ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2007, vol. 99, p. -
Measurement of the e+e-→π+π-J/ψ cross section via initial-state radiation at Belle
The cross section for e+e-→π+π-J/ψ between 3.8 and 5.5GeV/c2 is measured using a 548fb-1 data sample collected on or near the Υ(4S) resonance with the Belle detector at KEKB. A peak near 4.25GeV/c2, corresponding to the so called Y(4260), is observed. In addition, there is another cluster of events at around 4.05GeV/c2. 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. © 2007 The American Physical Society.