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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2009, vol. 103, p. -

Evidence for the ηb(1S) meson in radiative Υ(2S) decay

Aubert B., Bona M., Karyotakis Y., Lees J. P., Poireau V., Prencipe E., Prudent X., Tisserand V., Garra Tico J., Grauges E., Lopez L., Palano A., Pappagallo M., Eigen G., Stugu B., Sun L., Battaglia M., Brown D. N., Kerth L. T., Kolomensky Yu G., Lynch G., Osipenkov I. L., Tackmann K., Tanabe T., Hawkes C. M., Soni N., Watson A. T., Koch H., Schroeder T., Asgeirsson D. J., Fulsom B. G., Hearty C., Mattison T. S., McKenna J. A., Barrett M., Khan A., Randle-Conde A., Blinov V. E., Bukin A. D., Buzykaev A. R., Druzhinin V. P., Golubev V. B., Onuchin A. P., Serednyakov S. I., Skovpen Yu I., Solodov E. P., Todyshev K. Yu, Bondioli M., Curry S., Eschrich I., Kirkby D., Lankford A. J., Lund P., Mandelkern M., Martin E. C., Stoker D. P., Abachi S., Buchanan C., Atmacan H., Gary J. W., Liu F., Long O., Vitug G. M., Yasin Z., Zhang L., Sharma V., Campagnari C., Hong T. M., Kovalskyi D., Mazur M. A., Richman J. D., Beck T. W., Eisner A. M., Heusch C. A., Kroseberg J., Lockman W. S., Martinez A. J., Schalk T., Schumm B. A., Seiden A., Winstrom L. O., Cheng C. H., Doll D. A., Echenard B., Fang F., Hitlin D. G., Narsky I., Piatenko T., Porter F. C., Andreassen R., Mancinelli G., Meadows B. T., Mishra K., Sokoloff M. D., Bloom P. C., Ford W. T., Gaz A.

We have performed a search for the ηb(1S) meson in the radiative decay of the Υ(2S) resonance using a sample of 91.6×106 Υ(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at Eγ=609.3-4.5+4.6(stat)±1.9(syst)MeV, corresponding to an ηb(1S) mass of 9394.2-4.9+4.8(stat)±2.0(syst)MeV/c2. The branching fraction for the decay Υ(2S)→γηb(1S) is determined to be [3.9±1.1(stat)-0.9+1.1(syst)]×10-4. We find the ratio of branching fractions B[Υ(2S)→γηb(1S)]/B[Υ(3S) →γηb(1S)]=0.82±0.24(stat)-0.19+0.20(syst). © 2009 The American Physical Society.