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<p>We present a measurement of the doubly radiative decay <i>η</i> → <i>π</i><sup>0</sup><i>γγ</i> based on a sample of 82 million <i>η</i> mesons produced in the <i>e</i><sup>+</sup><i>e</i><sup><i>−</i></sup> → <i>ϕ</i> → <i>ηγ</i> process at the Frascati <i>ϕ</i>-factory DAΦNE. From the data analysis, 1246 ± 133 signal events were observed. By normalising the signal to the well-known <i>η</i> → 3<i>π</i><sup>0</sup> decay the branching fraction <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathcal{B}(\eta \to {\pi }^{0}\gamma \gamma )\)</EquationSource> </InlineEquation> is measured to be (0<i>.</i>98 ± 0<i>.</i>11<sub>stat</sub> ± 0<i>.</i>14<sub>syst</sub>) × 10<sup><i>−</i>4</sup>. This result agrees with a preliminary KLOE measurement, but is a factor of two smaller than the current world average. Results for <i>d</i>Γ(<i>η</i> →<i> π</i><sup>0</sup><i>γγ</i>)<i>/dM</i><sup>2</sup>(<i>γγ</i>) are also presented and compared with the latest theoretical predictions.</p>

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Measurement of η → π0γγ branching fraction with the KLOE detector

  • 期刊论文

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  • 发表日期：

    2026年1月15日

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  • D. Babusci,
  • P. Beltrame,
  • M. Berlowski,
  • C. Bloise,
  • F. Bossi,
  • P. Branchini,
  • B. Cao,
  • F. Ceradini,
  • P. Ciambrone,
  • L. Cotrozzi,
  • F. Curciarello,
  • E. Czerwiński,
  • G. D’Agostini,
  • R. D’Amico,
  • E. Danè,
  • V. De Leo,
  • E. De Lucia,
  • A. De Santis,
  • P. De Simone,
  • A. Di Domenico,
  • E. Diociaiuti,
  • D. Domenici,
  • A. D’Uffizi,
  • G. Fantini,
  • S. Fiore,
  • A. Gajos,
  • S. Gamrat,
  • P. Gauzzi,
  • S. Giovannella,
  • E. Graziani,
  • F. Ignatov,
  • X. Kang,
  • A. Kupsc,
  • G. Mandaglio,
  • M. Martini,
  • S. Miscetti,
  • P. Moskal,
  • A. Passeri,
  • V. Patera,
  • E. Perez del Rio,
  • L. Punzi,
  • F. Sborzacchi,
  • M. Schioppa,
  • A. Selce,
  • M. Silarski,
  • F. Sirghi,
  • E. P. Solodov,
  • T. Teubner,
  • G. Venanzoni,
  • N. Vestergaard,
  • W. Wiślicki,
  • M. Wolke,
  • E. Zaid

摘要

We present a measurement of the doubly radiative decay η → π0γγ based on a sample of 82 million η mesons produced in the e+e− → ϕ → ηγ process at the Frascati ϕ-factory DAΦNE. From the data analysis, 1246 ± 133 signal events were observed. By normalising the signal to the well-known η → 3π0 decay the branching fraction \(\mathcal{B}(\eta \to {\pi }^{0}\gamma \gamma )\) is measured to be (0.98 ± 0.11stat ± 0.14syst) × 10−4. This result agrees with a preliminary KLOE measurement, but is a factor of two smaller than the current world average. Results for dΓ(η → π0γγ)/dM2(γγ) are also presented and compared with the latest theoretical predictions.