Dalitz plot analysis and branching fraction measurement of D+ and Ds+ -> pi+pi-pi+

TL;DR

This paper presents a Dalitz plot analysis and branching fraction measurements for D+ and Ds+ decays into three pions, revealing a scalar resonance consistent with the sigma meson and detailed resonance contributions.

Contribution

It provides the first detailed Dalitz plot analysis of these decays, identifying a scalar sigma resonance and measuring properties of several scalar mesons.

Findings

Evidence for a scalar sigma resonance at 478 MeV/c^2

Significant contributions from multiple vector and scalar resonances in Ds+ decay

New measurements of f0(980) and f0(1370) resonance parameters

Abstract

Fermilab fixed target experiment E791 obtained a sample of $1172 \pm 61$ events of $D^+ \to \pi^- \pi^+ \pi^+$ and 848 $\pm 44$ events of $D_s^+ \to \pi^- \pi^+ \pi^+$ decays. We find respectively $B (D^+ \to \pi^- \pi^+ \pi^+) / B (D^+ \to K^- \pi^+ \pi^+) = 0.0311 \pm 0.0018 ^ {+0.0016}_{-0.0026}$ and $B(D_s^+ \to \pi^+ \pi^- \pi^+) / B(D_s^+ \to \phi \pi^+) = 0.245 \pm 0.028^{+0.019}_{-0.012}$. Using a coherent amplitude analysis to fit the Dalitz plot of the $D^+ \to \pi^- \pi^+ \pi^+$ decay, we find strong evidence for a scalar resonance of mass $478^{+24}_{-23} \pm 17 $MeV/$c^2$ and width $324^{+42}_{-40} \pm 21$ MeV/$c^2$, compatible with what is expected for the isoscalar meson $\sigma$ >. The $D^+ \to \sigma(500) \pi^+$ fraction accounts for approximately half of all three-charged-pion decays of the $D^+$ . From the Dalitz plot analysis of the $D_s^+ \to \pi^- \pi^+ \pi^+$ decay events, we find significant contributions from the channels $\rho^0(770)\pi^+$, $\rho^0(1450)\pi^+$, $f_0(980)\pi^+$, $f_2(1270)\pi^+$, and $f_0(1370)\pi^+$. We also present new measurement of the masses and widths of the isoscalar resonances $f_0(980)$ and $f_0(1370)$.