Σ⁺ production in pp collisions at √s = 13 TeV

The measurement of Σ⁺ production in pp collisions at √s = 13 TeV is presented. The measurement is performed at midrapidity in both minimum-bias and high-multiplicity pp collisions at √s = 13 TeV. The Σ⁺ is reconstructed via its weak-decay topology in the decay channel Σ⁺ → p + π⁰ with π⁰ → γ+ γ. In a novel approach, the neutral pion is reconstructed by combining photons that convert in the detector material with photons measured in the calorimeters. The transverse-momentum (pT) distributions of the Σ⁺ and its rapidity densities dN/dy in both event classes are reported. The pT spectrum in minimum-bias collisions is compared to QCD-inspired event generators. The ratio of Σ⁺ to previously measured $Λ$ baryons is in good agreement with calculations from the Statistical Hadronization Model. The high efficiency and purity of the novel reconstruction method for Σ⁺ presented here will enable future studies of the interaction of Σ⁺ with protons in the context of femtoscopic measurements, which could be crucial for understanding the equation of state of neutron stars.