The flavor changing neutral current decays $$t\rightarrow c X$$ ($$X=\gamma ,\,g,\, Z,\, H$$ ) and $$t\rightarrow c{{\bar{\ell }}}\ell $$ ($$\ell =\mu ,\,\tau $$ ) are studied in a renormalizable scalar leptoquark (LQ) model with no proton decay, where a scalar SU(2) doublet with hypercharge $$Y=7/6$$ is added to the standard model, yielding a non-chiral LQ $$\varOmega _{5/3}$$ . Analytical results for the one-loop (tree-level) contributions of a scalar LQ to the $$f_i\rightarrow f_j X$$ ($$f_i\rightarrow f_j {\bar{f}}_m f_l$$ ) decays, with $$f_a=q_a, \ell _a$$ , are presented. We consider the scenario where $$\varOmega _{5/3}$$ couples to the fermions of the second and third families, with its right- and left-handed couplings obeying $$\lambda _R^{\ell u_i}/\lambda _L^{\ell u_i}=O(\epsilon )$$ , where $$\epsilon $$ parametrizes the relative size between these couplings. The allowed parameter space is then found via the current constraints on the muon $$(g-2)$$ , the $$\tau \rightarrow \mu \gamma $$ decay, the LHC Higgs boson data, and the direct LQ searches at the LHC. For $$m_{\varOmega _{5/3}}=1$$ TeV and $$\epsilon =10^{-3}$$ , we find that the $$t\rightarrow c X$$ branching ratios are of similar size and can be as large as $$10^{-8}$$ in a tiny area of the parameter space, whereas $${\mathrm{Br}}(t\rightarrow c{{\bar{\tau }}}\tau )$$ [$${\mathrm{Br}}(t\rightarrow c{{\bar{\mu }}}\mu )$$ ] can be up to $$10^{-6}$$ ($$10^{-7}$$ ).
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"surname": "Bola\u00f1os",
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"full_name": "Bola\u00f1os, A.",
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"surname": "S\u00e1nchez-V\u00e9lez",
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"surname": "Tavares-Velasco",
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"title": "Flavor changing neutral current decays $$t\\rightarrow c X$$ <math><mrow><mi>t</mi><mo>\u2192</mo><mi>c</mi><mi>X</mi></mrow></math> ($$X=\\gamma ,\\,g,\\, Z,\\, H$$ <math><mrow><mi>X</mi><mo>=</mo><mi>\u03b3</mi><mo>,</mo><mspace width=\"0.166667em\"></mspace><mi>g</mi><mo>,</mo><mspace width=\"0.166667em\"></mspace><mi>Z</mi><mo>,</mo><mspace width=\"0.166667em\"></mspace><mi>H</mi></mrow></math> ) and $$t\\rightarrow c{{\\bar{\\ell }}}\\ell $$ <math><mrow><mi>t</mi><mo>\u2192</mo><mi>c</mi><mover><mrow><mi>\u2113</mi></mrow><mrow><mo>\u00af</mo></mrow></mover><mi>\u2113</mi></mrow></math> ($$\\ell =\\mu ,\\,\\tau $$ <math><mrow><mi>\u2113</mi><mo>=</mo><mi>\u03bc</mi><mo>,</mo><mspace width=\"0.166667em\"></mspace><mi>\u03c4</mi></mrow></math> ) via scalar leptoquarks"
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"value": "The flavor changing neutral current decays $$t\\rightarrow c X$$ <math><mrow><mi>t</mi><mo>\u2192</mo><mi>c</mi><mi>X</mi></mrow></math> ($$X=\\gamma ,\\,g,\\, Z,\\, H$$ <math><mrow><mi>X</mi><mo>=</mo><mi>\u03b3</mi><mo>,</mo><mspace width=\"0.166667em\"></mspace><mi>g</mi><mo>,</mo><mspace width=\"0.166667em\"></mspace><mi>Z</mi><mo>,</mo><mspace width=\"0.166667em\"></mspace><mi>H</mi></mrow></math> ) and $$t\\rightarrow c{{\\bar{\\ell }}}\\ell $$ <math><mrow><mi>t</mi><mo>\u2192</mo><mi>c</mi><mover><mrow><mi>\u2113</mi></mrow><mrow><mo>\u00af</mo></mrow></mover><mi>\u2113</mi></mrow></math> ($$\\ell =\\mu ,\\,\\tau $$ <math><mrow><mi>\u2113</mi><mo>=</mo><mi>\u03bc</mi><mo>,</mo><mspace width=\"0.166667em\"></mspace><mi>\u03c4</mi></mrow></math> ) are studied in a renormalizable