Are new nucleons formed in heavy-ion collisions?

In summary, new nucleons are created in heavy ion collisions at LHC energies, and it is easy to track their decay to baryons and antibaryons.
  • #1
hkyriazi
175
2
The subject heading says it all. In heavy-ion high energy collisions that form a quark gluon plasma (QGP), is it known whether new nucleons are formed from the added energy, or are all of the QGP's quarks ones that existed previously in the colliding heavy ion nuclei? More specifically, are there more nucleons (and not just their component quarks) after the collision--and after the QGP cools--than before? I'd like to know if stable nucleons are formed de novo in such experiments. I'm not familiar with the experimental details.
 
Physics news on Phys.org
  • #2
Yes - many. Central collisions at LHC energies produce thousands of new hadrons. Most of them are pions and kaons but there are also many protons and neutrons (and their antiparticles) and various other particles.
The total number of baryons is conserved, for every new baryon there is also a new antibaryon.
 
  • #3
Thanks, mfb! I'm curious how this is known. Is it assumed that any anti-proton or anti-neutron they see flying away out of such collisions must be new, and therefore the accompanying, ejected protons or neutrons must also be new (due to baryon number conservation)? Or are they able to do actual "housekeeping" on the numbers of nucleons present before and after?
 
  • #4
All protons are the same. You can never point to a proton and say ”that one existed before the collision” or ”this proton is the partner of that antiproton”. There simply is no possible test that could verify this. What you can do is to check the number of protons (and other nucleons) before and after collision.
 
  • Like
Likes hkyriazi
  • #5
Lead ions colliding in the LHC have 82 protons and 126 neutrons each, or combined 164 protons and 252 neutrons.
If you see more than that, then new nucleons were created, and all the antinucleons were created as well of course (where else would they come from?).

ALICE cannot measure particles that fly away close to the incoming beams (because there has to be space for the beams entering and leaving the detector, so counting everything doesn't work, but even the number of particles that hit the detector is much larger already.

This is not limited to heavy ion collisions, by the way. Proton proton collisions can produce new nucleons as well.
 
  • Like
Likes hkyriazi
  • #6
A beautiful meson has rest mass sufficient to produce a pair of a baryon and antibaryon. Indeed, sufficient to produce two pairs.
And the lifetime of a beautiful meson is so long that t*c is 0.5 mm for a charged beautiful meson and 0.45 mm for neutral ones.
If a heavy ion collision is observed to produce, besides a number of antibaryons and baryons of which it is not clear which specific ones existed before, some beautiful mesons which can be tracked to decay to baryons and antibaryons, can you confidently specify that a baryon formed in decay of a beautiful meson did not exist before formation of that beautiful meson?
 
  • #7
snorkack said:
can you confidently specify that a baryon formed in decay of a beautiful meson did not exist before formation of that beautiful meson?
Sure. Even more, the baryons only form when the B mesons decay.

This is easier to observe in proton-proton collisions where there are fewer other particles, but it works with lead-lead collisions as well.
 

1. What are nucleons?

Nucleons are particles found in the nucleus of an atom, including protons and neutrons.

2. How are new nucleons formed in heavy-ion collisions?

In heavy-ion collisions, high energy particles are accelerated and collide with the nuclei of atoms. This can cause nucleons to break apart and recombine, forming new nucleons.

3. Why are heavy-ion collisions used to study the formation of new nucleons?

Heavy-ion collisions provide a controlled environment to study the interactions between particles at high energies. By studying these collisions, scientists can gather information about the formation of new nucleons and the fundamental forces that govern them.

4. What is the significance of studying the formation of new nucleons?

Studying the formation of new nucleons can provide insights into the inner workings of the nucleus and the forces that hold it together. This research can also help us better understand the origins of the universe and the elements that make up matter.

5. How is data collected and analyzed in heavy-ion collision experiments?

Data from heavy-ion collision experiments is collected using specialized detectors that record the particles produced in the collisions. This data is then analyzed using computer simulations and statistical methods to understand the patterns and trends in the formation of new nucleons.

Similar threads

  • High Energy, Nuclear, Particle Physics
Replies
4
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
5
Views
1K
  • High Energy, Nuclear, Particle Physics
Replies
12
Views
3K
  • High Energy, Nuclear, Particle Physics
Replies
3
Views
2K
  • Introductory Physics Homework Help
Replies
1
Views
393
  • High Energy, Nuclear, Particle Physics
Replies
2
Views
9K
  • High Energy, Nuclear, Particle Physics
Replies
6
Views
2K
  • Beyond the Standard Models
Replies
11
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
4
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
7
Views
997
Back
Top