Dalitz Plot Analysis of the Decay D^+ --> K^- pi^+ pi^+ and Indication of a Low-Mass Scalar K pi Resonance

TL;DR

This paper analyzes the decay D^+ --> K^- pi^+ pi^+ using Dalitz plots, revealing the necessity of an additional low-mass scalar resonance to accurately model the decay, thus providing new insights into scalar mesons.

Contribution

It introduces evidence for a new low-mass scalar K pi resonance in D^+ decay analysis, improving understanding of scalar mesons in hadron spectroscopy.

Findings

Identification of a low-mass scalar resonance at ~797 MeV/c^2

Refined parameters for the K^*_0(1430) resonance

Improved fit quality with the additional scalar resonance

Abstract

We study the Dalitz plot of the decay D^+ --> K^- pi^+ pi^+ with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known K pi resonances and a uniform nonresonant term, we do not obtain an acceptable fit. If we allow the mass and width of the K^*_0(1430) to float, we obtain values consistent with those from PDG but the chi^2 per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797 +/- 19 +/- 43 MeV/c^2 and width 410 +/- 43 +/- 87 MeV/c^2. The mass and width of the K^*_0(1430) become 1459 +/- 7 +/- 5 MeV/c^2 and 175 +/- 12 +/- 12 MeV/c^2, respectively. Our results provide new information on the scalar sector in hadron spectroscopy.