This dissertation shows the first evidence of the process e +e− → γη c(1S) using data collected by the BESIII experiment operating at BEPCII. This process can be used as a probe to study the nature of recently discovered charmonium-like Y states between 4.0 and 4.6 GeV, including the Y(4260) and Y(4360). Data collected at six center-of-mass energies are analyzed, namely: 4.01, 4.23, 4.26, 4.36, 4.42, and 4.60 GeV, corresponding to a total integrated luminosity of 4.6 fb−1. We measure the Born cross section, σ E(e+e − → γηc(1 S)), at each energy using a combination of twelve η c(1S) decay channels. Because the significance of the signal is marginal at each energy (≤ 3.0σ), we also combine all six energies under various assumptions for the energy-dependence of the cross section. If a Y(4260) is assumed, we measure σ4 .26(e+e− → γηc(1S)) = 2.11 ± 0.49 (stat.) ± 0.33 (syst.) pb with a significance of 4.2σ. With our current statistics we are unable to distinguish the Y(4260) process from others.
|Advisor:||Shepherd, Matthew R., Mitchell, Ryan E.|
|Commitee:||Liu, Chen-Yu, Szczepaniak, Adam|
|School Location:||United States -- Indiana|
|Source:||DAI-B 78/02(E), Dissertation Abstracts International|
|Subjects:||Physics, Particle physics|
|Keywords:||Beijing electron positron collider, Beijing electron spectrometer, Hadronic decays of mesons, High energy particle physics, XYZ particles|
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