Badalov, A.Casanova Mohr, R.Garrido Beltrán, LluísGascon, D.Graciani Díaz, RicardoGraugés Pous, EugeniPicatoste Olloqui, EduardoMolina, V. RivesRuiz, Hugo (Ruiz Pérez)LHCb collaboration2022-05-172022-05-172015-07-300370-2693https://hdl.handle.net/2445/185663Proton-proton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0 fb−1 , are analysed to search for the charmless B0 → ρ 0ρ 0 decay. More than 600 B0 → (π +π −)(π +π −) signal decays are selected and used to perform an amplitude analysis, under the assumption of no CP violation in the decay, from which the B0 → ρ 0ρ 0 decay is observed for the first time with 7.1 standard deviations significance. The fraction of B0 → ρ 0ρ 0 decays yielding a longitudinally polarised final state is measured to be fL = 0.745+0.048 −0.058(stat) ± 0.034(syst). The B0 → ρ 0ρ 0 branching fraction, using the B0 → φK∗ (892)0 decay as reference, is also reported as B(B0 → ρ 0ρ 0 ) = (0.94 ± 0.17(stat) ± 0.09(syst) ± 0.06(BF)) × 10−6 .23 p.application/pdfengcc-by (c) Badalov, A. et al., 2015https://creativecommons.org/licenses/by/4.0/HadronsGran Col·lisionador d'HadronsFísica de partículesExperimentsHadronsLarge Hadron Collider (France and Switzerland)Particle physicsExperimentsinfo:eu-repo/semantics/article6567692022-05-17info:eu-repo/semantics/openAccess