arXiv subjects

B. S. Zou

Publications and source records attributed to B. S. Zou.

At least 19 recordsLinked to original sources

arXiv2024

Mini-Proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024)"

The mini proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024) [https://kds.kek.jp/event/46965]" held at J-PARC, February 19-21, 2024, are presented. The workshop was devoted to discussing the physics case that connects both the present and the future Hadron Experimental Facility at J-PARC, covering a wide range of topics in flavor, hadron, and nuclear physics related to both experimental and theoretical activities being conducted at the facility.

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arXiv2021

Molecular nature of $P_{cs} (4459)$ and its heavy quark spin partners

Inspired by the observation of the $P_{cs} (4459)$ state by LHCb recently, we reexamine the results of the interaction of the $J/ψΛ$ channel with its coupled channels, exploiting the coupled channel unitary approach combined with heavy quark spin and local hidden gauge symmetries. By tuning the only free parameter, we find a pole of $(4459.07+i6.89)$ MeV below the $\bar D^* Ξ_c$ threshold, which was consistent well with the mass and width of the $P_{cs} (4459)$ state. Thus, we assume the $P_{cs} (4459)$ state to be a $\bar D^* Ξ_c$ bound state with the uncertainties on its degeneracy with $J^P = \frac{1}{2}^-$ and $J^P = \frac{3}{2}^-$. For the degeneracy, it would have two-poles structure, like $P_c (4450)$ before. There is another pole in the $J^P = \frac{1}{2}^-$ sector, $(4310.53+i8.23)$ MeV, corresponding to a deep bound state of $\bar D Ξ_c$. Furthermore, the previously predicted loose bound states of $\bar D Ξ'_c$, $\bar D^* Ξ'_c$, $\bar D^* Ξ^*_c$ with $J=1/2,~I=0$ and $\bar D^* Ξ'_c$, $\bar D Ξ^*_c$, $\bar D^* Ξ_c^*$ with $J=3/2,~I=0$ may exist as either bound states or unbound virtual states. We hope that future experiments can search for the $\bar D^{(*)} Ξ_c$ molecular states in their dominant decay channels of $\bar D^{(*)}_s Λ_c$, also in the $J/ψΛ$ and $η_c Λ$ channels to reveal their different nature.

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arXiv2016

Evidence for Some New Hyperon Resonances -- to be Checked by $K_L$ Beam Experiments

Quenched and unquenched quark models predict very different patterns for the spectrum of the low excited hyperon states. Evidence is accumulating for the existence of some new hyperon resonances, such as a $Σ^*$ of spin-parity $J^P=1/2^-$ around 1400 MeV instead of 1620 MeV as listed in PDG, a new $Σ(1540)3/2^-$ resonance, a new narrow $Λ(1670)3/2^-$ resonance and a new $Λ(1680)3/2^+$ resonance. All these new hyperon resonances fit in the predicted pattern of the unquenched quark models very well. It is extremely important to check and establish the spectrum of these low excited hyperon states by the proposed $K_L$ beam experiments at JLAB.

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arXiv2015

Penta-quark States with Strangeness, Hidden Charm and Beauty

The classical quenched quark models with three constituent quarks provide a good description for the baryon spatial ground states, but fail to reproduce the spectrum of baryon excited states. More and more evidences suggest that unquenched effects with multi-quark dynamics are necessary ingredients to solve the problem. Several new hyperon resonances reported recently could fit in the picture of penta-quark states. Based on this picture, some new hyperon excited states were predicted to exist; meanwhile with extension from strangeness to charm and beauty, super-heavy narrow $N^*$ and $Λ^*$ resonances with hidden charm or beauty were predicted to be around 4.3 and 11 GeV, respectively. Recently, two of such $N^*$ with hidden charm might have been observed by the LHCb experiment. More of those states are expected to be observed in near future. This opens a new window in order to study hadronic dynamics for the multi-quark states.

