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 √ 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.