arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.02434hep-ex
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在$\sqrt{s} =$ 13 TeV的质子-质子碰撞中测量B $^0_\mathrm{s}$ $\to$ J $/ψ\, ϕ$(1020)$\to$ PDMATHAAF K PDMATHAAG K PDMATHAAH通道中的$CP$破坏相$ϕ_\mathrm{s}$

Measurement of the $CP$-violating phase $ϕ_\mathrm{s}$ in the B$^0_\mathrm{s}$ $\to$ J$/ψ\, ϕ$(1020) $\to$ $μ^+μ^-$K$^+$K$^-$ channel in proton-proton collisions at $\sqrt{s} =$ 13 TeV

CMS Collaboration

摘要:

在LHC上用CMS探测器测量了48500个重构的BPDMATHABMPPDMATHABMQJPDMATHABMR(1020)PDMATHABMQPDMATHABMSKPDMATHABMTKPDMATHABMU事例中的$ϕ_\mathrm{s}$破坏弱相位和轻重BPDMATHABMP质量本征态之间的衰变宽度差$ΔΓ_\mathrm{s}$.该测量基于对应于96.4 fb $^{-1}$的积分光度的数据样本,该数据样本是在2017-2018年$\sqrt{s} =$ 13 TeV的质子-质子碰撞中收集的。为了提取$ϕ_\mathrm{s}$和$ΔΓ_\mathrm{s}$的值,执行$μ^+μ^-$ K $^+$ K $^-$最终状态的时间相关和风味标记的角度分析。该分析采用了一个专用的标签触发器和一个新的对侧μ子风味标签的机器学习技术的基础上。测量产生$ϕ_\mathrm{s} = -$ 11 $\pm$ 50(统计)$\pm$ 10(系统)mrad和$ΔΓ_\mathrm{s} =$ 0.114 $\pm$ 0.014(统计)$\pm$ 0.007(系统)ps $^{-1}$,与标准模型预测一致。当与先前在$\sqrt{s} =$ 8 TeV下的CMS测量相结合时,获得以下值:$ϕ_\mathrm{s} = -$ 21 $\pm$ 44(stat)$\pm$ 10(syst)mrad,$ΔΓ_\mathrm{s} =$ 0.1032 $\pm$ 0.0095(stat)$\pm$ 0.0048(syst)ps $^{-1}$,与8 TeV结果相比有显著改善。

英文摘要:

The $CP$-violating weak phase $ϕ_\mathrm{s}$ and the decay width difference $ΔΓ_\mathrm{s}$ between the light and heavy B$^0_\mathrm{s}$ mass eigenstates are measured with the CMS detector at the LHC in a sample of 48 500 reconstructed B$^0_\mathrm{s}$ $\to$ J$/ψ\, ϕ$(1020) $\to$ $μ^+μ^-$K$^+$K$^-$ events. The measurement is based on a data sample corresponding to an integrated luminosity of 96.4 fb$^{-1}$, collected in proton-proton collisions at $\sqrt{s} =$ 13 TeV in 2017-2018. To extract the values of $ϕ_\mathrm{s}$ and $ΔΓ_\mathrm{s}$, a time-dependent and flavor-tagged angular analysis of the $μ^+μ^-$K$^+$K$^-$ final state is performed. The analysis employs a dedicated tagging trigger and a novel opposite-side muon flavor tagger based on machine learning techniques. The measurement yields $ϕ_\mathrm{s} = -$11 $\pm$ 50 (stat) $\pm$ 10 (syst) mrad and $ΔΓ_\mathrm{s} =$ 0.114 $\pm$ 0.014 (stat) $\pm$ 0.007 (syst) ps$^{-1}$, in agreement with the standard model predictions. When combined with the previous CMS measurement at $\sqrt{s} =$ 8 TeV, the following values are obtained: $ϕ_\mathrm{s} = -$21 $\pm$ 44 (stat) $\pm$ 10 (syst) mrad, $ΔΓ_\mathrm{s} =$ 0.1032 $\pm$ 0.0095 (stat) $\pm$ 0.0048 (syst) ps$^{-1}$, a significant improvement over the 8 TeV result.

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