Measurement of the ratio of the; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline">; <mml:msubsup>; <mml:mi>B</mml:mi>; <mml:mi>c</mml:mi>; <mml:mo>+</mml:mo>; </mml:msubsup>; <mml:mo stretchy="false">→</mml:mo>; <mml:mi>J</mml:mi>; <mml:mo>/</mml:mo>; <mml:mi>ψ</mml:mi>; <mml:msup>; <mml:mi>τ</mml:mi>; <mml:mo>+</mml:mo>; </mml:msup>; <mml:msub>; <mml:mi>ν</mml:mi>; <mml:mi>τ</mml:mi>; </mml:msub>; </mml:math>; and; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline">; <mml:msubsup>; <mml:mi>B</mml:mi>; <mml:mi>c</mml:mi>; <mml:mo>+</mml:mo>; </mml:msubsup>; <mml:mo stretchy="false">→</mml:mo>; <mml:mi>J</mml:mi>; <mml:mo>/</mml:mo>; <mml:mi>ψ</mml:mi>; <mml:msup>; <mml:mi>μ</mml:mi>; <mml:mo>+</mml:mo>; </mml:msup>; <mml:msub>; <mml:mi>ν</mml:mi>; <mml:mi>μ</mml:mi>; </mml:msub>; </mml:math>; branching fractions using three-prong; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline">; <mml:mi>τ</mml:mi>; </mml:math>; lepton decays | CU Experts

; The ratio between the; ; ; ; B; c; +; ; →; ; J; /; ψ; ; ; ; τ; +; ; ; ν; τ; ; ; and; ; ; ; B; c; +; ; →; ; J; /; ψ; ; ; ; μ; +; ; ; ν; μ; ; ; branching fractions is measured using a data sample of proton-proton collisions collected by CMS at a center-of-mass energy of; ; ; 13; ; ; TeV; ; ; in the years 2016–2018 and corresponding to an integrated luminosity of; ; 138; ; ; ; fb; ; −; 1; ; ; ; . The; ; J; /; ψ; ; meson is identified through its; ; ; J; /; ψ; ; →; ; ; μ; +; ; ; μ; −; ; ; ; decay and the tau lepton is reconstructed in the hadronic three-prong final state. The measured ratio of branching fractions in this tau decay mode,; ; ; R; ; J; /; ψ; ; had; ; =; 1.0; ; 4; ; −; 0.44; ; ; +; 0.50; ; ; ; , is combined with the previous analysis based on the; ; ; ; ; τ; ; ; +; ; ; →; ; ; μ; ; ; +; ; ; ; ; ν; ; ; μ; ; ; ; ; ; ; ν; ; ; ¯; ; ; ; ; τ; ; ; ; ; leptonic decay channel, leading to; ; ; R; ; J; /; ψ; ; ; =; ; 0.49; ±; 0.26; ; ; . As this result is consistent with the standard model prediction of; ; 0.258; ±; 0.004; ; , no evidence of lepton flavor universality violation is found.;

Chekhovsky V; Hayrapetyan A; Makarenko V; Tumasyan A; Adam W; Andrejkovic JW; Benato L; Bergauer T; Damanakis K; Dragicevic M

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