https://indico.ihep.ac.cn//event/8183/

First,Kai introduced measurement of e+e- -> Ds+ Ds- cross sections near threshold using initial-state radiation. The main content included event selection and cross section.Next,Kai answered some questions.

YuZhen:What is the difference of D+* and D+? Answer:spin of the quarks are different, leading to difference in mass, spin-parity, etc.

Amit:On Page:- 4,The following sources of background are considered.Point: 3 - The low momentum gamma photon is not reconstructed and Point: 4.The pi0miss is not reconstructed.I just want to know, why?Is this reconstruction not in the MC simulation or not in the data? Answer:

Ryuta:The cross section of ee->DsDs seems to be one order lower than ee->DD, however, this paper describes (in the page 1) the one of motivations as “The Y states, ,,, provide additional motivation to pursue all possible experimental information about the decomposition of charmed particle production in the charm-threshold region” . This description is fine, but thereafter, is there some discussion/paper on Y states (or anything else) where the information of ee->DsDs result is effectively used ?

Xin:On page 5, it says “The contribution of final state radiation is strongly suppressed …”, could you explain why? Answer:FSR is dominated by photons collinear to the final-state particles while ISR is dominated by photons collinear to the beam direction.This suggests that we should consider only events with photons well separated from the charged from the charged final-state particles and preferentially close to the beam.

Suyu:For the sidebands selection, they used 4 times as large as the signal region, 60MeV, and divided it into windows of the same width as that of the signal, 30MeV. Then they shifted the sidebands, to avoid signal oversubtraction, by 30MeV from the signal region.From my point of view, 2 sidebands have same parameters of course, e.g. c0, c1. Does it means that they exchange 2 sidebands(move sideband above the Ecm to lower energy side, and another lower than Ecm to higher energy side)? Anwser:Don’t know how to shift the sideband.

Yuhang:On page 3,To suppress backgrounds two cases are considered.1)the γISR is outside of the detector acceptance and the polar angle for the Ds+Ds- combination in the c.m. frame is in the arange|cos(θDs+Ds-)|>0.9;2) the γISR is within in the detector acceptance |cos(θDs+Ds-)|<0.9.How to understand this. Answer:momentum conservation.the ISR and the (Ds()Ds()) system should be back to back.

Shan:What is the advantage of BESIII compared to Bell in searching for the XYZ states? Answer:many advantages:directly producing Y states – larger data sample[ main challenge from BelleII ] – precise measurement of state parameters – not only simply observe many many new states, but build the connections between them!

Next,Shan introduce XYZ States at BESIII. The main content contained the X state,the Y state,the Z state and summary. Finally, Yuzhen introduced the motivation about next JC paper.