分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： 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 effect 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 configuration 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 different interpretations of the d∗ structure, as different pictures for the d∗ may result quite different partial decay width.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： We investigate the neutral hidden charm pentaquark states P0c(4380) and P0c(4450) in π−p→J/ψnreaction within an effective Lagrangian approach. The background contributions for the process mainly come from t-channel π and ρ meson exchanges. The contributions of P0c(4380) and P0c(4450) states give clear peak structures in the magnitude of 1 μb at center of mass energy 4.38 GeV and 4.45 GeV in the total cross sections. Hence, this reaction may provide a new good platform to search for neutral Pc states. It is expected that our estimated total cross sections together with the angular distributions can be tested by future experiments at J-PARC.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We report on a theoretical study of the π−p→D−D0p reaction near threshold within an effective Lagrangian approach. The production process is described by t channel D∗0 meson exchange, s-channel nucleon pole, and u channel Σ++c exchange. In our work, the final D0p results from the ground Λ+c(2286) state and also dominantly from the excited Λ+c(2940) state which is assumed as a D∗0p molecular state with spin parity JP=12+ or 12−. We calculate the total cross section of the π−p→D−D0p reaction. It is shown that the spin parity assignment of 12− for Λ+c(2940) gives a sizable enhancement for the total cross section in comparison with a choice of Jp=12+. However, our theoretical result of the total cross section is sensitive to the value of the cutoff parameter involved in the form factor of the exchanged off-shell particles. Moreover, we also calculate the second order differential cross section and find it can be used to determine the parity of the Λ+c(2940). It is expected that our model calculations can be tested by future experiments at J-PARC in Japan.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： 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.
分类： 物理学 >> 核物理学 提交时间： 2016-09-01
摘要： 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.
分类： 物理学 >> 核物理学 提交时间： 2016-09-01
摘要： We study the masses of open charm and bottom tetraquark states within the diquark-antidiquark scenario in the relativized quark model proposed by Godfrey and Isgur. The diquark and antidiquark masses are firstly solved by relativized quark potential, and then treated as the usual antiquark and quark, respectively. The masses of tetraquark states are obtained by solving the Schr\"{o}dinger-type equation between diquark and antidiquark. We find the masses of sqb¯q¯ tetraquark configuration are much higher than that of X(5568). This conclusion disfavors the possibility of X(5568) as a tetraquark state within the diquark-antidiquark scenario. Further experimental searches are needed to clarify the nature of the signal observed by D0 collaboration.
分类： 物理学 >> 核物理学 提交时间： 2016-08-31
摘要： We study the strong decay channels P+c(4380)→J/ψp and P+c(4450)→J/ψp under ΣcD¯∗ molecular state ansatz. With various spin-parity assignments, the partial decay widths of J/ψp final state are calculated. Our results show that all the P wave ΣcD¯∗ assignments are excluded, while S wave ΣcD¯∗ pictures for Pc(4380) and Pc(4450) are both allowed by present experimental data. The JP=3/2− Σ∗cD¯ and Σ∗cD¯∗ molecules are also discussed in the heavy quark limit, and find that the Σ∗cD¯ system for Pc(4380) is possible. More experimental information on spin-parities and partial decay widths and theoretical investigations on other decay modes are needed to clarify the nature of the two Pc states.
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