How large could the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi><mml:mi>P</mml:mi></mml:math> violation in neutral <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mm

<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>C</a:mi><a:mi>P</a:mi></a:math> violation in neutral <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>B</c:mi></c:math> meson oscillations is an experimental observable that could be directly related to the baryon asymmetry of the Universe through the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>B</e:mi></e:math>-mesogenesis mechanism. As this phenomenon is highly suppressed in the Standard Model, it could also be a sensitive probe for many new physics scenarios that modify neutral meson mixing. Motivated by these facts, and the timely <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>B</g:mi></g:math> physics program at the LHC and Belle II, we analyze how large <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>C</i:mi><i:mi>P</i:mi></i:math> violation in the mixing of neutral <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>B</k:mi><k:mi>d</k:mi></k:msub></k:math> and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msub><m:mi>B</m:mi><m:mi>s</m:mi></m:msub></m:math> meson systems could be. We answer this question, in light of current experimental data, within three different scenarios, namely: (i) generic heavy new physics only affecting the mass mixing <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:msubsup><o:mi>M</o:mi><o:mn>12</o:mn><o:mi>q</o:mi></o:msubsup></o:math>, (ii) vectorlike quark extensions that introduce deviations of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mn>3</q:mn><q:mo>×</q:mo><q:mn>3</q:mn></q:math> CKM unitarity, and (iii) light new physics modifying the decay mixing <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:msubsup><s:mi mathvariant="normal">Γ</s:mi><s:mn>12</s:mn><s:mi>q</s:mi></s:msubsup></s:math>. We find that enhancements of the semileptonic asymmetries, that measure the amount of <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mi>C</v:mi><v:mi>P</v:mi></v:math> violation in mixing, at the level of <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:msup><x:mn>10</x:mn><x:mrow><x:mo>−</x:mo><x:mn>3</x:mn></x:mrow></x:msup></x:math> for the <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"><z:msub><z:mi>B</z:mi><z:mi>d</z:mi></z:msub></z:math> system and <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline"><bb:msup><bb:mn>10</bb:mn><bb:mrow><bb:mo>−</bb:mo><bb:mn>4</bb:mn></bb:mrow></bb:msup></bb:math> for the <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:msub><db:mi>B</db:mi><db:mi>s</db:mi></db:msub></db:math> system can be achieved within scenarios (i) and (ii), while they are much more suppressed in realistic UV completions triggering scenario (iii). With respect to cosmology, the difficulty of finding large <fb:math xmlns:fb="http://www.w3.org/1998/Math/MathML" display="inline"><fb:mi>C</fb:mi><fb:mi>P</fb:mi></fb:math> asymmetries in our analysis puts the <hb:math xmlns:hb="http://www.w3.org/1998/Math/MathML" display="inline"><hb:mi>B</hb:mi></hb:math>-mesogenesis mechanism in tension. Finally, we conclude that upcoming experimental searches for <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML" display="inline"><jb:mi>C</jb:mi><jb:mi>P</jb:mi></jb:math> violation in <lb:math xmlns:lb="http://www.w3.org/1998/Math/MathML" display="inline"><lb:mi>B</lb:mi></lb:math> meson mixing at LHCb and Belle II are unlikely to detect a new physics signal for the most generic models. Published by the American Physical Society 2024