# About "baryon resonance"

In the reaction :e,p→e,p,η;
(p,η)is called a "baryon resonance",a state of which is "S11(1535)".

(http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.86.1702)

In Particle Data Group,there is an excited nucleon N(1535).Are they the same?

But how could a (p,η)resonce be called excited baryon?

The notation "S11(1535)" ,S means (p,η) orbital angular momentum,what the two "one"s mean?

## Answers and Replies

mfb
Mentor
arXiv link

The unique large branching fraction of N(1535) to Nη (~40%) in agreement between paper and PDG, the good agreement of the given width and the rough agreement in one quoted amplitude value (page 9) suggest they are the same particle.

But how could a (p,η)resonce be called excited baryon?
Why not? It is a baryon resonance that commonly decays to those particles.

11 look like the other quantum numbers similar to a hydrogen-like atom. I don't see how a bound state of those could work, however - it would not have enough energy to decay in this way, and it should be more long-living.