arXiv subjects

Stephan Narison

Publications and source records attributed to Stephan Narison.

At least 73 records · Page 4Linked to original sources

arXiv2002

Probing High-Energy Physics with High-Precision QED Measurements

I summarize our self-contained determinations of the lowest order hadronic contributions to the anomalous magnetic moments a_{μ,τ} of the muon and tau leptons, the running QED coupling α(M_Z) and the muonium hyperfine splitting ν. Using as a revised estimate of the light-by light scattering: a_μ(LL)=85(18) 10^{-11}, we deduce: a_μ^{SM} = 116 591 861(78) 10^{-11}, a_τ^{SM} = 117 759(7) 10^{-8}, giving: a_μ^{SM}-a_μ^{exp}=162(170) 10^{-11}. We also obtain: α^{-1}(M_Z)=128.926(25) and the Fermi energy splitting: ν_F^{SM}=4 459 031 783(229) {Hz}. Lower bounds on some eventual new physics are given, while ν_F^{SM} leads e.g. to m_μ/m_e=206.768 276(11) in remarkable agreement with the data.

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arXiv2002

Light and heavy quark masses, Flavour breaking of chiral condensates, Meson weak leptonic decay constants in QCD

We review the present status for the determinations of the light and heavy quark masses, the light quark chiral condensate and the decay constants of light and heavy-light (pseudo)scalar mesons from QCD spectral sum rules (QSSR). Bounds on the light quark running masses at 2 GeV are found to be: 6 MeV<(m_d+m_u)(2)<11 MeV and 71 MeV / =0.66\pm 0.10. The last section is dedicated to the QSSR determinations of f_{D_{(s)}} and f_{B_{(s)}}.

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arXiv2001

Muon and tau anomalies updated

We present a new independent evaluation of the hadronic vacuum polarization contributions a_l{had}(l.o)=(1/2)(g-2)_l{had}(l.o) to the anomalous magnetic moment (anomaly) of the muon and tau leptons using tau-decays and e+e- data. The alone theoretical input used for describing the high-energy region not accessible experimentally is perturbative QCD plus (negligible) additional effects due to the QCD vacuum condensates. We obtain: a_mu{had}(l.o)= 7020.6(75.6)10^{-11} and a_tau{had}(l.o)= 353.6(3.8)10^{-8}, which we compare with previous determinations. Our analysis leads to the Standard Model (SM) prediction: a_mu^{SM}=116~591~846.9(78.9)10^{-11}.Confronting a_mu^{SM} with the recent BNL measurement leads to a_mu{new}= a_mu{exp}-a_mu{SM}=176(170)10^{-11}. Combined with the mean existing determinations of a_mu^{had}(l.o), this leads to the conservative range: -42 < a_mu{new}10^{11} < 413 at 90% CL, from which we derive conservative lower bounds on the scales of some new physics. We also update our old predictions of the SM contributions to a_tau. Including QED to sixth order, higher order hadronic and electroweak contributions, we obtain a_tau{SM}=117 755(7)10^{-8}, waiting for a future precise measurement of a_tau.

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arXiv2001

New Evaluation of the QED Running Coupling and of the Muonium Hyperfine Splitting

We present a new independent evaluation of the hadronic and QCD contributions to the QED running coupling α(M_Z) and to the muonium hyperfine splitting ν. We obtain: Δα_{had}=2770(17)10^{-5} and Δν_{had}=232.5(2.5) Hz. Combined with the QED and Electroweak Standard Model contributions, they lead to: α^{-1}(M_Z)=128.926(25) and to the Fermi energy splitting ν_F=4~459~031~783(229) Hz, where for the latter, we have used, in addition, the precise measurement of the muonium hyperfine splitting ν_{exp}. We use ν_F in order to predict the ratios of masses m_μ/m_e=206.768~276(11) and of the magnetic moments μ_μ/μ^e_B=4.841~970~47(25)10^{-3}, which are in excellent agreement with the ones quoted by the Particle Data Group. These remarkable agreements can provide strong constraints on some contributions beyond the Standard Model.

