$$\Sigma ^{+}$$ production in pp collisions at $$\sqrt{\textit{s}}=13$$ TeV

Abstract The measurement of $$\Sigma ^{+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Σ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:math> production in pp collisions at $$\sqrt{s}=13$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> </mml:math> TeV is presented. The measurement is performed at midrapidity in both minimum-bias and high-multiplicity pp collisions at $$\sqrt{s} =13$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> </mml:math> TeV. The $$\Sigma ^{+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Σ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:math> is reconstructed via its weak-decay topology in the decay channel $$\Sigma ^{+} \rightarrow \mathrm{{p}} + \pi ^{0}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>Σ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>p</mml:mi> <mml:mo>+</mml:mo> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> </mml:mrow> </mml:math> with $$\pi ^{0} \rightarrow \gamma + \gamma .$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>γ</mml:mi> <mml:mo>+</mml:mo> <mml:mi>γ</mml:mi> <mml:mo>.</mml:mo> </mml:mrow> </mml:math> 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 $$(p_{\textrm{T}})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>p</mml:mi> <mml:mtext>T</mml:mtext> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> distributions of the $$\Sigma ^{+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Σ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:math> and its rapidity densities $${\textrm{d}}N$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>d</mml:mtext> <mml:mi>N</mml:mi> </mml:mrow> </mml:math> / $${\textrm{d}}y$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>d</mml:mtext> <mml:mi>y</mml:mi> </mml:mrow> </mml:math> in both event classes are reported. The $$p_{\textrm{T}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>p</mml:mi> <mml:mtext>T</mml:mtext> </mml:msub> </mml:math> spectrum in minimum-bias collisions is compared to QCD-inspired event generators. The ratio of $$\Sigma ^{+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Σ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:math> to previously measured $$\Lambda $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Λ</mml:mi> </mml:math> baryons is in good agreement with calculations from the Statistical Hadronization Model. The high efficiency and purity of the novel reconstruction method for $$\Sigma ^{+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Σ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:math> presented here will enable future studies of the interaction of $$\Sigma ^{+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">