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Register a new userObservation of e+e- to K+K-J/psi via Initial State Radiation at Belle
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The process e+e- to K+K-J/psi is observed for the first time via initial state radiation. The cross section of e+e- to K+K-J/psi for center-of-mass energies between threshold and 6.0 GeV is measured using 673 fb^{-1} of data collected with the Belle detector on and off the Upsilon(4S) resonance. We also find evidence for e+e- to K_S K_S J/psi in the same energy region.
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The cross sections of the processes $e^+ e^- to K^+ K^- J/psi$ and $K_S^0K_S^0J/psi$ are measured via initial state radiation at center-of-mass energies between the threshold and 6.0~GeV using a data sample of 980~fb$^{-1}$ collected with the Belle detector on or near the $Upsilon(nS)$ resonances, where $n=$1, 2, ..., 5. The cross sections for $e^+ e^- to K^+ K^- J/psi$ are at a few pb level and the average cross section for $e^+ e^- to K_S^0K_S^0J/psi$ is $1.8pm 0.6 (rm stat.)pm 0.3 (rm syst.)$~pb between 4.4 and 5.2~GeV. All of them are consistent with previously published results with improved precision. A search for resonant structures and associated intermediate states in the cross section of the process $e^+ e^- to K^+ K^- J/psi$ is performed.
The cross section for e^+e^- to pi^+pi^-J/psi between 3.8 and 5.5 GeV/c^2 is measured using a 548 fb^{-1} data sample collected on or near the Upsilon(4S) resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c^2, corresponding to the so called Y(4260), is observed. In addition, there is another cluster of events at around 4.05 GeV/c^2. A fit using two interfering Breit-Wigner shapes describes the data better than one that uses only the Y(4260), especially for the lower mass side of the 4.25 GeV enhancement.
We report measurement of the cross section of $e^+e^-to pi^+pi^-psi(2S)$ between 4.0 and $5.5 {rm GeV}$, based on an analysis of initial state radiation events in a $980 rm fb^{-1}$ data sample recorded with the Belle detector. The properties of the $Y(4360)$ and $Y(4660)$ states are determined. Fitting the mass spectrum of $pi^+pi^-psi(2S)$ with two coherent Breit-Wigner functions, we find two solutions with identical mass and width but different couplings to electron-positron pairs: $M_{Y(4360)} = (4347pm 6pm 3) {rm MeV}/c^2$, $Gamma_{Y(4360)} = (103pm 9pm 5) {rm MeV}$, $M_{Y(4660)} = (4652pm10pm 8) {rm MeV}/c^2$, $Gamma_{Y(4660)} = (68pm 11pm 1) rm MeV$; and ${cal{B}}[Y(4360)to pi^+pi^-psi(2S)]cdot Gamma_{Y(4360)}^{e^+e^-} = (10.9pm 0.6pm 0.7) rm eV$ and ${cal{B}}[Y(4660)to pi^+pi^-psi(2S)]cdot Gamma_{Y(4660)}^{e^+e^-} = (8.1pm 1.1pm 0.5) rm eV$ for one solution; or ${cal{B}}[Y(4360)to pi^+pi^-psi(2S)]cdot Gamma_{Y(4360)}^{e^+e^-} = (9.2pm 0.6pm 0.6) rm eV$ and ${cal{B}}[Y(4660)to pi^+pi^-psi(2S)]cdot Gamma_{Y(4660)}^{e^+e^-} = (2.0pm 0.3pm 0.2) rm eV$ for the other. Here, the first errors are statistical and the second systematic. Evidence for a charged charmoniumlike structure at $4.05 {rm GeV}/c^2$ is observed in the $pi^{pm}psi(2S)$ intermediate state in the $Y(4360)$ decays.
The process $e^+e^- to gammachi_{cJ}$ ($J$=1, 2) is studied via initial state radiation using 980 fb$^{-1}$ of data at and around the $Upsilon(nS)$ ($n$=1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No significant signal is observed except from $psi(2S)$ decays. Upper limits on the cross sections between $sqrt{s}=3.80$ and $5.56~{rm GeV}$ are determined at the 90% credibility level, which range from few pb to a few tens of pb. We also set upper limits on the decay rate of the vector charmonium [$psi(4040$), $psi(4160)$, and $psi(4415)$] and charmoniumlike [$Y(4260)$, $Y(4360)$, and $Y(4660)$] states to $gammachi_{cJ}$.
The cross section for $e^+ e^- to pi^+ pi^- J/psi$ between 3.8 GeV and 5.5 GeV is measured with a 967 fb$^{-1}$ data sample collected by the Belle detector at or near the $Upsilon(nS)$ ($n = 1, 2, ..., 5$) resonances. The Y(4260) state is observed, and its resonance parameters are determined. In addition, an excess of $pi^+ pi^- J/psi$ production around 4 GeV is observed. This feature can be described by a Breit-Wigner parameterization with properties that are consistent with the Y(4008) state that was previously reported by Belle. In a study of $Y(4260) to pi^+ pi^- J/psi$ decays, a structure is observed in the $M(pi^pmjpsi)$ mass spectrum with $5.2sigma$ significance, with mass $M=(3894.5pm 6.6pm 4.5) {rm MeV}/c^2$ and width $Gamma=(63pm 24pm 26)$ MeV/$c^{2}$, where the errors are statistical and systematic, respectively. This structure can be interpreted as a new charged charmonium-like state.
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