Implications of $$B \rightarrow K \nu {\bar{\nu }}$$ under rank-one flavor violation hypothesis

Abstract

Abstract We study the implications of the observed excess in $$B^+ \rightarrow K^+ \nu \bar{\nu }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>B</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mi>ν</mml:mi> <mml:mover> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:math> under the assumption of Rank-One Flavour Violation, i.e. that New Physics couples to a single specific direction in flavour space. By varying this direction we perform analyses at the level of the low-energy EFT, the SMEFT, and with explicit mediators such as leptoquarks and colorless vectors ( $$Z^\prime $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Z</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:math> and $$V^\prime $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>V</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:math> ). We study correlations with other flavour, electroweak and collider observables, finding that the most interesting ones are with $$K \rightarrow \pi \nu \bar{\nu }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>K</mml:mi> <mml:mo>→</mml:mo> <mml:mi>π</mml:mi> <mml:mi>ν</mml:mi> <mml:mover> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:math> , $$B_s \rightarrow \mu ^+ \mu ^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>B</mml:mi> <mml:mi>s</mml:mi> </mml:msub> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> , meson mixing and the LHC searches in $$\tau ^+ \tau ^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>τ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>τ</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> high-energy tails. Among the various mediators, the scalar leptoquarks $$\tilde{R}_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mi>R</mml:mi> <mml:mo>~</mml:mo> </mml:mover> <mml:mn>2</mml:mn> </mml:msub> </mml:math> and $$S_1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>S</mml:mi> <mml:mn>1</mml:mn> </mml:msub> </mml:math> offer the best fits of the Belle-II excess, while being consistent with the other bounds. On the other hand, colorless vectors are strongly constrained by meson mixing and resonance searches in $$p p \rightarrow \tau ^+ \tau ^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>p</mml:mi> <mml:mi>p</mml:mi> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>τ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>τ</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> . In all cases we find that a flavour alignment close to the third generation is generically preferred.

Topics & Concepts