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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2015, vol. 91, 11, p. -

Search for D<sup>0</sup> →γγ and improved measurement of the branching fraction for D<sup>0</sup> →π<sup>0</sup>π<sup>0</sup>

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., Ferroli R. Baldini, Ban Y., Bennett D. W., Bennett J. V., Bertani M., Bettoni D., Bian J. M., Bianchi F., Boger E., Bondarenko O., 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. J., Chen X., Chen X. R., Chen Y. B., Cheng H. P., Chu X. K., Cibinetto G., Cronin-Hennessy D., 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., Du S. X., Duan P. F., Fan J. Z., Fang J., Fang S. S., Fang X., Fang Y., Fava L., Feldbauer F., Felici G., Feng C. Q., Fioravanti E., Fritsch M., Fu C. D., Gao Q., Gao X. Y., Gao Y., Gao Z., Garzia I., Geng C., Goetzen K., Gong W. X., Gradl W., Greco M., Gu M. H., Gu Y. T., Guan Y. H., Guo A. Q., Guo L. B., Guo Y., Guo Y. P.

© 2015 American Physical Society. Using 2.92 fb<sup>-1</sup> of electron-positron annihilation data collected at √s = 3.773 GeV with the BESIII detector, we report the results of a search for the flavor-changing neutral current process D<sup>0</sup> →γγ using a double-tag technique. We find no signal and set an upper limit at 90% confidence level for the branching fraction of B(D<sup>0</sup> →γγ)< 3.8 × 10-6. We also investigate D<sup>0</sup>-meson decay into two neutral pions, obtaining a branching fraction of B(D<sup>0</sup> →π<sup>0</sup>π<sup>0</sup>)= (8.24 ± 0.21(stat) ± 0.30(syst)) × 10-4, the most precise measurement to date and consistent with the current world average.