TY  - JOUR
AU  - Bali, G.S.
AU  - Collins, S.
AU  - Göckeler, M.
AU  - Horsley, R.
AU  - Nakamura, Y.
AU  - Nobile, A.
AU  - Pleiter, D.
AU  - Rakow, P.E.L.
AU  - Sternbeck, A.
AU  - Schäfer, A.
AU  - Schierholz, G.
AU  - Zanotti, J.M.
TI  - A lattice study of the strangeness content of the nucleon
JO  - Progress in particle and nuclear physics
VL  - 67
SN  - 0146-6410
CY  - Oxford [u.a.]
PB  - Pergamon Press
M1  - PreJuSER-21703
SP  - 467 - 472
PY  - 2012
N1  - This work was supported by the European Union (grant 238353, ITN STRONGnet) and by the DFG SFB/Transregio 55. S.C. is supported by the Claussen-Simon-Foundation (Stifterverband fur die Deutsche Wissenschaft), A.St. by the EU IRG grant 256594 and J.Z. by the Australian Research Council grant FT100100005. Computations were performed on the SFB/TR55 QPACE supercomputers, the BlueGene/P (JuGene) and the Nehalem cluster (JuRoPA) of the JSC (Julich), the IBM BlueGene/L at the EPCC (Edinburgh), the SGI Altix ICE machines at HLRN (Berlin/Hannover) and Regensburg's Athene HPC cluster. The Chroma software suite [24] was used extensively in this work.
AB  - We determine the quark contributions to the nucleon spin Delta s, Delta u and Ad as well as their contributions to the nucleon mass, the a-terms. This is done by computing both, the quark line connected and disconnected contributions to the respective matrix elements, using the non-perturbatively improved Sheikholeslami-Wohlert Wilson Fermionic action. We simulate n(F) = 2 mass degenerate sea quarks with a pion mass of about 285 MeV and a lattice spacing a approximate to 0.073 fm. The renormalization of the matrix elements involves mixing between contributions from different quark flavours. The pion-nucleon a-term is extrapolated to physical quark masses exploiting the sea quark mass dependence of the nucleon mass. We obtain the renormalized value sigma(pi N) = (38 +/- 12) MeV at the physical point and the strangeness fraction f(Ts) = sigma s/m(N) = 0.012(14)(-3)(+10) at our larger than physical sea quark mass. For the strangeness contribution to the nucleon spin we obtain Delta s ((MS)) over bar(root 7.4 GeV) = -0.020(10)(1). (C) 2012 Published by Elsevier B.V.
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000303282200062
DO  - DOI:10.1016/j.ppnp.2012.01.012
UR  - https://juser.fz-juelich.de/record/21703
ER  -