Study of the electromagnetic transition form-factors in η → μ+ μ- γ and ω → μ+ μ- π0 decays with NA60

R. Arnaldi; K. Banicz; J. Castor; B. Chaurand; C. Cicalò; A. Colla; P. Cortese; S. Damjanovic; A. David; A. de Falco; A. Devaux; L. Ducroux; H. En'yo; J. Fargeix; A. Ferretti; M. Floris; A. Förster; P. Force; N. Guettet; A. Guichard; H. Gulkanian; J. M. Heuser; M. Keil; C. Lourenco; J. Lozano; F. Manso; P. Martins; A. Masoni; A. Neves; H. Ohnishi; C. Oppedisano; P. Parracho; P. Pillot; T. Poghosyan; G. Puddu; E. Radermacher; P. Ramalhete; P. Rosinsky; E. Scomparin; J. Seixas; S. Serci; R. Shahoyan; P. Sonderegger; H. J. Specht; R. Tieulent; G. Usai; R. Veenhof; H. K. Wöhri

doi:10.1016/j.physletb.2009.05.029

Study of the electromagnetic transition form-factors in η → μ⁺ μ^- γ and ω → μ⁺ μ^- π⁰ decays with NA60

R. Arnaldi, K. Banicz, J. Castor, B. Chaurand, C. Cicalò, A. Colla, P. Cortese, S. Damjanovic, A. David, A. de Falco, A. Devaux, L. Ducroux, H. En'yo, J. Fargeix, A. Ferretti, M. Floris, A. Förster, P. Force, N. Guettet, A. GuichardH. Gulkanian, J. M. Heuser, M. Keil, C. Lourenco, J. Lozano, F. Manso, P. Martins, A. Masoni, A. Neves, H. Ohnishi, C. Oppedisano, P. Parracho, P. Pillot, T. Poghosyan, G. Puddu, E. Radermacher, P. Ramalhete, P. Rosinsky, E. Scomparin, J. Seixas, S. Serci, R. Shahoyan, P. Sonderegger, H. J. Specht, R. Tieulent, G. Usai, R. Veenhof, H. K. Wöhri

Research output: Contribution to journal › Article › peer-review

147 Citations (Scopus)

Abstract

The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In-In collisions. The mass and p_T spectra associated with peripheral collisions can quantitatively be described by the known neutral meson decays. The high data quality has allowed to remeasure the electromagnetic transition form factors of the Dalitz decays η → μ⁺ μ^- γ and ω → μ⁺ μ^- π⁰. Using the usual pole approximation F = (1 - M² / Λ²)^{- 1} for the form factors, we find Λ^-2 (in GeV^-2) to be 1.95 ± 0.17 (stat.) ± 0.05 (syst.) for the η and 2.24 ± 0.06 (stat.) ± 0.02 (syst.) for the ω. While the values agree with previous results from the Lepton-G experiment, the errors are greatly improved, confirming now on the level of 10σ the strong enhancement of the ω form factor beyond the expectation from vector meson dominance. An improved value of the branching ratio BR (ω → μ⁺ μ^- π⁰) = [1.73 ± 0.25 (stat.) ± 0.14 (syst.)] × 10^{- 4} has been obtained as a byproduct.

Original language	English
Pages (from-to)	260-266
Number of pages	7
Journal	Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume	677
Issue number	5
DOIs	https://doi.org/10.1016/j.physletb.2009.05.029
Publication status	Published - 2009 Jun 29
Externally published	Yes

Keywords

Conversion decays
Lepton pairs
Transition form factor

ASJC Scopus subject areas

Nuclear and High Energy Physics

Access to Document

10.1016/j.physletb.2009.05.029

Cite this

Arnaldi, R., Banicz, K., Castor, J., Chaurand, B., Cicalò, C., Colla, A., Cortese, P., Damjanovic, S., David, A., de Falco, A., Devaux, A., Ducroux, L., En'yo, H., Fargeix, J., Ferretti, A., Floris, M., Förster, A., Force, P., Guettet, N., ... Wöhri, H. K. (2009). Study of the electromagnetic transition form-factors in η → μ⁺ μ^- γ and ω → μ⁺ μ^- π⁰ decays with NA60. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 677(5), 260-266. https://doi.org/10.1016/j.physletb.2009.05.029

