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.).
Jan Steggemann, Konstantin Androsov, Anna Mascellani, Joanna Malgorzata Wanczyk
Olivier Schneider, Aurelio Bay, Guido Haefeli, Tatsuya Nakada, Frédéric Blanc, Lesya Shchutska, Elena Graverini, Sebastian Schulte, Donal Patrick Hill, Marie Theres Christin Bachmayer, Serhii Cholak, Ettore Zaffaroni, Aravindhan Venkateswaran, Luis Miguel Garcia Martin, Vitalii Lisovskyi, Elisabeth Maria Niel, Federico Ronchetti, Radoslav Marchevski, Anni Matilda Kauniskangas, Dimitrios Kaminaris, Raphaël van Laak, Pierre Paul Louis Mayencourt, Brianna Leililani Thielen, Arnaud Merlin Gauthey, Gianluca Zunica, Abdul-Kerim Guseinov, Esteban Curras Rivera, Yifei Song, Roberto Ribatti, Alexandre Brea Rodriguez, Rita De Sousa Ataíde Da Silva