Constraints on scalar leptoquarks from lepton and kaon physics

Mandal, Rusa; Pich, Antonio

doi:10.1007/jhep12(2019)089

Cited by 98 publications

(87 citation statements)

References 152 publications

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“…(3.2). The K + decay implies the upper bound [58] 1 TeV The KOTO collaboration has recently reported the observation of four K 0 L → π 0 νν events, with an expected background of only 0.05 ± 0.02 events [62]. Removing one of the events that is suspected to originate in underestimated upstream activity background, the quoted single event…”

Section: Constraints On Scalar Leptoquarks From Rare Kaon Decaysmentioning

confidence: 96%

“…Rare kaon decays put strong constraints on NP interactions with non-trivial flavour dynamics. As an illustration, and motivated by the flavour anomalies reported recently in B decays [57], let us consider the implications of kaon data on generic couplings of hypothetical scalar leptoquarks (LQs) to the SM fermions [58]:…”

Section: Constraints On Scalar Leptoquarks From Rare Kaon Decaysmentioning

confidence: 99%

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Rare kaon decays and CP violation

Pich¹

2020

Proceedings of 18th International Conference on B-Physics at Frontier Machines — PoS(Beauty2019)

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Owing to the strong suppression of flavour-changing neutral-current transitions in the Standard Model, rare kaon decays constitute a superb tool to constrain hypothetical new-physics interactions. At the same time, they provide many interesting tests of the Standard Model itself, being sensitive both to short-distance electroweak scales and to the long-distance QCD dynamics. A brief overview of the current status is presented. The Standard Model prediction for the direct CP-violating ratio ε /ε is also discussed.

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Section: Constraints On Scalar Leptoquarks From Rare Kaon Decaysmentioning

confidence: 96%

Section: Constraints On Scalar Leptoquarks From Rare Kaon Decaysmentioning

confidence: 99%

Rare kaon decays and CP violation

Pich¹

2020

Proceedings of 18th International Conference on B-Physics at Frontier Machines — PoS(Beauty2019)

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“…This implies that the LFV parts of eq. (5.21) for BR(K + → π + νν) in [29] and of eq. (5.22) therein obey the GN bound.…”

Section: Lnv Amplitudes From ∆I = 1/2 Interaction Onlymentioning

confidence: 96%

“…However, applying the Cauchy-Schwarz inequality to the lepton-flavor-violating (LFV) part of eq. (5.22) in [29] for BR(…”

Section: Lnv Amplitudes From ∆I = 1/2 Interaction Onlymentioning

confidence: 99%

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Breaking the Grossman-Nir bound in kaon decays

Dong

Tandean

et al. 2020

J. High Energ. Phys.

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The ratio B(K L → π 0 νν)/B(K + → π + νν) of the branching fractions of kaon decays K L → π 0 νν and K + → π + νν has a maximum of about 4.3 under the assumption that the underlying interactions change isospin by ∆I = 1/2. This is referred to as the Grossman-Nir (GN) bound, which is respected by the standard model (SM) and by many scenarios beyond it. Recent preliminary results of the KOTO and NA62 Collaborations searching for these kaon modes seem to imply a violation of this bound. The KOTO findings also suggest that B(K L → π 0 νν) could be much larger, by nearly two orders of magnitude, than that predicted in the SM. In this work we study the possibility of violating the GN bound in an effective field theory approach with only SM fields. We show that the bound holds, in addition to the original GN scenarios, whether or not the kaon decays conserve lepton number. We demonstrate that the inclusion of ∆I = 3/2 operators can lead to a violation of the GN bound and illustrate with an example of how the KOTO numbers may be reached with a new physics scale of order tens of GeV.Recently the KOTO Collaboration has presented a preliminary report on its latest search for the flavor-changing neutral current (FCNC) decay of neutral kaon K L into a neutral pion π 0 and an unobserved neutrino pair (2ν), having achieved a single event sensitivity of 6.9 × 10 −10 and showing 3 candidate events in the signal region [1]. Should these turn out to be real signal events, they would imply a branching fraction of B(K L → π 0 2ν) 2.1 × 10 −9 , which is greater by almost two orders of magnitude than the standard model (SM) prediction [2-4]: B(K L → π 0 νν) SM = (3.0 ± 0.2) × 10 −11 . If confirmed in the future, this huge enhancement seen by KOTO would constitute early evidence for new physics (NP) beyond the SM in the quark sector. For comparison, KOTO [5] earlier set the limit B(K 0 L → π 0 2ν) KOTO15 < 3.0 × 10 −9 at 90% confidence level (CL).

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Low-energy phenomenology of scalar leptoquarks at one-loop accuracy

Gherardi

Marzocca

Venturini

2021

J. High Energ. Phys.

107

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We perform a complete study of the low-energy phenomenology of S1 and S3 leptoquarks, aimed at addressing the observed deviations in B-meson decays and the muon magnetic dipole moment. Leptoquark contributions to observables are computed at one-loop accuracy in an effective field theory approach, using the recently published complete one-loop matching of these leptoquarks to the Standard Model effective field theory. We present several scenarios, discussing in each case the preferred parameter space and the most relevant observables.

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Constraints on scalar leptoquarks from lepton and kaon physics

Cited by 98 publications

References 152 publications

Rare kaon decays and CP violation

Rare kaon decays and CP violation

Breaking the Grossman-Nir bound in kaon decays

Low-energy phenomenology of scalar leptoquarks at one-loop accuracy

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