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arXiv2001

c,b quark masses and f_D_(s), f_B_(s) decay constants from pseudoscalar sum rules in full QCD to order alpha_s^2

The pseudoscalar sum rules of the heavy-light quark systems are used for extracting simultaneously the c,b quark masses and the decay constants f_D_(s),f_B_(s) of the D_(s),B_(s) mesons. To order alpha_s^2, one obtains the running quark masses: m_c(m_c)=(1.10 \pm 0.04) GeV, m_b(m_b)=(4.05\pm 0.06) GeV, the perturbative pole masses: M_c=(1.46\pm 0.04) GeV, M_b=(4.69\pm 0.06) GeV, and the decay constants: f_D=(205\pm 20) MeV, f_B=(203\pm 23) MeV and f_D_s=(235\pm 24) MeV, f_B_s=(236\pm 30) MeV, in the normalization where f_π= 130.56 MeV. The fitted values of the pole and running masses satisfy quite well their three-loop perturbative relation. The value f_D = f_B confirms earlier findings from the sum rule that the 1/M_P^1/2 heavy quark symmetry scaling law is affected by large 1/M_P corrections.

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arXiv2000

Scalar Mesons in QCD

We review the analysis of the quark and gluon substructures of the scalar mesons from QCD spectral sum rules and some low-energy theorems applied to the scalar QCD anomaly current. The present data favour equal components of \bar uu+ \bar dd and of gg in the wave functions of the low-mass (below 1 GeV) scalar mesons, which make the wide σand the narrow f_0(980) as η'-like particles, which can have strong couplings to meson pairs through OZI violations. A coherent picture of the other I=0 scalar mesons spectra within this mixing scheme is shortly discussed. We also expect the a_0(980) to be the lowest isovector \bar ud state, and the K^*_0(1430) its \bar ds partner.

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arXiv2000

New QCD estimate of the kaon penguin matrix elements and epsilon'/epsilon

Firstly, we use the recent ALEPH/OPAL data on the V-A spectral functions for fixing the continuum threshold with which the first and second Weinberg sum rules should be satisfied in the chiral limit. Then, we predict the values of the low-energy constants m_{π^+}-m_{π^0}, {L}_{10}, and test the values of the electroweak kaon penguin matrix elements _{2π} obtained from DMO--like sum rules. Secondly, we use the data on the τ-total hadronic width R_{τ,V/A} for extracting , in the {MS}\bar scheme, and propose some new sum rules for < Q_7^{3/2}>_{2π} in the chiral limit, where the latter require more accurate data for the spectral functions near the $τ$-mass. Thirdly, we analyze the effects to the matrix element _{2π}, of the S_2\equiv(\bar uu+\bar dd) component of the I=0 scalar meson, with its parameters fixed from QCD spectral sum rules. Our results should stimulate a further attention on the rôle of the (expected large) gluonium component of the I=0 scalar meson and of the associated operator in the K--->ππamplitude. Finally, using our previous determinations, we deduce, in the Standard Model (SM), the conservative upper bound for the CP-violating ratio: ε'/ε< (22\pm 9) 10^{-4}, which is in agreement with the present measurements.

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arXiv2000

V-A hadronic tau decays : a QCD laboratory

Recent ALEPH/OPAL data on the V-A spectral functions from hadronic tau decays are used for fixing the QCD continuum threshold at which the first and second Weinberg sum rules should be satisfied in the chiral limit, and for predicting the values of the low-energy constants f_π,~m_{π^+}-m_{π^0} and {L}_{10}. Some DMO-like sum rules and the $τ$-total hadronic widths R_{τ,V-A} are also used for extracting the values of the D=6,~8 QCD vacuum condensates and the corresponding (in the chiral limit) electroweak kaon penguin matrix elements Q^{3/2}_{8,7}\ra_{2π},, where a deviation from the vacuum saturation estimate has been obtained. Combining these results with the one of the QCD penguin matrix element Q^{1/2}_{6}\ra_{2π} obtained from a (maximal) \bar qq-gluonium mixing scheme from the scalar meson sum rules, we deduce, in the Electroweak Standard Model (ESM), the conservative upper bound for the CP-violating ratio: ε'/ε\leq (22\pm 9) 10^{-4}, in agreement with the present measurements.