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arXiv2014

Low-lying $Ω$ states with negative parity in an extended quark model with Nambu-Jona-Lasinio interaction

Here we investigate mixing of the low-lying three- and five-quark $Ω$ states with spin-parity quantum numbers $\frac{1}{2}^{-}$ and $\frac{3}{2}^{-}$, employing the quark-antiquark creation triggered by Nambu-Jona-Lasinio (NJL) interaction. Wave functions of the three- and five-quark configurations are constructed using the extended constituent quark model, within which the hyperfine interaction between quarks is also taken to be the NJL interaction induced one. Numerical results show that the NJL-induced pair creation results in vanishing mixing between three- and five-quark $Ω$ configurations with spin-parity $1/2^{-}$, but mixing between three- and five-quark $3/2^{-}$ $Ω$ states should be very strong. And the mixing decreases energy of the lowest $3/2^{-}$ $Ω$ state to be $1785\pm25$~MeV, which is lower than energy of the lowest $1/2^{-}$ state in this model. This is consistent with our previous predictions within the instanton-induced quark-antiquark creation model.

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arXiv2013

Mixing of the low-lying three- and five-quark $Ω$ states with negative parity

Mixing of the low-1/2^{-}$ and $3/2^{-}$ is investigated, employing an instanton-induced quark-antiquark pair creation model, which precludes transitions between $s^{3}$ and $s^{4}\bar{s}$ configurations. Models with hyperfine interactions between quarks of three different kinds, namely, one-gluon-exchange, Goldstone-boson-exchange (GBE) and an instanton-induced interaction (INS) are called OGE, GBE and INS models, respectively. Numerical results show that the instanton-induced pair creation causes strong mixing between the three- and five-quark configurations with spin 3/2, and that this mixing decreases the energy of the lowest spin 3/2 states in all three different hyperfine interaction models to $\sim 1750\pm50$ MeV. On the other hand, transition couplings between $s^3$ and $s^{3}q\bar{q}$ states with spin 1/2 caused by instanton-induced $q\bar{q}$ creation is very small and the resulting mixing of three- and five-quark configurations in the OGE and INS models is negligible, while the mixing of the spin 1/2 states in GBE model is not, but effects of this mixing on energies of mixed states are also very small. Accordingly, the lowest $Ω$ states with negative parity in all three hyperfine interactions models have spin 3/2.

hep-ph↗

arXiv2013

Sigma_c Dbar and Lambda_c Dbar states in a chiral quark model

The S-wave Sigma_c Dbar and Lambda_c Dbar states with isospin I=1/2 and spin S=1/2 are dynamically investigated within the framework of a chiral constituent quark model by solving a resonating group method (RGM) equation. The results show that the interaction between Sigma_c and Dbar is attractive, which consequently results in a Sigma_c Dbar bound state with the binding energy of about 5-42 MeV, unlike the case of Lambda_c Dbar state, which has a repulsive interaction and thus is unbound. The channel coupling effect of Sigma_c Dbar and Lambda_c Dbar is found to be negligible due to the fact that the gap between the Sigma_c Dbar and Lambda_c Dbar thresholds is relatively large and the Sigma_c Dbar and Lambda_c Dbar transition interaction is weak.

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arXiv2013

Spectrum of low-lying $s^{3}Q\bar{Q}$ configurations with negative parity

Spectrum of low-lying five-quark configurations with strangeness quantum number $S=-3$ and negative parity is studied in three kinds of constituent quark models, namely the one gluon exchange, Goldstone Boson exchange, and instanton-induced hyperfine interaction models, respectively. Our numerical results show that the lowest energy states in all the three employed models are lying at $\sim$1800 MeV, about 200 MeV lower than predictions of various quenched three-quark models. In addition, it is very interesting that the state with the lowest energy in one gluon exchange model is with spin 3/2, but 1/2 in the other two models.

hep-ph↗

arXiv2013

Prediction of super-heavy $N^$ and $Λ^$ resonances with hidden beauty

The meson-baryon coupled channel unitary approach with the local hidden gauge formalism is extended to the hidden beauty sector. A few narrow $N^*$ and $Λ^*$ resonances around 11 GeV are predicted as dynamically generated states from the interactions of heavy beauty mesons and baryons. Production cross sections of these predicted resonances in $pp$ and $ep$ collisions are estimated as a guide for the possible experimental search at relevant facilities.

