A Precision Measurement of the Muon Decay Parameters $ρ$ and $δ$

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dc.creatorTWIST Collaboration
dc.creatorMacDonald, R. P.
dc.creatorBayes, R.
dc.creatorBueno, J.
dc.creatorDavydov, Yu. I.
dc.creatorDepommier, P.
dc.creatorFaszer, W.
dc.creatorFujiwara, M. C.
dc.creatorGagliardi, C. A.
dc.creatorGaponenko, A.
dc.creatorGill, D. R.
dc.creatorGrossheim, A.
dc.creatorGumplinger, P.
dc.creatorHasinoff, M. D.
dc.creatorHenderson, R. S.
dc.creatorHillairet, A.
dc.creatorHu, J.
dc.creatorJamieson, B.
dc.creatorKitching, P.
dc.creatorKoetke, D. D.
dc.creatorMarshall, G. M.
dc.creatorMathie, E. L.
dc.creatorMischke, R. E.
dc.creatorMusser, J. R.
dc.creatorNozar, M.
dc.creatorOlchanski, K.
dc.creatorOlin, A.
dc.creatorOpenshaw, R.
dc.creatorPoutissou, J. -M.
dc.creatorPoutissou, R.
dc.creatorQuraan, M. A.
dc.creatorSelivanov, V.
dc.creatorSheffer, G.
dc.creatorShin, B.
dc.creatorStanislaus, T. D. S.
dc.creatorTacik, R.
dc.creatorTribble, R. E.
dc.date2008-07-07
dc.date2008-07-16
dc.date.accessioned2026-07-07T11:52:22Z
dc.date.available2026-07-07T11:52:22Z
dc.descriptionThe TWIST collaboration has performed new measurements of two of the parameters that describe muon decay: $ρ$, which governs the shape of the overall momentum spectrum, and $δ$, which governs the momentum dependence of the parity-violating decay asymmetry. This analysis gives the results $ρ=0.75014\pm 0.00017(\text{stat})\pm 0.00044(\text{syst})\pm 0.00011(η)$, where the last uncertainty arises from the correlation between $ρ$ and the decay parameter $η$, and $δ= 0.75067\pm 0.00030(\text{stat})\pm 0.00067(\text{syst})$. These are consistent with the value of 3/4 given for both parameters in the Standard Model of particle physics, and are a factor of two more precise than the measurements previously published by TWIST. A new global analysis of all available muon decay data incorporating these results is presented. Improved lower and upper limits on the decay parameter $P_μ^πξ$ of $0.99524 < P_μ^πξ\leq ξ< 1.00091$ at 90% confidence are determined, where $P_μ^π$ is the polarization of the muon when it is created during pion decay, and $ξ$ governs the muon decay asymmetry. These results set new model-independent constraints on the possible weak interactions of right-handed particles. Specific implications for left-right symmetric models are discussed.
dc.description14 pages, 14 figs, accepted for publication in Phys. Rev. D
dc.identifierhttps://arxiv.org/abs/0807.1125
dc.identifierhttp://arxiv.org/abs/0807.1125
dc.identifierPhys.Rev.D78:032010,2008
dc.identifierdoi:10.1103/PhysRevD.78.032010
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/204205
dc.subjectHigh Energy Physics - Experiment
dc.subjectNuclear Experiment
dc.titleA Precision Measurement of the Muon Decay Parameters $ρ$ and $δ$
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