An estimate of dibaryon production in the process of pp→d^(∗)(2380)+pn at Panda facility

Although d∗(2380)was first observed by WASA@COSY,its existence has yet to be further confirmed in different types of processes at other facilities.In this work,the possible production of the single dibaryon state d^(∗)(2380)in the process of pp→d^(∗)(2380)pn in a future experiment at the Panda facility is estimated.Following the method used in our previous study(Chin.Phys.C 46,023105),a phenomenological Lagrangian approach is employed to study the single d^(∗)production.Based on the conclusions obtained by the non-relativistic constituent quark model,the cross section of the pp→d^(∗)(2380)pn reaction via the ΔΔ intermediate state is estimated,which is in the order of nb.It is shown that the dominant contribution comes from the diagram with the ΔΔ→pn subprocess.However,it is difficult to measure owing to the large background.Further,although the cross section of the diagram with the d^(∗)→pn subprocess is small,i.e.,only approximately 3%∼4% of the total cross section or even smaller,the corresponding number of events is still sufficiently large and can be measured at Panda because the outgoing p and n come from the same source d^(∗).

Constituent counting rule and the production of d~*(2380) at high energies

The constituent counting rule, determining the scaling behavior of the transition amplitudes in an exclusive process at high energies, is applied to probe the internal structure of the newly observed d*(2380) resonance. Several selected exclusive processes at high energies for the production of d* are discussed. Results of two structural scenarios for d*(2380), a hexaquark dominant compact system in the quark degrees of freedom, and a threebody bound state in the hadronic degrees of freedom, are analyzed and compared. A rather remarkable difference between the results of these two scenarios for the mentioned processes are addressed.

Possible dibaryon production at Panda with a Lagrangian approach

In order to confirm the existence of the dibaryon state d^(*)(2380)observed at WASA@COSY,we estimate the cross section for production of the possible dibaryon and anti-dibaryon pair d^(*)d^(*)in the energy region of the upcoming experiments at Panda.Based on some qualitative properties of d^(*)extracted from the analyses in the non-relativistic quark model,the production cross section for this spin-3 particle pair are calculated with the help of a phenomenological effective relativistic and covariant Lagrangian approach.

On the decays of d^＊(2380) in a constituent chiral quark model

After summarizing the experimental results and present status of the d^＊（2380） observed at WASA@COSY,two “extreme” models for explaining its structure, a compact hexaquark dominated model and a loose △△＇-D_（12）π model, are briefly discussed, especially the former. By comparing their results with the corresponding data, the differences of the two models are addressed. As a remedy for the latter model, a mixing model and its result are also quoted for a comparison. It is shown that the compact hexaquark dominated structure might be more promising.However, the mixing model is also a possible structure, and more accurate Γ_（d^＊）→NN_π data are needed for confirmation.

Phenomenological study on the decay widths of Υ(nS)→d~*(2380)+X

The decay widths of Υ（nS）→d^＊（2380）＋X with n=1,2,3 are studied in a phenomenological way. With the help of crossing symmetry, the decay widths are obtained by investigating the imaginary part of the forward scattering amplitudes between d^＊ and Υ（nS）. The wave functions of d^＊ and deuteron obtained in previous studies are used for calculating the amplitude. The interaction between d^＊（d） and Υ is governed by the quark-meson interaction, where the coupling constant is determined by fitting the observed widths of Υ（nS）→d＋X. The numerical results show that the decay widths of Υ（nS）→d^＊＋X are about 2-10 times smaller than that of d＋X. The calculated momentum of d^＊ is in the range 0.3-0.8 GeV. Therefore, it is very likely that one can find d^＊（2380） in these semi-inclusive decay processes.