Arnaldi, R, Banicz, K, Castor, J, Chaurand, B, Cicalò, C, Colla, A, Cortese, P, Damjanovic, S, David, A, de Falco, A, Devaux, A, Ducroux, L, En'yo, H, Fargeix, J, Ferretti, A, Floris, M, Förster, A, Force, P, Guettet, N, Guichard, A, Gulkanian, H, Heuser, JM, Keil, M, Lourenco, C, Lozano, J, Manso, F, Martins, P, Masoni, A, Neves, A, Ohnishi, H, Oppedisano, C, Parracho, P, Pillot, P, Poghosyan, T, Puddu, G, Radermacher, E, Ramalhete, P, Rosinsky, P, Scomparin, E, Seixas, J, Serci, S, Shahoyan, R, Sonderegger, P, Specht, HJ, Tieulent, R, Usai, G, Veenhof, R & Wöhri, HK 2009, 'Study of the electromagnetic transition form-factors in η → μ⁺ μ^- γ and ω → μ⁺ μ^- π⁰ decays with NA60', Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, vol. 677, no. 5, pp. 260-266. https://doi.org/10.1016/j.physletb.2009.05.029

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title = "Study of the electromagnetic transition form-factors in η → μ+ μ- γ and ω → μ+ μ- π0 decays with NA60",

abstract = "The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In-In collisions. The mass and pT spectra associated with peripheral collisions can quantitatively be described by the known neutral meson decays. The high data quality has allowed to remeasure the electromagnetic transition form factors of the Dalitz decays η → μ+ μ- γ and ω → μ+ μ- π0. Using the usual pole approximation F = (1 - M2 / Λ2)- 1 for the form factors, we find Λ-2 (in GeV-2) to be 1.95 ± 0.17 (stat.) ± 0.05 (syst.) for the η and 2.24 ± 0.06 (stat.) ± 0.02 (syst.) for the ω. While the values agree with previous results from the Lepton-G experiment, the errors are greatly improved, confirming now on the level of 10σ the strong enhancement of the ω form factor beyond the expectation from vector meson dominance. An improved value of the branching ratio BR (ω → μ+ μ- π0) = [1.73 ± 0.25 (stat.) ± 0.14 (syst.)] × 10- 4 has been obtained as a byproduct.",

keywords = "Conversion decays, Lepton pairs, Transition form factor",

author = "R. Arnaldi and K. Banicz and J. Castor and B. Chaurand and C. Cical{\`o} and A. Colla and P. Cortese and S. Damjanovic and A. David and {de Falco}, A. and A. Devaux and L. Ducroux and H. En'yo and J. Fargeix and A. Ferretti and M. Floris and A. F{\"o}rster and P. Force and N. Guettet and A. Guichard and H. Gulkanian and Heuser, {J. M.} and M. Keil and C. Lourenco and J. Lozano and F. Manso and P. Martins and A. Masoni and A. Neves and H. Ohnishi and C. Oppedisano and P. Parracho and P. Pillot and T. Poghosyan and G. Puddu and E. Radermacher and P. Ramalhete and P. Rosinsky and E. Scomparin and J. Seixas and S. Serci and R. Shahoyan and P. Sonderegger and Specht, {H. J.} and R. Tieulent and G. Usai and R. Veenhof and W{\"o}hri, {H. K.}",

note = "Funding Information: We acknowledge support from the BMBF (Heidelberg group) as well as from the C. Gulbenkian Foundation and the Swiss Fund Kidagan (YerPHI group).",

year = "2009",

month = jun,

day = "29",

doi = "10.1016/j.physletb.2009.05.029",

language = "English",

volume = "677",

pages = "260--266",

journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",

issn = "0370-2693",

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TY - JOUR

T1 - Study of the electromagnetic transition form-factors in η → μ+ μ- γ and ω → μ+ μ- π0 decays with NA60

AU - Arnaldi, R.

