Nucleon and Delta baryons (resonances)

In summary: Friedrich Gauss discovered the nulceon and delta resonances in the early 1800s. The nulceon resonance is a series of excited states of the electron, and the delta resonance is a series of excited states of the proton. The nucleon has six resonances, and the Delta baryon has four resonances. The nucleon resonances arespin and/or isospin excitations of the nucleon. The Delta baryon resonances are spin-excited equivalent in the JP = 3/2- decuplet.
  • #1
CarlB
Science Advisor
Homework Helper
1,239
34
Okay, I decided to start trying to understand the nulceon and delta resonances. Does anyone have suggestions for a good explanation of how these work? How many resonances are there? How are they distinguished? Etc.

Here's the PDG information:

http://pdg.lbl.gov/2006/listings/bxxxcomb.html

I'll add more information as I dredge it up from the web. What I'm really looking for is suggestions on a good reference book.

Okay, here's a good place to get things:
http://www.jlab.org/div_dept/physics_division/events/campaign_blocks_1B.html
In particular, the 6MB 154 page document:
http://www.jlab.org/div_dept/physics_division/talks/Background/Hall_B/Burkert_2004_StAndrews.pdf
 
Last edited:
Physics news on Phys.org
  • #2
CarlB said:
Okay, I decided to start trying to understand the nulceon and delta resonances. Does anyone have suggestions for a good explanation of how these work? How many resonances are there? How are they distinguished? Etc.

Here's the PDG information:

http://pdg.lbl.gov/2006/listings/bxxxcomb.html

I'll add more information as I dredge it up from the web. What I'm really looking for is suggestions on a good reference book.

Okay, here's a good place to get things:
http://www.jlab.org/div_dept/physics_division/events/campaign_blocks_1B.html
In particular, the 6MB 154 page document:
http://www.jlab.org/div_dept/physics_division/talks/Background/Hall_B/Burkert_2004_StAndrews.pdf

That last document you linked to is nice. The nucleon resonances are understood as (someone correct me if I am wrong) spin and/or isospin excitations of the nucleon. The earliest understandings of the Delta were that it could be seen as a composite state of the nucleon and a pion.
 
  • #3
This is a good start you guys have here... good selection of articles too.

The Delta baryons are a spin excitation of the nucleon doublet. Since the nucleon is the non-strange isospin-1/2 group in the JP = 1/2+ octet (ground state), the Delta resonances are the spin-excited equivalent in the JP = 3/2- decuplet. While the nucleon will have two quark spins aligned and one opposite, and hence only two possible flavor states (uud, udd) corresponding to isospin-1/2, the Delta baryons will have all three quark spins aligned. This allows for the isospin to extend to 3/2 for the Delta's, so there are four possible flavor states (uuu, uud, udd, ddd). The bag model gives a good estimate for the masses of the Delta's in relation to the nucleons, and so does the basic vector-gluon exchange model, both with simple expressions.

The Delta baryon has an interesting historical note attached to it. The Delta++ and Delta- were the first baryons to grab attention when theorists were first considering the problem of partons. You see, the problem is that the Pauli Exclusion Principle does not allow for identical Fermionic particles to fall into the same energy state. As quarks are fermions, and they are grouped in three's to form baryons, then there should be no more than two identical in any grouping of three. But the Delta++ has three identical up quarks in it! This meant that, in order to preserve the Pauli Principle in the Delta++ baryon, there needed to be another quantum number or property that distinguished each of the identical quarks from one another. This became the new SU(3) gauge group of "color", which went along with the non-Abelian "colored" vector gluons.

Since the advent of the non-Abelian gauge group of QCD, the masses of the baryons and mesons alike have been much better understood in such frameworks as the MIT bag model and others. The Delta baryons allowed physicists to discover this important element of nature.
 
  • #4
Try this link for a good article, putting together the data more conveniently than the PDG, though it might be a few years out of date:

Baryon resonances and strong QCD
E. Klempt
http://www.arxiv.org/abs/nucl-ex/0203002

Carl
 
Last edited:

1. What are nucleon and delta baryons?

Nucleon and delta baryons are subatomic particles that belong to the baryon family, which includes all particles that are composed of three quarks. Nucleons are the building blocks of atomic nuclei and consist of two up quarks and one down quark, while delta baryons have one up quark and two down quarks.

2. What are resonances in relation to nucleon and delta baryons?

Resonances refer to excited states of nucleon and delta baryons, where the particles are in a higher energy state than their ground state. These resonances can be created by collisions between high-energy particles, and they decay quickly back to their ground state, emitting other particles in the process.

3. How do nucleon and delta baryons contribute to the structure of matter?

Nucleon and delta baryons play a crucial role in the structure of matter, as they are the fundamental particles that make up atomic nuclei. They also interact with other particles, such as electrons, to form atoms, which are the building blocks of all matter in the universe.

4. What are the differences between nucleon and delta baryons?

Although nucleon and delta baryons have similar structures and properties, there are a few key differences between them. Nucleons are more stable and have a longer lifetime compared to delta baryons, which tend to decay quickly due to their higher energy states. Additionally, nucleons have a net electric charge, while delta baryons have a neutral charge.

5. How do scientists study nucleon and delta baryons?

Scientists study nucleon and delta baryons by colliding particles at high energies in particle accelerators, such as the Large Hadron Collider. By analyzing the particles produced in these collisions, scientists can gather information about the properties and behavior of nucleon and delta baryons. They also use theoretical models and simulations to further understand these particles and their interactions.

Back
Top