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arXiv 2002.06393hep-ex
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在$\sqrt{s} =$ 13 TeV质子-质子碰撞中测量$Υ$(1 S)对产生截面和寻找衰减到$Υ$(1 S)$μ^+μ^-$的共振

Measurement of the $Υ$(1S) pair production cross section and search for resonances decaying to $Υ$(1S)$μ^+μ^-$ in proton-proton collisions at $\sqrt{s} =$ 13 TeV

CMS Collaboration

摘要:

在质心能量为13 TeV的质子-质子碰撞中,在两个$Υ$(1 S)介子的绝对快度都低于2.0的区域,$Υ$(1 S)对产生的基准截面被测量为79 $\pm$ 11(stat)$\pm$ 6(syst)$\pm$ 3($\mathcal{B}$)pb,假设介子是非极化产生的。最后一个不确定度对应于$Υ$(1 S)介子双μ子分支分数的不确定度。测量是使用2016年在LHC的CMS实验收集的质子-质子碰撞数据在最终状态下使用四个μ子进行的,对应于35.9 fb $^{-1}$的积分光度。该过程作为标准模型参考,用于搜索在相同最终状态下衰减到$Υ$(1 S)$μ^+μ^-$的窄共振。这样的共振可能表明存在一个四夸克,它是两个b夸克和两个$\bar{\mathrm{b}}$反夸克的束缚态。四夸克搜索的质量在四倍的底夸克质量附近,在17.5和19.5 GeV之间,而对其他共振的一般搜索是在16.5和27 GeV之间的质量。在数据中没有观察到与窄共振相容的显著过量的事件。通过中间$Υ$(1 S)共振的生产截面倍分支分数到四个μ子的限制被设置为共振质量的函数。

英文摘要:

The fiducial cross section for $Υ$(1S) pair production in proton-proton collisions at a center-of-mass energy of 13 TeV in the region where both $Υ$(1S) mesons have an absolute rapidity below 2.0 is measured to be 79 $\pm$ 11 (stat) $\pm$ 6 (syst) $\pm$ 3 ($\mathcal{B}$) pb assuming the mesons are produced unpolarized. The last uncertainty corresponds to the uncertainty in the $Υ$(1S) meson dimuon branching fraction. The measurement is performed in the final state with four muons using proton-proton collision data collected in 2016 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. This process serves as a standard model reference in a search for narrow resonances decaying to $Υ$(1S)$μ^+μ^-$ in the same final state. Such a resonance could indicate the existence of a tetraquark that is a bound state of two b quarks and two $\bar{\mathrm{b}}$ antiquarks. The tetraquark search is performed for masses in the vicinity of four times the bottom quark mass, between 17.5 and 19.5 GeV, while a generic search for other resonances is performed for masses between 16.5 and 27 GeV. No significant excess of events compatible with a narrow resonance is observed in the data. Limits on the production cross section times branching fraction to four muons via an intermediate $Υ$(1S) resonance are set as a function of the resonance mass.

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