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arXiv 1902.00571hep-ex
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$\sqrt{s} =$ ~(13)TeV pp碰撞中B $^+_\mathrm{c}$激发态的观测和B $^+_\mathrm{c}$(2S)质量的测量

Observation of two excited B$^+_\mathrm{c}$ states and measurement of the B$^+_\mathrm{c}$(2S) mass in pp collisions at $\sqrt{s} =$ 13 TeV

CMS Collaboration

摘要:

在$\sqrt{s} =$ 13 TeV的质子-质子碰撞中观察到与B $^+_\mathrm{c}$(2S)和B $^{*+}_\mathrm{c}$(2S)状态一致的信号,事件样本对应于2015-2018年LHC运行期间CMS实验收集的143 fb $^{-1}$的积分光度。在B $^+_\mathrm{c}π^+π^-$不变质谱中观察到这些激发的$\bar{\mathrm{b}}$ c态,基态B $^+_\mathrm{c}$通过其衰变到J/ $ψ\,π^+$而重建。这两个状态被重建为两个分辨良好的峰,在质量上分开29.1 PDMATHAMT 1.5(stat)PDMATHAMT 0.7(syst)MeV。观察到两个峰,而不是一个峰,其显著性超过五个标准差。B $^+_\mathrm{c}$(2S)介子的质量被测量为6871.0 $\pm$ 1.2(stat)$\pm$ 0.8(syst)$\pm$ 0.8(B $^+_\mathrm{c}$)MeV,其中最后一项对应于世界平均B $^+_\mathrm{c}$质量的不确定性。

英文摘要:

Signals consistent with the B$^+_\mathrm{c}$(2S) and B$^{*+}_\mathrm{c}$(2S) states are observed in proton-proton collisions at $\sqrt{s} =$ 13 TeV, in an event sample corresponding to an integrated luminosity of 143 fb$^{-1}$, collected by the CMS experiment during the 2015-2018 LHC running periods. These excited $\bar{\mathrm{b}}$c states are observed in the B$^+_\mathrm{c}π^+π^-$ invariant mass spectrum, with the ground state B$^+_\mathrm{c}$ reconstructed through its decay to J/$ψ\,π^+$. The two states are reconstructed as two well-resolved peaks, separated in mass by 29.1 $\pm$ 1.5 (stat) $\pm$ 0.7 (syst) MeV. The observation of two peaks, rather than one, is established with a significance exceeding five standard deviations. The mass of the B$^+_\mathrm{c}$(2S) meson is measured to be 6871.0 $\pm$ 1.2 (stat) $\pm$ 0.8 (syst) $\pm$ 0.8 (B$^+_\mathrm{c}$) MeV, where the last term corresponds to the uncertainty in the world-average B$^+_\mathrm{c}$ mass.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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