Measurement of the decay $B^0\toπ^-\ell^+ν$ and determination of $|V_{ub}|$

H. Ha, E. Won, I. Adachi, H. Aihara, T. Aziz, A. M. Bakich, V. Balagura, E. Barberio, A. Bay, K. Belous, V. Bhardwaj, B. Bhuyan, M. Bischofberger, A. Bondar, A. Bozek, M. Bracko, T. E. Browder, Y. Chao, A. Chen, P. Chen, B. G. Cheon, C. -C. Chiang, I. -S. Cho, K. Cho, K. -S. Choi, Y. Choi, J. Dalseno, M. Danilov, Z. Dolezal, A. Drutskoy, W. Dungel, S. Eidelman, N. Gabyshev, B. Golob, J. Haba, K. Hayasaka, H. Hayashii, Y. Horii, Y. Hoshi, W. -S. Hou, Y. B. Hsiung, H. J. Hyun, T. Iijima, K. Inami, R. Itoh, M. Iwabuchi, Y. Iwasaki, N. J. Joshi, T. Julius, J. H. Kang, T. Kawasaki, C. Kiesling, H. J. Kim, H. O. Kim, M. J. Kim, S. K. Kim, Y. J. Kim, K. Kinoshita, B. R. Ko, S. Korpar, P. Krizan, T. Kuhr, T. Kumita, A. Kuzmin, Y. -J. Kwon, S. -H. Kyeong, J. S. Lange, M. J. Lee, S. -H. Lee, Y. Li, A. Limosani, C. Liu, Y. Liu, D. Liventsev, R. Louvot, S. McOnie, K. Miyabayashi, H. Miyata, Y. Miyazaki, G. B. Mohanty, T. Mori, Y. Nagasaka, E. Nakano, M. Nakao, H. Nakazawa, Z. Natkaniec, S. Neubauer, S. Nishida, K. Nishimura, O. Nitoh, T. Nozaki, S. Ogawa, T. Ohshima, S. Okuno, S. L. Olsen, P. Pakhlov, G. Pakhlova, C. W. Park, H. Park, H. K. Park, R. Pestotnik, M. Petric, L. E. Piilonen, M. Rohrken, S. Ryu, H. Sahoo, Y. Sakai, O. Schneider, C. Schwanda, A. J. Schwartz, K. Senyo, M. E. Sevior, M. Shapkin, C. P. Shen, J. -G. Shiu, F. Simon, P. Smerkol, Y. -S. Sohn, A. Sokolov, S. Stanic, M. Staric, T. Sumiyoshi, Y. Teramoto, K. Trabelsi, S. Uehara, T. Uglov, Y. Unno, S. Uno, S. E. Vahsen, G. Varner, K. E. Varvell, A. Vossen, C. H. Wang, M. -Z. Wang, P. Wang, M. Watanabe, Y. Watanabe, Y. Yamashita, Z. P. Zhang, P. Zhou, V. Zhulanov, T. Zivko, A. Zupanc

Published 2010-12-01, updated 2011-01-28Version 4

We present a measurement of the charmless semileptonic decay $B^0\to\pi^-\ell^+\nu$ using a data sample containing 657$\times 10^6$ $B\bar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider operating near the $\Upsilon(4S)$ resonance. We determine the total branching fraction of the decay, $\mathcal{B}(B^0\to\pi^-\ell^+\nu)=(1.49\pm 0.04{(\mathrm{stat})}\pm 0.07{(\mathrm{syst})})\times 10^{-4}$. We also report a new precise measurement of the differential decay rate, and extract the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ using model-independent and -dependent approaches. From a simultaneous fit to the measured differential decay rate and lattice QCD results, we obtain $|V_{ub}|=(3.43\pm 0.33)\times 10^{-3}$, where the error includes both statistical and systematic uncertainties.