Evidence for a narrow |S |= 1 baryon state at a mass of 1528 MeV in quasi-real photoproduction
Evidence for a narrow |S |= 1 baryon state at a mass of 1528 MeV in quasi-real photoproduction
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DOI：
10.1016/j.physletb.2004.01.079
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发表时间：
2003-12
影响因子：
4.4
通讯作者：
H. C. A. Airapetian;E. al.
中科院分区：
文献类型：
--
作者：
H. C. A. Airapetian;E. al.
重子窄态的证据是在氘靶上通过衰变通道pK 0 S →pπ+π−的准实光生中发现的。在pK 0 Sinvariant质谱中，在1528±2.6（stat）±2.1（syst）MeV处观察到一个峰。根据背景模型，峰的原始统计显著性为4-6个标准差，其宽度可能略大于σ=4.3-6.2 MeV的实验分辨率。这个态可以解释为预言的S=+1奇异Θ+（uudd s θ）五夸克重子。在pK+不变质量分布中没有观察到假设的Θ++重子的信号。不存在这样的信号表明等张量Θ被排除并且等矢量Θ不太可能。
Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel pK0S→pπ+π−. A peak is observed in the pK0Sinvariant mass spectrum at 1528±2.6(stat)±2.1(syst) MeV. Depending on the background model, the naive statistical significance of the peak is 4–6 standard deviations and its width may be somewhat larger than the experimental resolution of σ=4.3–6.2 MeV. This state may be interpreted as the predicted S=+1 exotic Θ+(uudd s ̄ ) pentaquark baryon. No signal for an hypothetical Θ++baryon was observed in the pK+invariant mass distribution. The absence of such a signal indicates that an isotensor Θ is excluded and an isovector Θ is unlikely.