Evidence for the decay τ−→ντωπ−

Albrecht, H.; Binder, U.; Böckmann, P.; Gläser, R.; Harder, G.; Lembke-Koppitz, I.; Schmidt‐Parzefall, W.; Schröder, H.; Schulz, H. D.; Wurth, R.; Yagil, A.; Donker, J. P.; Drescher, A.; Kamp, D.; Matthiesen, U.; Scheck, H.; Spaan, B.; Spengler, J.; Wegener, D.; Gabriel, J. C.; Schubert, K. R.; Stiewe, J.; Strahl, K.; Waldi, R.; Weseler, S.; Edwards, K. W.; Frisken, W. R.; Gilkinson, D. J.; Gingrich, D. M.; Kapitza, H.; Kim, P. C. H.; Kutschke, R.; MacFarlane, D. B.; McKenna, J. A.; McLean, K. W.; Nilsson, Anders; Orr, R. S.; Padley, P.; Parsons, J. A.; Patel, P. M.; Prentice, J. D.; Seywerd, H.; Swain, J.; Tsipolitis, G.; Yoon, T. S.; Yun, J. C.; Ammar, R.; Coppage, D.; Davis, R.; Kanekal, S.; Kwak, N.; Boštjančič, B.; Kernel, G.; Pleško, M.; Jönsson, L.; Babaev, A.; Danilov, M.; Golutvin, A.; Gorelov, I.; Lubimov, V.; Matveev, V.; Nagovitsin, V.; Ryltsov, V.; Semenov, A.; Shevchenko, V.; Soloshenko, V.; Tchistilin, V.; Tichomirov, I.; Zaitsev, Yu.; Childers, R.; Darden, C. W.; Oku, Y.; Gennow, H.

doi:10.1016/0370-2693(87)91559-0

Cited by 64 publications

(16 citation statements)

References 13 publications

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“…The joint fit of the CLEO data [7] results in the considerably improved accuracy of the determination of the ρ ′ 2 resonance parameters as compared to the earlier fit [2] of the ARGUS data [15]. Here also the ρ ′ 1 resonance is unnecessary, and the data are well described by the only ρ ′ 2 resonance in addition to the ρ(770).…”

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confidence: 89%

Masses, branching ratios, and full widths of heavy ρ′, ρ″ and ω′, ω″ resonances

Achasov

Кожевников

2000

Phys. Rev. D

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Based on the previous and recent fits of multiple data on the reactions of e + e − annihilation, τ lepton decay, and the reaction K − p → π + π − Λ, the magnitude of the branching ratios and total widths of the isovector ρ ′ , ρ ′′ , and the isoscalar ω ′ , ω ′′ resonances are calculated. Some topics on the spectroscopy of the ρ(1450) and ω (1420) , with isospin zero is still far from being clear. Although the characteristic peaks corresponding to these resonances were observed in a number of channels of the one-photon e + e − annihilation, τ lepton decays, NN annihilation, photoproduction, etc., the specific masses and branching ratios are not properly established and hence are not given in the Tables [1]. Recently, the present authors undertook an attempt to fit then existing data on e + e − annihilation, τ lepton decays, and the reactionwhere the above heavy resonances were observed, in the framework of the unified approach. The approach is based on the scheme that takes into account both energy dependence of the partial widths and the mixing via common decay modes among the latter and the ground state ρ(770) and ω(782) resonances, in the respective isovector [2] and isoscalar [3] channels. When so doing, the masses and coupling constants of the resonances were taken as free parameters to be determined from the fit. This choice is convenient because, first, it is just these parameters that are essential in identifying the nature of heavy resonances with J CP = 1 −− . Second, the function χ 2 used in obtaining the intervals of the variation of the extracted parameters is represented in this case as the sum of independent contributions, so that the covariance matrix (see the statistics section in Ref.[1]) is diagonal. However, the results of the measurements are often represented in terms of the masses and branching ratios. In view of the excessive size of the publications [2,3] we refrained at that time from the calculation of the partial widths with the parameters found in [2,3]. Here we fill this gap and calculate the branching ratios and total widths of the ρ ′ 1,2 and ω ′ 1,2 resonances using the new data on the cross section of the reactions, and the data on the spectral function v 1 measured in the decays τ. We also comment on the issue of why the resonances with the masses greater than 1400 MeV should be wide in the conventional qq model, and why their bare masses get shifted towards the greater values as compared to the visible peak positions. The latter point, as will be shown below, is of the direct relevance to the hadronic spectroscopy of the ρ(1300) resonance reported by the LASS group [8], and the ω(1200) resonance reported by the SND team [5].First, let us try to understand why the situation with the resonances possessing the masses greater than 1400 MeV is so complicated despite the numerous experiments aimed at the determination of their masses and partial widths. As is known [1], the indications on the existance of the ρ ′ 1,2 and ω ′ 1,2 resonances were obtained, in particular, in th...