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arXiv2013

Hadron spectroscopy from strangeness to charm and beauty

Quarks of different flavors have different masses, which will cause breaking of flavor symmetries of QCD. Flavor symmetries and their breaking in hadron spectroscopy play important role for understanding the internal structures of hadrons. Hadron spectroscopy with strangeness reveals the importance of unquenched quark dynamics. Systematic study of hadron spectroscopy with strange, charm and beauty quarks would be very revealing and essential for understanding the internal structure of hadrons and its underlying quark dynamics.

hep-ph↗

arXiv2012

Interaction of vector mesons with baryons and nuclei

After some short introductory remarks on particular issues on the vector mesons in nuclei, in this paper we present a short review of recent developments concerning the interaction of vector mesons with baryons and with nuclei from a modern perspective using the local hidden gauge formalism for the interaction of vector mesons. We present results for the vector baryon interaction and in particular for the resonances which appear as composite states, dynamically generated from the interaction of vector mesons with baryons, taking also the mixing of these states with pseudoscalars and baryons into account. We then venture into the charm sector, reporting on hidden charm baryon states around 4400 MeV, generated from the interaction of vector mesons and baryons with charm, which have a strong repercussion on the properties of the $J/ΨN$ interaction. We also address the interaction of $K^*$ with nuclei and make suggestions to measure the predicted huge width in the medium by means of the transparency ratio. The formalism is extended to study the phenomenon of $J/ψ$ suppression in nuclei via $J/ψ$ photoproduction reactions.

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arXiv2012

Isospin breaking and $f_0(980)$-$a_0(980)$ mixing in the $η(1405) \to π^{0} f_0(980)$ reaction

We make a theoretical study of the $η(1405) \to π^{0} f_0(980)$ and $η(1405) \to π^{0} a_0(980)$ reactions with an aim to determine the isospin violation and the mixing of the $f_0(980)$ and $a_0(980)$ resonances. We make use of the chiral unitary approach where these two resonances appear as composite states of two mesons, dynamically generated by the meson-meson interaction provided by chiral Lagrangians. We obtain a very narrow shape for the $f_0(980)$ production in agreement with a BES experiment. As to the amount of isospin violation, or $f_0(980)$ and $a_0(980)$ mixing, assuming constant vertices for the primary $η(1405)\rightarrow π^{0}K\bar{K}$ and $η(1405)\rightarrow π^{0}π^{0}η$ production, we find results which are much smaller than found in the recent experimental BES paper, but consistent with results found in two other related BES experiments. We have tried to understand this anomaly by assuming an I=1 mixture in the $η(1405)$ wave function, but this leads to a much bigger width of the $f_0(980)$ mass distribution than observed experimentally. The problem is solved by using the primary production driven by $η' \to K^* \bar K$ followed by $K^* \to K π$, which induces an extra singularity in the loop functions needed to produce the $f_0(980)$ and $a_0(980)$ resonances. Improving upon earlier work along the same lines, and using the chiral unitary approach, we can now predict absolute values for the ratio $Γ(π^0, π^+ π^-)/Γ(π^0, π^0 η)$ which are in fair agreement with experiment. We also show that the same results hold if we had the $η(1475)$ resonance or a mixture of these two states, as seems to be the case in the BES experiment.

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arXiv2012

$Σ$ Resonances from $K^- N\rightarrow πΛ$ reactions with the center of mass energy from 1550 to 1676 MeV

For the study of the $Σ$ resonances, we analyze the differential cross sections and $Λ$ polarizations for the reactions $K^-n\toπ^-Λ$ and $K^-p\toπ^0Λ$ with an effective Lagrangian approach. Data of an early experiment and the recent Crystal Ball experiment at BNL are included in the analysis with the c.m. energy from 1550 to 1676 MeV. Our results clearly support the existence of a $Σ$ resonance with $J^P={1\over 2}^+$, mass near 1633 MeV, and width about 120 MeV, which confirms the 3-star $Σ(1660) 1/2^+$ in PDG. Meanwhile, our results do not support the existence of the 2-star $Σ(1620){1\over 2}^-$ in PDG. The analysis results for the parameters of the relevant $Σ$ resonances and couplings are presented.

