14302817
Vector mesons and dense skyrmion matter
Abstract In our continuing effort to understand hadronic matter at high density, we have developed a unified field theoretic formalism for dense skyrmion matter using a single Lagrangian to describe simultaneously both matter and meson fluctuations and studied in-medium properties of hadrons. Dropping the quartic Skyrme term, we incorporate into our previous Lagrangian the vector mesons ρ and ω in a form which is consistent with the symmetries of QCD. The results that we have obtained, reported here, expose a hitherto unsuspected puzzle associated with the role the ω meson plays at short distance. Since the ω meson couples to baryon density, it leads to a pseudo-gap scenario for the chiral symmetry phase transition, which is at variance with standard scenario of QCD at the phase transition. We find that in the presence of the ω mesons, the scale-anomaly dilaton field is prevented from developing a vanishing vacuum expectation value at the chiral restoration, as a consequence of which the in-medium pion decay constant does not vanish. This seems to indicate that the ω degree of freedom obstructs the “vector manifestation” which is considered to be a generic feature of effective field theories matched to QCD.
34315779
Heavy quark symmetry and the Skyrme model.
We present a consistent way of describing heavy baryons containing a heavy quark as bound states of an SU(2) soliton and heavy mesons. The resulting mass formula reveals the heavy quark symmetry explicitly. By extending the model to the orbitally excited states, we establish the generic structure of the heavy baryon spectrum. As anticipated from the heavy quark spin symmetry, the [ital c] factor denoting the hyperfine splitting constant [ital vanishes] and the baryons with the same angular momentum of light degrees of freedom form degenerate doublets. This approach is also applied to the pentaquark exotic baryons, where the conventional [ital c] factor no longer plays the role of the hyperfine constant. After diagonalizing the Hamiltonian of order [ital N][sub [ital c]][sup [minus]1], we get the degenerate doublets, which implies the vanishing of genuine hyperfine splitting.
116131889
Chiral Model Predictions for Strange Form Factors
120803195
Skyrmion and Dense Matter
Skyrme model can provide valuable insights (though qualitative) on high density physics of mesons and baryons in a unified way. First, the dense hadronic matter can be described by the soliton configuration of given meson Lagrangian, which undergoes an interesting chiral phase transition as the baryon density increases. Then, by incorporating the meson fluctuations on top of such ground state we can investigate the in-medium properties of mesons.
119245089
Dense baryonic matter in the hidden local symmetry approach: Half-skyrmions and nucleon mass
Hadron properties in dense medium are treated in a unified way in a skyrmion model constructed with an effective Lagrangian, in which the rho and omega vector mesons are introduced as hidden gauge bosons, valid up to O(p^4) terms in chiral expansion including the homogeneous Wess-Zumino terms. All the low energy constants - apart from f_pi and m_rho - are fixed by the master formula derived from the relation between 5-D hQCD and 4-D HLS. This allows one to pin down the density n_1/2 at which the skyrmions in medium fractionize into half-skyrmions, bringing in a drastic change in the EoS of dense matter. We find that the U(1) field that figures in the CS term in the hQCD action or equivalently the omega field in the hWZ term in the dimensionally reduced HLS action plays a crucial role in the half-skyrmion phase. The importance of the omega degree of freedom may be connected to what happens in the instanton structure of elementary baryon noticed in hQCD. The most striking and intriguing in what is found in the model is that f_pi that smoothly drops with increasing density in the skyrmion phase stops decreasing at n_1/2 and remains nearly constant in the half-skyrmion phase. In accordance with the large N_c consideration, the baryon mass also stays non-scaling in the half-skyrmion phase. This feature which is reminiscent of the parity-doublet baryon model with a chirally invariant mass m_0 is supported by the nuclear EFT with the parameters of the Lagrangian scaling modified at the skyrmion-half-skyrmion phase transition. It also matches with one-loop RG analysis based on HLS. A link between a non-vanishing m_0 and the origin of nucleon mass distinctive from dynamically generated mass is suggested. We briefly discuss the possible consequences of the topology change found in this paper on the forthcoming experiments at the RIB machines under construction.
15479695
Excited states of heavy baryons in the Skyrme model.
We obtain the spectra of excited heavy baryons containing one heavy quark by quantizing the exactly solved heavy meson bound states to the Skyrme soliton. The results are comparable to the recent experimental observations and quark model predictions, and are consistent with heavy quark spin symmetry. However, the somewhat large dependence of the results on the heavy quark mass strongly calls for the incorporation of the soliton-recoil effects. {copyright} {ital 1996 The American Physical Society.}
181523075
Measurements of pion nucleon charge exchange near the Delta resonance using the NMS at LAMPF