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HK: Physik der Hadronen und Kerne

HK 26: Theory IV

HK 26.4: Vortrag

Mittwoch, 10. März 2004, 11:45–12:00, D

Excited nucleons on the lattice with chirally improved fermions — •Dirk Brömmel¹, Peter Crompton¹, Christof Gattringer¹, Leonid Ya. Glozman², C.B. Lang², Stefan Schaefer³, and Andreas Schäfer¹ — ¹Universität Regensburg — ²Universität Graz — ³University of Colorado at Boulder

We study positive and negative parity nucleons on the lattice using the chirally improved lattice Dirac operator. Our analysis is based on a set of three operators χ_i with the nucleon quantum numbers. We use a variational method to separate ground state and excited states and determine the mixing coefficients for the optimal nucleon operators in terms of the χ_i. We clearly identify the negative parity resonances N(1535) and N(1650) and their masses agree well with experimental data. The mass of the observed excited positive parity state is too high to be interpreted as the Roper state. Our results for the mixing coefficients indicate that chiral symmetry is important for N(1535) and N(1650) states.