AU - Banicz, K.

AU - Castor, J.

AU - Chaurand, B.

AU - Cicalò, C.

AU - Colla, A.

AU - Cortese, P.

AU - Damjanovic, S.

AU - David, A.

AU - de Falco, A.

AU - Devaux, A.

AU - Ducroux, L.

AU - En'yo, H.

AU - Fargeix, J.

AU - Ferretti, A.

AU - Floris, M.

AU - Förster, A.

AU - Force, P.

AU - Guettet, N.

AU - Guichard, A.

AU - Gulkanian, H.

AU - Heuser, J. M.

AU - Keil, M.

AU - Lourenco, C.

AU - Lozano, J.

AU - Manso, F.

AU - Martins, P.

AU - Masoni, A.

AU - Neves, A.

AU - Ohnishi, H.

AU - Oppedisano, C.

AU - Parracho, P.

AU - Pillot, P.

AU - Poghosyan, T.

AU - Puddu, G.

AU - Radermacher, E.

AU - Ramalhete, P.

AU - Rosinsky, P.

AU - Scomparin, E.

AU - Seixas, J.

AU - Serci, S.

AU - Shahoyan, R.

AU - Sonderegger, P.

AU - Specht, H. J.

AU - Tieulent, R.

AU - Usai, G.

AU - Veenhof, R.

AU - Wöhri, H. K.

N1 - Funding Information: We acknowledge support from the BMBF (Heidelberg group) as well as from the C. Gulbenkian Foundation and the Swiss Fund Kidagan (YerPHI group).

PY - 2009/6/29

Y1 - 2009/6/29

N2 - The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In-In collisions. The mass and pT spectra associated with peripheral collisions can quantitatively be described by the known neutral meson decays. The high data quality has allowed to remeasure the electromagnetic transition form factors of the Dalitz decays η → μ+ μ- γ and ω → μ+ μ- π0. Using the usual pole approximation F = (1 - M2 / Λ2)- 1 for the form factors, we find Λ-2 (in GeV-2) to be 1.95 ± 0.17 (stat.) ± 0.05 (syst.) for the η and 2.24 ± 0.06 (stat.) ± 0.02 (syst.) for the ω. While the values agree with previous results from the Lepton-G experiment, the errors are greatly improved, confirming now on the level of 10σ the strong enhancement of the ω form factor beyond the expectation from vector meson dominance. An improved value of the branching ratio BR (ω → μ+ μ- π0) = [1.73 ± 0.25 (stat.) ± 0.14 (syst.)] × 10- 4 has been obtained as a byproduct.

AB - The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In-In collisions. The mass and pT spectra associated with peripheral collisions can quantitatively be described by the known neutral meson decays. The high data quality has allowed to remeasure the electromagnetic transition form factors of the Dalitz decays η → μ+ μ- γ and ω → μ+ μ- π0. Using the usual pole approximation F = (1 - M2 / Λ2)- 1 for the form factors, we find Λ-2 (in GeV-2) to be 1.95 ± 0.17 (stat.) ± 0.05 (syst.) for the η and 2.24 ± 0.06 (stat.) ± 0.02 (syst.) for the ω. While the values agree with previous results from the Lepton-G experiment, the errors are greatly improved, confirming now on the level of 10σ the strong enhancement of the ω form factor beyond the expectation from vector meson dominance. An improved value of the branching ratio BR (ω → μ+ μ- π0) = [1.73 ± 0.25 (stat.) ± 0.14 (syst.)] × 10- 4 has been obtained as a byproduct.

KW - Conversion decays

KW - Lepton pairs

KW - Transition form factor

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U2 - 10.1016/j.physletb.2009.05.029

DO - 10.1016/j.physletb.2009.05.029

M3 - Article

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VL - 677

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EP - 266

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

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