possible that the other heavier quarks may be present, but the experiments might be difficult. Maybe LHC might find something?

Bill_K

Naturally if you hit a proton hard enough, heavy quarks will be produced. I thought your question was, is there a significant percentage of heavy quarks already in the proton. And to answer this, as described in the ref, you want to do low energy experiments with high accuracy.

mathman

My confusion is how do you tell what was there already as compared to what happens when protons collide with something.

mfb

With simulations - you cannot "see" this directly in detectors, you can just compare (statistical) experimental results with the simulated results.