CP violation in η muonic decays

Sánchez-Puertas, Pablo

doi:10.1007/jhep01(2019)031

Cited by 13 publications

(33 citation statements)

References 45 publications

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“…The uncertainty on the predictions from Model 1 is the propagated error from the input parameters σ P , σ V , F P γγ , F P , and the η-η mixing parameters. In all cases we observe good agreement with the literature [46,47,49,124], which demonstrates that in addition to fulfilling the various SDCs, our Regge models capture the properties of the TFFs most relevant for the g − 2 integral.…”

Section: Excited-pseudoscalar Contributions To (G − 2) µsupporting

confidence: 84%

Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

Colangelo

Hagelstein

Hoferichter

et al. 2020

J. High Energ. Phys.

285

166

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While the low-energy part of the hadronic light-by-light (HLbL) tensor can be constrained from data using dispersion relations, for a full evaluation of its contribution to the anomalous magnetic moment of the muon (g − 2) µ also mixed-and high-energy regions need to be estimated. Both can be addressed within the operator product expansion (OPE), either for configurations where all photon virtualities become large or one of them remains finite. Imposing such short-distance constraints (SDCs) on the HLbL tensor is thus a major aspect of a model-independent approach towards HLbL scattering. Here, we focus on longitudinal SDCs, which concern the amplitudes containing the pseudoscalar-pole contributions from π 0 , η, η . Since these conditions cannot be fulfilled by a finite number of pseudoscalar poles, we consider a tower of excited pseudoscalars, constraining their masses and transition form factors from Regge theory, the OPE, and phenomenology. Implementing a matching of the resulting expressions for the HLbL tensor onto the perturbative QCD quark loop, we are able to further constrain our calculation and significantly reduce its model dependence. We find that especially for the π 0 the corresponding increase of the HLbL contribution is much smaller than previous prescriptions in the literature would imply. Overall, we estimate that longitudinal SDCs increase the HLbL contribution by ∆a LSDC µ = 13(6) × 10 −11 . A Anomalous Pseudoscalar-Vector-Vector Coupling 46 B Alternative model for pion, η, and η transition form factors 48 1 Introduction Current Standard Model (SM) evaluations of the anomalous magnetic moment of the muon, a µ = (g − 2) µ /2, differ from the value measured at the Brookhaven National Laboratory [1]a exp µ = 116 592 089(63) × 10 −11 , (1.1) by around 3.5 σ. In the near future, the new Fermilab E989 experiment [2] will be able to reduce the experimental uncertainty by a factor 4, and the E34 experiment at J-PARC [3] will provide an important cross check, see ref.[4] for a comparison of the experimental methods. Therefore, the theoretical calculation of a µ needs to be improved accordingly. The uncertainty of the SM prediction mainly stems from hadronic contributions, such as hadronic vacuum polarization (HVP), see figure 1 (a), and HLbL scattering, see figure 1 (b). Since the HVP contribution can be systematically calculated with a data-driven dispersive approach [5-9], lattice QCD [10][11][12][13][14][15][16], and potentially be accessed independently by the proposed MUonE experiment [17,18], which aims to measure the space-like finestructure constant α(t) in elastic electron-muon scattering, the HLbL contribution may end up dominating the theoretical error. 1 Apart from lattice QCD [27][28][29], recent data-driven approaches towards HLbL scattering are again rooted in dispersion theory, either for the HLbL tensor [30][31][32][33][34][35], the Pauli 1 Note that higher-order insertions of HVP [5,19,20] and HLbL [21] are already under sufficient control, as are hadronic corrections in the anomalou...

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Section: Excited-pseudoscalar Contributions To (G − 2) µsupporting

confidence: 84%

Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

Colangelo

Hagelstein

Hoferichter

et al. 2020

J. High Energ. Phys.

285

166

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“…By construction, the ground-state pseudoscalar-pole contributions to (g − 2) µ reproduce literature values [32][33][34]85] within errors, while the sum over excitedpseudoscalar poles leads to the increase:…”

Section: Large-nc Regge Modelmentioning

confidence: 70%

Short-distance constraints on hadronic light-by-light scattering in the anomalous magnetic moment of the muon

et al. 2020

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A key ingredient in the evaluation of hadronic light-by-light (HLbL) scattering in the anomalous magnetic moment of the muon (g − 2)µ concerns short-distance constraints (SDCs) that follow from QCD by means of the operator product expansion. Here we concentrate on the most important such constraint, in the longitudinal amplitudes, and show that it can be implemented efficiently in terms of a Regge sum over excited pseudoscalar states, constrained by phenomenological input on masses, two-photon couplings, as well as SDCs on HLbL scattering and the pseudoscalar transition form factors (TFFs). Our estimate of the effect of the longitudinal SDCs on the HLbL contribution is: ∆a LSDC µ = 13(6) × 10 −11 . This is significantly smaller than previous estimates, which mostly relied on an ad-hoc modification of the pseudoscalar poles and led to up to a 40% increase with respect to the nominal pseudoscalar-pole contributions, when evaluated with modern input for the relevant TFFs. We also comment on the status of the transversal SDCs and, by matching to perturbative QCD, argue that the corresponding correction will be significantly smaller than its longitudinal counterpart.

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“…There are three kinds of such operators: those containing leptons (and photons), those containing quarks and gluons(photons), and those containing quarks and leptons. For the first category, the electron and muon EDMs set strong bounds such that these operators can be ignored [6,5]. Concerning the second-hadronic-category, that we name CP H , for our process of interest it will manifest as new CP -violating transition form factors, so the η coupling to two (generally virtual) photons reads…”

Section: The Smeft and Hadronizationmentioning

confidence: 99%

“…However, it is very important for the preliminary studies to assess whether the proposed experiment is competitive with different observables that set stringent bounds, as it is the case here when connecting with electric dipole moments (EDMs). In this work [5], we carry on such a study, for which we will assumme that new physics is heavy enough to use the SMEFT. The basic ingredients we need and the hadronization details are outlined in Section 2, while the muon polarization in different η muonic decays is computed in Section 3-where the experimental sensitivity is assessed.…”

Section: Introductionmentioning

confidence: 99%

“…The basic ingredients we need and the hadronization details are outlined in Section 2, while the muon polarization in different η muonic decays is computed in Section 3-where the experimental sensitivity is assessed. Finally, in Section 4, we study the bounds that different observables put on these processes (including a new processes not considered originally in [5]), finding that is still possible to observe CP -violation in η → µ + µ − decays.…”

Section: Introductionmentioning

confidence: 99%

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New-physics searches in $C\!P$-violating $η$ muonic decays

Sánchez-Puertas¹

2019

Preprint

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In this work we investigate the possibility to observe CP -violation in η decays containing muons at the proposed REDTOP experiment. Employing the SMEFT to parametrize the new-physics CP -violating effects, we find that a single operator exists for which is possible to observe CP -violation at REDTOP in η → µ + µ − decays, while evading bounds from the neutron electric dipole moment and D − → µν meson decays.

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CP violation in η muonic decays

Cited by 13 publications

References 45 publications

Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

Short-distance constraints on hadronic light-by-light scattering in the anomalous magnetic moment of the muon

New-physics searches in $C\!P$-violating $η$ muonic decays

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