Narrow Results

Consistent SU(6) and SU(8) spin-flavor extensions of the SU(3) flavor Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian are constructed, which incorporate vector meson degrees of freedom. In the charmless sector, the on-shell approximation to the Bethe-Salpeter (BS) approach successfully reproduces previous SU(3) WT results for the lowest-lying s–wave negative parity baryon resonances. It also provides some information on the dynamics of heavier ones and of the lightest d-wave negative parity resonances, as e.g. the Λ(1520). For charmed baryons the scheme is consistent with heavy quark symmetry, and our preliminary results in the strangeness-less charm C = +1 sector describe the main features of the three-star J^P = 1/2⁻ Λ_c(2595) and J^P = 3/2⁻ Λ_c(2625) resonances. We also find a second broad J^P = 1/2⁻ state close to the Λ_c(2595).

We explain the main idea of the chiral doublers scenario, originating from simultaneous constraints of chiral symmetry and of heavy quark spin symmetry on effective theories of heavy-light hadrons. In particular we discuss chiral doublers for mesons, chiral doublers for excited mesons, chiral doublers for baryons and chiral doublers for excited baryons. We point out the arguments why new states D_s(2317) and D_s(2457) might be viewed as chiral doublers of D_s and . Then we comment on non-strange mesons D₀(2308) and D′₁(2427) observed by Belle and Focus, and on Θ_c(3099) signal observed by H1. Finally, we point out that very recent discovery by SELEX of D_s(2632), if confirmed by other experiments and if spin-parity of this state is 1^-, may be interpreted as a signal for chiral doubler of D_s1(2536). Such an identification implies another narrow, spin-parity 2^-D_s state ca 37 MeV above the new 1^-, corresponding to chiral partner of D_s2.

According to the heavy-quark flavor symmetry, the B→π, K transition form-factors could be related to the corresponding ones of D-meson decays near the zero recoil point. With the recent precisely measured exclusive semileptonic decays D →πℓν and D→K ℓν, we perform a phenomenological study of B →π, K transition form-factors based on this symmetry. Using BK, BZ and Series Expansion parametrizations of the form-factor slope, we extrapolate B →π, K transition form-factors from to q² = 0. It is found that, although being consistent with each other within error bars, the central values of our results for B →π, K form-factors at q² = 0, , are smaller than predictions of the QCD light-cone sum rules, but are in good agreements with the ones extracted from hadronic B-meson decays within the SCET framework. Moreover, smaller form-factors are also favored by the QCD factorization approach for hadronic B-meson decays.

We discuss the extension of the superflavor symmetry of doubly heavy baryons to states which contain an excited heavy diquark and we examine some of the consequences of this symmetry for the spectra of doubly heavy baryons and heavy mesons. We explore the ramifications of a proposed symmetry that relates heavy diquarks to doubly heavy mesons. We present a method for determining how the excitation energy of a system containing two heavy quarks will scale as one changes the strength of the interactions and the reduced mass of the system. We use this to derive consequences of the heavy diquark-doubly heavy meson symmetry. We compare these consequences to the results of a quark model as well as the experimental data for doubly and singly heavy mesons. We also discuss the possibility of treating the strange quark as a heavy quark and apply the ideas developed here to strange hadrons.

The heavy diquark symmetry (HDS) of doubly heavy baryons (DHBs) provides new insights into the spectroscopy of these hadrons. We derive the consequences of this symmetry for the mass spectra and the decay widths of DHBs. We compare these symmetry constraints to results from a nonrelativistic quark model for the mass spectra and results from the ³P₀ model for strong decays. The quark model we implement was not constructed with these symmetries and contains interactions which explicitly break HDS. Nevertheless these symmetries emerge. We argue that the ³P₀ model and any other model for strong transitions which employs a spectator assumption explicitly respects HDS. We also explore the possibility of treating the strange quark as a heavy quark and apply these ideas to Ξ, Ξ_c and Ξ_b baryons.

About two decades ago, Gerry Brown pushed me to study hadron physics using hadronic models based on the hidden local symmetry (HLS). Since then, I have been involving many works related to the HLS. In this contribution to Gerry’s memorial, I will summarize my recent analyses associated with the HLS. After a very brief summary of the HLS, I will show a way to determine parameters of the HLS model from holographic QCD models. This model provides a soliton solution which is identified with the nucleon. I will briefly introduce a model in which the solitons are put onto a crystal lattice for simulating nuclear matter. The results suggest existence of the chiral invariant mass of nucleon. I also briefly review my recent analyses on the nuclear matter by using a hadronic model including nucleon field together with the $\pi$, $\sigma$, $\rho$ and $\omega$ mesons based on the parity doublet structure of nucleon combined with the HLS, in which the chiral invariant mass of the nucleon is naturally embedded. The result implies that studying effective masses of nucleons will give a clue for the chiral invariant mass. Finally, I will show our recent analysis on the medium modification of charmed meson masses using a chiral model based on the chiral doubling structure of charmed mesons. The result shows that the masses of the chiral partners of charmed mesons become closer in high density reflecting the particle chiral symmetry restoration in medium.

The properties of X(3872) are analyzed starting from a correlation function written in terms of the quark and gluon degrees of freedom. It is shown that in the infinite charm quark mass limit, X(3872) meson should have three other degenerate meson partners. The possible isospin structure of X(3872) is also analyzed and it is concluded that although the observed isospin violation in the decays of X(3872) into the final states J/ψρ and J/ψω is small, X(3872) can contain a sizable I = 1 component.

We present some recent results from soliton model calculations for the spectrum of baryons with a single heavy quark. The model comprises chiral symmetry for light flavors and (approximate) heavy spin–flavor symmetry for the heavy quarks. We focus on flavor symmetry breaking for strangeness degrees of freedom.

We report on a robust prediction of heavy K^* meson by solving the Faddeev equations with fixed-center approximation for the three-body $KD{\overline{D}}^{*}$ system. As the excited Kaon state, K^* is an exotic hidden charm meson with M − iΓ/2 = 4307 ± 2 − i9 ± 2 MeV and I(J^P) = 1/2(1⁻). We further performed the evaluation of the decay width of K^*(4307) to the open two-body channels. We expect that the above findings inspire an experimental investigation of this exotic K^* meson and to study the so far unexplored heavy strange meson sector.

About two decades ago, Gerry Brown pushed me to study hadron physics using hadronic models based on the hidden local symmetry (HLS). Since then, I have been involving many works related to the HLS. In this contribution to Gerry’s memorial, I will summarize my recent analyses associated with the HLS. After a very brief summary of the HLS, I will show a way to determine parameters of the HLS model from holographic QCD models. This model provides a soliton solution which is identified with the nucleon. I will briefly introduce a model in which the solitons are put onto a crystal lattice for simulating nuclear matter. The results suggest existence of the chiral invariant mass of nucleon. I also briefly review my recent analyses on the nuclear matter by using a hadronic model including nucleon field together with the π, σ, ρ and ω mesons based on the parity doublet structure of nucleon combined with the HLS, in which the chiral invariant mass of the nucleon is naturally embedded. The result implies that studying effective masses of nucleons will give a clue for the chiral invariant mass. Finally, I will show our recent analysis on the medium modification of charmed meson masses using a chiral model based on the chiral doubling structure of charmed mesons. The result shows that the masses of the chiral partners of charmed mesons become closer in high density reflecting the particle chiral symmetry restoration in medium.