Impact of new invisible particles on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>B</mml:mi> <mml:mo stretchy="false">→</mml:mo> <mml:msup> <mml:mi>K</mml:mi> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mo>*</mml:mo> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:msup> <mml:msub> <mml:mi>E</mml:mi> <mml:mrow> <mml:mi>miss</mml:mi> </mml:mrow> </mml:msub> </mml:math> observables

Abstract

Motivated by a recent Belle II measurement that suggests an excess in the rare decay <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>B</a:mi> <a:mo stretchy="false">→</a:mo> <a:mi>K</a:mi> <a:msub> <a:mi>E</a:mi> <a:mrow> <a:mi>miss</a:mi> </a:mrow> </a:msub> </a:math> , and building upon our recent differential decay rate likelihood analysis of the existing experimental information, we investigate possible new physics (NP) scenarios in which light invisible states participate in flavor-changing <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:mi>b</d:mi> <d:mo stretchy="false">→</d:mo> <d:mi>s</d:mi> </d:math> transitions. In particular, we consider the total and differential <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>B</g:mi> <g:mo stretchy="false">→</g:mo> <g:msup> <g:mi>K</g:mi> <g:mo>*</g:mo> </g:msup> <g:msub> <g:mi>E</g:mi> <g:mrow> <g:mi>miss</g:mi> </g:mrow> </g:msub> </g:math> decay rates and <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"> <j:msup> <j:mi>K</j:mi> <j:mo>*</j:mo> </j:msup> </j:math> polarization effects in each NP scenario preferred by the <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"> <l:mi>B</l:mi> <l:mo stretchy="false">→</l:mo> <l:mi>K</l:mi> <l:msub> <l:mi>E</l:mi> <l:mrow> <l:mi>miss</l:mi> </l:mrow> </l:msub> </l:math> measurement. We show that future measurements of these <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:mi>B</o:mi> <o:mo stretchy="false">→</o:mo> <o:msup> <o:mi>K</o:mi> <o:mo>*</o:mo> </o:msup> <o:msub> <o:mi>E</o:mi> <o:mrow> <o:mi>miss</o:mi> </o:mrow> </o:msub> </o:math> observables will offer decisive discrimination among the different NP explanations. Our results highlight the strong complementarity of the rare semi-invisible <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"> <r:mi>b</r:mi> </r:math> -hadron decay observables, and underline the importance of analysing their momentum transfer spectra when probing extensions of the Standard Model that feature new light degrees of freedom.

Topics & Concepts