118107909
Status of Excited baryons at BES II
The πN system in J/ψ → NNπ is limited to be pure isospin 1/2 due to isospin conservation. This is a big advantage in studying N* → πN from the J/ψ decays, compared with πN and γN experiments which mix isospin 1/2 and 3/2 for πN system. Based on the 58 million J/ψ data collected at the Beijing Electron Positron Collider,J/ψ → pπ−n and other decay channels are analyzed. In the decay J/ψ → pπ−n, three peaks show up very clearly at 1400 MeV/c2, 1500 MeV/c2 and 1670 MeV/c2 in the πN invariant mass spectrum with additional peak around 2030 MeV/c2 which may be caused by a new N* resonance.
120957793
New hadronic states observed at BES II
Abstract.The report includes the new observation of X(1835) in J/ψ→γη′π+π-, the ωφ threshold enhancement in J/ψ→γωφ, the ωω structure in J/ψ→γωω and the broad 1- structure at the low K+K- invariant-mass spectrum in J/ψ→K+K-π0.
115761963
Comment on "Subleading Corrections to Parity Violating Pion Photoproduction"
In a recent preprint, hep-ph/0012253, Zhu et al. calculated a part of the next-to-leading order corrections to parity-violating pion photoproduction (pol)gamma p-> pi^+ n in heavy-baryon chiral perturbation theory. They claim they have found the contribution as large as the leading-order. If correct, the process will not be a clean way to extract the longest range PV pion-nucleon coupling constant h_{\pi NN}^(1), as was asserted in our previous publications (hep-ph/0011230, nucl-th/0011100). In this comment we show that there is no solid evidence to support Zhu et al.'s claim. Moreover, we show that the subleading parity-violating coupling h_V cannot be extracted from observables at the order of interest based on the formalism of effective field theory.
18068604
Photon structure functions from quenched lattice QCD
We calculate the first moment of the photon structure function, {sup {gamma}}={integral}{sub 0}{sup 1}dxF{sub 2}{sup {gamma}}(x,Q{sup 2}), on the quenched lattices with {beta}=6.0 using the formalism developed by the authors recently. In this exploratory study, we take into account only the connected contractions. The result is compared with the experimental data as well as model predictions.