Detailed study of the K ± → π 0 π 0 e ± ν (K e4 00 ) decay properties

Batley, J. R.; Kalmus, G.; Lazzeroni, C.; Munday, D.J.; Slater, M. W.; Wotton, S. A.; Arcidiacono, R.; Bocquet, G.; Cabibbo, N.; Ceccucci, A.; Cundy, D.; Falaleev, V.; Fidecaro, M.; Gatignon, L.; Gonidec, A.; Kubischta, W.; Norton, A.; Maier, A.; Patel, M.; Peters, A.; Balev, S.; Frabetti, P. L.; Gersabeck, E.; Goudzovski, E.; Hristov, P.; Kekelidze, V.; Kozhuharov, V.; Litov, L.; Madigozhin, D.; Molokanova, N.; Polenkevich, I.; Potrebenikov, Yu.; Stoynev, S.; Zinchenko, A.; Monnier, E.; Swallow, E. C.; Winston, R.; Rubin, P.; Walker, A.; Baldini, W.; Ramusino, A. Cotta; Dalpiaz, P.; Damiani, C.; Fiorini, M.; Gianoli, A.; Martini, M.; Petrucci, F.; Savrié, M.; Scarpa, M.; Wahl, H.; Bizzeti, A.; Lenti, M.; Veltri, M.; Calvetti, M.; Celeghini, E.; Iacopini, E.; Ruggiero, G.; Behler, M.; Eppard, K.; Gersabeck, M.; Kleinknecht, K.; Marouelli, P.; Masetti, L.; Moosbrugger, U.; Morales, C. Morales; Renk, B.; Wache, M.; Wanke, R.; Winhart, A.; Coward, D.; Dabrowski, A.; Martin, T. Fonseca; Shieh, M.; Szleper, M.; Velasco, M.; Wood, Max; Cenci, P.; Pepé, M.; Petrucci, M. C.; Anzivino, G.; Imbergamo, E.; Nappi, A.; Piccini, M.; Raggi, M.; Valdata‐Nappi, M.; Cerri, C.; Fantechi, R.; Collazuol, G.; DiLella, L.; Lamanna, G.; Mannelli, I.; Michetti, A.; Costantini, F.; Doble, N.; Fiorini, L.; Giudici, S.; Pierazzini, G.; Sozzi, M.; Venditti, S.; Bloch-Devaux, B.; Cheshkov, C.; Chèze, J.B.; Beer, M. De; Derré, J.; Marel, G.; Mazzucato, E.; Peyaud, B.; Vallage, B.; Holder, M.; Ziolkowski, M.; Biino, C.; Cartiglia, N.; Marchetto, F.; Bifani, S.; Clemencic, M.; Lopez, S. Goy; Dibon, H.; Jeitler, M.; Markytan, M.; Mikulec, I.; Neuhofer, G.; Widhalm, L.

doi:10.1007/jhep08(2014)159

“…The situation simplifies even further in the 𝐾 00 𝑒4 decay where dependence on R drops out as a consequence of the very small positron mass. In previous experiments [19][20][21], the 𝐾 ± 𝑒4 , 𝐾 00 𝑒4 and 𝐾 ± 𝜇4 decays were observed. In the following section, the analysis leading to the first observation of the 𝐾 00 decay at NA48/2 is described.…”

Section: The Na48/2 𝐾mentioning

confidence: 97%

Precision Measurements and Prospects with Kaons at CERN

Hives

2024

Proceedings of 16th International Conference on Heavy Quarks and Leptons — PoS(HQL2023)

0

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The NA62 experiment at the CERN SPS collected the world's largest dataset of charged kaon decays during 2016-2018. The dataset was used for the most precise measurement of the branching fraction of the ultra-rare decay 𝐾 + → 𝜋 + 𝜈 ν. In this proceedings, the NA62 experiment reports recent results from analyses of decays 𝐾 + → 𝜋 0 𝑒 + 𝜈𝛾 (𝐾 𝑒3𝛾 ), 𝐾 + → 𝜋 + 𝜇 + 𝜇 − (𝐾 𝜋 𝜇𝜇 ) and 𝐾 + → 𝜋 + 𝛾𝛾 (𝐾 𝜋𝛾𝛾 ). The radiative 𝐾 𝑒3𝛾 decay has a data sample of O (100𝑘) candidates with sub-percent background contamination. Published results with the most precise measurement of the branching fraction and T-asymmetry are presented. The 𝐾 𝜋 𝜇𝜇 sample comprises about 27k signal events with negligible background contamination, and the results include the most precise determination of the branching ratio and the form factor. The 𝐾 𝜋𝛾𝛾 sample contains about 4k signal events with 10 % background contamination, and the analysis improves the precision of the branching ratio measurement by a factor of 3 with respect to the previous measurements. Recent results from the NA48/2 experiment from the analysis of the decay 𝐾 ± → 𝜋 0 𝜋 0 𝜇 ± 𝜈 (𝐾 00 𝜇4 ) are also reported in this proceedings. The sample consists of 2437 events with 15 % background contamination. The result is compared with a newly calculated theoretical prediction to 1-loop level, including previously neglected 𝑅 1 form factor. The NA62 experiment is approved to take data until the CERN Long Shutdown 3. A proposal for next-generation kaon experiments at CERN, called HIKE, was submitted to the SPSC in November 2023 and is also presented in this proceedings. In its first phase, HIKE will continue to study decays of charged kaons at significantly higher beam intensities than NA62 using a new detector system. Neutral kaon decays will be then studied in the second phase of HIKE.

