Köln 2004 – wissenschaftliches Programm
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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 χi 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 χi. 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.