A precision measurement of muon decay

Quraan, Maher A.; Amaudruz, P.; Andersson, W.; Comyn, M.; Davydov, Yu. I.; Depommier, P.; Doornbos, J.; Faszer, W.; Gagliardi, C. A.; Gill, D. R.; Green, P.; Gumplinger, P.; Hardy, J.C.; Hasinoff, M.; Helmer, R. L.; Henderson, R.; Khruchinsky, A.; Kitching, P.; Koetke, D. D.; Korkmaz, E.; Lachin, Yu.Yu.; Mass, D.; Macdonald, J. A.; Manweiler, R.; Mathie, T.; Musser, J.; Nord, P. M.; Olin, A.; Ottewell, D.; Openshaw, R.; Piilonen, L. E.; Porcelli, T. A.; Poutissou, J. M.; Poutissou, R.; Rodning, N.; Schaapman, J.; Selivanov, V. I.; Sheffer, Gabriel; Shin, Yong Moon; Sobratee, F.; Soukup, J.; Stanislaus, T. D. S.; Stinson, G. M.; Tacik, R.; Torokhov, V.; Tribble, R. E.; Vasiliev, M. A.; Walter, H. K.; Wright, D. H.

doi:10.1016/s0375-9474(99)00793-9

Cited by 9 publications

(11 citation statements)

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“…We employ the numerical values m µ = 105.658357 MeV and m e = 0.510998902 MeV and the on-shell value of the QED coupling constant, α = 1/137.0359895. For numerical estimates we consider electron energies in the range 0.3 ≤ x ≤ 0.95, which matches the acceptance of the TWIST experiment [12]. We have checked that integrating our result over x reproduces the correction to the total decay rate found in [10], within numerical integration errors.…”

Section: Resultsmentioning

confidence: 87%

The electron energy spectrum in muon decay through 𝒪(α²)

Anastasiou¹,

Melnikov²,

Petriello³

2007

J. High Energy Phys.

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We compute the complete O(α 2 ) QED corrections to the electron energy spectrum in unpolarized muon decay, including the full dependence on the electron mass. Our calculation reduces the theoretical uncertainty on the electron energy spectrum well below 10 −4 , the precision anticipated by the TWIST experiment at TRIUMF, which is currently performing this measurement. For this calculation, we extend techniques we have recently developed for performing next-to-next-toleading order computations to handle the decay spectra of massive particles. Such an extension enables further applications to precision predictions for b, t, and Higgs differential decay rates.The decay of a muon into an electron and a pair of neutrinos, µ → eν µνe , occupies an important role in particle physics. The measurement of the muon lifetime [1] leads to the most accurate determination of the Fermi coupling constant, G F . The muon anomalous magnetic moment is one of the most precisely measured quantities in nature [2,3], and provides important constraints on physics beyond the Standard Model (SM) [4]. Searches for lepton flavor-violating decays of the muon, such as µ → eγ and µ → eee, constrain the flavor sector of many SM extensions [5].The calculations of radiative corrections to muon decay have a long and storied history [6]. The one-loop QED corrections were first performed within the Fermi theory of weak interactions in the 1950s [7]. The cancellation of mass singular terms such as ln(m µ /m e ) in the total rate, but not in distributions such as the electron energy spectrum, led to the development of the Kinoshita-Lee-Nauenberg theorem, which explains how to construct "infrared-safe" observables in quantum field theory where such effects cancel [8]. The calculation of the full one-loop corrections in the SU(2)×U(1) theory of the electroweak interactions was one of the first such computations performed [9]. The full two-loop corrections to the muon lifetime in the Fermi model, needed for a precision determination of G F , were completed several years ago [10]; recently, the two-loop results in the full electroweak theory were obtained [11].Muon decay continues to be of interest in particle physics. The TWIST experiment at TRIUMF [12] measures the electron energy and angular distributions in polarized muon decay; the first results were recently reported in [13]. It is anticipated that TWIST will eventually measure the Michel parameters [14], which describe muon decay for the most general form of the four-fermion interaction, to a precision of ≈ 10 −4 . This significantly increases the sensitivity of muon decay to deviations arising from new physics. For example, the lower bound on the mass of the W R in the manifest left-right symmetric model is improved from M W R > 400 GeV to M W R > 800 GeV, competitive with limits coming from the Tevatron, while the bounds on the left-right mixing parameter ζ are improved by nearly an order of magnitude [5]. Such precision requires a careful consideration of the higher order corrections. As noted ab...

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Section: Resultsmentioning

confidence: 87%

The electron energy spectrum in muon decay through 𝒪(α²)

Anastasiou¹,

Melnikov²,

Petriello³

2007

J. High Energy Phys.

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“…[14]. Nevertheless, this is still worse than the experimental precision 1 · 10 −4 planned at T WIST [3,4]. Assuming that a theoretical precision of about one third (or less) of the experimental one would not spoil results of an experiment, we see a challenge for further investigations.…”

Section: Discussionmentioning

confidence: 92%

“…In this paper we discuss the present theoretical precision of the polarized muon decay spectrum description. The study is motivated by the experiment T WIST [3,4], which is currently running at Canada's National Laboratory TRIUMF. The experiment is going to measure the spectrum with the accuracy level of about 1 · 10 −4 .…”

Section: Introductionmentioning

confidence: 99%

Higher order QED corrections to muon decay spectrum

Arbuzov¹

2003

J. High Energy Phys.

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“…Precise determinations of those observables test the Standard Model and can be used to search for possible "new physics" effects [6]. This motivates ongoing studies of the positron transverse [7] and longitudinal polarization [8] and angular/energy distributions [9,10]. Muon lifetime is also being remeasured [11,12].…”

Section: Introductionmentioning

confidence: 99%