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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2016, vol. 94, 7, p. -

Measurement of the Ds+ →+ν branching fractions and the decay constant f Ds+

Ablikim M., Achasov M. N., Ai X. C., Albayrak O., Albrecht M., Ambrose D. J., Amoroso A., An F. F., An Q., Bai J. Z., Bakina O., Baldini Ferroli R., Ban Y., Bennett D. W., Bennett J. V., Bertani M., Bettoni D., Bian J. M., Bianchi F., Boger E., Boyko I., Briere R. A., Cai H., Cai X., Cakir O., Calcaterra A., Cao G. F., Cetin S. A., Chang J. F., Chelkov G., Chen G., Chen H. S., Chen H. Y., Chen J. C., Chen M. L., Chen S., Chen S. J., Chen X., Chen X. R., Chen Y. B., Cheng H. P., Chu X. K., Cibinetto G., Dai H. L., Dai J. P., Dbeyssi A., Dedovich D., Deng Z. Y., Denig A., Denysenko I., Destefanis M., De Mori F., Ding Y., Dong C., Dong J., Dong L. Y., Dong M. Y., Dou Z. L., Du S. X., Duan P. F., Fan J. Z., Fang J., Fang S. S., Fang X., Fang Y., Farinelli R., Fava L., Feldbauer F., Felici G., Feng C. Q., Fioravanti E., Fritsch M., Fu C. D., Gao Q., Gao X. L., Gao X. Y.

© 2016 American Physical Society.Using 482 pb-1 of e+e- collision data collected at a center-of-mass energy of s=4.009 GeV with the BESIII detector, we measure the branching fractions of the decays Ds+→μ+νμ and Ds+→τ+ντ. By constraining the ratio of decay rates of Ds+ to τ+ντ and to μ+νμ to the Standard Model prediction, the branching fractions are determined to be B(Ds+→μ+νμ)=(0.495±0.067±0.026)% and B(Ds+→τ+ντ)=(4.83±0.65±0.26)%. Using these branching fractions, we obtain a value for the decay constant fDs+ of (241.0±16.3±6.5) MeV, where the first error is statistical and the second systematic.