J/ψ and ψ(2S) polarization in proton-proton collisions at energies available at the CERN Large Hadron Collider using PYTHIA8

The production mechanisms of charmonium states in both hadronic and heavy-ion collisions hold great significance for investigating the hot and dense QCD matter. Studying charmonium polarization in ultrarelativistic collisions can also provide insights into the underlying production mechanisms. With this motivation, we explore the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>J</a:mi><a:mo>/</a:mo><a:mi>ψ</a:mi></a:mrow></a:math> and <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mi>ψ</b:mi><b:mo>(</b:mo><b:mn>2</b:mn><b:mi>S</b:mi><b:mo>)</b:mo></b:mrow></b:math> polarization in proton<c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mo>+</c:mo></c:math>proton collisions at <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:msqrt><d:mi>s</d:mi></d:msqrt><d:mo>=</d:mo><d:mn>7</d:mn></d:math>, 8, and 13 TeV using a pQCD-inspired Monte Carlo event generator called 8. This work considers reconstructed quarkonia through their dimuons decay channel in the ALICE forward rapidity acceptance range of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mn>2.5</e:mn><e:mo><</e:mo><e:msub><e:mi>y</e:mi><e:mrow><e:mi>μ</e:mi><e:mi>μ</e:mi></e:mrow></e:msub><e:mo><</e:mo><e:mn>4</e:mn></e:mrow></e:math>. Further, we calculate the polarization parameters <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:msub><f:mi>λ</f:mi><f:mi>θ</f:mi></f:msub><f:mo>,</f:mo><f:mo> </f:mo><f:msub><f:mi>λ</f:mi><f:mi>ϕ</f:mi></f:msub><f:mo>,</f:mo><f:mo> </f:mo><f:msub><f:mi>λ</f:mi><f:mrow><f:mi>θ</f:mi><f:mi>ϕ</f:mi></f:mrow></f:msub></f:math> from the polar and azimuthal angular distributions of the dimuons in helicity and Collins-Soper frames. This study presents a comprehensive measurement of the polarization parameters as a function of transverse momentum, charged-particle multiplicity, and rapidity at the LHC energies. Our findings of charmonium polarization are in qualitative agreement with the corresponding experimental data.