scalar leptoquark (LQ) model with no proton decay, where a scalar SU(2) doublet with hypercharge $$Y=7/6$$ <math><mrow><mi>Y</mi><mo>=</mo><mn>7</mn><mo>/</mo><mn>6</mn></mrow></math> is added to the standard model, yielding a non-chiral LQ $$\\varOmega _{5/3}$$ <math><msub><mi>\u03a9</mi><mrow><mn>5</mn><mo>/</mo><mn>3</mn></mrow></msub></math> . Analytical results for the one-loop (tree-level) contributions of a scalar LQ to the $$f_i\\rightarrow f_j X$$ <math><mrow><msub><mi>f</mi><mi>i</mi></msub><mo>\u2192</mo><msub><mi>f</mi><mi>j</mi></msub><mi>X</mi></mrow></math> ($$f_i\\rightarrow f_j {\\bar{f}}_m f_l$$ <math><mrow><msub><mi>f</mi><mi>i</mi></msub><mo>\u2192</mo><msub><mi>f</mi><mi>j</mi></msub><msub><mover><mrow><mi>f</mi></mrow><mrow><mo>\u00af</mo></mrow></mover><mi>m</mi></msub><msub><mi>f</mi><mi>l</mi></msub></mrow></math> ) decays, with $$f_a=q_a, \\ell _a$$ <math><mrow><msub><mi>f</mi><mi>a</mi></msub><mo>=</mo><msub><mi>q</mi><mi>a</mi></msub><mo>,</mo><msub><mi>\u2113</mi><mi>a</mi></msub></mrow></math> , are presented. We consider the scenario where $$\\varOmega _{5/3}$$ <math><msub><mi>\u03a9</mi><mrow><mn>5</mn><mo>/</mo><mn>3</mn></mrow></msub></math> couples to the fermions of the second and third families, with its right- and left-handed couplings obeying $$\\lambda _R^{\\ell u_i}/\\lambda _L^{\\ell u_i}=O(\\epsilon )$$ <math><mrow><msubsup><mi>\u03bb</mi><mi>R</mi><mrow><mi>\u2113</mi><msub><mi>u</mi><mi>i</mi></msub></mrow></msubsup><mo>/</mo><msubsup><mi>\u03bb</mi><mi>L</mi><mrow><mi>\u2113</mi><msub><mi>u</mi><mi>i</mi></msub></mrow></msubsup><mo>=</mo><mi>O</mi><mrow><mo>(</mo><mi>\u03f5</mi><mo>)</mo></mrow></mrow></math> , where $$\\epsilon $$ <math><mi>\u03f5</mi></math> parametrizes the relative size between these couplings. The allowed parameter space is then found via the current constraints on the muon $$(g-2)$$ <math><mrow><mo>(</mo><mi>g</mi><mo>-</mo><mn>2</mn><mo>)</mo></mrow></math> , the $$\\tau \\rightarrow \\mu \\gamma $$ <math><mrow><mi>\u03c4</mi><mo>\u2192</mo><mi>\u03bc</mi><mi>\u03b3</mi></mrow></math> decay, the LHC Higgs boson data, and the direct LQ searches at the LHC. For $$m_{\\varOmega _{5/3}}=1$$ <math><mrow><msub><mi>m</mi><msub><mi>\u03a9</mi><mrow><mn>5</mn><mo>/</mo><mn>3</mn></mrow></msub></msub><mo>=</mo><mn>1</mn></mrow></math> TeV and $$\\epsilon =10^{-3}$$ <math><mrow><mi>\u03f5</mi><mo>=</mo><msup><mn>10</mn><mrow><mo>-</mo><mn>3</mn></mrow></msup></mrow></math> , we find that the $$t\\rightarrow c X$$ <math><mrow><mi>t</mi><mo>\u2192</mo><mi>c</mi><mi>X</mi></mrow></math> branching ratios are of similar size and can be as large as $$10^{-8}$$ <math><msup><mn>10</mn><mrow><mo>-</mo><mn>8</mn></mrow></msup></math> in a tiny area of the parameter space, whereas $${\\mathrm{Br}}(t\\rightarrow c{{\\bar{\\tau }}}\\tau )$$ <math><mrow><mi>Br</mi><mo>(</mo><mi>t</mi><mo>\u2192</mo><mi>c</mi><mover><mrow><mi>\u03c4</mi></mrow><mrow><mo>\u00af</mo></mrow></mover><mi>\u03c4</mi><mo>)</mo></mrow></math> [$${\\mathrm{Br}}(t\\rightarrow c{{\\bar{\\mu }}}\\mu )$$ <math><mrow><mi>Br</mi><mo>(</mo><mi>t</mi><mo>\u2192</mo><mi>c</mi><mover><mrow><mi>\u03bc</mi></mrow><mrow><mo>\u00af</mo></mrow></mover><mi>\u03bc</mi><mo>)</mo></mrow></math> ] can be up to $$10^{-6}$$ <math><msup><mn>10</mn><mrow><mo>-</mo><mn>6</mn></mrow></msup></math> ($$10^{-7}$$ <math><msup><mn>10</mn><mrow><mo>-</mo><mn>7</mn></mrow></msup></math> )."
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