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Time-dependent analysis of the decay B0 → ρ0ρ0

Aubert B., Bona M., Boutigny D., Karyotakis Y., Lees J. P., Poireau V., Prudent X., Tisserand V., Zghiche A., Garra Tico J., Grauges E., Lopez L., Palano A., Pappagallo M., Eigen G., Stugu B., Sun L., Abrams G. S., Battaglia M., Brown D. N., Button-Shafer J., Cahn R. N., Groysman Y., Jacobsen R. G., Kadyk J. A., Kerth L. T., Kolomensky Yu G., Kukartsev G., Lopes Pegna D., Lynch G., Mir L. M., Orimoto T. J., Osipenkov I. L., Ronan M. T., Tackmann K., Tanabe T., Wenzel W. A., Del Amo Sanchez P., Hawkes C. M., Watson A. T., Koch H., Schroeder T., Walker D., Asgeirsson D. J., Cuhadar-Donszelmann T., Fulsom B. G., Hearty C., Mattison T. S., McKenna J. A., Khan A., Saleem M., Teodorescu L., Blinov V. E., Bukin A. D., 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., Foulkes S. D., Gary J. W., Liu F., Long O., Shen B. C., Vitug G. M., Zhang L., Paar H. P., Rahatlou S., Sharma V., Berryhill J. W., Campagnari C., Cunha A., Dahmes B., Hong T. M., Kovalskyi D., Richman J. D., Beck T. W., Eisner A. M., Flacco C. J., Heusch C. A., Kroseberg J., Lockman W. S., Schalk T., Schumm B. A., Seiden A., Wilso M. G., Winstrom L. O.

We study the decay B0 → ρ0ρ0 in a sample of about 427 million γ(4S) → BB decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find the branching fraction B = (0.84 ± 0.29 ± 0.17) × 10-6 and longitudinal polarization fraction of fL = 0.70 ± 0.14 ± 0.05, where the first uncertainty is statistical, and the second is systematic. The evidence for the B0 → ρ0ρ0signal has 3.6σ significance. We investigate the proper-time dependence of the longitudinal component in the decay and measure the CP-violating coefficients S00 L = (0.5± 0.9 ± 0.2) and C00 L = (0.4 ± 0.9 ± 0.2), corresponding to the sine and cosine terms in the time evolution of asymmetry. We study the implication of these results for penguin contributions in B → ρρ decays and for the CKM unitarity angle α.