RT Journal Article T1 Observation of the B0→ρ0ρ0 decay from an amplitude analysis of B0→(π+π−)(π+π−)decays A1 LHCb Collaboration, A1 Adeva Andany, Bernardo A1 Dosil Suárez, Álvaro A1 Fernández Albor, Víctor Manuel A1 Gallas Torreira, Abraham Antonio A1 García Pardiñas, Julián A1 Hernando Morata, José Ángel A1 Plo Casasus, Máximo A1 Romero Vidal, Antonio A1 Saborido Silva, Juan José A1 Sanmartín Sedes, Brais A1 Santamarina Ríos, Cibrán A1 Vázquez Regueiro, Pablo A1 Vázquez Sierra, Carlos A1 Vieites Díaz, María AB Proton–proton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0fb−1, are analysed to search for the charmless B0→ρ0ρ0decay. 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→ρ0ρ0decay is observed for the first time with 7.1 standard deviations significance. The fraction of B0→ρ0ρ0decays yielding a longitudinally polarised final state is measured to be fL=0.745+0.048−0.058(stat) ±0.034(syst). The B0→ρ0ρ0branching fraction, using the B0→φK∗(892)0decay as reference, is also reported as B(B0→ρ0ρ0)=(0.94±0.17(stat)±0.09(syst)±0.06(BF))×10−6 PB Elsevier SN 0370-2693 YR 2015 FD 2015 LK http://hdl.handle.net/10347/21833 UL http://hdl.handle.net/10347/21833 LA eng NO Aaij, R., Adeva, B., Adinolfi, M., Affolder, A., Ajaltouni, Z., Akar, S., ... & Alkhazov, G. (2015). Observation of the B0→ ρ0ρ0 decay from an amplitude analysis of B0→(π+ π−)(π+ π−) decays. Physics Letters B, 747, 468-478 DS Minerva RD 28 abr 2026