Mon·Aug 25, 2003Monday·August 25, 2003

1. 01*

   Nucleon electromagnetic form factors from lattice QCD

   J. D. Ashley🇦🇺 · D. B. Leinweber🇦🇺 · A. W. Thomas🇦🇺 · R. D. Young🇦🇺

   It is imperative that lattice QCD serve to develop our understanding of hadron structure and, where possible, to guide the interpretation of experimental data. There is now a great deal of effort directed at the calculation of the electroweak form factors of the nucleon, where for example, measurements at Jefferson Laboratory have recently revealed surprising behaviour in the ratio $G_E/G_M$. While, for the present, calculations within the framework of lattice QCD are limited to relatively large quark mass, there has been considerable progress in our understanding of how to extrapolate to the chiral limit. Here we report the results of the application of these techniques to the most recent form factor data from the QCDSF Collaboration. The level of agreement with all of the form factors, for $Q^2$ below 1 GeV${}^2$, is already impressive.

   hep-latEPJA(2004)·47 citations
2. 02*

   ${\Theta }^{+}$ in a chiral constituent quark model and its interpolating fields

   L. Ya. Glozman🇦🇹

   The recently discovered pentaquark ${\Theta }^{+}$ is described within the chiral constituent quark model. Within this picture the flavor-spin interaction between valence quarks inverts the $(1s{)}^4$ and $(1s{)}^3(1p)$ levels of the four-quark subsystem and consequently the lowest-lying pentaquark is a positive parity, I=0, J=1/2 state of the flavor antidecuplet, similar to the soliton model prediction. Contrary to the soliton model, however, the quark picture predicts its spin-orbit partner with $J=3/2$. Different interpolating fields intended for lattice calculations of ${\Theta }^{+}$ are constructed, which have a maximal overlap with this baryon if it is indeed a quark excitation in the 5Q system.

   ↳ hep-phhep-exhep-latnucl-thPLB(2003)·98 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.