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Register a new userObservation of the $psi(1^3D_2)$ state in $e^+e^-topi^+pi^-gammachi_{c1}$ at BESIII
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We report the observation of the $X(3823)$ in the process $e^+e^-to pi^+pi^-X(3823) to pi^+pi^-gammachi_{c1}$ with a statistical significance of $6.2sigma$, in data samples at center-of-mass energies $sqrt{s}=$4.230, 4.260, 4.360, 4.420 and 4.600~GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the $X(3823)$ is $(3821.7pm 1.3pm 0.7)$~MeV/$c^2$, where the first error is statistical and the second systematic, and the width is less than $16$~MeV at the 90% confidence level. The products of the Born cross sections for $e^+e^-to pi^+pi^-X(3823)$ and the branching ratio $mathcal{B}[X(3823)to gammachi_{c1,c2}]$ are also measured. These measurements are in good agreement with the assignment of the $X(3823)$ as the $psi(1^3D_2)$ charmonium state.
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Using a data set with an integrated luminosity of 2.93 fb$^{-1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider, we extract the $e^+e^-rightarrow pi^+pi^-$ cross section and the pion form factor $|F_pi|^2$ in the energy range between 600 and 900 MeV. We exploit the method of initial state radiation for this measurement, yielding a systematic uncertainty of 0.9%. We calculate the contribution of the measured cross section to the leading-order hadronic vacuum polarization contribution to $(g-2)_mu$.
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.
With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process $e^{+} e^{-} to gamma X(3872)$ is observed for the first time with a statistical significance of $6.3sigma$. The measured mass of the $X(3872)$ is ($3871.9pm 0.7_{rm stat.}pm 0.2_{rm sys.}$) MeV/$c^2$, in agreement with previous measurements. Measurements of the product of the cross section $sigma[e^{+} e^{-} to gamma X(3872)]$ and the branching fraction $mathcal{B}[X(3872) to pi^{+} pi^{-} J/psi]$ at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process $Y(4260) to gamma X(3872)$.
We report searches for the processes $e^+e^-topi^+pi^-pi^0chi_{bJ}$ and $e^+e^-tophichi_{bJ}$ (J=1,2) based on data samples collected by the Belle experiment at the KEKB collider. We report the first observation of the process $e^+e^-to (pi^+pi^-pi^0)_{rm non-omega}chi_{b1}$ and first evidence for $e^+e^-toomegachi_{bJ}$ in the vicinity of the $Upsilon(11020)$ resonance, with center-of-mass energies from 10.96 to 11.05~GeV. The significances for $(pi^+pi^-pi^0)_{rm non-omega}chi_{b1}$ and $omegachi_{bJ}$ are greater than $5.3sigma$ and $4.0sigma$, respectively. We also investigate the energy dependence of the $e^+e^-topi^+pi^-pi^0chi_{bJ}$ cross section, but we cannot determine whether the contributions are from the $Upsilon(10860)$ and $Upsilon(11020)$ resonances or non-resonant continuum processes. The signals for $e^+e^-to phichi_{bJ}$ are not significant, and the upper limits of the Born cross sections at the 90% confidence level are $0.7$ and $1.0$~pb for $e^+e^-to phichi_{b1}$ and $phichi_{b2}$, respectively, for center-of-mass energies from 10.96 to 11.05~GeV.
We study the process $e^+e^-topsi(2S)pi^{+}pi^{-}$ with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BaBar detector at center-of-mass energies at and near the $Upsilon(mathrm{nS})$ (n = 2, 3, 4) resonances and correspond to an integrated luminosity of 520$fb^{-}$. We investigate the $psi(2S)pi^{+}pi^{-}$ mass distribution from 3.95 to 5.95 $GeV/c^{2}$, and measure the center-of-mass energy dependence of the associated $e^+e^-to psi(2S)pi^{+}pi^{-}$ cross section. The mass distribution exhibits evidence of two resonant structures. A fit to the $psi(2S)pi^{+}pi^{-}$ mass distribution corresponding to the decay mode $psi(2S)to J/psi pi^{+}pi^{-}$ yields a mass value of $4340 pm16$ (stat) $pm 9$ (syst) ${mathrm {MeV/c^{2}}}and a width of $94 pm 32$ (stat) $pm 13$ (syst) MeV for the first resonance, and for the second a mass value of $4669 pm 21$ (stat) $pm 3$ (syst) ${mathrm {MeV/c^{2}}}$ and a width of $104 pm 48$ (stat) $pm 10$ (syst) MeV. In addition, we show the $pi^{+}pi^{-}$ mass distributions for these resonant regions.
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