Searching for the B0d,s → ∅π+ π- decays
Abstract
Using 3 fb-1 of pp collision data collected at √s = 7 and 8 TeV by the LHCb
experiment in the 2011 and 2012 data taking periods, the decays B⁰s → ϕπ+π-
and B⁰d → ϕπ+π- have been studied in the π+π- invariant mass range below
1600 MeV/c². The B⁰s,d → ϕπ+π- branching fractions are determined to be:
B(B⁰s → ϕπ+π-;mππ < 1600) = [3:72 ± 0:18 ± 0:38 ± 0:38] x 10-6
B(B⁰d → ϕπ+π-,mππ < 1600) = [1:75 ± 0:25 ± 0:42 ± 0:14] x 10-7
where the first uncertainty is statistical, the second is systematic, and the third
comes from the normalisation mode B⁰s → ϕϕ. From the π+π- mass distribution
and fits to angular distributions, the resonant decay mode B⁰s → ϕf₀(980) is observed and the branching fraction is measured to be:
B(B⁰s → ϕf₀(980); f₀(980) → π+π-) = [1:23 ± 0:15 ± 0:12 ± 0:12] x 10-6
The fit also requires contributions from B⁰s → ϕf2(1270). A search for a P-wave contribution from B⁰s → ϕρ⁰(770) finds evidence at ~ 4σ but confirmation will require more data. An upper limit of the B⁰s → ϕρ⁰(770) decay branching fraction
at 90% C.L. is measured to be:
B(B⁰s → ϕρ⁰(770)) < 4 x 10-7