The anatomy of $$K^+\rightarrow \pi ^+\nu {\bar{\nu }}$$ distributions

Gorbahn, Martin, Moldanazarova, Ulserik, Sieja, Kai Henryk, Stamou, Emmanuel and Tabet, Mustafa (2024) The anatomy of $$K^+\rightarrow \pi ^+\nu {\bar{\nu }}$$ distributions. The European Physical Journal C, 84 (7). 680-.

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Abstract

<jats:title>Abstract</jats:title><jats:p>The excellent experimental prospects to measure the invisible mass spectrum of the <jats:inline-formula><jats:alternatives><jats:tex-math>$$K^+\rightarrow \pi ^+\nu {\bar{\nu }}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>π</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></jats:alternatives></jats:inline-formula> decay opens a new path to test generalised quark–neutrino interactions with flavour changing <jats:inline-formula><jats:alternatives><jats:tex-math>$$s\rightarrow d$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>s</mml:mi> <mml:mo>→</mml:mo> <mml:mi>d</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> transitions and as such to novel probes of Physics beyond the Standard Model. Such signals can be a consequence of new lepton-number violating or lepton-number conserving interactions, with their interpretations depending on the Majorana versus Dirac nature of the neutrinos. Furthermore, the possible existence of new massive sterile neutrinos can be tested via their distinctive imprints in the invariant mass spectrum. Within the model-independent framework of the weak effective theory at dimension-six, we study the New Physics effects of Majorana and Dirac neutrinos on the differential distribution of <jats:inline-formula><jats:alternatives><jats:tex-math>$$K^+\rightarrow \pi ^+\nu {\bar{\nu }}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>π</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></jats:alternatives></jats:inline-formula> allowing for lepton-number violating interactions and potential new sterile neutrinos. We determine the current and expected future sensitivity on the corresponding <jats:inline-formula><jats:alternatives><jats:tex-math>$$\Delta S=1$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:mi>S</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> neutral-current Wilson coefficients using the distribution measured by the NA62 collaboration and accounting for expected improvements based on the HIKE experiment. We present single-operator fits and also determine correlations among different type of operators. Even though we focus on <jats:inline-formula><jats:alternatives><jats:tex-math>$$s\rightarrow d\nu \nu $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>s</mml:mi> <mml:mo>→</mml:mo> <mml:mi>d</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>ν</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> transitions, the operator bases for Majorana and Dirac and the classification of lepton-number-violating/conserving interactions is applicable also for the study of <jats:inline-formula><jats:alternatives><jats:tex-math>$$b\rightarrow s/d\nu \nu $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>b</mml:mi> <mml:mo>→</mml:mo> <mml:mi>s</mml:mi> <mml:mo>/</mml:mo> <mml:mi>d</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>ν</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$$c\rightarrow u\nu \nu $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>c</mml:mi> <mml:mo>→</mml:mo> <mml:mi>u</mml:mi> <mml:mi>ν</mml:mi> <mml:mi>ν</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> transitions relevant in current phenomenology.</jats:p>

Item Type:	Article
Uncontrolled Keywords:	5106 Nuclear and Plasma Physics, 5107 Particle and High Energy Physics, 51 Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	02 Aug 2024 07:44
Last Modified:	02 Aug 2024 07:45
DOI:	10.1140/epjc/s10052-024-13027-7
Related URLs:	Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3183290