The LHCb detector provides accurate vertex reconstruction and hadronic particle identification, which make the experiment an ideal place to look for light long-lived particles (LLP) decaying into Standard Model (SM) hadrons. In contrast with the typical search strategy relying on energetic jets and a high multiplicity of tracks from the LLP decay, LHCb can identify LLPs in exclusive, specific hadronic final states. To illustrate the idea, we study the sensitivity of LHCb to an exotic Higgs decay h → SS , followed by the displaced decay of GeV-scale scalars into charged kaons S → K + K − . We show that the reconstruction of kaon vertices in narrow invariant mass windows can efficiently eliminate the combinatorial backgrounds from B -meson decays. While the same signal is extremely difficult to probe in the existing displaced jet searches at ATLAS/CMS, the LHCb search we propose can probe the branching ratio BR( h → SS ) down to 0 . 1% (0 . 02%) level with 15 (300) fb − 1 of data. We also apply this projected bound to two scenarios with Higgs portal couplings, where the scalar mediator S either couples to a) the SM quarks only, or b) to both quarks and leptons in the minimal flavor violation paradigm. In both scenarios we compare the reach of our proposed search with the expected constraints from ATLAS and CMS on the invisible Higgs width and with the constraints from rare B-decays studies at LHCb. We find that for 1 GeV < m S < 2 GeV and 0 . 5 mm ≲ cτ ≲ 10 mm our proposed search will be competitive with the ATLAS and CMS projections, while at the same time providing crucial information of the hadronic interactions of S , which can not be obtained from the indirect measurement of the Higgs invisible width.

中文翻译：

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LHC 前沿区域的独家置换强子特征

LHCb 探测器提供准确的顶点重建和强子粒子识别，这使该实验成为寻找衰变为标准模型 (SM) 强子的轻长寿命粒子 (LLP) 的理想场所。与依赖于高能喷流和来自 LLP 衰变的大量轨迹的典型搜索策略相比，LHCb 可以识别处于排他性、特定强子最终状态的 LLP。为了说明这个想法，我们研究了 LHCb 对奇异希格斯衰变 h → SS 的敏感性，然后是 GeV 尺度标量置换衰变为带电 kaons S → K + K − 。我们表明，在狭窄的不变质量窗口中重建 kaon 顶点可以有效地消除 B 介子衰变的组合背景。虽然在 ATLAS/CMS 现有的置换射流搜索中很难探测到相同的信号，但我们建议的 LHCb 搜索可以探测到 0 的分支比 BR( h → SS )。1% (0 . 02%) 水平与 15 (300) fb − 1 数据。我们还将这种投影绑定应用于具有希格斯门户耦合的两个场景，其中标量介体 S 要么耦合到 a) 仅 SM 夸克，要么 b) 在最小风味违反范式中耦合到夸克和轻子。在这两种情况下，我们将我们提出的搜索范围与 ATLAS 和 CMS 对不可见希格斯宽度的预期约束以及 LHCb 上罕见的 B 衰变研究的约束进行了比较。我们发现对于 1 GeV < m S < 2 GeV 和 0 。5 mm ≲ cτ ≲ 10 mm 我们提议的搜索将与 ATLAS 和 CMS 预测竞争，