scholarly journals STATUS OF THE HADRONIC τ DETERMINATION OF Vus

2008 ◽  
Vol 23 (21) ◽  
pp. 3191-3195 ◽  
Author(s):  
K. MALTMAN ◽  
C. E. WOLFE ◽  
S. BANERJEE ◽  
M. RONEY ◽  
I. NUGENT
Keyword(s):  
Sum Rules ◽  
Branching Fractions ◽  
Sum Rule ◽  
Slow Convergence ◽  
Decay Data ◽  
Decay Modes ◽  
Good Agreement

We update the extraction of Vus from hadronic τ decay data in light of recent BaBar and Belle results on the branching fractions of a number of important strange decay modes. A range of sum rule analyses is employed, particular attention being paid to those based on “non-spectral weights”, developed previously to bring the slow convergence of the relevant integrated D = 2 OPE series under improved control. Results from the various sum rules are in good agreement with one another, but ~ 3σ below expectations based on 3-family unitarity.

scholarly journals Current Status of inclusive hadronic tau determinations of |V_us|

2019 ◽  
Author(s):  
Kim Maltman ◽  
P. A. Boyle ◽  
R. J. Hudspith ◽  
T. Izubuchi ◽  
A. Juttner ◽  
...  
Keyword(s):  
Sum Rules ◽  
Branching Fractions ◽  
Finite Energy ◽  
Current Status ◽  
Decay Data ◽  
The Status ◽  
Hadronic Tau

We review the status of the determination of \vert V_{us}\vert|Vus| from both flavor-breaking finite-energy sum rules based on inclusive non-strange and strange hadronic \tauτ decay data and the recent lattice-based analysis of inclusive strange hadronic \tauτ decay data. In particular, we update the results from these analysis frameworks taking into account recent improvements to a number of strange branching fractions reported by HFLAV at CKM2018 and this meeting. We find that inclusive \tauτ decay data yields results for \vert V_{us}\vert|Vus| compatible within errors with the expectations of three-family unitarity.

scholarly journals Resolving the τ vs. Electroproduction Discrepancy for the I = 1 Vector Spectral Function and Implications for the SM Prediction for aμ

2006 ◽  
Vol 21 (04) ◽  
pp. 813-816 ◽  
Author(s):  
Kim Maltman
Keyword(s):  
Spectral Function ◽  
Vacuum Polarization ◽  
Sum Rules ◽  
High Scale ◽  
Sum Rule ◽  
Decay Data ◽  
Polarization Contribution ◽  
Model Predictions ◽  
Weighted Integrals ◽  
Good Agreement

Using only independent high-scale OPE input, we investigate QCD sum rule constraints on two currently incompatible versions of the isovector vector spectral function, one obtained from electroproduction (EM) data, the other from hadronic τ decay data. Sum rules involving weighted integrals over the spectral function, from threshold to a variable upper endpoint s0, are employed. It is shown that both the normalization and slope with respect to s0 of the EM spectral integrals disagree with the corresponding OPE expectations, while both normalization and slope are in good agreement when hadronic τ decay data is used instead. These results favor determinations of the leading hadronic vacuum polarization contribution to aμ obtained using the τ decay data, and hence Standard Model predictions for aμ compatible with the current experimental determination.

scholarly journals ON THE QCD SUM RULE DETERMINATION OF THE STRANGE QUARK MASS

2001 ◽  
Vol 16 (supp01b) ◽  
pp. 588-590 ◽  
Author(s):  
NELLO PAVER
Keyword(s):  
Spectral Function ◽  
Quark Mass ◽  
Strange Quark ◽  
Sum Rules ◽  
Sum Rule ◽  
Strange Quark Mass ◽  
Current Quark Mass ◽  
Current Quark

I briefly review recent QCD Sum Rules determinations of the strange current quark mass, based on the analysis of the two-point ΔS=1 scalar correlators and discuss, in particular, the role of resonances and non-resonant background in the spectral function.

scholarly journals The strong coupling from $e^+e^-\to$~hadrons

2019 ◽  
Author(s):  
Diogo Boito ◽  
Maarten Golterman ◽  
Alex Keshavarzi ◽  
Kim Maltman ◽  
Daiskuke Nomura ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Strong Coupling ◽  
Sum Rules ◽  
Finite Energy ◽  
Order Perturbation ◽  
Decay Data ◽  
Systematic Effects ◽  
Fixed Order ◽  
Charm Mass ◽  
Good Agreement

