Experimental study of rare charged pion decays

Počanić, D.; Frlež, E.; Schaaf, A. van der

doi:10.1088/0954-3899/41/11/114002

Cited by 21 publications

(33 citation statements)

References 95 publications

(198 reference statements)

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“…in the π + → π 0 e + ν 4 decay. However, in contrast to nuclear beta decay, events ascribed to the decay π + → π 0 e + ν e were identified by the diphoton decay of the π 0 , and the e + energy was not systematically measured, e.g., in the PIBETA experiment at PSI [74,75]. Hence, one could not do a kink search for this decay, which would be quite difficult anyway because of the very small branching ratio of 10 −8 for pion beta decay.…”

Section: Limit On Emission Of Massive Neutrinos In Nuclear Beta Dmentioning

confidence: 99%

“…where r πβ,ν4 denotes the ratio of the kinematic factor for the π + → π 0 e + ν 4 decay divided by that for the decay into neutrinos of negligibly small mass, and, including radiative corrections [74,75], BR(π + → π 0 e + ν e ) SM = (1.039 ± 0.001) × 10 −8 . (3.9)…”

Section: Limit On Emission Of Massive Neutrinos In Nuclear Beta Dmentioning

confidence: 99%

“…The current value listed by the Particle Data Group, dominated by the PIBETA measurement [74,75], is [13] BR(π + → π 0 e + ν e ) = (1.036 ± 0.006) × 10 −8 . (3.11) This is in good agreement with the SM prediction (3.9), yielding…”

Section: Limit On Emission Of Massive Neutrinos In Nuclear Beta Dmentioning

confidence: 99%

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Constraints on sterile neutrinos in the MeV to GeV mass range

2019

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A detailed discussion is given of the analysis of recent data to obtain improved upper bounds on the couplings |Ue4| 2 and |Uµ4| 2 for a mainly sterile neutrino mass eigenstate ν4. Using the excellent agreement among Ft values for superallowed nuclear beta decay, an improved upper limit is derived for emission of a ν4. The agreement of the ratios of branching ratios R (π) e/µ = BR(π + → e + νe)/BR(π + → µ + νµ), R (K) e/µ , R (Ds) e/τ , R (Ds) µ/τ , and R (D)e/τ , and the branching ratios BR(B + → e + νe) and BR(B + → µ + νµ) decays with predictions of the Standard Model, is utilized to derive new constraints on ν4 emission covering the ν4 mass range from MeV to GeV. We also discuss constraints from peak search experiments probing for emission of a ν4 via lepton mixing, as well as constraints from pion beta decay, CKM unitarity, µ decay, leptonic τ decay, and other experimental inputs.

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Section: Limit On Emission Of Massive Neutrinos In Nuclear Beta Dmentioning

confidence: 99%

Section: Limit On Emission Of Massive Neutrinos In Nuclear Beta Dmentioning

confidence: 99%

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Constraints on sterile neutrinos in the MeV to GeV mass range

2019

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“…DOI: 10.1103/PhysRevLett.115.162001 PACS numbers: 13.60.Hb, 13.40.Gp, 24.85.+p High precision measurements of beta decay observables play an important role in beyond the standard model (BSM) physics searches, as they allow us to probe couplings other than of the V − A type, which could appear at the low energy scale. Experiments using cold and ultracold neutrons [1][2][3][4], nuclei [5][6][7][8], and meson rare decays [9] are being performed, or have been planned, that can reach the per-mil level or even higher precision. Effective field theory (EFT) allows one to connect these measurements and BSM effects generated at TeV scales.…”

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confidence: 99%

Beyond-Standard-Model Tensor Interaction and Hadron Phenomenology

Courtoy¹,

Baeßler²,

González–Alonso³

et al. 2015

Phys. Rev. Lett.

