RD(*) and survival of the fittest scalar leptoquark

Motivated by the long-standing discrepancy in lepton flavor universality ratios <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>R</a:mi><a:mi>D</a:mi></a:msub></a:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msub><c:mi>R</c:mi><c:msup><c:mi>D</c:mi><c:mo>*</c:mo></c:msup></c:msub></c:math> we assess the status of scalar leptoquark states <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msub><e:mi>R</e:mi><e:mn>2</e:mn></e:msub></e:math>, <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msub><g:mover accent="true"><g:mi>R</g:mi><g:mo stretchy="false">˜</g:mo></g:mover><g:mn>2</g:mn></g:msub></g:math> and <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>S</k:mi><k:mn>1</k:mn></k:msub></k:math> which can in principle provide a desired enhancement of <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi mathvariant="script">B</m:mi><m:mo stretchy="false">(</m:mo><m:mi>B</m:mi><m:mo stretchy="false">→</m:mo><m:msup><m:mi>D</m:mi><m:mrow><m:mo stretchy="false">(</m:mo><m:mo>*</m:mo><m:mo stretchy="false">)</m:mo></m:mrow></m:msup><m:mi>τ</m:mi><m:mi>ν</m:mi><m:mo stretchy="false">)</m:mo></m:math> in a minimal setup with two Yukawa couplings only. We consider unavoidable low-energy constraints, <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"><u:mi>Z</u:mi></u:math>-pole measurements as well as high-<w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:msub><w:mi>p</w:mi><w:mi>T</w:mi></w:msub></w:math> constraints. After setting the mass of each leptoquark to 1.5 TeV we find that of all considered states only <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"><y:msub><y:mi>S</y:mi><y:mn>1</y:mn></y:msub></y:math> leptoquark, coupled to both chiralities of leptons and quarks, is still a completely viable solution while the scenario with <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:msub><ab:mi>R</ab:mi><ab:mn>2</ab:mn></ab:msub></ab:math> is in growing tension with <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" display="inline"><cb:mi mathvariant="normal">Γ</cb:mi><cb:mo stretchy="false">(</cb:mo><cb:mi>Z</cb:mi><cb:mo stretchy="false">→</cb:mo><cb:mi>τ</cb:mi><cb:mi>τ</cb:mi><cb:mo stretchy="false">)</cb:mo></cb:math> and with the LHC constraints on the ditau tails at high-<ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" display="inline"><ib:msub><ib:mi>p</ib:mi><ib:mi>T</ib:mi></ib:msub></ib:math>. We comment on the future experimental tests of the <kb:math xmlns:kb="http://www.w3.org/1998/Math/MathML" display="inline"><kb:msub><kb:mi>S</kb:mi><kb:mn>1</kb:mn></kb:msub></kb:math> scenario.