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“…But F form factor measured in K 00 e4 analysis may be used for K 00 µ4 decay due to the lepton universality. The measurements of K 00 e4 from NA48/2 [3] represent the best determinations of the F form factor shape F(K e4 ) and the absolute normalization f parameter (F = f • F(K e4 ), where f = 6.079 ± 0.012 st at ± 0.027 syst ± 0.046 ext ).…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…[2] is used with ChPT one-loop form factor R(1loop), H = 0, G = 0 and zero complex phase between F and R. The experimental F(K e4 ) form factor shape from Ref. [3] is used with the normalization F = 5 • F(K e4 ) providing a reasonable agreement with one-loop F calculation. Signal acceptance A S is defined for the signal missing mass region, while the normalization acceptance A N is calculated for all the selected events.…”

Section: Acceptances and Signal Backgroundmentioning

confidence: 99%

“…The uncertainty due to the modelling of form factors is estimated by the MC events weighting according to the following modifications of the matrix element: 1) implementation of the small complex phase between F and R, that is calculated in 1-loop approximation [2]; 2) R(tree) form factor usage instead of R(1loop) [2]; 3) 20% change of the general relation between F and R, covering the difference between the MC generator and the measured F(K e4 ) [3]; 4) shifts of the measured F(K e4 ) parameters by their total uncertainties [3].…”

Section: Acceptances and Signal Backgroundmentioning

confidence: 99%

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Precise measurement of the Decay K± ➞ π0 π0 µ± ν

Madigozhin¹

2022

Proceedings of 41st International Conference on High Energy Physics — PoS(ICHEP2022)

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We report the first observation of the decay K ± → π 0 π 0 µ ± ν (K 00 µ4 ) by the NA48/2 experiment at the CERN SPS. From 2437 detected signal candidates with a S/B ratio of about 6, the branching ratio of the decay is determined with high precision. In the region of squared dilepton mass above 0.03 GeV 2 /c 4 , the branching ratio is found to be BR(K 00 µ4 , S l > 0.03) = (0.65 ± 0.03) × 10 −6 . The full phase space result BR(K 00 µ4 ) = (3.4 ± 0.2) × 10 −6 , depending on the decay model extrapolation, is in a reasonable agreement with the R form factor prediction from 1-loop Chiral Perturbation Theory.

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“…See also ref [51]. for the analysis of K + → π 0 π 0 , but this process has less statistics and we will not consider it in our present study.…”

mentioning

confidence: 99%

New physics in s → d semileptonic transitions: rare hyperon vs. kaon decays

Geng

¹

,

Camalich

²

,

Shi

³

2022

J. High Energ. Phys.

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We investigate the potential of rare hyperon decays to probe the short distance structure in the $$ s\to dv\overline{v} $$ s → dv v ¯ and s → dℓ+ℓ− transitions. Hyperon decays into neutrinos $$ \left({B}_1\to {B}_2v\overline{v}\right) $$ B 1 → B 2 v v ¯ can be reliably predicted by using form factors determined in baryon chiral perturbation theory. Their decay rates are sensitive to different short-distance operators, as compared to their kaon counterparts, and the corresponding branching fractions are in the range of 10−14 ∼ 10−13 in the standard model. In the context of the low-energy effective theory, we find that the anticipated BESIII measurements of the $$ {B}_1\to {B}_2v\overline{v} $$ B 1 → B 2 v v ¯ decays would lead to constraints on new physics in the purely axial vector $$ \overline{d}{\gamma}_{\mu }{\gamma}_5s $$ d ¯ γ μ γ 5 s current that are stronger than the present limits from their kaon siblings $$ K\to \pi \pi v\overline{v} $$ K → ππv v ¯ . On the other hand, although hyperon decays into charged leptons are dominated by long-distance hadronic contributions, angular observable such as the leptonic forward-backward asymmetry is sensitive to the interference between long- and short-distance contributions. We discuss the sensitivity to new physics of a potential measurement of this observable in comparison with observables in the kaon decays KL→ μ+μ− and K+→ π+μ+μ−. We conclude that the current kaon bounds are a few orders of magnitude better than those that could be obtained from Σ+→ pμ+μ− except for two scenarios with new physics in the $$ \left(\overline{d}{\gamma}^{\mu }s\right)\left(\overline{\mathrm{\ell}}{\gamma}_{\mu }{\gamma}_5\mathrm{\ell}\right) $$ d ¯ γ μ s ℓ ¯ γ μ γ 5 ℓ and $$ \left(\overline{d}{\gamma}^{\mu }{\gamma}_5s\right)\left(\overline{\mathrm{\ell}}{\gamma}_{\mu}\mathrm{\ell}\right) $$ d ¯ γ μ γ 5 s ℓ ¯ γ μ ℓ currents. Finally, we point out that the loop effects from renormalization group evolution are important in this context, when relating the low-energy effective field theory to new physics models in the UV.

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Detailed study of the K ± → π 0 π 0 e ± ν (K e4 00 ) decay properties

Cited by 10 publications

References 28 publications

Precision Measurements and Prospects with Kaons at CERN

Precision Measurements and Prospects with Kaons at CERN

Precise measurement of the Decay K± ➞ π0 π0 µ± ν

New physics in s → d semileptonic transitions: rare hyperon vs. kaon decays

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