在COMPASS搜索$X(3872)$的多产物和新状态$\widetilde{X}(3872)$的指示
Search for muoproduction of $X(3872)$ at COMPASS and indication of a new state $\widetilde{X}(3872)$
摘要：
我们已经寻找了独特的生产charmonia的反应$μ^+~N \rightarrow μ^+ (J\!/\!ψπ^+π^-)π^{\pm}~N'$使用COMPASS数据收集的传入μ子的160 GeV/ $c$和200 GeV/ $c$动量。在$J\!/\!ψπ^+π^-$质量分布中，我们观察到具有4.1 $σ$统计学显著性的信号。其质量和宽度与$X(3872)$一致。从观察到的衰变为$J\!/\!ψπ^+π^-$的$π^+π^-$质量分布的形状显示出与先前对$X(3872)$的观察不一致。观测到的信号可能被解释为一个新的粲偶素状态的可能证据。它可能与$X(3872)$的中性伴侣有关，而$C = -1$由四夸克模型预测。截面积与观测态衰变为$J\!/\!ψπ^+π^-$的分支分数的乘积被确定为71 $\pm$ 28（stat）$\pm$ 39（syst）pb。
英文摘要：
We have searched for exclusive production of exotic charmonia in the reaction $μ^+~N \rightarrow μ^+ (J\!/\!ψπ^+π^-)π^{\pm}~N'$ using COMPASS data collected with incoming muons of 160 GeV/$c$ and 200 GeV/$c$ momentum. In the $J\!/\!ψπ^+π^-$ mass distribution we observe a signal with a statistical significance of 4.1 $σ$. Its mass and width are consistent with those of the $X(3872)$. The shape of the $π^+π^-$ mass distribution from the observed decay into $J\!/\!ψπ^+π^-$ shows disagreement with previous observations for $X(3872)$. The observed signal may be interpreted as a possible evidence of a new charmonium state. It could be associated with a neutral partner of $X(3872)$ with $C = -1$ predicted by a tetraquark model. The product of cross section and branching fraction of the decay of the observed state into $J\!/\!ψπ^+π^-$ is determined to be 71$\pm$28(stat)$\pm$39(syst) pb.
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