Gauge dependence of chiral condensate and fermion mass by an unquenched model

Based on three-dimensional quantum electrodynamics theory,a set of truncated Dyson-Schwinger（D-S） equations are solved to study photon and fermion propagators with the effect of vacuum polarization.Numerical studies show that condensation and the value of fermion mass depends heavily on how the D-S equations are truncated.By solving a set of coupled D-S equations,it is also found that the fermion propagator shows a clear dependence on the order parameter.The truncated D-S equations under unquenched approximation are used to study the mass-function and chiral condensation of the fermions.The results under the unquenched approximation are clearly different from the ones under quenched approximation.With the increase in the order parameter,the fermion condensation in the unquenched approximation decreases when 0≤ξ5,while it increases when ξ5.However,nothing like this is observed in the quenched approximation,which indicates that there may be flaws in the quenched approximations.

1-27 Unquenched Quark-model Calculation of Excited p Resonances and P-wave  Phase Shifts

In Ref. [1], (770) vector resonance, its radial recurrences, and the corresponding P-wave  phase shifts were investigated in an unquenched quark model with all classes of relevant decay channels included, viz. pseudoscalarpseudoscalar,vector-pseudoscalar, vector-vector, vector-scalar, axialvector-pseudoscalar, and axialvector-vector, totalling26 channels.

Light quarkonium and charmonium mass shifts in an unquenched quark model

The unquenched quark model for the light quarkonium and charmonium states is explored in this study.The quark-pair creation operator in the^(3)P_(0) model,which combines the two-quark and four-quark components,is modified by considering the effects of the created quark pair's energy.Furthermore,the separation between the created quark pair and valence quark pair is modified.All the wave functions,including those for the mesons and the relative motion between two mesons,are obtained by solving the corresponding Schrodinger equation using the Gaussian expansion method.The aim of this study is to find a new set of parameters that can accurately describe the mass spectrum of low-lying light quarkonium and charmonium states.Moreover,certain exotic states,such as X(3872),can be described well in the unquenched quark model.

1-31 Unquenching Weak Substructure

On assuming that weak substructure has a dynamics which is similar to quantum chromodynamics but much stronger, we conclude that unquenching is indispensable for predictions on the spectrum of weak-substructure resonances[1].

Evidence for a new resonance Σ~* (1380) with J^P=1/2^(-*)

A new particle Σ^ ＊ with J ^P = 1/2^-was predicted by unquenched quark models with its mass around the well established Σ ＊ （1385） with J P = 3/2 ＋ .Here we re-examine some old data of the K^-p → Λπ^-π^ ＋ reaction.Firstly we re-fit the data for kaon beam momenta in the range of 1.0 - 1.8 GeV.Secondly we study the reaction at the energies around Λ＊（1520） peak.Both studies show evidence for the existence of Σ＊with J^ P = 1/2^-around 1380 MeV.Higher statistic data on relevant reactions are needed to clarify the situation.

Using Less Oil Despite the unquenchable thirst for oil to fuel nina's fast growing economy,the oil consumption growth rate is dropping

At first glance, the official figures of China's oil consumption in 2005 seem a bit confusing. With a robust economic growth and rising annual oil imports, China made the surprise announcement that its oil consumption growth rate was dropping sharply, from 15.3 percent in 2004 to 2.1 percent in 2005. Earlier, China's Ministry