Joint explanation of the <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:mi>π</mml:mi> <mml:mi>K</mml:mi> </mml:math> puzzle and the <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:mi>K</mml:mi> <mml:mi>ν</mml:mi> <mml:mover accent="true"> <mml:mi>ν</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:math> excess

Abstract

In light of the recent branching fraction measurement of the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mi>B</a:mi> <a:mo>+</a:mo> </a:msup> <a:mo stretchy="false">→</a:mo> <a:msup> <a:mi>K</a:mi> <a:mo>+</a:mo> </a:msup> <a:mi>ν</a:mi> <a:mover accent="true"> <a:mi>ν</a:mi> <a:mo stretchy="false">¯</a:mo> </a:mover> </a:math> decay by Belle II and its poor agreement with the Standard Model expectation, we analyze the effects of an axionlike particle (ALP) in <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:mi>B</f:mi> </f:math> meson decays. We assume a long-lived ALP with a mass of the order of the pion mass that decays to two photons. We focus on a scenario where the ALP decay length is of the order of meters such that the ALP has a non-negligible probability to decay outside the detector volume of Belle II, mimicking the <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:msup> <h:mi>B</h:mi> <h:mo>+</h:mo> </h:msup> <h:mo stretchy="false">→</h:mo> <h:msup> <h:mi>K</h:mi> <h:mo>+</h:mo> </h:msup> <h:mi>ν</h:mi> <h:mover accent="true"> <h:mi>ν</h:mi> <h:mo stretchy="false">¯</h:mo> </h:mover> </h:math> signal. Remarkably, such an arrangement is also relevant for the long-standing <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:mi>B</m:mi> <m:mo stretchy="false">→</m:mo> <m:mi>π</m:mi> <m:mi>K</m:mi> </m:math> puzzle by noting that the measured <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"> <p:msup> <p:mi>B</p:mi> <p:mn>0</p:mn> </p:msup> <p:mo stretchy="false">→</p:mo> <p:msup> <p:mi>π</p:mi> <p:mn>0</p:mn> </p:msup> <p:msup> <p:mi>K</p:mi> <p:mn>0</p:mn> </p:msup> </p:math> and <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:msup> <s:mi>B</s:mi> <s:mo>+</s:mo> </s:msup> <s:mo stretchy="false">→</s:mo> <s:msup> <s:mi>π</s:mi> <s:mn>0</s:mn> </s:msup> <s:msup> <s:mi>K</s:mi> <s:mo>+</s:mo> </s:msup> </s:math> decays could have a <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"> <v:msup> <v:mi>B</v:mi> <v:mn>0</v:mn> </v:msup> <v:mo stretchy="false">→</v:mo> <v:mi>a</v:mi> <v:msup> <v:mi>K</v:mi> <v:mn>0</v:mn> </v:msup> </v:math> and <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"> <y:msup> <y:mi>B</y:mi> <y:mo>+</y:mo> </y:msup> <y:mo stretchy="false">→</y:mo> <y:mi>a</y:mi> <y:msup> <y:mi>K</y:mi> <y:mo>+</y:mo> </y:msup> </y:math> component, respectively. We also argue based on our results that the required ALP-photon effective coupling belongs to a region of parameter space that can be extensively probed in future beam dump experiments like SHiP.

Topics & Concepts