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arXiv2000

On the Quark and Gluon Substructure of the Sigma and other Scalar Mesons

Within the increasing experimental evidence of the existence of the I=0 scalar low mass and wide σmeson, we review the {\it first} analysis of its quark and gluon substructure from QCD spectral sum rules and some low-energy theorems. The present data favour equal components of \bar uu+ \bar dd and of gg in its wave function, which make the wide sigma and the narrow f_0(980) as η'-like particles. A coherent picture of the other I=0 scalar mesons spectra within this mixing scheme is shortly discussed. We also expect the a_0(980) to be the lowest isovector \bar ud state, and the K^*_0(1430) its \bar ds partner.

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arXiv2000

Light Hybrid Mesons in QCD

Including the radiative perturbative corrections and the short distance tachyonic gluon mass effects which mimic the ones of UV renormalons, we re-estimate the decay amplitudes, masses and widths of light hybrid mesons from QCD spectral sum rules. We show that the effects are tiny and confirm the previous lowest order results. We discuss the phenomenological impacts of our results for the vector hybrids.

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arXiv2000

Light Quark Masses 99

I give a short historical and a critical review of the determinations of light quark masses from QCD at dawn of the next millennium. QCD spectral sum rules combined with ChPT give, to order $α_s^3$, the world average for the running masses: $\bar{m}_s$(2 GeV)= $(118.9\pm 12.2)$ MeV, $\bar{m}_d(2~{GeV})=(6.3\pm 0.8)$ MeV, $\bar{m}_u(2~{GeV})=(3.5\pm 0.4)$ MeV and the corresponding values of the invariant masses given in Eq. 24. Lower and upper bounds derived from the positivity of spectral moments are presented in Tables 2 and 3. For a comparison, we critically review the recent lattice results (section 8 and Table 5) and attempt to deduce the present {\it QCD grand average} determination (Table 6): $\bar{m}_s$(2 GeV)= $(110.9\pm 8.8)$ MeV, to be used with a great care. Then, we deduce the value: $B_6^{1/2}-0.45(\rm resp.~0.32)B_8^{3/2}\simeq 1.6\pm 0.4~(\rm resp.~1.1\pm 0.3)$ and the lower bound $1.1\pm 0.2$ (resp. $0.7\pm 0.1$), for the combination of the penguin operators, governing the CP-violating parameters $ε'/ε$ without (resp. with) the inclusion of the final state interaction effects. The result signals a possible deviation from the leading 1/N prediction by about $1\sim 3σ$, which should be tested using accurate non-perturbative calculations.

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arXiv1999

Strange-quark mass from combined e+e- and tau-decay data:test of the isospin symmetry and implications on epsilon'/εand m_{u,d}

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 $α_s^3$: $\bar{m}_s$(1 GeV) = $(178\pm 33)$ MeV $\lrar \~\bar{m}_s$(2 GeV) = $(129\pm 24)$ MeV, while the positivity of the spectral function leads to the upper bound: $\bar{m}_s(1 {\rm GeV})\leq (200\pm 28) {MeV} \Longrightarrow~\bar{m}_s(2~{\rm GeV})\leq (145\pm 20) {MeV}$. 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 $e^+e^-\rar$ 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 $ε'/ε$, we can estimate, within the standard model, the four-quark weak matrix elements $B_6^{1/2}-0.54 B^{3/2}_8$ to be about $ (2.8\pm 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: $\bar{m}_d(2 {\rm GeV})= (6.4\pm 1.1) {\rm MeV}$ and $\bar{m}_u(2 {\rm GeV})= (2.3\pm 0.4) {\rm MeV}$.

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arXiv1999

Gluonia, Scalar and Hybrid Mesons in QCD

For some experimental guidelines of the next millenium, I review the determinations of the masses, decays and mixings of the gluonia, scalar and hybrid mesons from QCD spectral sum rules and low-energy theorems, and compare them with the lattice.