We use a new compilation of the hadronic RR-ratio from available data for the process e^+e^-\toe+e−→ hadrons below the charm mass to determine the strong coupling \alpha_sαs, using finite-energy sum rules. Quoting our results at the \tauτ mass to facilitate comparison to the results obtained from similar analyses of hadronic \tauτ-decay data, we find \alpha_s(m_\tau^2)=0.298\pm 0.016\pm 0.006αs(mτ2)=0.298±0.016±0.006 in fixed-order perturbation theory, and \alpha_s(m_\tau^2)=0.304\pm 0.018\pm 0.006αs(mτ2)=0.304±0.018±0.006 in contour-improved perturbation theory, where the first error is statistical, and the second error combines various systematic effects. These values are in good agreement with a recent determination from the OPAL and ALEPH data for hadronic \tauτ decays. We briefly compare the R(s)R(s)-based analysis with the \tauτ-based analysis.

scholarly journals Theory determination of $$\varvec{\bar{B}\rightarrow D^{(*)}\ell ^-\bar{\nu }}$$ form factors at $$\varvec{\mathcal {O}(1/m_c^2)}$$

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Marzia Bordone ◽  
Martin Jung ◽  
Danny van Dyk
Keyword(s):  
Experimental Data ◽  
Light Cone ◽  
Sum Rules ◽  
Form Factors ◽  
Longitudinal Polarization ◽  
Polarization Fraction ◽  
Theoretical Results ◽  
Good Agreement ◽  
Lepton Flavour

Abstract We carry out an analysis of the full set of ten $$\bar{B}\rightarrow D^{(*)}$$B¯→D(∗) form factors within the framework of the Heavy-Quark Expansion (HQE) to order $$\mathcal {O}\left( \alpha _s,\,1/m_b,\,1/m_c^2\right) $$Oαs,1/mb,1/mc2, both with and without the use of experimental data. This becomes possible due to a recent calculation of these form factors at and beyond the maximal physical recoil using QCD light-cone sum rules, in combination with constraints from lattice QCD, QCD three-point sum rules and unitarity. We find good agreement amongst the various theoretical results, as well as between the theoretical results and the kinematical distributions in $$\bar{B}\rightarrow D^{(*)}\lbrace e^-,\mu ^-\rbrace \bar{\nu }$$B¯→D(∗){e-,μ-}ν¯ measurements. The coefficients entering at the $$1/m_c^2$$1/mc2 level are found to be of $$\mathcal {O}(1)$$O(1), indicating convergence of the HQE. The phenomenological implications of our study include an updated exclusive determination of $$|V_{cb}|$$|Vcb| in the HQE, which is compatible with both the exclusive determination using the BGL parametrization and with the inclusive determination. We also revisit predictions for the lepton-flavour universality ratios $$R_{D^{(*)}}$$RD(∗), the $$\tau $$τ polarization observables $$P_\tau ^{D^{(*)}}$$PτD(∗), and the longitudinal polarization fraction $$F_L$$FL. Posterior samples for the HQE parameters are provided as ancillary files, allowing for their use in subsequent studies.

scholarly journals Determination of perturbative QCD coupling from ALEPH $$\tau $$ decay data using pinched Borel–Laplace and Finite Energy Sum Rules

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
César Ayala ◽  
Gorazd Cvetič ◽  
Diego Teca
Keyword(s):  
Perturbation Theory ◽  
Perturbative Qcd ◽  
Sum Rules ◽  
Finite Energy ◽  
Operator Product ◽  
Decay Data ◽  
Fixed Order ◽  
Principal Value ◽  
Adler Function

AbstractWe present a determination of the perturbative QCD (pQCD) coupling using the V+A channel ALEPH $$\tau $$ τ -decay data. The determination involves the double-pinched Borel–Laplace Sum Rules and Finite Energy Sum Rules. The theoretical basis is the Operator Product Expansion (OPE) of the V+A channel Adler function in which the higher order terms of the leading-twist part originate from a model based on the known structure of the leading renormalons of this quantity. The applied evaluation methods are contour-improved perturbation theory (CIPT), fixed-order perturbation theory (FOPT), and Principal Value of the Borel resummation (PV). All the methods involve truncations in the order of the coupling. In contrast to the truncated CIPT method, the truncated FOPT and PV methods account correctly for the suppression of various renormalon contributions of the Adler function in the mentioned sum rules. The extracted value of the $${\overline{\mathrm{MS}}}$$ MS ¯ coupling is $$\alpha _s(m_{\tau }^2) = 0.3116 \pm 0.0073$$ α s ( m τ 2 ) = 0.3116 ± 0.0073 [$$\alpha _s(M_Z^2)=0.1176 \pm 0.0010$$ α s ( M Z 2 ) = 0.1176 ± 0.0010 ] for the average of the FOPT and PV methods, which we regard as our main result. On the other hand, if we include in the average also the CIPT method, the resulting values are significantly higher, $$\alpha _s(m_{\tau }^2) = 0.3194 \pm 0.0167$$ α s ( m τ 2 ) = 0.3194 ± 0.0167 [$$\alpha _s(M_Z^2)=0.1186 \pm 0.0021$$ α s ( M Z 2 ) = 0.1186 ± 0.0021 ].

