Abstract:
The production of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>η</a:mi></a:math> and <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:msup><b:mi>η</b:mi><b:mo>′</b:mo></b:msup></b:math> mesons is studied in proton-proton and proton-lead collisions collected with the LHCb detector. Proton-proton collisions are studied at center-of-mass energies of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mn>5.02</c:mn></c:mrow></c:math> and <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mn>13</d:mn><d:mspace width="4pt"/><d:mi>TeV</d:mi></d:mrow></d:math> and proton-lead collisions are studied at a center-of-mass energy per nucleon of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mrow><f:mn>8.16</f:mn><f:mspace width="4pt"/><f:mi>TeV</f:mi></f:mrow></f:math>. The studies are performed in center-of-mass (c.m.) rapidity regions <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mrow><h:mn>2.5</h:mn><h:mo><</h:mo><h:msub><h:mi>y</h:mi><h:mrow><h:mi mathvariant="normal">c</h:mi><h:mo>.</h:mo><h:mi mathvariant="normal">m</h:mi><h:mo>.</h:mo></h:mrow></h:msub><h:mo><</h:mo><h:mn>3.5</h:mn></h:mrow></h:math> (forward rapidity) and <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:mo>−</k:mo><k:mn>4.0</k:mn><k:mo><</k:mo><k:msub><k:mi>y</k:mi><k:mrow><k:mi mathvariant="normal">c</k:mi><k:mo>.</k:mo><k:mi mathvariant="normal">m</k:mi><k:mo>.</k:mo></k:mrow></k:msub><k:mo><</k:mo><k:mo>−</k:mo><k:mn>3.0</k:mn></k:mrow></k:math> (backward rapidity) defined relative to the proton beam direction. The <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"><n:mi>η</n:mi></n:math> and <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"><o:msup><o:mi>η</o:mi><o:mo>′</o:mo></o:msup></o:math> production cross sections are measured differentially as a function of transverse momentum for <p:math xmlns:p="http://www.w3.org/1998/Math/MathML"><p:mrow><p:mn>1.5</p:mn><p:mo><</p:mo><p:msub><p:mi>p</p:mi><p:mi mathvariant="normal">T</p:mi></p:msub><p:mo><</p:mo><p:mn>10</p:mn><p:mspace width="4pt"/><p:mi>GeV</p:mi></p:mrow></p:math> and <s:math xmlns:s="http://www.w3.org/1998/Math/MathML"><s:mrow><s:mn>3</s:mn><s:mo><</s:mo><s:msub><s:mi>p</s:mi><s:mi mathvariant="normal">T</s:mi></s:msub><s:mo><</s:mo><s:mn>10</s:mn><s:mspace width="4pt"/><s:mi>GeV</s:mi></s:mrow></s:math>, respectively. The differential cross sections are used to calculate nuclear modification factors. The nuclear modification factors for <v:math xmlns:v="http://www.w3.org/1998/Math/MathML"><v:mi>η</v:mi></v:math> and <w:math xmlns:w="http://www.w3.org/1998/Math/MathML"><w:msup><w:mi>η</w:mi><w:mo>′</w:mo></w:msup></w:math> mesons agree at both forward and backward rapidity, showing no significant evidence of mass dependence. The differential cross sections of <x:math xmlns:x="http://www.w3.org/1998/Math/MathML"><x:mi>η</x:mi></x:math> mesons are also used to calculate <y:math xmlns:y="http://www.w3.org/1998/Math/MathML"><y:mrow><y:mi>η</y:mi><y:mo>/</y:mo><y:msup><y:mi>π</y:mi><y:mn>0</y:mn></y:msup></y:mrow></y:math> cross-section ratios, which show evidence of a deviation from the world average. These studies offer new constraints on mass-dependent nuclear effects in heavy-ion collisions, as well as <z:math xmlns:z="http://www.w3.org/1998/Math/MathML"><z:mi>η</z:mi></z:math> and <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML"><ab:msup><ab:mi>η</ab:mi><ab:mo>′</ab:mo></ab:msup></ab:math> meson fragmentation. ©2024 CERN, for the LHCb Collaboration 2024 CERN
Tópico:
High-Energy Particle Collisions Research
