Z-boson production in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 8.16 TeV and Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV
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<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>Measurement of Z-boson production in p-Pb collisions at <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s_{\mathrm{NN}}} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:msub> <mml:mi>s</mml:mi> <mml:mi>NN</mml:mi> </mml:msub> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 8<jats:italic>.</jats:italic>16 TeV and Pb-Pb collisions at <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s_{\mathrm{NN}}} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:msub> <mml:mi>s</mml:mi> <mml:mi>NN</mml:mi> </mml:msub> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 5<jats:italic>.</jats:italic>02 TeV is reported. It is performed in the dimuon decay channel, through the detection of muons with pseudorapidity <jats:italic>−</jats:italic>4 <jats:italic>< η</jats:italic><jats:sub><jats:italic>μ</jats:italic></jats:sub><jats:italic>< −</jats:italic>2<jats:italic>.</jats:italic>5 and transverse momentum <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {p}_{\mathrm{T}}^{\mu } $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>p</mml:mi> <mml:mi>T</mml:mi> <mml:mi>μ</mml:mi> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula><jats:italic>></jats:italic> 20 GeV/<jats:italic>c</jats:italic> in the laboratory frame. The invariant yield and nuclear modification factor are measured for opposite-sign dimuons with invariant mass 60 <jats:italic>< m</jats:italic><jats:sub><jats:italic>μμ</jats:italic></jats:sub><jats:italic><</jats:italic> 120 GeV/<jats:italic>c</jats:italic><jats:sup>2</jats:sup> and rapidity 2<jats:italic>.</jats:italic>5 <jats:italic><</jats:italic><jats:inline-formula><jats:alternatives><jats:tex-math>$$ {y}_{\mathrm{cms}}^{\mu \mu} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>y</mml:mi> <mml:mi>cms</mml:mi> <mml:mi>μμ</mml:mi> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula><jats:italic><</jats:italic> 4. They are presented as a function of rapidity and, for the Pb-Pb collisions, of centrality as well. The results are compared with theoretical calculations, both with and without nuclear modifications to the Parton Distribution Functions (PDFs). In p-Pb collisions the center-of-mass frame is boosted with respect to the laboratory frame, and the measurements cover the backward (<jats:italic>−</jats:italic>4<jats:italic>.</jats:italic>46 <jats:italic><</jats:italic><jats:inline-formula><jats:alternatives><jats:tex-math>$$ {y}_{\mathrm{cms}}^{\mu \mu} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>y</mml:mi> <mml:mi>cms</mml:mi> <mml:mi>μμ</mml:mi> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula><jats:italic>< −</jats:italic>2<jats:italic>.</jats:italic>96) and forward (2<jats:italic>.</jats:italic>03 <jats:italic><</jats:italic><jats:inline-formula><jats:alternatives><jats:tex-math>$$ {y}_{\mathrm{cms}}^{\mu \mu} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>y</mml:mi> <mml:mi>cms</mml:mi> <mml:mi>μμ</mml:mi> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula><jats:italic><</jats:italic> 3<jats:italic>.</jats:italic>53) rapidity regions. For the p-Pb collisions, the results are consistent within experimental and theoretical uncertainties with calculations that include both free-nucleon and nuclear-modified PDFs. For the Pb-Pb collisions, a 3<jats:italic>.</jats:italic>4<jats:italic>σ</jats:italic> deviation is seen in the integrated yield between the data and calculations based on the free-nucleon PDFs, while good agreement is found once nuclear modifications are considered.</jats:p>
収録刊行物
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- Journal of High Energy Physics
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Journal of High Energy Physics 2020 (9), 2020-09
Springer Science and Business Media LLC