Evidence for e+e−→γηc(1S) at center-of-mass energies between 4.01 and 4.60 GeV

Abstract

We present first evidence for the process e + e − → γηc(1S) at six center-of-mass energies between 4.01 and 4.60 GeV using data collected by the BESIII experiment operating at BEPCII. These data sets correspond to a total integrated luminosity of 4.6 fb −1 . We measure the Born cross section at each energy using a combination of twelve ηc(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 the process is assumed to proceed via the Y (4260), we measure a peak Born cross section σ peak (e + e − → γηc(1S)) = 2.11 ± 0.49(stat.) ± 0.36(syst.) pb with a statistical significance of 4.2σ.

NNLO QCD corrections to γ + η c (η b ) exclusive production in electron-positron collision

“…With the NNLO correction, the production rate in this region is greatly suppressed, about 3 times reduced from the LO result, and the NNLO cross section varies more smoothly than LO and NLO results with the change of CMS energy, as expected. Recently, BESIII collaboration performed a measurement on e + e − → γ + η c process with CMS energy between 4.01 and 4.60 GeV in data set corresponding to a total integrated luminosity of 4.6 fb −1 [43], and found no evidence of direct γ + η c (1S) production, which is in accord with the higher order QCD predictions. That is to say, the NNLO result also prefers the enhancement in e + e − → γ + η c process between 4.23 and 4.36 GeV being from exotic particle Y (4260) decay.…”

The $XYZ$ states: experimental and theoretical status and perspectives

“…energies between 4.01 π + π − ψ(2S ) [165], and ωχ c0 [163] from the BESIII Collaboration. and 4.60 GeV corresponding to a total integrated luminosity of 4.6 fb −1 [177]. The final distribution of σ(e + e − → γη c ) is shown as the points in Fig.…”

Observation of e+e−→γχc1 and search for Jia1, Wang2, Shen3 et al. 2018Phys. Rev. DSelf Cite164150View full textAdd to dashboardCite

“…The BESIII experiment measured e þ e − → γχ cJ cross sections at ffiffi ffi s p ¼ 4.01 GeV, 4. 23, 4.26, and 4.36 GeV and e þ e − → γη c cross section at the same energies and additionally at 4.42 and 4.60 GeV [11,12]. At none of the individual energy points does the statistical significance for production of χ cJ or η c exceed 3σ, and when the data from all energy points are combined, the statistical significances for χ c1 , χ c2 , and η c are 3.0σ, 3.4σ, and greater than 3.6σ, respectively.…”