We observe a narrow enhancement near 2m(p) in the invariant mass spectrum of pp pairs from radiative J/psi-->gammapp decays. No similar structure is seen in J/psi-->pi(0)pp decays. The results are based on an analysis of a 58 x 10(6) event sample of J/psi decays accumulated with the BESII detector at the Beijing electron-positron collider. The enhancement can be fit with either an S- or P-wave Breit-Wigner resonance function. In the case of the S-wave fit, the peak mass is below 2m(p) at M=1859(+3)(-10) (stat)+5-25(syst) MeV/c(2) and the total width is Gamma<30 MeV/c(2) at the 90% confidence level. These mass and width values are not consistent with the properties of any known particle.
The method of threshold-photodetachment spectroscopy has been used to measure the electron aSnity of Li. Changes in the partial cross sections for the resolved hv+Li (2'S)~Li(2 S)+e (ep) ( Sap) and h v+Li (2 'S)~Li(2 P)+e (es) ( Pcs) channels were separately investigated in the vicinity of the 2 P threshold. The near-threshold data in the Pcs channel were fitted to a Wigner law to determine a threshold photon energy of 19884.8+1.6 cm '. An electron affinity of 4980.9+1.6 cm (617.6+0.2 meV) is obtained upon subtraction of the well-known 2 P excitation energy. The position of the Wigner cusp in the Sap channel was measured to be 19882.4+4.0 cm ', in agreement with the more precise Pcs-channel threshold energy. PACS number(s): 32.80.Fb, 35.10.Hn 610 596248 608 615
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