Observation of the $ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $ decay and measurement of its branching ratio

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2025年2月27日

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E. Cortina Gil,
J. Jerhot,
N. Lurkin,
T. Numao,
B. Velghe,
V. W. S. Wong,
D. Bryman,
Z. Hives,
T. Husek,
K. Kampf,
M. Kolesar,
M. Koval,
B. De Martino,
M. Perrin-Terrin,
L. Petit,
B. Döbrich,
S. Lezki,
J. Schubert,
A. T. Akmete,
R. Aliberti,
M. Ceoletta,
L. Di Lella,
N. Doble,
L. Peruzzo,
C. Polivka,
S. Schuchmann,
H. Wahl,
R. Wanke,
P. Dalpiaz,
R. Negrello,
I. Neri,
F. Petrucci,
M. Soldani,
L. Bandiera,
N. Canale,
A. Cotta Ramusino,
A. Gianoli,
M. Romagnoni,
A. Sytov,
M. Lenti,
P. Lo Chiatto,
I. Panichi,
G. Ruggiero,
A. Bizzeti,
F. Bucci,
A. Antonelli,
V. Kozhuharov,
G. Lanfranchi,
S. Martellotti,
M. Moulson,
T. Spadaro,
G. Tinti,
F. Ambrosino,
M. D’Errico,
R. Fiorenza,
M. Francesconi,
R. Giordano,
P. Massarotti,
M. Mirra,
M. Napolitano,
I. Rosa,
G. Saracino,
G. Anzivino,
P. Cenci,
V. Duk,
R. Lollini,
P. Lubrano,
M. Pepe,
M. Piccini,
F. Costantini,
M. Giorgi,
S. Giudici,
G. Lamanna,
E. Lari,
E. Pedreschi,
J. Pinzino,
M. Sozzi,
R. Fantechi,
F. Spinella,
I. Mannelli,
M. Raggi,
A. Biagioni,
P. Cretaro,
O. Frezza,
A. Lonardo,
M. Turisini,
P. Vicini,
R. Ammendola,
V. Bonaiuto,
A. Fucci,
A. Salamon,
F. Sargeni,
R. Arcidiacono,
B. Bloch-Devaux,
E. Menichetti,
E. Migliore,
C. Biino,
A. Filippi,
F. Marchetto,
D. Soldi,
Y. Mukhamejanov,
A. Mukhamejanova,
N. Saduyev,
S. Sakhiyev,
A. Briano Olvera,
J. Engelfried,
N. Estrada-Tristan,
R. Piandani,
M. A. Reyes Santos,
K. A. Rodriguez Rivera,
P. Boboc,
A. M. Bragadireanu,
S. A. Ghinescu,
O. E. Hutanu,
T. Blazek,
V. Cerny,
T. Velas,
R. Volpe,
J. Bernhard,
L. Bician,
M. Boretto,
F. Brizioli,
A. Ceccucci,
M. Corvino,
H. Danielsson,
F. Duval,
L. Federici,
E. Gamberini,
R. Guida,
E. B. Holzer,
B. Jenninger,
Z. Kucerova,
G. Lehmann Miotto,
P. Lichard,
K. Massri,
E. Minucci,
M. Noy,
V. Ryjov,
J. Swallow,
M. Zamkovsky,
X. Chang,
A. Kleimenova,
R. Marchevski,
J. R. Fry,
F. Gonnella,
E. Goudzovski,
J. Henshaw,
C. Kenworthy,
C. Lazzeroni,
C. Parkinson,
A. Romano,
C. Sam,
J. Sanders,
A. Sergi,
A. Shaikhiev,
A. Tomczak,
H. Heath,
D. Britton,
A. Norton,
D. Protopopescu,
J. B. Dainton,
L. Gatignon,
R. W. L. Jones,
P. Cooper,
D. Coward,
P. Rubin,
A. Baeva,
D. Baigarashev,
V. Bautin,
D. Emelyanov,
T. Enik,
V. Falaleev,
V. Kekelidze,
D. Kereibay,
A. Korotkova,
L. Litov,
D. Madigozhin,
M. Misheva,
N. Molokanova,
I. Polenkevich,
Yu. Potrebenikov,
K. Salamatin,
S. Shkarovskiy,
S. Fedotov,
K. Gorshanov,
E. Gushchin,
S. Kholodenko,
A. Khotyantsev,
Y. Kudenko,
V. Kurochka,
V. Kurshetsov,
A. Mefodev,
V. Obraztsov,
A. Okhotnikov,
A. Sadovskiy,
V. Sugonyaev,
O. Yushchenko

摘要

A measurement of the $K^{+} \to π^{+} ν \bar{ν}$ $ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $ decay by the NA62 experiment at the CERN SPS is presented, using data collected in 2021 and 2022. This dataset was recorded, after modifications to the beamline and detectors, at a higher instantaneous beam intensity with respect to the 2016–2018 data taking. Combining NA62 data collected in 2016–2022, a measurement of $B (K^{+} \to π^{+} ν \bar{ν}) = ({13.0}_{- 3.0}^{+ 3.3}) \times 10^{- 11}$ $ \mathcal{B}\left({K}^{+}\to {\pi}^{+}\nu \overline{\nu}\right)=\left({13.0}_{-3.0}^{+3.3}\right)\times {10}^{-11} $ is reported. With 51 signal candidates observed and an expected background of $18_{- 2}^{+ 3}$ $ {18}_{-2}^{+3} $ events, $B (K^{+} \to π^{+} ν \bar{ν})$ $ \mathcal{B}\left({K}^{+}\to {\pi}^{+}\nu \overline{\nu}\right) $ becomes the smallest branching ratio measured with a signal significance above 5σ.

Observation of the \( {K}^{+}\to {\pi}^{+}\nu \overline{\nu} \) decay and measurement of its branching ratio

摘要