Abstract

The process \(e^{+}e^{-}\to\eta\pi^{0}\gamma\) is studied in the range of center-of-mass (c.m.) collision energies between 1.05 and 2.00 GeV on the basis of data corresponding to an integrated luminosity of 94.5 pb\({}^{-1}\) that were accumulated in an experiment with the SND detector at the VEPP-2000 \(e^{+}e^{-}\) collider. The cross section for this process was measured for the first time and was found to receive a dominant contribution from the mechanism of a transition through an \(\omega\eta\) intermediate state. The cross section measured for the process \(e^{+}e^{-}\to\omega\eta\to\eta\pi^{0}\gamma\) agrees with the results of earlier measurements in the channel \(e^{+}e^{-}\to\pi^{+}\pi^{-}\pi^{0}\eta\). At a level of 5.7 standard deviations (5.7 \(\sigma\)), it is established that the process \(e^{+}e^{-}\to\eta\pi^{0}\gamma\) is not fully described by hadronic intermediate states of the \(VP\) type. The cross section was measured for this missing contribution, which may be generated by radiative processes—for example, \(e^{+}e^{-}\to a_{0}(1450)\gamma\). It ranges from 15 to 20 pb over a broad energy interval extending from 1.3 to 1.9 GeV.

中文翻译：

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研究过程$$ {e} ^ {{+}} {e} ^ {{-}} {\ to} {\ eta \ pi} ^ {{0}} {\ gamma} $$ $$ \ sqrt {{s}} {=} {1.05 {-} 2.00} $$ GeV的能量范围

摘要

研究了\（e ^ {+} e ^ {-} \ to \ eta \ pi ^ {0} \ gamma \）在1.05和2.00 GeV之间的质心（cm）碰撞能量范围内的过程。在VEPP-2000 \（e ^ {+} e ^ {-}的SND检测器实验中积累的与94.5 pb \（{} ^ {-1} \）的综合亮度对应的数据基础\）对撞机。首次测量了此过程的横截面，发现该横截面从通过\（\ omega \ eta \）中间状态过渡的机制中获得了主要贡献。为过程\（e ^ {+} e ^ {-} \ to \ omega \ eta \ to \ eta \ pi ^ {0} \ gamma \）测量的横截面与通道中较早的测量结果一致\（e ^ {+} e ^ {-} \ to \ pi ^ {+} \ pi ^ {-} \ pi ^ {0} \ eta \）。在5.7个标准偏差（5.7 \（\ sigma \））的水平上，确定过程\（e ^ {+} e ^ {-} \ to \ eta \ pi ^ {0} \ gamma \）为\（VP \）类型的强子中间状态不能完全描述。测量该缺失贡献的横截面，该贡献可能是由辐射过程生成的，例如\（e ^ {+} e ^ {-} \到a_ {0}（1450）\ gamma \）。在从1.3 GeV到1.9 GeV的宽泛能量区间内，其范围为15至20 pb。