Gil, E Cortina, Kleimenova, A, Minucci, E, Padolski, S, Petrov, P, Shaikhiev, A, Volpe, R, Numao, T, Petrov, Y, Velghe, B et al (show 192 more authors)
(2021)
Measurement of the very rare K<SUP>+</SUP>→π+νν<mml:mo stretchy="true"><overbar></mml:mover> decay.
JOURNAL OF HIGH ENERGY PHYSICS, 2021 (6).
93-.
Abstract
<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>The NA62 experiment reports the branching ratio measurement <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathrm{BR}\left({K}^{+}\to {\pi}^{+}\nu \overline{\nu}\right)=\left({10.6}_{-3.4}^{+4.0}\left|{}_{\mathrm{stat}}\right.\pm {0.9}_{\mathrm{syst}}\right)\times {10}^{-11} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>BR</mml:mi> <mml:mfenced> <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:mi>ν</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:mrow> </mml:mfenced> <mml:mo>=</mml:mo> <mml:mfenced> <mml:mrow> <mml:msubsup> <mml:mn>10.6</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>4.0</mml:mn> </mml:mrow> </mml:msubsup> <mml:mfenced> <mml:msub> <mml:mrow /> <mml:mtext>stat</mml:mtext> </mml:msub> </mml:mfenced> <mml:mo>±</mml:mo> <mml:msub> <mml:mn>0.9</mml:mn> <mml:mtext>syst</mml:mtext> </mml:msub> </mml:mrow> </mml:mfenced> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>11</mml:mn> </mml:mrow> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016–2018. This provides evidence for the very rare <jats:italic>K</jats:italic><jats:sup>+</jats:sup><jats:italic>→</jats:italic><jats:inline-formula><jats:alternatives><jats:tex-math>$$ {\pi}^{+}\nu \overline{\nu} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mi>ν</mml:mi> <mml:mover> <mml:mi>ν</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula> decay, observed with a significance of 3.4<jats:italic>σ</jats:italic>. The experiment achieves a single event sensitivity of (0<jats:italic>.</jats:italic>839 <jats:italic>±</jats:italic> 0<jats:italic>.</jats:italic>054) <jats:italic>×</jats:italic> 10<jats:sup><jats:italic>−</jats:italic>11</jats:sup>, corresponding to 10.0 events assuming the Standard Model branching ratio of (8<jats:italic>.</jats:italic>4 <jats:italic>±</jats:italic> 1<jats:italic>.</jats:italic>0) <jats:italic>×</jats:italic> 10<jats:sup><jats:italic>−</jats:italic>11</jats:sup>. This measurement is also used to set limits on BR(<jats:italic>K</jats:italic><jats:sup>+</jats:sup><jats:italic>→ π</jats:italic><jats:sup>+</jats:sup><jats:italic>X</jats:italic>), where <jats:italic>X</jats:italic> is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.</jats:p>
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | FCNC Interaction, Flavour Changing Neutral Currents, Rare decay, Fixed target experiments, Flavor physics |
| Divisions: | Faculty of Science and Engineering > School of Physical Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 16 Nov 2021 08:44 |
| Last Modified: | 14 Mar 2024 23:01 |
| DOI: | 10.1007/JHEP06(2021)093 |
| Open Access URL: | https://link.springer.com/content/pdf/10.1007/JHEP... |
| Related URLs: | |
| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3143203 |
Dimensions
Dimensions
