No-Go Theorem for Nonstandard Explanations of the 
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Cirigliano, Vincenzo; Crivellin, Andreas; Hoferichter, Martin

doi:10.1103/physrevlett.120.141803

Cited by 55 publications

(227 citation statements)

References 78 publications

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“…[21,28,29], the tensor form factor was assumed to be a real constant, which is motivated by the analysis of K 3 (K → π ν with = e, µ) data [16], and the relative strong phase, being now just the phase of the vector form factor, was found to be large enough to produce a sizable CP asymmetry. This assumption was, however, pointed out to be incorrect by Cirigliano, Crivellin and Hoferichter [24]. They demonstrated that, as the same spin-1 resonances contributing to the vector form factor will equivalently contribute to the tensor one, the crucial interference between vector and tensor phases is suppressed by at least two orders of magnitude due to Watson's final-state-interaction theorem [30], and the amount of CP asymmetry that a tensor operator can produce is, therefore, strongly suppressed [24].…”

Section: Introductionmentioning

confidence: 99%

“…This assumption was, however, pointed out to be incorrect by Cirigliano, Crivellin and Hoferichter [24]. They demonstrated that, as the same spin-1 resonances contributing to the vector form factor will equivalently contribute to the tensor one, the crucial interference between vector and tensor phases is suppressed by at least two orders of magnitude due to Watson's final-state-interaction theorem [30], and the amount of CP asymmetry that a tensor operator can produce is, therefore, strongly suppressed [24].…”

Section: Introductionmentioning

confidence: 99%

“…Motivated by such an anomaly, possible direct CP violations due to non-standard interactions in τ → K S πν τ decays have been explored in Refs. [21][22][23][24][25][26]. As argued in Refs.…”

Section: Introductionmentioning

confidence: 99%

“…As argued in Refs. [21,24], due to the lack of a relative strong phase, an explanation with scalar operators is already excluded 2 , and only the interference of vector and tensor operators can provide a possible strong phase difference, leaving new tensor interactions as the only potential NP explanation. Here, whether the tensor interaction is admissible to account for the anomaly or not depends crucially on the Kπ tensor form factor.…”

Section: Introductionmentioning

confidence: 99%

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CP asymmetry in τ→KSπντ decays within the standard model and beyond

Chen

Yang

et al. 2019

Phys. Rev. D

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This work aims to explore the 2.8σ discrepancy observed between the BaBar measurement and the Standard Model prediction of the CP asymmetry in τ → K S πν τ decays. Firstly, we reproduce the known CP asymmetry due to K 0 −K 0 mixing by means of the reciprocal basis, which is convenient when a K S(L) is involved in the final state. As the Kπ tensor form factor plays a crucial role in generating an extra direct CP asymmetry that can arise only from the interference of vector and tensor operators, we then present a dispersive representation of this form factor, with its phase obtained in the context of chiral theory with resonances, which fulfills the requirements of unitarity and analyticity. Finally, the τ → K S πν τ decays are analyzed both within a model-independent low-energy effective theory framework and in a scalar leptoquark scenario. It is observed that the CP anomaly can be accommodated in the model-independent framework, even at the 1σ level, together with the constraint from the branching ratio of this decay; it can be, however, marginally reconciled only at the 2σ level, due to the specific relation between the scalar and tensor operators in the scalar leptoquark scenario.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

CP asymmetry in τ→KSπντ decays within the standard model and beyond

Chen

Yang

et al. 2019

Phys. Rev. D

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“…We translate the result of shall rely on theoretical considerations only. The key observation is that the tensor form factor admits an Omnès dispersive representation [35,37,38,64,65]. We thus write the general two-meson ( ′ ) tensor form factor as…”