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We evaluate the impact of recent developments in hadron phenomenology on extracting possible fundamental tensor interactions beyond the standard model. We show that a novel class of observables, including the chiral-odd generalized parton distributions, and the transversity parton distribution function can contribute to the constraints on this quantity. Experimental extractions of the tensor hadronic matrix elements, if sufficiently precise, will provide a, so far, absent testing ground for lattice QCD calculations. DOI: 10.1103/PhysRevLett.115.162001 PACS numbers: 13.60.Hb, 13.40.Gp, 24.85.+p High precision measurements of beta decay observables play an important role in beyond the standard model (BSM) physics searches, as they allow us to probe couplings other than of the V − A type, which could appear at the low energy scale. Experiments using cold and ultracold neutrons [1][2][3][4], nuclei [5][6][7][8], and meson rare decays [9] are being performed, or have been planned, that can reach the per-mil level or even higher precision. Effective field theory (EFT) allows one to connect these measurements and BSM effects generated at TeV scales. In this approach that complements collider searches, the new interactions are introduced in an effective Lagrangian describing semileptonic transitions at the GeV scale including four-fermion terms, or operators up to dimension six for the scalar, tensor, pseudoscalar, and V þ A interactions (for a review of the various EFT approaches, see Ref.[10]). Because the strength of the new interactions is defined with respect to the strength of the known SM interaction, the coefficients of the various terms, ϵ i , (i ¼ S; T; P; L; R) depend on the ratio m 2 W =Λ 2 i , where Λ i is the new physics scale relevant for these nonstandard interactions, and mW Þ. Therefore, the precision with which ϵ i ∝ m 2 W =Λ 2 i , is known determines a lower limit for Λ i . The scalar (S) and tensor (T) operators, in particular, contribute linearly to the beta decay parameters through their interference with the SM amplitude, and they are, therefore, more easily detectable. The matrix elements or transition amplitudes between neutron and proton states of all quark bilinear Lorentz structures in the effective Lagrangian which are relevant for beta decay observables, involve products of the BSM couplings, ϵ i , and the corresponding hadronic charges, g i , i.e., considering only terms with left-handed neutrinos,whereSðTÞ , characterize nucleon structure; however, at variance with the electroweak currents, there exists no fundamental coupling to these charges in the standard model. Therefore, they cannot be measured directly in elastic scattering processes. This Letter is concerned with an alternative approach aimed at extracting the hadronic charges from experimental data obtained in electron scattering. In previous work, various approaches have been developed to calculate these quantities including lattice QCD [11][12][13][14][15], and most recently, Dyson-Schwinger equations [16,17]. Lattice QCD ...

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“…The first has been completely analyzed, the latter two have completed their data taking and are in their analysis phases. The reader is referred to excellent recent reviews on rare charged pion decays [44,82]. One preliminary conclusion is that further improvement of the experimental sensitivities in pion decay will require major efforts and appear very challenging.…”

Section: Experiments With Pionsmentioning

confidence: 99%

The Virtue of Precision Particle Physics

Kirch

2015

Proceedings of the 2nd International Symposium on Science at J-Parc — Unlocking the Mysteries of Life, Matter and the Universe

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Precision studies and tests of fundamental interactions and symmetries are a focus point of modern particle physics. With the success of the present Standard Model (SM) of particle physics and simultaneously with the need for new physics to fix known deficiencies a broad search program is under way to probe at all energy scales for the unknown. Precision measurements of quantities which can be accurately predicted in the SM and also especially those which are predicted to be null or negligibly small turn out to provide some of the most stringent constraints for many new physics scenarios. Besides some detours, this paper concentrates on precision physics using neutrons, pions and muons, the lightest unstable particles of their kind, produced at the most powerful proton accelerators.KEYWORDS: precision particle physics, symmetry, lepton flavor, charge parity, dipole moment, weak interaction, rare decay, exotic atom, spectroscopy Setting the sceneComplementarity is a buzz word in today's research. Here it is used to describe the relation between the direct production of new particles and observations of virtual contributions from such particles. Direct production of new heavy particles and resonances and their detection through their decays is the realm of high energy collider particle physics. The recent discovery of a Higgs boson [1,2] displaying so far all features expected for the Standard Model (SM) Higgs is the latest discovery and triumph of this successful line of research. Indeed, the careful investigation of this Higg's particle properties (see, e.g. [3]) and the continued search for possible new particles with larger masses is the ongoing high priority program at CERN's LHC which will resume operation at higher energy soon.The broader look at 'fundamental physics in the era of LHC' has identified many complementary efforts and established the case and the need for a program at the high intensity, low energy, precision physics frontier, e.g. [4][5][6]. The observation of indirect, short distance effects of virtual particles becomes possible in the comparison of precision measurements and precision theoretical predictions. As it turns out, many of these experiments at low energy probe physics at considerably higher energy scale than direct collider searches, often multi-TeV or even 1000 TeV.Some finite observables allow, both, very precise and accurate experimental determinations and very precise and accurate, often multi-loop, calculations within the SM or some of its extensions. Prime examples for these observables are the anomalous magnetic moments a e/µ = (g − 2)/2 of the electron [7] and the muon [8,9]. For instance, the best determination today of the fine structure constant α relies on the a e measurement and a high precision QED calculation [10]. Likewise, the electron mass [11] is obtained by comparing a high precision quantum jump spectroscopy measurement in a Penning trap with a high precision calculation of the bound electron g-factor. More examples can be easily found, as the extraction of fu...

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Experimental study of rare charged pion decays

Cited by 21 publications

References 95 publications

Constraints on sterile neutrinos in the MeV to GeV mass range

Constraints on sterile neutrinos in the MeV to GeV mass range

Beyond-Standard-Model Tensor Interaction and Hadron Phenomenology

The Virtue of Precision Particle Physics

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