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Decay width of d (2380) ! NN process in a chiral constituent quark model

Yubing Dong; Fei Huang; Pengnian Shen; Zongye ZhangSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

The width of three-body single-pion decay process d? → NNπ0,± is calculated by using the d? wave function obtained from our chiral SU(3) constituent quark model calculation. The e?ect of the dynamical structure on the width of d? is taken into account in both the single ?? channel and cou-pled ??+CC two-channel approximations. Our numerical result shows that in the coupled-channel approximation, namely, the hidden-color con?guration being considered, the obtained partial decay width of d? → NNπ is about several hundred KeV, while in the single ?? channel it is just about 2 ? 3 MeV. We, therefore, conclude that the partial width in the single-pion decay process of d? is much smaller than the widths in its double-pion decay processes. Our prediction may provide a criterion for judging di?erent interpretations of the d? structure, as di?erent pictures for the d? may result quite di?erent partial decay width. |

String point of view for heavy-light mesons

Yubing Dong; Qi-Fang L?1); Takayuki MatsukiSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

An approximate rotational symmetry of a heavy-light meson is viewed from a string picture. Using a simple string configuration, we derive a formula, (M?mc)2 = πσL, whose coefficient of the r.h.s. is just 1/2 of that of a light meson with two light quarks. A numerical plot is obtained for Dmesons of experimental data as well as several theoretical models, which shows good agreement with this formula. |

Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

There is a puzzle in the +c family, i.e., one member with JP = 3/2+ is missing in a L = 2 multiplet which the heavy quark effective theory predicts, and JP’s of c(2765)+ and c(2940)+ are unknown. Using a light diquark picture to calculate baryon masses, we study possible assignments of two c’s with unknown JP and the missing +c with 3/2+ for L = 2, and we find the most probable possibility that the peak corresponding to c(2880)+ actually includes a missing member with spin 3/2+ for L = 2 and that quantum numbers of c(2765)+ and c(2940)+ are 2S (1/2+) and 2P(1/2?), respectively. |

Electromagnetic $N-\Delta(1232)$ transitions within the point-form of relativistic quantum mechanics

Yubing Dong; Mauro Giannini; Elena Santopinto; Andrea VassalloSubjects: Physics >> Nuclear Physics

The electromagnetic?N?Δ(1232)?transition amplitudes are calculated using the point-form of relativistic quantum mechanics. The relativistic effects incorporated in the electromagnetic matrix elements give a good description of the transition amplitudes to the?Δ(1232)?resonance, reproducing well the?Q2?behaviour of the data, apart from the low?Q2?one. |

A study of the $d^*(2380) \to d \pi \pi$ decay width

Yubing Dong; Pengnian Shen; Fei Huang; Zongye ZhangSubjects: Physics >> Nuclear Physics

The decay widths of the?$\ds\to d \pi^0\pi^0$?and?$\ds\to d \pi^+\pi^-$?processes are explicitly calculated in terms of our chiral quark model. By using the experimental ratios of cross sections between various decay channels, the partial widths of the?$\ds\to pn \pi^0\pi^0$,?$\ds\to pn \pi^+\pi^-$,?$\ds\to pp \pi^0\pi^-$, and?$\ds\to nn \pi^+\pi^0$?channels are also extracted. Further including the estimated partial width for the?$\ds\to pn$?process, the total width of the?$\ds$resonance is obtained. In the first step of the practical calculation, the effect of the dynamical structure on the width of$\ds$?is studied in the single?ΔΔ?channel approximation. It is found that the width is reduced by few tens of MeV, in comparison with the one obtained by considering the effect of the kinematics only. This presents the importance of such effect from the dynamical structure. However, the obtained width with the single?ΔΔ?channel wave function is still too large to explain the data. It implies that the?$\ds$?resonance will not consist of the?ΔΔ?structure only, and instead there should be enough room for other structure such as the hidden-color (CC) component. Thus, in the second step, the width of?$\ds$?is further evaluated by using a wave function obtained in the coupled?ΔΔ?and CC channel calculation in the framework of the Resonating Group Method (RGM). It is shown that the resultant total width for?$\ds$?is about 69 MeV, which is compatible with the experimental observation of about 75 MeV and justifies our assertion that the?$\ds$?resonance is a hexaquark-dominated exotic state. |

Decay width of $d^*(2380)\to NN \pi\pi$ processes

Yubing Dong; Fei Huang; Pengnian Shen; Zongye ZhangSubjects: Physics >> Nuclear Physics

The decay widths of four-body double-pion decays?$\ds\to pn \pi^0\pi^0$,?$\ds\to pn \pi^+\pi^-$, and iso-scalar parts of?$\ds\to pp \pi^0\pi^-$?and?$\ds\to nn \pi^+\pi^0$?are explicitly calculated with the help of the?d??wave function obtained in a chiral SU(3) quark model calculation. The effect of the dynamical structure on?$\ds$'s width is analyzed both in the single?ΔΔ?channel and coupled?ΔΔ?and?CC?channel approximations. It is found that in the coupled-channel approximation, the obtained partial decay widths of?$\ds\to pn \pi^0\pi^0$,?$\ds\to pn \pi^+\pi^-$, and those of?d??to the iso-scalar parts of?ppπ0π??and?nnπ+π0?are about?7.4MeV,?16.4MeV,?3.5MeV and?3.5MeV, respectively As a consequence, the total width is about?64.5MeV. These widths are consistent with those estimated by using the corresponding cross section data in our previous investigation and also the observed data. But in the single?ΔΔ?channel approximation, the widths are still almost 2-times larger than the measured values. Apparently, the explicitly calculated width together with the evaluated mass of?d??in the coupled?ΔΔ?and?CC?channel approximation can well explain the observed data, which again supports our assertion that the?$\ds$resonance is a six-quark dominated exotic state. |

Approximate degeneracy of heavy-light mesons with the same $L$

Takayuki Matsuki; Qi-Fang Lu; Yubing Dong; Toshiyuki MoriiSubjects: Physics >> Nuclear Physics

Careful observation of the experimental spectra of heavy-light mesons tells us that heavy-light mesons with the same angular momentum?L?are almost degenerate. The estimate is given how much this degeneracy is broken in our relativistic potential model, and it is analytically shown that expectation values of a commutator between the lowest order Hamiltonian and?L???2?are of the order of?1/mQ?with a heavy quark mass?mQ. It turns out that nonrelativistic approximation of heavy quark system has a rotational symmetry and hence degeneracy among states with the same?L. This feature can be tested by measuring higher orbitally and radially excited heavy-light meson spectra for?D/Ds/B/Bs?in LHCb and forthcoming BelleII. |

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