Measurements of Chemical Potentials in Pb-Pb Collisions at sNN=5.02 TeV

This Letter presents the most precise measurement to date of the matter-antimatter imbalance at midrapidity in Pb-Pb collisions at a center-of-mass energy per nucleon pair <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msqrt><a:mrow><a:msub><a:mrow><a:mi>s</a:mi></a:mrow><a:mrow><a:mi>NN</a:mi></a:mrow></a:msub></a:mrow></a:msqrt><a:mo>=</a:mo><a:mn>5.02</a:mn><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi>TeV</a:mi></a:mrow></a:math>. Using the Statistical Hadronization framework, it is possible to obtain the value of the electric charge and baryon chemical potentials, <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:msub><c:mrow><c:mi>μ</c:mi></c:mrow><c:mrow><c:mi>Q</c:mi></c:mrow></c:msub><c:mo>=</c:mo><c:mo>−</c:mo><c:mn>0.18</c:mn><c:mo>±</c:mo><c:mn>0.90</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:mi>MeV</c:mi></c:mrow></c:math> and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:msub><e:mrow><e:mi>μ</e:mi></e:mrow><e:mrow><e:mi>B</e:mi></e:mrow></e:msub><e:mo>=</e:mo><e:mn>0.71</e:mn><e:mo>±</e:mo><e:mn>0.45</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:mi>MeV</e:mi></e:mrow></e:math>, with unprecedented precision. A centrality-differential study of the antiparticle-to-particle yield ratios of charged pions, protons, <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi mathvariant="normal">Ω</g:mi></g:math> baryons, and light (hyper)nuclei is performed. These results indicate that the system created in Pb-Pb collisions at the LHC is on average baryon-free and electrically neutral at midrapidity.