Observation of a near-threshold enhancement in the e+e- -->Lambdac+Lambdac- cross section using initial-state radiation
Abstract
We report a measurement of the exclusive e+e- -->Lambdac+ Lambdac- cross section as a function of center-of-mass energy near the Lambdac+ Lambdac- threshold. A clear peak with a significance of 8.2 sigma is observed in the Lambdac+ Lambdac- 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 Gammatot=(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 (4S) resonance and nearby continuum with an integrated luminosity of 695/fb at the KEKB asymmetric-energy e+e- collider.
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