Enhanced Production of Λb0 Baryons in High-Multiplicity pp Collisions at s<mml:mo…

The production rate of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msubsup><a:mi mathvariant="normal">Λ</a:mi><a:mi>b</a:mi><a:mn>0</a:mn></a:msubsup></a:math> baryons relative to <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:msup><d:mi>B</d:mi><d:mn>0</d:mn></d:msup></d:math> mesons in <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mi>p</f:mi><f:mi>p</f:mi></f:math> collisions at a center-of-mass energy <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:mrow><h:msqrt><h:mrow><h:mi>s</h:mi></h:mrow></h:msqrt><h:mo>=</h:mo><h:mn>13</h:mn><h:mtext> </h:mtext><h:mtext> </h:mtext><h:mi>TeV</h:mi></h:mrow></h:math> is measured by the LHCb experiment. The ratio of <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:msubsup><j:mi mathvariant="normal">Λ</j:mi><j:mi>b</j:mi><j:mn>0</j:mn></j:msubsup></j:math> to <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msup><m:mi>B</m:mi><m:mn>0</m:mn></m:msup></m:math> production cross sections shows a significant dependence on both the transverse momentum and the measured charged-particle multiplicity. At low multiplicity, the ratio measured at LHCb is consistent with the value measured in <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:msup><o:mi>e</o:mi><o:mo>+</o:mo></o:msup><o:msup><o:mi>e</o:mi><o:mo>−</o:mo></o:msup></o:math> collisions, and increases by a factor of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mo>∼</q:mo><q:mn>2</q:mn></q:math> with increasing multiplicity. At relatively low transverse momentum, the ratio of <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:msubsup><s:mi mathvariant="normal">Λ</s:mi><s:mi>b</s:mi><s:mn>0</s:mn></s:msubsup></s:math> to <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:msup><v:mi>B</v:mi><v:mn>0</v:mn></v:msup></v:math> cross sections is higher than what is measured in <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:msup><x:mi>e</x:mi><x:mo>+</x:mo></x:msup><x:msup><x:mi>e</x:mi><x:mo>−</x:mo></x:msup></x:math> collisions, but converges with the <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"><z:msup><z:mi>e</z:mi><z:mo>+</z:mo></z:msup><z:msup><z:mi>e</z:mi><z:mo>−</z:mo></z:msup></z:math> ratio as the momentum increases. These results imply that the evolution of heavy <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline"><bb:mi>b</bb:mi></bb:math> quarks into final-state hadrons is influenced by the density of the hadronic environment produced in the collision. Comparisons with several models and implications for the mechanisms enforcing quark confinement are discussed.