Section: Scalar Contributionsmentioning

confidence: 99%

Exclusive hadronic tau decays as probes of non-SM interactions

et al. 2020

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A B S T R A C TWe perform a global analysis of exclusive hadronic tau decays into one and two mesons using the lowenergy limit of the Standard Model Effective Field Theory up to dimension six, assuming left-handed neutrinos. A controlled theoretical input on the Standard Model hadronic form factors, based on chiral symmetry, dispersion relations, data and asymptotic QCD properties, has allowed us to set bounds on the New Physics effective couplings using the present experimental data. Our results highlight the importance of semileptonic decays in complementing the traditional low-energy probes, such nuclear decays or semileptonic pion and kaon decays, and the high-energy measurements at LHC scales. This makes yet another reason for considering hadronic tau decays as golden modes at Belle-II.

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CP asymmetry in the angular distributions of τ → KSπντ decays. Part II. General effective field theory analysis

Chen

Peng

et al. 2022

J. High Energ. Phys.

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In this work, we proceed to study the CP asymmetry in the angular distributions of τ → KSπντ decays within a general effective field theory framework including four-fermion operators up to dimension-six. It is found that, besides the commonly considered scalar-vector interference, the tensor-scalar interference can also produce a non-zero CP asymmetry in the angular distributions, in the presence of complex couplings. Using the dispersive representations of the Kπ form factors as inputs, and taking into account the detector efficiencies of the Belle measurement, we firstly update our previous SM predictions for the CP asymmetries in the same four Kπ invariant-mass bins as set by the Belle collaboration. Bounds on the effective couplings of the non-standard scalar and tensor interactions are then obtained under the combined constraints from the CP asymmetries measured in the four bins and the branching ratio of τ−→ KSπ−ντ decay, with the numerical results given respectively by $$ \operatorname{Im}\left[{\hat{\upepsilon}}_S\right] $$ Im ϵ ̂ S = −0.008 ± 0.027 and $$ \operatorname{Im}\left[{\hat{\upepsilon}}_T\right] $$ Im ϵ ̂ T = 0.03 ± 0.12, at the renormalization scale μτ = 2 GeV in the $$ \overline{\mathrm{MS}} $$ MS ¯ scheme. Using the best-fit values, we also find that the distributions of the CP asymmetries can deviate significantly from the SM expectation in almost the whole Kπ invariant-mass region. Nevertheless, the current bounds on $$ \operatorname{Im}\left[{\hat{\upepsilon}}_S\right] $$ Im ϵ ̂ S and $$ \operatorname{Im}\left[{\hat{\upepsilon}}_T\right] $$ Im ϵ ̂ T are still plagued by large experimental uncertainties, but will be improved with more precise measurements from the Belle II experiment as well as the proposed Tera-Z and STCF facilities. Assuming further that the non-standard scalar and tensor interactions originate from a weakly-coupled heavy new physics well above the electroweak scale, the SU(2)L invariance of the resulting SMEFT Lagrangian would indicate that very strong limits on $$ \operatorname{Im}\left[{\hat{\upepsilon}}_S\right] $$ Im ϵ ̂ S and $$ \operatorname{Im}\left[{\hat{\upepsilon}}_T\right] $$ Im ϵ ̂ T could also be obtained from the neutron electric dipole moment and the $$ {D}^0-{\overline{D}}^0 $$ D 0 − D ¯ 0 mixing. With the bounds from these processes taken into account, it is then found that, unless there exist extraordinary cancellations between the new physics contributions, neither the scalar nor the tensor interaction can produce any significant effects on the CP asymmetries (relative to the SM predictions) in the processes considered, especially under the “single coefficient dominance” assumption.

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No-Go Theorem for Nonstandard Explanations of the τ→KSπντ

Cited by 55 publications

References 78 publications

CP asymmetry in τ→KSπντ decays within the standard model and beyond

CP asymmetry in τ→KSπντ decays within the standard model and beyond

Exclusive hadronic tau decays as probes of non-SM interactions

CP asymmetry in the angular distributions of τ → KSπντ decays. Part II. General effective field theory analysis

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