Baryonic resonances close to the Kbar-N threshold: the case of Sigma(1385)^+ in pp collisions

TL;DR

This study measures the properties and production cross-section of the Sigma(1385)^+ hyperon in proton-proton collisions at 3.5 GeV, providing detailed invariant mass and angular distribution data.

Contribution

It offers the first exclusive measurement of Sigma(1385)^+ in pp collisions, including mass, width, cross-section, and decay dynamics, enhancing understanding of baryonic resonances near the Kbar-N threshold.

Findings

Mass of Sigma(1385)^+ at 1383.2 MeV/c^2

Width of 40.2 MeV/c^2

Production cross-section of 22.27 μb

Abstract

We present results of an exclusive measurement of the first excited state of the Sigma hyperon, Sigma(1385)^+, produced in p+p -> Sigma^+ + K^+ + n at 3.5 GeV beam energy. The extracted data allow to study in detail the invariant mass distribution of the Sigma(1385)^+. The mass distribution is well described by a relativistic Breit-Wigner function with a maximum at m_0 = 1383.2 +- 0.9 MeV/c^2 and a width of 40.2 +- 2.1 MeV/c^2. The exclusive production cross-section comes out to be 22.27 +- 0.89 +- 1.56 +3.07 -2.10 mu b. Angular distributions of the Sigma(1385)^+ in different reference frames are found to be compatible with the hypothesis that 33 % of Sigma(1385)^+ result from the decay of an intermediate Delta^{++} resonance.