SMEFT analysis of charged lepton flavor violating B -meson decays

Charged lepton flavor violation (cLFV) processes, potentially important for various beyond the Standard Model physics scenarios are analyzed in the Standard Model effective field theory framework. We consider the most relevant two-quark–two-lepton <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mo stretchy="false">(</a:mo><a:mn>2</a:mn><a:mi>q</a:mi><a:mn>2</a:mn><a:mo>ℓ</a:mo><a:mo stretchy="false">)</a:mo></a:math> operators for the leptonic and semileptonic LFV <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>B</e:mi></e:math>-decay (LFVBD) processes <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msub><g:mi>B</g:mi><g:mi>s</g:mi></g:msub><g:mo stretchy="false">→</g:mo><g:msup><g:mi>μ</g:mi><g:mo>+</g:mo></g:msup><g:msup><g:mi>e</g:mi><g:mo>−</g:mo></g:msup><g:mo>,</g:mo><g:msup><g:mi>B</g:mi><g:mo>+</g:mo></g:msup><g:mo stretchy="false">→</g:mo><g:msup><g:mi>K</g:mi><g:mo>+</g:mo></g:msup><g:msup><g:mi>μ</g:mi><g:mo>+</g:mo></g:msup><g:msup><g:mi>e</g:mi><g:mo>−</g:mo></g:msup><g:mo>,</g:mo><g:msup><g:mi>B</g:mi><g:mn>0</g:mn></g:msup><g:mo stretchy="false">→</g:mo><g:msup><g:mi>K</g:mi><g:mrow><g:mo>*</g:mo><g:mn>0</g:mn></g:mrow></g:msup><g:msup><g:mi>μ</g:mi><g:mo>+</g:mo></g:msup><g:msup><g:mi>e</g:mi><g:mo>−</g:mo></g:msup></g:math>, and <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:msub><l:mi>B</l:mi><l:mi>s</l:mi></l:msub><l:mo stretchy="false">→</l:mo><l:mi>ϕ</l:mi><l:msup><l:mi>μ</l:mi><l:mo>−</l:mo></l:msup><l:msup><l:mi>e</l:mi><l:mo>+</l:mo></l:msup></l:math>. We analyze the interplay among the Wilson coefficients responsible for these LFVBDs and other cLFV processes, like <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>CR</o:mi><o:mo stretchy="false">(</o:mo><o:mi>μ</o:mi><o:mo stretchy="false">→</o:mo><o:mi>e</o:mi><o:mo stretchy="false">)</o:mo></o:math>, <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline"><t:msub><t:mo>ℓ</t:mo><t:mi>i</t:mi></t:msub><t:mo stretchy="false">→</t:mo><t:msub><t:mo>ℓ</t:mo><t:mi>j</t:mi></t:msub><t:mi>γ</t:mi></t:math>, <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:msub><w:mo>ℓ</w:mo><w:mi>i</w:mi></w:msub><w:mo stretchy="false">→</w:mo><w:msub><w:mo>ℓ</w:mo><w:mi>j</w:mi></w:msub><w:msub><w:mo>ℓ</w:mo><w:mi>k</w:mi></w:msub><w:msub><w:mo>ℓ</w:mo><w:mi>m</w:mi></w:msub></w:math>, and <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"><z:mi>Z</z:mi><z:mo stretchy="false">→</z:mo><z:msub><z:mo>ℓ</z:mo><z:mi>i</z:mi></z:msub><z:msub><z:mo>ℓ</z:mo><z:mi>j</z:mi></z:msub></z:math>, to find the maximal possible LFV effects in <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" display="inline"><cb:mi>B</cb:mi></cb:math>-meson decays. We probe the scale of new physics in relation to the constraints imposed by both classes of the LFV decays while considering both the present bounds and future expectations. In view of proposed experiments at LHCb-II and Belle II to study charged LFV processes, we have also provided the upper limits on the indirect constraints on such LFVBDs. For the processes where the <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline"><eb:mi>B</eb:mi></eb:math> meson is decaying to <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML" display="inline"><gb:msup><gb:mi>μ</gb:mi><gb:mo>±</gb:mo></gb:msup></gb:math> and <ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" display="inline"><ib:msup><ib:mi>e</ib:mi><ib:mo>∓</ib:mo></ib:msup></ib:math>, we show that new physics can be constrained by an enhancement of 2–4 orders of magnitude on the current sensitivities of the branching ratios of <kb:math xmlns:kb="http://www.w3.org/1998/Math/MathML" display="inline"><kb:msup><kb:mi>B</kb:mi><kb:mo>+</kb:mo></kb:msup><kb:mo stretchy="false">→</kb:mo><kb:msup><kb:mi>K</kb:mi><kb:mo>+</kb:mo></kb:msup><kb:msup><kb:mi>μ</kb:mi><kb:mo>+</kb:mo></kb:msup><kb:msup><kb:mi>e</kb:mi><kb:mo>−</kb:mo></kb:msup><kb:mo>,</kb:mo><kb:msup><kb:mi>B</kb:mi><kb:mn>0</kb:mn></kb:msup><kb:mo stretchy="false">→</kb:mo><kb:msup><kb:mi>K</kb:mi><kb:mrow><kb:mo>*</kb:mo><kb:mn>0</kb:mn></kb:mrow></kb:msup><kb:msup><kb:mi>μ</kb:mi><kb:mo>+</kb:mo></kb:msup><kb:msup><kb:mi>e</kb:mi><kb:mo>−</kb:mo></kb:msup></kb:math>, and <ob:math xmlns:ob="http://www.w3.org/1998/Math/MathML" display="inline"><ob:msub><ob:mi>B</ob:mi><ob:mi>s</ob:mi></ob:msub><ob:mo stretchy="false">→</ob:mo><ob:mi>ϕ</ob:mi><ob:msup><ob:mi>μ</ob:mi><ob:mo>±</ob:mo></ob:msup><ob:msup><ob:mi>e</ob:mi><ob:mo>∓</ob:mo></ob:msup></ob:math>. Published by the American Physical Society 2024