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arXiv2012

Nucleon Resonances with Hidden Charm in Coupled-Channel Models

The model dependence of the predictions of nucleon resonances with hidden charm is investigated. We consider several coupled-channel models which are derived from relativistic quantum field theory by using (1) a unitary transformation method, and (2) the three-dimensional reductions of Bethe-Salpeter Equation. With the same vector meson exchange mechanism, we find that all models give very narrow molecular-like nucleon resonances with hidden charm in the mass range of 4.3 GeV $ < M_R < $ 4.5 GeV, in consistent with the previous predictions.

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arXiv2012

Study of $qqqc\bar{c}$ five quark system with three kinds of quark-quark hyperfine interaction

The low-lying energy spectra of five quark systems $uudc\bar{c}$ (I=1/2, S=0) and $udsc\bar{c}$ (I=0, S=-1) are investigated with three kinds of schematic interactions: the chromomagnetic interaction, the flavor-spin dependent interaction and the instanton-induced interaction. In all the three models, the lowest five quark state ($uudc\bar{c}$ or $udsc\bar{c}$) has an orbital angular momentum L=0 and the spin-parity $J^{P}=1/2^{-}$; the mass of the lowest $udsc\bar{c}$ state is heavier than the lowest $uudc\bar{c}$ state.

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arXiv2011

Partial wave analysis of pbar-p annihilation channels in flight with I=1, C=+1

A combined analysis is reported of 3pizero, pizero-eta and pizero-etaprime data in the mass range 1960 to 2410 MeV. This analysis is made consistent also with eta-eta-pizero data, reported separately. The analysis requires s-channel resonances with a spectrum close to that published earlier for C = +1 states with I = 0; masses for I=1 states are lower on average by 20 MeV. Two alternative solutions are found, differing only for J^P = 2^+ and 4^+ states by small amounts in masses and widths. Both 3pizero and eta-pizero data prefer one of these two solutions. For this preferred solution, observed states have J^PC, masses and widths (M,Gamma) in MeV as follows: 4^-+: (2250+-15, 215+-25), 4^++: (2255+-40, 330 ^{+110}_{-50}) and (2005 ^{+25}_{-45}, 180+-30), 3^++: (2275+-35, 350 ^{+100}_{-50}) and (2031+-12, 150 \pm 18), 2^-+: (2245+-60, 320 ^{+100}_{-40}) and (2005+-15, 200+-40, 2^++: (2255+-20, 230+-15), (2175+-40, 310^{+90}_{-45}) and (2030+-20, 205+-30), and 1^++: (2270 ^{+55}_{-40}, 305 ^{+70}_{-35}). There are indications of further 2^-+, 2^++ and 1^++ contributions just below the available mass range, and also a 0^++ state at ~2025 MeV.

hep-ex↗

arXiv2011

A partial wave analysis of pbar-p -> eta-eta-pizero

A partial wave analysis of pbar-p -> eta-eta-pizero data from the Crystal Barrel experiment is made in terms of s-channel resonances. The decay channels a_0(980)-eta, f_0(1770)-pi and f_0(2105)-pi provide evidence for two I = 1 J^{PC} = 0^{-+} resonances. The first has mass M =2360 +- 25 MeV and width Gamma = 300^{+100}_{-50} MeV, and the second M =2070 \pm 35 MeV, Gamma = 310^{+100}_{-50} MeV. There is also evidence for a J^{PC} = 2^{-+} state with M = 2005 +- 15 MeV and Gamma = 200 +- 40 MeV, decaying strongly to a_0(980)-pi.

hep-ex↗

arXiv2011

Study of pbar-p -> eta-eta-pizero-pizero in flight

An analysis of data on pbar-p -> eta-eta-pizero-pizero is presented at pbar beam momenta 600 to 1940 MeV/c. There is evidence for an I = 1, J^PC = 2^-+ resonance in eta-eta-pizero with mass M = 1880 +- 20 MeV and width 255 +- 45 MeV, decaying strongly a2(1320)-eta; it is too strong to be explained as the high mass tail of π_2(1670) -> a2(1320)-eta. There is tentative evidence also for weak decays to f_0(1500)π. It makes a natural partner to the eta 2(1860).

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