https://indico.ihep.ac.cn//event/9242/

First,Amit introduced Search for Invisible Decays of a Dark Photon Produced in e + e − Collisions at BABAR. Next, Amit answered some questions.

Kiuchi: : Q. At the very begining, one of motivation of the dark photon search is described as “models attempting to explain certain astrophysical observations [1-4]”. Could you introduce one(or some) of these astrophysical observations, especially how we can interprete the results to the dark photon (excess of e+/e- events ?) ? Answer:We can discuss about this Fermi-LAT paper.

Xin:In the paper, it says: “These limits assume that the dominant decays of the A0 are to the visible SM particles, but are not valid if there are low-mass invisible degrees of freedom. Could you explain a bit more?

Answer:For this answer, I need to read the reference paper 8-16. There are constraints on invisible decays of the A0 from kaon decays [17–19] and from the recent search for missing energy events in electron-nucleus scattering [20]

Yuhang:In fig.3,Why use the Mx2 on the Horizontal axis, not Mx？ Is there any special physical meaning?

Shan:In the sentence “we assume that a single A0 state exists in the range 0 < mA0 ≤ 8 GeV,” What is the basis for this energy interval setting? Next,Kai introduce selected highlights on the previous BESIII Collaboration meeting. Finally,Amit introduced the motivation about next JC paper.

Yuzhen:In Fig5, what is NA64? Is it an experiment? can you introduce some? Answer: NA64 is an experiment at the CERN SPS.

Next, Yuhang introduced μS+B fit. The main content include process,likelihood fit principle,fit method, and fit result.