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Register a new userDetermination of the $Lambda_c^+$ spin via the reaction $e^+e^-toLambda_c^+barLambda_c^-$
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We report on a comparison of two possible $Lambda_c^+$ spin hypotheses, $J=frac{1}{2}$ and $frac{3}{2}$, via the process $e^+e^-toLambda_c^+barLambda_c^-$, using the angular distributions of $Lambda_c^+$ decays into $pK_S^0$, $Lambdapi^+$, $Sigma^0pi^+$, and $Sigma^+pi^0$. The data were recorded at $sqrt s = 4.6$ GeV with the BESIII detector and correspond to an integrated luminosity of 587 pb$^{-1}$. The $Lambda_c^+$ spin is determined to be $J=frac{1}{2}$, with this value favored over the $frac{3}{2}$ hypothesis with a significance corresponding to more than 6 Gaussian standard deviations.
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A simultaneous fit is performed to the $e^+e^-to Lambda_c^+Lambda_c^-$ cross section data measured by Belle and BESIII from threshold up to 5.4 GeV. In order to accommodate both the BESIII measurement near threshold and the Belle observation of a resonance $Y(4630)$, we build a composite PDF with a Breit-Wigner resonance and a continuum contribution to model the full cross section line shape of $e^+e^-to Lambda_c^+Lambda_c^-$. The fit gives a mass of $M=[4636.1_{-7.2}^{+9.8} ($stat$)pm 8.0($syst$)]$~MeV/$c^2$, a width of $Gamma_{rm tot}=[34.5_{-16.2}^{+21.0} ($stat$)pm 5.6($syst$)]$~MeV, and $Gamma_{e^+ e^-}mathcal{B}[Y(4630)toLambda_c^+Lambda_c^-]=[18.3_{-6.1}^{+8.8} ($stat$)pm 1.1($syst$)]$~eV/$c^2$ for the resonance. The width of $Y(4630)$ from our study is narrower than the previous Belle fit. The mass and width of $Y(4630)$ also show good agreement with a vector resonance $Y(4626)$ recently observed in $D_s^+D_{s1}(2536)^-$ by Belle.
We report a measurement of the exclusive e+e- -->Lambda_c+ Lambda_c- cross section as a function of center-of-mass energy near the Lambda_c+ Lambda_c- threshold. A clear peak with a significance of 8.2 sigma is observed in the Lambda_c+ Lambda_c- invariant mass distribution just above threshold. With an assumption of a resonance origin for the observed peak, a mass and width of M=(4634^{+8}_{-7}(stat.)^{+5}_{-8}(sys.))Mev/c2 and Gamma_tot=(92^{+40}_{-24}(stat.)}^{+10}_{-21}(sys.))MeV are determined. The analysis is based on a study of events with initial-state-radiation photons in a data sample collected with the Belle detector at the Upsilon(4S) resonance and nearby continuum with an integrated luminosity of 695/fb at the KEKB asymmetric-energy e+e- collider.
In the experiment with the SND detector at the VEPP-2M $e^+e^-$ collider measuring the $e^+e^-to etagamma$ cross section in the energy range $0.6<sqrt{s}<1.38 mathrm{GeV}$ the reanalysis of data is performed. The goal is to improve the accuracy of the previous results by analysing ambiguities in the approximation of energy dependence of the $e^+e^-to etagamma$ cross section, which were not taken into account in our previous study. We report new results on the approximation of the $e^+e^-to etagamma$ cross section based on Vector Dominance Model under new model parameter assumptions.
We study the process $e^+e^-to J/psipi^{+}pi^{-}$ 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 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454 $mathrm{fb^{-1}}$. We investigate the $J/psi pi^{+}pi^{-}$ mass distribution in the region from 3.5 to 5.5 $mathrm{GeV/c^{2}}$. Below 3.7 $mathrm{GeV/c^{2}}$ the $psi(2S)$ signal dominates, and above 4 $mathrm{GeV/c^{2}}$ there is a significant peak due to the Y(4260). A fit to the data in the range 3.74 -- 5.50 $mathrm{GeV/c^{2}}$ yields a mass value $4244 pm 5$ (stat) $ pm 4$ (syst)$mathrm{MeV/c^{2}}$ and a width value $114 ^{+16}_{-15}$ (stat)$ pm 7$(syst)$mathrm{MeV}$ for this state. We do not confirm the report from the Belle collaboration of a broad structure at 4.01 $mathrm{GeV/c^{2}}$. In addition, we investigate the $pi^{+}pi^{-}$ system which results from Y(4260) decay.
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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