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arXiv1999

Short-distance tachyonic gluon mass and 1/Q^2 corrections

We consider the assumption that a tachyonic gluon mass imitates short-distance nonperturbative physics of QCD. The phenomenological implications include modifications of the QCD sum rules for correlators of currents with various quantum numbers. The new 1/Q^2 terms allow to resolve in a natural way old puzzles in the pion and scalar-gluonium channels. They lead to a slight reduction of the values of the running light quark masses from the (pseudo)scalar sum rules and of alpha_s(M_τ) from tau decay data. Further tests can be provided by precision measurements of the correlators on the lattice and by the e^+e^- --> hadrons data.

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arXiv1998

Extracting m_c(M_c) and f_{D_s,B} from the pseudoscalar sum rules

I report here on the (first) direct extraction of the running charm quark mass m_c(ν) from the D-meson sum rules, and on the implications of this result for the estimate of the leptonic decay constants f_{D_s}. The outputs: m_c(M_c)=(1.08\pm 0.11) GeV, f_{D}= (1.52\pm 0.16)f_π, f_{D_s}= (1.75\pm 0.18)f_πand f_B=(1.44\pm 0.07)f_πare in good agreement with the existing sum rule results obtained using the pole mass. In particular, the result f_D\approx f_B supports early '87 sum rule results \cite{SNFB}, which indicated a huge 1/m correction to the heavy quark symmetry expectation. This talk is based on the paper hep-ph/9712386 and updates the discussions given there.

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arXiv1997

Running charm quark mass versus M_D and the D_(s) into μνdecay

I study (for the first time) the dependence of M_D and of the leptonic decay constant f_D on the variation of the running charm quark mass m_c(ν). I conclude that the present data on f_{D_s} from D_s into μνdecay give a weaker constraint than M_D, where the latter leads to the result, m_c(M_c)=(1.08\pm 0.11) GeV, to two-loop accuracy in the {MS}-bar scheme, in good agreement with the value m_c(M_c)=(1.23^{+0.04}_{-0.05}) GeV extracted directly, within the same approximation, from M_{J/ψ}. The agreement of the corresponding perturbative pole mass with the one extracted directly from the data can indicate that the non-perturbative effects to the pole mass are negligible. Inversely, injecting the average value of m_c(M_c) from M_D and M_{J/ψ} into the m_c behaviour of f_D, I obtain f_D\simeq (1.52\pm 0.16)f_π, which combined with the sum rule prediction for f_{D_s}/f_D, gives f_{D_s}\simeq (1.75\pm 0.18)f_πin good agreement with the data. The extension of the analysis to the case of f_B and f_{D^*} is discussed.

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arXiv1997

Masses, decays and mixings of gluonia in QCD

This is a review of the estimate of the gluonia masses, decay and mixings from QCD spectral sum rules and low-energy theorems. Some phenomenological maximal gluonium-quarkonium mixing shemes in the scalar sector are presented. This talk is a compact version of the work in Ref.[1] (hep-ph/9612457) having the same title.

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arXiv1997

Masses, decays and mixings of gluonia in QCD

We compute the masses and decay widths of gluonia using QCD spectral sum rules and low-energy theorems. In the scalar sector, one finds a gluonium having a mass $M_G=(1.5\pm 0.2)$ GeV, which decays mainly into the $U(1)_A$ channels $ηη'$ and 4$π^0$. However, for a consistency of the whole approach, one needs broad-low mass gluonia (the $σ$ and its radial excitation), which couple strongly to the quark degrees of freedom similarly to the $η'$ of the $U(1)_A$ sector. Combining these results with the ones for the $\bar qq$ quarkonia, we present maximal quark-gluonium mixing schemes, which can provide quite a good description of the complex spectra and various decay widths of the observed scalar mesons $σ(1.0),f_0(0.98),f_0(1.37),f_0(1.5)$ and $f_J(1.71)$. In the tensor sector, the gluonium mass is found to be $M_T\simeq (2.05\pm 0.19)$ GeV, which makes the $ζ(2.2)$ a good $2^{++}$ gluonium candidate, even though we expect a rich population of $2^{++}$ gluonia in this region. In the pseudoscalar channel, the gluonium mass is found to be $M_P\simeq (2.05\pm 0.19)$ GeV, while we also show that the $E/ι(1.44)$ couples more weakly to the gluonic current than the $η'$, which can favour its interpretation as the first radial excitation of the $η'(0.96)$.

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