THE ELECTROMAGNETIC MASS DIFFERENCE OF PIONS FROM QCD

1990 ◽  
Vol 05 (04) ◽  
pp. 747-753 ◽  
Author(s):  
M. MARGVELASHVILI
Keyword(s):  
Current Algebra ◽  
Sum Rules ◽  
Mass Difference ◽  
Electromagnetic Mass ◽  
Vacuum Condensate ◽  
Qcd Sum Rules ◽  
Standard Value ◽  
Good Agreement

It is shown that the two point functions of definite class can be calculated, at small spacelike momenta, as subtraction constants in the Borel transformed QCD sum rules. Using the results of current algebra and PCAC, we obtain three different sum rules for determination of the electromagnetic mass difference of pions. The result is in a good agreement with experiment, and confirms the standard value for the four-quark vacuum condensate.

Sum Rule Photodisintegration Cross Sections of 6Li

1974 ◽  
Vol 52 (3) ◽  
pp. 202-206
Author(s):  
H. L. Yadav ◽  
B. K. Srivastava
Keyword(s):  
Charge Distribution ◽  
Cross Sections ◽  
Sum Rules ◽  
Wave Functions ◽  
Radial Wave ◽  
Sum Rule ◽  
Dependent Potential ◽  
Good Agreement

We apply the sum rules of Levinger and Bethe to calculate the integrated [Formula: see text] cross sections for 6Li using the Gaussian and Irving forms of radial wave functions whose parameters are determined by fitting the r.m.s. radius of charge distribution in 6Li. For the potential in the σint calculation we use the central velocity-dependent potential of Herndon et al. Our results for σint and σb for 6Li show reasonably good agreement with experiments.

scholarly journals QCD parameter correlations from heavy quarkonia

2018 ◽  
Vol 33 (10) ◽  
pp. 1850045 ◽  
Author(s):  
Stephan Narison
Keyword(s):  
Sum Rules ◽  
Axial Vector ◽  
Gluon Condensate ◽  
Sum Rule ◽  
Channel One ◽  
Vector Channel ◽  
Stability Point ◽  
Pseudo Scalar ◽  
First Time ◽  
Good Agreement

Correlations between the QCD coupling [Formula: see text], the gluon condensate [Formula: see text] and the [Formula: see text], [Formula: see text]-quark running masses [Formula: see text] in the [Formula: see text]-scheme are explicitly studied (for the first time) from the (axial-)vector and (pseudo)scalar charmonium and bottomium ratios of Laplace sum rules (LSR) evaluated at the [Formula: see text]-subtraction stability point where perturbative (PT) @N2LO, N3LO and [Formula: see text] @NLO corrections are included. Our results clarify the (apparent) discrepancies between different estimates of [Formula: see text] from [Formula: see text] sum rule and also show the sensitivity of the sum rules on the choice of the [Formula: see text]-subtraction scale which does not permit a high-precision estimate of [Formula: see text]. We obtain from the (axial-)vector [respectively (pseudo)scalar] channels: [Formula: see text] [respectively [Formula: see text] GeV4, [Formula: see text] [respectively 1266(16)] MeV and [Formula: see text] MeV. Combined with our recent determinations from vector channel, one obtains the average: [Formula: see text] MeV and [Formula: see text] MeV. Adding the two above values of the gluon condensate to different previous estimates in Table 1, one obtains the 2018 sum rule average: [Formula: see text] GeV4. The mass-splittings [Formula: see text] give @N2LO: [Formula: see text] in good agreement with the world average.

COMPARATIVE ACTION OF VARIOUS OESTROGENIC COMPOUNDS ON MOUSE VAGINAL SIALIC ACIDS (II)

1969 ◽  
Vol 62 (4) ◽  
pp. 663-670 ◽  
Author(s):  
Lars Carlborg
Keyword(s):  
Sialic Acid ◽  
Response Curve ◽  
Sialic Acids ◽  
Clear Cut ◽  
Suitable Parameter ◽  
Sufficient Degree ◽  
Comparative Action ◽  
Relative Potencies ◽  
Good Agreement

ABSTRACT Oestrogens administered in lower doses than necessary to induce full cornification of the mouse vagina induce mucification. It was shown previously that the degree of mucification could be estimated by quantitative determination of sialic acids. A suitable parameter for oestrogen assay was the measurement of vaginal sialic acid concentration which exhibited a clear cut dose response curve. Eleven assays of various oestrogens were performed with this method. Their estimated relative potencies were in good agreement with other routine oestrogen assays. A statistically sufficient degree of precision was found. The sensitivity was of the same order, or slightly higher, than the Allen-Doisy test.

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