Observation of the Y(4230) and evidence for a new vector charmoniumlike state Y(4710) in e+ e- & RARR; K0SK0SJ/& psi;

• Cross sections for the process e thorn e- & RARR; K0SK0SJ=& psi; at center-of-mass energies from 4.128 to 4.950 GeV are measured using data samples with a total integrated luminosity of 21.2 fb-1 collected by the BESIII detector operating at the BEPCII storage ring. The Yo4230 thorn state is observed in the energy dependence of the e thorn e- & RARR; K0SK0 SJ=& psi; cross section for the first time with a statistical significance of 26.0 & sigma;. In addition, an enhancement around 4.710 GeV, labeled as the Yo4710 thorn , is seen with a statistical significance of 4.2 & sigma;. There is no clear structure around 4.484 GeV. Using a fit with a coherent sum of three Breit-Wigner functions, we determine the mass and width of the Yo4230 thorn state to be 4226.9 ⠂ 6.6 ⠂ 22.0 MeV=c2 and 71.7 ⠂ 16.2 ⠂ 32.8 MeV, respectively, and the mass and width of the Yo4710 thorn state to be 4704.0 ⠂ 52.3 ⠂ 69.5 MeV=c2 and 183.2 ⠂ 114.0 ⠂ 96.1 MeV, respectively, where the first uncertainties are statistical and the second are systematic. In addition, the average Born cross section ratio & sigma;Bornoe thorn e-& RARR;K thorn K-J=& psi; thorn is measured to be 0.388 thorn 0.035 & sigma;Bornoe thorn e-& RARR;K0 SK0 SJ=& psi; thorn -0.028 ⠂0.016, or 0.426 thorn 0.038 -0.031 ⠂ 0.018 if three-body phase space is considered.

Subject headings

NATURVETENSKAP  -- Fysik -- Subatomär fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Subatomic Physics (hsv//eng)

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ref (subject category)

art (subject category)