Amplitude analysis of the D+ → π−π+π+ decay and measurement of the π−π+ S-wave amplitude

Abstract

An amplitude analysis of the D+→ π−π+π+ decay is performed with a sample corresponding to 1.5 fb−1 of integrated luminosity of pp collisions at a centre-of-mass energy $$ \sqrt{s} $$ s = 8 TeV collected by the LHCb detector in 2012. The sample contains approximately six hundred thousand candidates with a signal purity of 95%. The resonant structure is studied through a fit to the Dalitz plot where the π−π+ S-wave amplitude is extracted as a function of π−π+ mass, and spin-1 and spin-2 resonances are included coherently through an isobar model. The S-wave component is found to be dominant, followed by the ρ(770)0π+ and f2(1270)π+ components. A small contribution from the ω(782) → π−π+ decay is seen for the first time in the D+→ π−π+π+ decay.