A discovery of the rare decay B+ -> pi(+)mu(+)mu(-) is presented. This decay is observed for the first time, with 5.2 sigma significance. The observation is made using p p collision data, corresponding to an integrated luminosity of 1.0 fb(-1), collected with the LHCb detector. The measured branching fraction is (2.3 +/- 0.6 (stat.) +/- 0.1 (syst.)) x 10(-8), and the ratio of the B+ -> pi(+)mu(+)mu(-) and B+ -> K+mu(+)mu(-) branching fractions is measured to be 0.053 +/- 0.014 (stat.) +/- 0.001 (syst.).
Rakesh Chawla, Andrea Rizzi, Matthias Finger, Federica Legger, Matteo Galli, Sun Hee Kim, João Miguel das Neves Duarte, Tagir Aushev, Hua Zhang, Alexis Kalogeropoulos, Yixing Chen, Tian Cheng, Ioannis Papadopoulos, Gabriele Grosso, Valérie Scheurer, Meng Xiao, Qian Wang, Michele Bianco, Varun Sharma, Joao Varela, Sourav Sen, Ashish Sharma, Seungkyu Ha, David Vannerom, Csaba Hajdu, Sanjeev Kumar, Sebastiana Gianì, Kun Shi, Abhisek Datta, Siyuan Wang, Anton Petrov, Jian Wang, Yi Zhang, Muhammad Ansar Iqbal, Yong Yang, Xin Sun, Muhammad Ahmad, Donghyun Kim, Matthias Wolf, Anna Mascellani, Paolo Ronchese, Kai Yi, Ji Hyun Kim, , , , , , , , , , , , , , , , , , ,