Nuclear medium effects on <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msup><a:mrow><a:mi>B</a:mi></a:mrow><a:mrow><a:mo>+</a:mo></a:mrow></a:msup></a:mrow></a:math> meson production are studied using the binary-collision scaled cross section ratio between events of different charged-particle multiplicities from proton-lead collisions. Data, collected by the CMS experiment in 2016 at a nucleon-nucleon center-of-mass energy of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:msqrt><c:mrow><c:msub><c:mrow><c:mi>s</c:mi></c:mrow><c:mrow><c:mi>NN</c:mi></c:mrow></c:msub></c:mrow></c:msqrt><c:mo>=</c:mo><c:mn>8.16</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:mi>TeV</c:mi></c:mrow></c:math>, corresponding to an integrated luminosity of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>175</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:msup><e:mi>nb</e:mi><e:mrow><e:mo>−</e:mo><e:mn>1</e:mn></e:mrow></e:msup></e:math>, were used. The scaling factors in the ratio are determined using a novel approach based on the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:mi>Z</g:mi><g:mo stretchy="false">→</g:mo><g:msup><g:mrow><g:mi>μ</g:mi></g:mrow><g:mrow><g:mo>−</g:mo></g:mrow></g:msup><g:msup><g:mrow><g:mi>μ</g:mi></g:mrow><g:mrow><g:mo>+</g:mo></g:mrow></g:msup></g:mrow></g:math> cross sections measured in the same events. The scaled ratio for <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mrow><j:msup><j:mrow><j:mi>B</j:mi></j:mrow><j:mrow><j:mo>+</j:mo></j:mrow></j:msup></j:mrow></j:math> is consistent with unity for all event multiplicities, putting stringent constraints on nuclear modification for heavy flavor. © 2025 CERN, for the CMS Collaboration 2025 CERN