αs from tau decays

Narison, Stéphan

doi:10.1016/0920-5632(95)00129-w

Cited by 11 publications

(7 citation statements)

References 35 publications

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“…We use the more recent and precise value of R τ,1 from Fig. 17 of ALEPH [27] (see also OPAL [28]), which agrees within the errors with the one estimated in SN and in [35,21] from e + e − → hadrons data. Then, we consider the SU (3)-breaking τ -like sum rule:…”

Section: S From ∆ 1φsupporting

confidence: 58%

“…In order to be conservative, we shall consider this effect as a source of systematic errors. One can estimate [18] the constant term k 3 a 3 s of the two-point correlator, by assuming a "naïve" geometric growth of the perturbative coefficients, as usually done (BNP, [20,21]). Assuming a 50% error in this estimate, one then obtains: k 3 ≈ 24.1415 2 /2.6667 ≃ (218.554 ± 109.268).…”

Section: Normalizations and Notationmentioning

confidence: 99%

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About Stephan Narison

Narison¹

2004

QCD as a Theory of Hadrons

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Strange-quark mass from combined e + e − and τ -decay data: test of the isospin symmetry and implications on ǫ ′ /ǫ and m u,d Abstract I extract the strange-quark mass using a τ -like decay sum rule for the φ-meson, and some other sum rules involving its difference with the vector component of the hadronic τ -decay. As a conservative estimate, one obtains to order α 3 s : m s (1 GeV) = (178 ± 33) MeV =⇒ m s (2 GeV) = (129 ± 24) MeV, while the positivity of the spectral function leads to the upper bound: m s (1 GeV) ≤ (200 ± 28) MeV =⇒ m s (2 GeV) ≤ (145 ± 20) MeV. These results are in good agreement with the existing sum rule and τ -decay results, and, in particular, with the result from the the sum rule involving the difference of the isoscalar and isovector components of the e + e − → hadrons data. This signals small effects of the SU (2) isospin violation due to the ω-ρ mixing parameters, and questions the reliability of the existing sum rule estimates of these parameters. Combining our result with the recent data on ǫ ′ /ǫ, we can estimate, within the standard model, the four-quark weak matrix elements B 1/2 6 − 0.54B 3/2 8 to be about (2.8 ± 1.3). This result may suggest a large violation of the vacuum saturation estimate similarly to the case of the four-quark condensates obtained from the sum rules analysis, and can serve as a guide for a future accurate non-perturbative extraction of such matrix elements. Combining our result with the sum rule estimate of m u + m d and with the Dashen formula for the mass ratio, one can deduce the update values: m d (2 GeV) = (6.4 ± 1.1) MeV and m u (2 GeV) = (2.3 ± 0.4) MeV.

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Section: S From ∆ 1φsupporting

confidence: 58%

Section: Normalizations and Notationmentioning

confidence: 99%

About Stephan Narison

Narison¹

2004

QCD as a Theory of Hadrons

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show abstract

“…17 of ALEPH [27] (see also OPAL [28]), which agrees within the errors with the one estimated in SN and in [35,21] from e + e − → hadrons data. Then, we consider the SU (3)-breaking τ -like sum rule:…”

Section: Normalizations and Notationsupporting

confidence: 78%

“…One can estimate [18] the constant term k 3 a 3 s of the two-point correlator, by assuming a "naïve" geometric growth of the perturbative coefficients, as usually done (BNP, [20,21]). Assuming a 50% error in this estimate, one then obtains: k 3 ≈ 24.1415 2 /2.6667 ≃ (218.554 ± 109.268).…”

Section: Normalizations and Notationmentioning

confidence: 99%

Strange-quark mass from combined e+e− and τ-decay data: test of the isospin symmetry and implications on ϵ′/ϵ and mu,d

Narison

1999

Physics Letters B

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I extract the strange-quark mass using a τ -like decay sum rule for the φ-meson, and some other sum rules involving its difference with the vector component of the hadronic τ -decay. As a conservative estimate, one obtains to order α 3 s : m s (1 GeV) = (178 ± 33) MeV =⇒ m s (2 GeV) = (129 ± 24) MeV, while the positivity of the spectral function leads to the upper bound: m s (1 GeV) ≤ (200 ± 28) MeV =⇒ m s (2 GeV) ≤ (145 ± 20) MeV. These results are in good agreement with the existing sum rule and τ -decay results, and, in particular, with the result from the the sum rule involving the difference of the isoscalar and isovector components of the e + e − → hadrons data. This signals small effects of the SU (2) isospin violation due to the ω-ρ mixing parameters, and questions the reliability of the existing sum rule estimates of these parameters. Combining our result with the recent data on ǫ ′ /ǫ, we can estimate, within the standard model, the four-quark weak matrix elements B 1/2 6 − 0.54B 3/2 8 to be about (2.8 ± 1.3). This result may suggest a large violation of the vacuum saturation estimate similarly to the case of the four-quark condensates obtained from the sum rules analysis, and can serve as a guide for a future accurate non-perturbative extraction of such matrix elements. Combining our result with the sum rule estimate of m u + m d and with the Dashen formula for the mass ratio, one can deduce the update values: m d (2 GeV) = (6.4 ± 1.1) MeV and m u (2 GeV) = (2.3 ± 0.4) MeV.

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“…Inclusive τ -decay provides an ideal arena for extracting information about the low energy domain of the strong interactions, in particular the QCD coupling constant α s (M 2 τ ). A detailed theoretical analysis of this process has been presented in [1] (see also [2][3][4][5][6][7][8][9]). There has been recent interest in trying to estimate the intrinsic uncertainty in such results due to the finite order truncation of the perturbative series.…”

Section: Introductionmentioning

confidence: 99%

Nonperturbative Expansion, Renormalons and τ-Decay

1997

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We analyze inclusive τ decay using a modified version of the a expansion, a non-perturbative technique in which the effective coupling is analytic in the infrared region. The modification involves renormalization group improvement of the integrand in a spectral representation for the D-function prior to implementing the a expansion. The advantage of this approach is that it enables us to monitor the structure of the induced power corrections and to ensure that these are consistent with the operator product expansion. Numerically the method agrees well with experiment: the comparison is made with the physical quantity R Z using R τ as input.

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αs from tau decays

Abstract: We review the present status in the determination of the accurate value of α s from τ -decays, where we discuss in detail the different sources of theoretical errors. * ) Talk given at the third Workshop on Tau Lepton Physics,

Cited by 11 publications

References 35 publications

About Stephan Narison

About Stephan Narison

Strange-quark mass from combined e+e− and τ-decay data: test of the isospin symmetry and implications on ϵ′/ϵ and mu,d

Nonperturbative Expansion, Renormalons and τ-Decay

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