Roper resonance and S 11(1535) from lattice QCD

N. Mathur, Y. Chen, S. J. Dong, T. Draper, I. Horváth, F. X. Lee, K. F. Liu, J. B. Zhang

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108 Scopus citations


Using the constrained-curve fitting method and overlap fermions with the lowest pion mass at 180 MeV, we observe that the masses of the first positive and negative parity excited states of the nucleon tend to cross over as the quark masses are taken to the chiral limit. Both results at the physical pion mass agree with the experimental values of the Roper resonance (N1/2+(1440)) and S11 (N1/2-(1535)). This is seen for the first time in a lattice QCD calculation. These results are obtained on a quenched Iwasaki 163×28 lattice with a=0.2 fm. We also extract the ghost η′N states (a quenched artifact) which are shown to decouple from the nucleon interpolation field above mπ∼300 MeV. From the quark mass dependence of these states in the chiral region, we conclude that spontaneously broken chiral symmetry dictates the dynamics of light quarks in the nucleon.

Original languageEnglish
Pages (from-to)137-143
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1-2
StatePublished - Jan 6 2005

Bibliographical note

Funding Information:
This work is partially supported by DOE Grants DE-FG05-84ER40154 and DE-FG02-95ER40907. We wish to thank A. Bernstein, G.E. Brown, L. Glozman, D.O. Riska, and S. Sasaki for useful discussions.

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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