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arXiv 0910.0046hep-ex
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粲偶素辐射跃迁的高阶多极振幅

Higher-order multipole amplitudes in charmonium radiative transitions

M. Artuso

备注：
32 pages, 7 figures, acceptance update
发表信息：
Phys.Rev.D80:112003,2009
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摘要：

使用24万$ψ' \equiv ψ(2S)$在CLEO-c衰变，我们已经在charmonia的电偶极子为主的辐射跃迁中寻找更高的多极混合物。我们发现我们的数据和理论预测的磁四极（M2）的振幅在过渡$ψ' \to γχ_{c1,2}$和$χ_{c1,2} \to γJ/ψ$，在鲜明的对比，一些以前的测量之间的协议。令$b_2^J$和$a_2^J$表示在上述各个衰变中的归一化M2振幅，其中上标$J$指的是$χ_{cJ}$的角动量。通过对完整的五参数角分布进行未分组的最大似然拟合，我们确定了比率$a_2^{J=1}/a_2^{J=2} = 0.67^{+0.19}_{-0.13}$和$a_2^{J=1}/b_2^{J=1} = -2.27^{+0.57}_{-0.99}$，其中理论预测与粲夸克磁矩无关，并且是$a_2^{J=1}/a_2^{J=2} = 0.676 \pm 0.071$和$a_2^{J=1}/b_2^{J=1} = -2.27 \pm 0.16$。

英文摘要：

Using 24 million $ψ' \equiv ψ(2S)$ decays in CLEO-c, we have searched for higher multipole admixtures in electric-dipole-dominated radiative transitions in charmonia. We find good agreement between our data and theoretical predictions for magnetic quadrupole (M2) amplitudes in the transitions $ψ' \to γχ_{c1,2}$ and $χ_{c1,2} \to γJ/ψ$, in striking contrast to some previous measurements. Let $b_2^J$ and $a_2^J$ denote the normalized M2 amplitudes in the respective aforementioned decays, where the superscript $J$ refers to the angular momentum of the $χ_{cJ}$. By performing unbinned maximum likelihood fits to full five-parameter angular distributions, we determine the ratios $a_2^{J=1}/a_2^{J=2} = 0.67^{+0.19}_{-0.13}$ and $a_2^{J=1}/b_2^{J=1} = -2.27^{+0.57}_{-0.99}$, where the theoretical predictions are independent of the charmed quark magnetic moment and are $a_2^{J=1}/a_2^{J=2} = 0.676 \pm 0.071$ and $a_2^{J=1}/b_2^{J=1} = -2.27 \pm 0.16$.

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