Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/59002
 Type: Conference paper Title: Low-lying positive-parity excited states of the nucleon Author: Mahbub, M.Cass, A.Kamleh, W.Lasscock, B.Leinweber, D.Williams, A. Citation: Proceedings of the XXVII International Symposium on Lattice Field Theory (LAT 2009) Publisher: POS Publisher Place: online Issue Date: 2009 ISSN: 1824-8039 Conference Name: International Symposium on Lattice Field Theory (27th : 2009 : Beijing, China) Statement ofResponsibility: M. S. Mahbub, Alan ´O Cais, Waseem Kamleh, B.G. Lasscock, Derek B. Leinweber and Anthony G. Williams Abstract: We present an overview of the correlation-matrix methods developed recently by the CSSM Lattice Collaboration for the isolation of excited states of the nucleon. Of particular interest is the first positive-parity excited-state of the nucleon known as the Roper resonance. Using eigenvectors of the correlation matrix we construct parity and eigenstate projected correlation functions which are analysed using standardized methods. The robust nature of this approach for extracting the eigenstate energies is presented. We report the importance of using a variety of source and sink smearings in achieving this. Ultimately the independence of the eigenstate energies from the interpolator basis is demonstrated. In particular we consider $4\times 4$ correlation matrices built from a variety of interpolators and smearing levels. Using FLIC fermions to access the light quark mass regime, we explore the curvature encountered in the energy of the states as the chiral limit is approached. We report a low-lying Roper state contrasting earlier results using correlation matrices. To the best of our knowledge, this is the first time a low-lying Roper resonance has been found using correlation matrix methods. Finally, we present our results in the context of the Roper results reported by other groups. Rights: All contributions are published in PoS under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. Every author submitting his/her contribution to PoS retains the copyright, and upon submission (s)he applies this license to his/her work. RMID: 0020097174 Appears in Collections: Physics publications

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