Seminar

Title: Coupled-channel interpretation of the LHCb double-J/ψ spectrum 

Speaker: Prof. Feng-Kun Guo  郭奉坤 (ITP, CAS)

Time: 10:00  (Beijing Time), Tuesday, 2020-10-13

Place: R319, TPD, IHEP, CAS

Abstract: Recently, the LHCb Collaboration reported pronounced structures in the invariant mass spectrum of J/ψ-pairs produced in proton-proton collisions at the Large Hadron Collider. In this Letter, we argue that the data can be very well described within two variants of a unitary coupled-channel approach: (i) with just two channels, J/ψJ/ψ and ψ(2S)J/ψ, as long as energy-dependent interactions in these channels are allowed, or (ii) with three channels J/ψJ/ψ, ψ(2S)J/ψ and ψ(3770)J/ψ with just constant contact interactions. Both formulations hint at the existence of a near-threshold state in the J/ψJ/ψ system with the quantum numbers JPC=0++ or 2++, which we refer to as X(6200). We suggest experimental tests to check the existence of this state and discuss what additional channels need to be studied experimentally to allow for distinctive tests between the two mechanisms proposed.

I will also show how to use the programming language julia and the package IMinuit.jl to make a fit.