Structure of the P(11) (1440 MeV) resonance from alpha p and pi N scattering
2000
10 pages
Published in:
- Phys.Rev.C 61 (2000) 024002
Citations per year
Abstract: (APS)
To understand the various results on the N*(1440MeV) resonance in a consistent way, the data on α−p scattering at Eα=4.2GeV were reanalyzed assuming projectile and target excitation, and their interference. A quantitative fit of the spectrum is obtained, assuming for the N* mass distribution a threshold modified Breit-Wigner shape with momentum-dependent width and resonance parameters M=1390±20MeV and Γ=190±30MeV. This, however, is not consistent with the data on π-N scattering which, in general, require a higher resonance mass and a larger width. Both systems, α-p and π-N, can be described consistently in a T-matrix formalism, assuming two structures in the P11(1440MeV) resonance, from which only the first one is observed in α-p. For this structure the elastic π-N width is small and the decay into the 2π(s)−N channel is large. This strongly supports the conclusions drawn from α-p scattering. The second structure at higher mass has a strong decay into the πΔ channel and can be well understood as a second-order excitation of the Δ(1230MeV). The two resonance picture of the P11(1440MeV) resonance is supported by γ-induced reactions; no evidence is found for the first N*, however, the second resonance is observed (although more or less obscured by nonresonant π-Δ production). A further crucial test of the existence of two structures in the Roper resonance is provided by exclusive α-p experiments; a N* decay pattern should be found quite different from π-N with a very strong 2π decay.- pi nucleus: elastic scattering
- p nucleus: inelastic scattering
- helium
- pi: hadroproduction
- Feynman graph
- N(1440): mass
- energy spectrum: missing-energy
- S-matrix
- partial wave analysis
- N(1440): model
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