Study of radially excited Ds(2^1S0)and Ds(3P)

The unobserved J^P= 0^-radial excitation Ds（2^1S0） is anticipated to have mass 2650 Me V（denoted as Ds（2650））. Study of hadronic production is an important way to identify highly excited states. We study hadronic production of Ds（2650） from higher excited resonances in a3P0 model. Relevant hadronic partial decay widths are found to be very small, which implies it is difficult to observe Ds（2650） in hadronic decays of higher excited resonances. Hadronic decay widths of radially excited Ds（3P） have also been estimated. The total decay widths of four Ds（3P） are large, but the branching ratios in the Ds（2650）η channel are very small, which implies that it seems impossible to observe Ds（2650） in hadronic decays of Ds（3P）. The dominant decay channels of the four Ds（3P） have been pointed out, and D1（2420）, D1（2430）, D＊2（2460）, D（2550）, D（2600）,（1-1D2）D（2750） and D3^（2760） are possible to observe in hadronic production from Ds（3P）.

Direct pion emission in D＊＋ → D＋π decays

The QCD multipole expansion （QCDME） is based on quantum field theory and has been extensively applied to study transitions among Y and ψ family members. As it refers to non-perturbative QCD, however, it has only a certain application range. Even though it successfully explains the transition data among members of the T （ψ ） family, as Eichten indicates, beyond the production threshold of mediate states it fails to match data by several orders of magnitude. In this work, by studying a simple decay mode D＊ → D ＋ π, where a pion may be emitted before D＊ transitions into D, we analyze the contribution of QCD multipole expansion. As the Dπ portal is open, the dominant contribution is an OZI-allowed process where a light quark-pair is excited out from vacuum, and its contribution can be evaluated by the 3P0 model. Since direct pion emission is OZI-suppressed and violates isospin conservation, its contribution must be much smaller than the dominant one. By a careful calculation, we estimate that the QCDME contribution should be 34 orders smaller than the dominant contribution and this result can offer a quantitative interpretation for Eichten＇s statement.

Systematic analysis of D_J（2580）, D＊_J（2650）, D_J（2740）, D＊_J（2760）,D_J（3000） and D＊_J（3000） in the D meson family

In this work, we tentatively assign the charmed mesons D J（2580）, D＊J（2650）, D J（2740）, D＊J（2760）,D J（3000） and D＊J（3000） observed by the LHCb collaboration according to their spin, parity and masses, then systematically study their strong decays to ground state charmed mesons plus pseudoscalar mesons with the3P0 decay model. Based on these studies, we assign the D＊J（2760） as the 1D5/23-state, the D＊J（3000） as the 1F5/22＋or 1F7/24＋state, the D J（3000） as the 1F7/23＋or 2P1/21＋state in the D meson family. As a byproduct, we also study the strong decays of the states 2P1/20＋, 2P3/22＋, 3S1/21-, 3S1/20-etc, which will be valuable in searching for the partners of these D mesons.

Strong decays of newly observed heavy flavor hadrons

In this talk, we briefly review the experimental status of newly observed charmed hadrons during the past years. Then we introduce the theoretical progresses on these charmed hadrons, especially our studies on the strong decays of new charmed hadrons during the past one year.