Abstract
The production of resonances in electron-positron annihilation has only been observed for states with quantum numbers JPC = 1−−, while C = +1 resonances appear only among the decay products. The direct production of the 1++ states could happen through two-photon or neutral current. Due to the smallness of the production rate, this process has never been verified experimentally. With the high luminosity and good performance of the BESIII experiment, a search of the direct production of the 1++ state in charmonium region, χc1, is undergoing with dedicated data samples around the χc1 mass. An overview of the data analysis will be presented.
Highlights
IntroductionThe contribution from two-photon annihilation dominates the production rate [1]
Up to now, only the production of resonances with the quantum numbers JPC = 1−− has been observed in e+e− annihilation through a virtual photon, states with other quantum numbers are appeared only among the decay products
The electronic width of χcJ has been revisited within the Vector Dominance Model (VDM) [3] and the NRQCD [4] framework, the values from the new estimations are at 0.1 eV level
Summary
The contribution from two-photon annihilation dominates the production rate [1]. The production rate, which is proportional to the electronic width, has already been calculated a long time ago [1, 2]. The lower limit of the electronic width of χc is calculated to be Γee > 0.044 eV, while in Vector Dominance Model (VDM), the prediction is Γee = 0.46 eV [1]. The study focuses on the radiative decay of χcJ to γJ/ψ, followed by J/ψ → μ+μ−, and its interference with the continuum background process, e+e− → γISRμ+μ−, where the photon is from radiative corrections. With the high luminosity and excellent performance of the Beijing Electron Positron Collider (BEPCII) and the BESIII detector [6, 7], a study has been launched at the BESIII experiment to search for the direct production of χc
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