Muon decay spectrum: Leading logarithmic approximation

Arbuzov, A. B.; Czarnecki, Andrzej; Gaponenko, A.

doi:10.1103/physrevd.65.113006

Cited by 46 publications

(54 citation statements)

References 34 publications

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“…The goal of the experiment is to extract Michel parameters [25] from the electron energy spectrum with a relative precision at the level of 10 −4 . Known results on O(α 2 ln n (m µ /m e )), n = 1, 2 terms [5,26] suggest that O(α 2 ) corrections without logarithmic enhancement might be important for an unambiguous interpretation of the experimental result. With the initial condition for the fragmentation function at hand, one can obtain the electron energy spectrum in muon decay by computing the energy spectrum for massless electron, removing collinear divergencies by MS renormalization and convoluting decay rate, obtained in this way, with the initial condition for the fragmentation function derived in this paper.…”

Section: Discussionmentioning

confidence: 99%

Perturbative heavy quark fragmentation function throughO(αs2)

2004

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We derive the initial condition for the perturbative fragmentation function of a heavy quark through order O(α 2 s ) in the MS scheme. This initial condition is useful for computing heavy quark (or lepton, in case of QED) energy distributions from calculations with massless partons. In addition, the initial condition at O(α 2 s ) can be used to resum collinear logarithms ln(Q 2 /m 2 ) in heavy quark energy spectrum with next-to-next-to-leading logarithmic accuracy by solving the DGLAP equation.

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Section: Discussionmentioning

confidence: 99%

Perturbative heavy quark fragmentation function throughO(αs2)

2004

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“…6. The effect of second and higher order contributions and of taking into account the finite electron mass to the muon decay rate is discussed in some detail in [33][34][35][36].…”

Section: Systematic Uncertaintiesmentioning

confidence: 99%

Muon polarization in the MEG experiment: predictions and measurements

et al. 2016

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The MEG experiment makes use of one of the world's most intense low energy muon beams, in order to search for the lepton flavour violating process μ + → e + γ . We determined the residual beam polarization at the thin stopping target, by measuring the asymmetry of the angular distribution of Michel decay positrons as a function of B. I. Khazin Deceased. a e-mail: fabrizio.cei@pi.infn.it energy. The initial muon beam polarization at the production is predicted to be P μ = −1 by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be P μ = −0.86 ± 0.02 (stat) +0.05 −0.06 (syst) at the stopping target, which is consistent with the SM predictions when the depolarizing effects occurring during the muon production, propagation and moderation in the target are taken into account. The knowledge of beam polarization is of fundamental importance in order to model the background of our μ + → e + γ search induced by the muon radiative decay: μ + → e +ν μ ν e γ .

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“…Because this corresponds to a strict expansion in z, we expect good agreement for large x e as noticed in [25]. In Figure 5 we compare the two results and see that the differences are compatible with the constant (logarithm-free) terms missing in [39,40]. These terms were computed numerically and shown in a plot for x e > 0.3 in [41].…”

Section: The Electron Energy Spectrummentioning

confidence: 58%

A subtraction scheme for massive QED

Engel

Signer

Ulrich

2020

J. High Energ. Phys.

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We present an extension of the FKS subtraction scheme beyond nextto-leading order to deal with soft singularities in fully differential calculations within QED with massive fermions. After a detailed discussion of the next-to-next-to-leading order case, we show how to extend the scheme to even higher orders in perturbation theory. As an application we discuss the computation of the next-to-next-to-leading order QED corrections to the muon decay and present differential results with full electron mass dependence.

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Muon decay spectrum: Leading logarithmic approximation

Abstract: O"␣ 2 ln 2 (m /m e )… QED corrections to the electron spectrum and angular distribution in muon decay are evaluated. The impact on the determination of Michel parameters is estimated. The current theoretical uncertainty in the muon decay distributions is discussed.

Cited by 46 publications

References 34 publications

Perturbative heavy quark fragmentation function throughO(αs2)

Perturbative heavy quark fragmentation function throughO(αs2)

Muon polarization in the MEG experiment: predictions and measurements

A subtraction scheme for massive QED

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