2004/12/27 by Ricardo D. Matheus, Stephan Narison · 1 citation
Physics and Astronomy · #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #Quantum and Classical Electrodynamics #hep-ex #hep-lat #hep-ph #nucl-th
paper · pdf · doi:10.1016/j.nuclphysbps.2005.08.045
published as Nucl.Phys.Proc.Suppl.152:236-241,2006 · Latex file 6 pages, 5 ps.figures. Contribution to the QCD 04 International Conference (Montpellier-5-9th July 2004) and to HEP-MAD 04 International Conference (Antananarivo 27th Sept-2nd Oct. 2004). To appear in Nucl. Phys. B (Proc. Suppl.) and in SLAC Econf. on-line Proceedings. Comments and References added
arxiv created 2004/12/27 · openalex publication_date 2006/02/01 · arxiv updated 2010/05/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We rewiew and scrutinize the existing mass determinations of the pentaquarks from the exponential Laplace Sum Rules (LSR). We do not find any sum rule window for extracting optimal and reliable results from the LSR, due to the unusual slow convergence of the OPE and to the exceptional important role of the QCD continuum into the spectral function in this channel. Instead, we use in this channel,for the first time, Finite Energy Sum Rules (FESR), which exhibit a nice stability in the QCD continuum threshold tc, at which one can extract, with a good accuracy, the mass of the lowest resonance. Including the D=7, 9 condensate contributions in the OPE, we obtain MTheta=(1513+- 114) MeV, and the corresponding residue lambdaTheta2= -(0.14-- 0.49)x 10-9 GeV12, which favours the I=0, J=1/2, and negative parity S-wave interpretation of the Theta (1540). However, our analysis indicates a degeneracy between the unmixed I=0 and I=1 S-wave states. In the I=0, J=1/2, P-wave channel, we obtain, for the P-resonance, MP = (1.99+- 0.19) GeV and lambdaP= -(0.7--7.1)x 10-9 GeV14, which we expect to be discovered experimentally. Our results also suggest that some intuitive choices of the continuum threshold used in the LSR literature are inconsistent with the FESR results. Finally, a study of the Theta-K-N coupling using a vertex sum rule shows that, for the I=0, S-wave channel, the leading OPE contributions only start to order alphas2 in the chiral limit ms=0, indicating that the Theta is very narrow.