Improved Measurement of B + → ρ + ρ 0 and Determination of the Quark-Mixing Phase Angle α

• Published in: Physical review letters 2009-07, Vol.102 (14), Article 141802
• Main Authors: Aubert, B., 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., Hirschauer, J. F., Nagel, M., Nauenberg, U., Smith, J. G.
• Format: Article
• Language: English
• Subjects: ASYMMETRY; B MESONS; DECAY; Experiment-HEP,HEPEX; High Energy Physics - Experiment; ISOSPIN; PARTICLE ACCELERATORS; Physics; POLARIZATION; STANFORD LINEAR ACCELERATOR CENTER
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.102.141802

We present improved measurements of the branching fraction ${\cal B}$, the longitudinal polarization fraction $f_L$, and the direct {\ensuremath{CP}\xspace} asymmetry {\ensuremath{{\cal A}_{CP}}\xspace} in the $B$ meson decay channel $B^+\to\rho^+\rho^0$. The data sample was collected with the {{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}}} detector at SLAC. The results are ${\cal B} (\Bp\ra\rprz)=(23.7\pm1.4\pm1.4)\times10^{-6}$, $f_L=0.950\pm0.015\pm0.006$, and $\Acp=-0.054\pm0.055\pm0.010$, where the uncertainties are statistical and systematic, respectively. Based on these results, we perform an isospin analysis and determine the CKM weak phase angle $\alpha$ to be $(92.4^{+6.0}_{-6.5})^{\circ}$.