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confidence: 89%

Masses, branching ratios, and full widths of heavy ρ′, ρ″ and ω′, ω″ resonances

Achasov

Кожевников

2000

Phys. Rev. D

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“…The e [5], under assumption of the Conserved Vector Current (CVC). The results are in good agreement, thus confirming the CVC hypothesis [6].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the e+e−→ωπ0→π0π0γ reaction in the energy domain near the φ-meson

et al. 2000

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The e + e − → ωπ 0 → π 0 π 0 γ process was investigated in the SND experiment at the VEPP-2M collider. A narrow energy interval near the φ-meson was scanned. The observed cross-section reveals, at the level of three standard deviation, the interference effect caused by φ → π 0 π 0 γ decay. The cross-section parameters, as well as the real and imaginary parts of the φ-meson related amplitude, were measured.

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“…Since the charged current spectral function is now measured rather accurately in τ decay [1][2][3], CVC can be tested experimentally, provided, that is, one can extract the isovector spectral function from data on e + e − → hadrons [4][5][6][7][8]. In the absence of isospin breaking, this extraction is straightforward since, for example, for n-pion final states, a state with an even (odd) number of pions has even (odd) G-parity and hence can be produced only through the isovector (isoscalar) component of the hadronic EM current.…”

Section: Introductionmentioning

confidence: 99%

“…In the presence of isospin breaking, all of the neutral vector mesons, in principle, mix with one another, so the physical states are of mixed isospin. If we consider the ππ final state mediated by the ω exchange then, to leading order in isospin breaking, this transition is indeed mediated by the isoscalar component of the EM current (the intermediate ω contribution generated by the isovector current is second order in isospin breaking, one factor from the coupling F (3) ω , and one from the isospin violating ω → π + π − decay vertex), and hence should be removed if one wishes to extract only the isovector contributions. The remaining ρ exchange contributions are, for a similar reason, however, not purely isovector.…”

Section: Introductionmentioning

confidence: 99%

“…The remaining ρ exchange contributions are, for a similar reason, however, not purely isovector. The reason is that if one considers the ρ exchange contribution to the EM spectral function, the 38 component is first order in isospin breaking (being proportional to F (3) ρ F (8) ρ ). Thus, the ρ contribution to e + e − → π + π − necessarily contains a piece first order in isospin breaking, and associated with the 38 part of the EM spectral function, which must be subtracted in order to isolate the purely isovector 33 component.…”

Section: Introductionmentioning

confidence: 99%

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Isospin-breaking effects in the extraction of isoscalar and isovector spectral functions frome+e−→hadrons

Maltman¹

1998

Phys. Rev. D

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We investigate the problem of the extraction of the isovector and isoscalar spectral functions from data on e + e − → hadrons, in the presence of non-zero isospin breaking. It is shown that the conventional approach to extracting the isovector spectral function in the ρ resonance region, in which only the isoscalar contribution associated with ω → ππ is subtracted, fails to fully remove the effects of the isoscalar component of the electromagnetic current. The additional subtractions required to extract the pure isovector and isoscalar spectral functions are estimated using results from QCD sum rules. It is shown that the corrections are small (∼ 2%) in the isovector case (though relevant to precision tests of CVC), but very large (∼ 20%) in the case of the ω contribution to the isoscalar spectral function. The reason such a large effect is natural in the isoscalar channel is explained, and implications for other applications, such as the extraction of the sixth order chiral low-energy constant, Q, are discussed.

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Evidence for the decay τ−→ντωπ−

Cited by 64 publications

References 13 publications

Masses, branching ratios, and full widths of heavy ρ′, ρ″ and ω′, ω″ resonances

Masses, branching ratios, and full widths of heavy ρ′, ρ″ and ω′, ω″ resonances

Investigation of the e+e−→ωπ0→π0π0γ reaction in the energy domain near the φ-meson

Isospin-breaking effects in the extraction of isoscalar and isovector spectral functions frome+e−→hadrons

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