Pion form factor from 480 MeV to 1100 MeV

Quenzer, A.; Ribes, M.; Rumpf, F.; Bertrand, J.L.; Bizot, J.C.; Chase, R. L.; Cordier, A.; Delcourt, B.; Eschstruth, P.; Fulda, F.; Grosdidier, G.; Jeanjean, J.; Jeanjean, M.; Madaras, R. J.; Masnou, J. L.; Perez-Y-Jorba, J.

doi:10.1016/0370-2693(78)90918-8

Cited by 159 publications

(72 citation statements)

References 21 publications

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“…The central value for a μ (ππ) is slightly shifted downwards by about 1 σ with a negligible gain in precision. One also observes that the fit probability makes a large jump ( 50% ⇒ 90%), reflecting the larger uncertainties in the data from [49,51] compared to those from [19][20][21]. This once more shows that the systematics in the data sets from [49,51] have been conservatively estimed.…”

Section: Global Fit Results and E + E − Datamentioning

confidence: 88%

“…The first of these reports the result obtained when fitting using all available π + π − data sets-except for KLOE [18]; this turns out to include into the fitted data the so-called "Old Timelike Data" [49,51] (82 measurements) besides the "New Timelike Data" (127 measurements). The central value for a μ (ππ) is slightly shifted downwards by about 1 σ with a negligible gain in precision.…”

Section: Global Fit Results and E + E − Datamentioning

confidence: 99%

“…As can be seen in Table 3, this reflects the low contributions to the χ 2 yielded by the old ππ data [49,51] (χ 2 /n 0.6) and by the (recent) e + e − → (π 0 /η)γ data [35][36][37][38][39][40] (χ 2 /n 0.75). Instead, the newly collected ππ data sets [19][20][21] yield χ 2 /n 0.9 and the 3-pion data [19, [41][42][43][44][45]] χ 2 /n 1.1, quite comparable to CLEO data χ 2 /n 1.3.…”

Section: Final Global Fits To E + E − and τ Datamentioning

confidence: 91%

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A global treatment of VMD physics up to the φ: II. τ decay and hadronic contributions to g−2

et al. 2010

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Relying on the Hidden Local Symmetry (HLS) model equipped with a mechanism breaking the U(3)/SU(3)/ SU(2) symmetries and generating a dynamical vector meson mixing, it has been shown that a global fit successfully describes the cross sections for the e + e − → π + π − , e + e − → (π 0 /η)γ and e + e − → π 0 π + π − annihilation channels. One extends this global fit in order to include also the dipion spectra from the τ decay, taking into account all reported information on their statistical and systematic errors. A model accounting for lineshape distortions of the ρ ± spectrum relative to ρ 0 is also examined when analyzing the τ data behavior within the global fit framework. One shows that a successful account for e + e − annihilation data and τ spectra can be simultaneously reached. Then, issues related with nonperturbative hadronic contributions to the muon g −2 are examined in details. It is shown that all e + e − data considered together allow for improved and motivated estimates for the a μ (π + π − ), the π + π − loop contribution to the muon g − 2; for instance, integrated between 0.630 and 0.958 GeV, we find a μ (π + π − ) = 359.62 ± 1.62 (in units of 10 −10 ), a 40% improvement of the current uncertainty. The effects of the various τ samples in the context of a global fit procedure leads to conclude that different lineshape distortions are revealed by the ALEPH, BELLE and CLEO data samples. Relying on global fits to the data quoted above, one also provides motivated estimates of the π + π − , π 0 γ , ηγ and π 0 π + π − contributions to a μ up to 1 GeV with the smallest possible uncertainties. These estimates are based on various global fit configurations, each yielding a good probability.

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Section: Global Fit Results and E + E − Datamentioning

confidence: 88%

Section: Global Fit Results and E + E − Datamentioning

confidence: 99%

Section: Final Global Fits To E + E − and τ Datamentioning

confidence: 91%

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A global treatment of VMD physics up to the φ: II. τ decay and hadronic contributions to g−2

et al. 2010

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“…A large number of e + e − → π + π − cross section measurements are available. Older measurements stem from OLYA [22,23], TOF [24], CMD [22], DM1 [25] and DM2 [26]. 4 They are affected by an incomplete or undocumented application of radiative corrections.…”

Section: Introductionmentioning

confidence: 99%

Reevaluation of the hadronic contribution to the muon magnetic anomaly using new e + e −→π + π − cross section data from BABAR

et al. 2010

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Using recently published, high-precision π + π − cross section data by the BABAR experiment from the analysis of e + e − events with high-energy photon radiation in the initial state, we reevaluate the lowest order hadronic contribution (a had,LO μ ) to the anomalous magnetic moment of the muon. We employ newly developed software featuring improved data interpolation and averaging, more accurate error propagation and systematic validation. With the new data, the discrepancy between the e + e − -and τ -based results for the dominant two-pion mode reduces from previously 2.4σ to 1.5σ in the dispersion integral, though significant local discrepancies in the spectra persist. We obtain for the e + e − -based evaluation a had,LO μ = (695.5 ± 4.1) × 10 −10 , where the error accounts for all sources. The full Standard Model prediction of a μ differs from the experimental value by 3.2σ .

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“…Figure 3. Left: cross section of e + e − → π + π − in the ρ-peak region from OLYA [16], CMD [17], SND [18], DM1 [19], KLOE [20], and BABAR [21]. Right: relative difference between BABAR and KLOE.…”

Section: Hadronic Cross Sectionsmentioning

confidence: 99%

Testing the Standard Model at the precision frontier: the anomalous magnetic moment of the muon

Hafner

2014

EPJ Web of Conferences

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Abstract. The anomalous magnetic moment of the muon (g − 2) μ is one of the most precisely measured quantities in particle physics (0.54 ppm). There is a long-standing discrepancy of 3-4 standard deviations between the direct measurement of (g − 2) μ and its theoretical evaluation. This theoretical prediction is subdivided into three contributions: QED, weak and hadronic. The QED and weak parts can be determined in perturbative approaches with very high precision. Thus, the hadronic uncertainty dominates the total theoretical uncertainty. Within the hadronic uncertainty, the largest contribution stems from the vacuum polarization term, which can be evaluated with the measurement of the inclusive hadronic cross section in e + e − annihilation. The second largest contribution to the hadronic uncertainty stems from the so-called Light-by-Light amplitudes. They have to be evaluated via theoretical models. These models require transition form factor measurements as input. Existing and future measurements of the relevant hadronic cross sections and transition form factors are presented.

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Pion form factor from 480 MeV to 1100 MeV

Cited by 159 publications

References 21 publications

A global treatment of VMD physics up to the φ: II. τ decay and hadronic contributions to g−2

A global treatment of VMD physics up to the φ: II. τ decay and hadronic contributions to g−2

Reevaluation of the hadronic contribution to the muon magnetic anomaly using new e + e −→π + π − cross section data from BABAR

Testing the Standard Model at the precision frontier: the anomalous magnetic moment of the muon

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