Measurement of the decay π+→e+νee+e− and search for a light Higgs boson

Egli, S.; Engfer, R.; Grab, C.; Hermes, E.A.; Kraus, N.; Pruys, H.; Schaaf, A. van der; Eichler, R.; Kozłowski, T.; Niebuhr, C.; Walter, H. K.; Bertl, W.; Lordong, N.; Vermeulen, D.; Bellgardt, U.; Otter, G.

doi:10.1016/0370-2693(89)90358-4

Cited by 53 publications

(21 citation statements)

References 14 publications

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“…Experimentally, searches for the π + → e + ν e (h → e + e − ) decay, where h is a light scalar Higgs, constrain the branching ratio of this decay to be < ∼ 10 −9 [87] for m h > ∼ 10 MeV (for comparison, the π + → e + ν e e + e − branching ratio is measured to be (3.2 ± 0.5) × 10 −9 [87]). Taking a toy model where X couples only to electrons, and not to pions or neutrinos (e.g.…”

Section: Radiation From Charged Current Decaysmentioning

confidence: 99%

Dark forces coupled to nonconserved currents

2017

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New light vectors with dimension-4 couplings to Standard Model states have (energy/vector mass) 2 enhanced production rates unless the current they couple to is conserved. These processes allow us to derive new constraints on the couplings of such vectors, that are significantly stronger than the previous literature for a wide variety of models. Examples include vectors with axial couplings to quarks and vectors coupled to currents (such as baryon number) that are only broken by the chiral anomaly. Our new limits arise from a range of processes, including rare Z decays and flavor changing meson decays, and rule out a number of phenomenologically-motivated proposals.

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Section: Radiation From Charged Current Decaysmentioning

confidence: 99%

Dark forces coupled to nonconserved currents

2017

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“…The vector form factor F V is related to the decay rate of the π 0 → γγ decay [1,5] by the vector current conservation, so it was easier to find it using the lifetime of π 0 . On the other hand, it took many years to measure unambiguously the axial-vector form factors [6][7][8][9][10][11][12][13][14]. Some years ago, PIBETA Collaboration [15] conducted a precise measurement of the pion weak form factors, reporting the values of the vector and axial-vector form factors respectively as F V (0) = 0.0258 (17) and F A (0) = 0.0117 (17).…”

Section: Introductionmentioning

confidence: 99%

“…There is yet the second axial-vector form factor which comes into play when the photon is virtual. The SINDRUM Collaboration [12] reported the first measurement of the decay π + → e + ν e e + e − in which the off-mass-shell photon decays into e + e − , and yielded the second axial-vector form factor to be R A (0) = 0.059 +0.009 −0.008 .…”

Section: Introductionmentioning

confidence: 99%

Pion radiative weak decay from the instanton vacuum

Shim

Kim

2017

Physics Letters B

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We investigate the vector and axial-vector form factors for the pion radiative weak decays $\pi^+\to e^+\nu_e \gamma$ and $\pi^+\to e^+\nu_e e^+ e^-$, based on the gauged effective chiral action from the instanton vacuum in the large $N_c$ limit. The nonlocal contributions, which arise from the gauging of the action, enhance the vector form factor by about $20\,\%$, whereas the axial-vector form factor is reduced by almost $30\,\%$. Both the results for the vector and axial-vector form factors at the zero momentum transfer are in good agreement with the experimental data. The dependence of the form factors on the momentum transfer is also studied. The slope parameters are computed and compared with other works.Comment: 13 pages, 7 figures. Final version accepted for publication in Phys.Lett.

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“…In previous experiments [20], using the stopped pion technique, the radiative pion decay has been measured in a limited phase space region where V + A contributions dominate, leaving to an ambiguity on the sign of γ. In more recent experiments [21,22], the investigated larger portion of the phase space allowed to determine the sign of γ as well, which has also been confirmed by the π + → e + νe + e − measurement [25].…”

Section: Radiative π + Decaysmentioning

confidence: 59%

Light mesons and muon radiative decays and photon polarization asymmetry

Gabrielli

Trentadue

2008

Nuclear Physics B

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We systematically compute and discuss meson and muon polarized radiative decays. Doubly differential distributions in terms of momenta and helicities of the final lepton and photon are explicitly computed. The undergoing dynamics giving rise to lepton and photon polarizations is examined and analyzed in the soft and hard region of momenta. The particular configurations made by right-handed leptons with accompanying photons are investigated and interpreted as a manifestation of the axial anomaly. The photon polarization asymmetry is evaluated. Finiteness of polarized amplitudes against infrared and collinear singularities is shown to take place with mechanisms distinguishing between right handed and left handed final leptons. We propose a possible test using photon polarization to clarify a recently observed discrepancy in radiative meson decays.

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Measurement of the decay π+→e+νee+e− and search for a light Higgs boson

Cited by 53 publications

References 14 publications

Dark forces coupled to nonconserved currents

Dark forces coupled to nonconserved currents

Pion radiative weak decay from the instanton vacuum

Light mesons and muon radiative decays and photon polarization asymmetry

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