arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 1910.09581hep-phhep-ex
收藏

四顶作为光顶探测器--新物理学

Four-top as probe of light top-philic New Physics

Ezequiel Alvarez, Aurelio Juste, Rosa María Sandá Seoane

摘要:

我们研究了LHC中的四顶末态,作为新物理(NP)效应的探针,由于新粒子主要与顶夸克耦合,其质量低于顶夸克对产生阈值。我们考虑简单的NP模型包含一个新的粒子与自旋0,自旋1,或自旋2,并找到与目前的实验结果兼容的基准点。我们发现,NP和QED振幅之间的干扰效应可以很大,指出NLO贡献的必要性,明确计算和考虑NP时,是本。我们研究这些模型和标准模型(SM)在部分子水平和重建水平之间的运动学差异。在后一种情况下,我们专注于选择需要两个相同符号的轻子和多个喷流的事件。我们调查如何不同的洛伦兹结构的光NP影响的运动硬度,偏振,自旋相关性,和角分布的部分子级和/或最终状态的粒子。我们发现自旋为2的轻NP比SM更难被运动学识别。我们还表明,相同符号的轻子之间的角间距是一个敏感的观察自旋0 NP。自旋为0和自旋为2的NP情况也会在$t\bar t γγ$中产生一个信号,光子的不变质量指示新粒子的质量。自旋为1的NP可以通过四顶信号的过量和其他可观测量的轻微或无修改来识别,例如由于朗道-杨定理,$t\bar t γγ$中缺少信号。我们评论的机会,将打开从运动学重建的一些顶夸克在四顶态。我们的研究结果提供了新的手柄,以探测轻亲顶NP作为正在进行的实验计划的一部分,在大型强子对撞机运行2及以后的四顶生产搜索。

英文摘要:

We study the four-top final state at the LHC as a probe for New Physics (NP) effects due to new particles that couple predominantly to the top quark and whose masses are below the top-quark-pair production threshold. We consider simple NP models containing a new particle with either spin 0, spin 1, or spin 2, and find benchmark points compatible with current experimental results. We find that interference effects between NP and QED amplitudes can be large, pointing out the necessity of NLO contributions to be explicitly computed and taken into account when NP is present. We examine kinematic differences between these models and the Standard Model (SM) at the parton level and the reconstructed level. In the latter case, we focus on events selected requiring two same-sign leptons and multiple jets. We investigate how the different Lorentz structure of the light NP affects the kinematic hardness, the polarization, the spin correlations, and the angular distributions of the parton-level and/or final-state particles. We find that spin-2 light NP would be identified by harder kinematics than the SM. We also show that the angular separation between the same-sign leptons is a sensitive observable for spin-0 NP. The spin-0 and spin-2 NP cases would also yield a signal in $t\bar t γγ$ with the invariant mass of the photons indicating the mass of the new particle. The spin-1 NP would be identified through an excess in four-top signal and slight or not modification in other observables, as for instance the lack of signal in $t\bar t γγ$ due to the Landau-Yang theorem. We comment on the opportunities that would open from the kinematic reconstruction of some of the top quarks in the four-top state. Our results provide new handles to probe for light top-philic NP as part of the ongoing experimental program of searches for four-top production at the LHC Run 2 and beyond.

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。

↑