论文标题

利用异国情调的LHC数据集进行长寿的新粒子搜索

Exploiting exotic LHC datasets for long-lived new particle searches

论文作者

Faham, Hesham El, Giammanco, Andrea, Hajer, Jan

论文摘要

由于期望新物理学可能以非常重的新粒子的形式表现出来的动机,LHC的大部分操作时间都以最高可实现的能量和碰撞速率专用于$ pp $碰撞。较大的碰撞率意味着紧密的触发要求,包括最终粒子的横向动量$ p_ {t} $上的高阈值以及在同一束交叉期间发生的不同碰撞产生的粒子堆积形式的固有背景。对于几种良好动机的新物理模型,这种策略可能是最佳的,在这些模型中,新粒子并不特别重,并且由于其轻质质量和小耦合而可以避免多功能LHC实验的在线选择标准。 LHC实验通常收集的补充数据集可以提供解决方案。其中包括重离子碰撞,用于精确物理的低螺旋杆以及所谓的“停车”和“侦察”数据集。尽管其中一些是受其他物理目标的激励,但它们都具有与触发器级别的常见$ p_ {t} $阈值的使用。在这项研究中,我们评估了这些数据集的相对优点对于代表模型,其特殊的清洁签名具有长寿命的共振,产生了dimuon顶点。我们比较跨这些数据集的覆盖范围以进行简单分析,在运行2中模拟LHC数据,并使用Delphes模拟运行3个条件。我们显示,仅使用部分检测器信息并分别延迟事件重建,侦察和停车数据集可提供低 - $ P_ {t} $触发阈值,它可以与标准的$ pp $ dataset相当。我们还表明,对于此签名,重离子和低螺旋杆数据集的竞争力远不如竞争力。

Motivated by the expectation that new physics may manifest itself in the form of very heavy new particles, most of the operation time of the LHC is devoted to $pp$ collisions at the highest achievable energies and collision rates. The large collision rates imply tight trigger requirements that include high thresholds on the final-state particles' transverse momenta $p_{T}$ and an intrinsic background in the form of particle pileup produced by different collisions occurring during the same bunch crossing. This strategy is potentially sub-optimal for several well-motivated new physics models where new particles are not particularly heavy and can escape the online selection criteria of the multi-purpose LHC experiments due to their light mass and small coupling. A solution may be offered by complementary datasets that are routinely collected by the LHC experiments. These include heavy ion collisions, low-pileup runs for precision physics, and the so-called 'parking' and 'scouting' datasets. While some of them are motivated by other physics goals, they all have the usage of mild $p_{T}$ thresholds at the trigger-level in common. In this study, we assess the relative merits of these datasets for a representative model whose particular clean signature features long-lived resonances yielding displaced dimuon vertices. We compare the reach across those datasets for a simple analysis, simulating LHC data in Run 2 and Run 3 conditions with the Delphes simulation. We show that the scouting and parking datasets, which afford low-$p_{T}$ trigger thresholds by only using partial detector information and delaying the event reconstruction, respectively, have a reach comparable to the standard $pp$ dataset with conventional thresholds. We also show that heavy ion and low-pileup datasets are far less competitive for this signature.

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