Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider
Juliette Alimena, James Beacham, Martino Borsato, Yangyang Cheng, Xabier Cid Vidal, Giovanna Cottin, Albert De Roeck, Nishita Desai, David Curtin, Jared A. Evan… 展开作者
Juliette Alimena, James Beacham, Martino Borsato, Yangyang Cheng, Xabier Cid Vidal, Giovanna Cottin, Albert De Roeck, Nishita Desai, David Curtin, Jared A. Evans, Simon Knapen, Sabine Kraml, Andre Lessa, Zhen Liu, Sascha Mehlhase, Michael J. Ramsey-Musolf, Heather Russell, Jessie Shelton, Brian Shuve, Monica Verducci, Jose Zurita, Todd Adams, Michael Adersberger, Cristiano Alpigiani, Artur Apresyan, Robert John Bainbridge, Varvara Batozskaya, Hugues Beauchesne, Lisa Benato, S. Berlendis, Eshwen Bhal, Freya Blekman, Christina Borovilou, Jamie Boyd, Benjamin P. Brau, Lene Bryngemark, Oliver Buchmueller, Malte Buschmann, William Buttinger, Mario Campanelli, Cari Cesarotti, Chunhui Chen, Hsin-Chia Cheng, Sanha Cheong, Matthew Citron, Andrea Coccaro, V. Coco, Eric Conte, Félix Cormier, Louie D. Corpe, Nathaniel Craig, Yanou Cui, Elena Dall'Occo, C. Dallapiccola, M. R. Darwish, Alessandro Davoli, Annapaola de Cosa, Andrea De Simone, Luigi Delle Rose, Frank F. Deppisch, Biplab Dey, Miriam D. Diamond, Keith R. Dienes, Sven Dildick, Babette Döbrich, Marco Drewes, Melanie Eich, M. ElSawy, Alberto Escalante del Valle, Gabriel Facini, Marco Farina, Jonathan L. Feng, Oliver Fischer, H. U. Flaecher, Patrick Foldenauer, Marat Freytsis, Benjamin Fuks, Iftah Galon, Yuri Gershtein, Stefano Giagu, Andrea Giammanco, Vladimir V. Gligorov, Tobias Golling, Sergio Grancagnolo, Giuliano Gustavino, Andrew Haas, Kristian Hahn, Jan Hajer, Ahmed Hammad, Lukas Heinrich, Jan Heisig, J. C. Helo, Gavin Hesketh, Christopher S. Hill, Martin Hirsch, M. Hohlmann, W. Hulsbergen, John Huth, Philip Ilten, Thomas Jacques, Bodhitha Jayatilaka, Geng-Yuan Jeng, K. A. Johns, Toshiaki Kaji, Gregor Kasieczka, Yevgeny Kats, Malgorzata Kazana, Henning Keller, Maxim Yu. Khlopov, Felix Kling, Ted R. Kolberg, Igor Kostiuk, Emma Sian Kuwertz, Audrey Kvam, Greg Landsberg, Gaia Lanfranchi, Iñaki Lara, Alexander Ledovskoy, Dylan Linthorne, Jia Liu, Iacopo Longarini, Steven Lowette, Henry Lubatti, Margaret Lutz, Jingyu Luo, Judita Mamužić, Matthieu Marinangeli, Alberto Mariotti, Daniel Marlow, Matthew McCullough, Kevin McDermott, P. Mermod, David Milstead, Vasiliki A. Mitsou, Javier Montejo Berlingen, Filip Moortgat, Alessandro Morandini, Alice Polyxeni Morris, David Michael Morse, Stephen Mrenna, Benjamin Nachman, Miha Nemevšek, Fabrizio Nesti, Christian Ohm, Silvia Pascoli, Kevin Pedro, Cristián Peña, Karla Josefina Pena Rodriguez, Jónatan Piedra, James L. Pinfold, Antonio Policicchio, Goran Popara, Jessica Prisciandaro, Mason Proffitt, Giorgia Rauco, Federico Redi, Matthew Reece, Allison Reinsvold Hall, H. Rejeb Sfar, Sophie Renner, Amber Roepe, Manfredi Ronzani, Ennio Salvioni, Arka Santra, Ryu Sawada, Jakub Scholtz, Philip Schuster, Pedro Schwaller, Cristiano Sebastiani, Sezen Sekmen, Michele Selvaggi, Weinan Si, Livia Soffi, Daniel Stolarski, David Stuart, John Stupak, Kevin Sung, Wendy Taylor, Sebastian Templ, Brooks Thomas, Emma Torró-Pastor, Daniele Trocino, Sebastian Trojanowski, Marco Trovato, Yuhsin Tsai, C. G. Tully, Tamás Álmos Vámi, Juan Carlos Vasquez, Carlos Vázquez Sierra, K. Vellidis, Basile Vermassen, Martina Vit, Devin G. E. Walker, Xiao-Ping Wang, Gordon Watts, Si Xie, Melissa Yexley, Charles Young, Jiang-Hao Yu, Piotr Zalewski, Yongchao Zhang
Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton-proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments --- as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER --- to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the High-Luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity "dark showers", highlighting opportunities for expanding the LHC reach for these signals.
Light neutralinos could be copiously produced from the decays of mesons generated in cosmic-ray air showers. These neutralinos can be long-lived particles in the context of R-parity violating (RPV) supersymmetric models, implying that they could be capable of reaching the surface of the earth and decay within the instrumental volume of large neutrino detectors. In this letter, we use atmospheric neutrino data from the Super-Kamiokande experiment to derive novel constraints for the RPV couplings involved in the production of long-lived light neutralinos from the decays of charged $D$-mesons and…
Many models of dark matter predict long-lived particles (LLPs) that can give rise to striking signatures at the LHC. Existing searches for displaced vertices are however tailored towards heavy LLPs. In this work we show that this bias severely affects their sensitivity to LLPs with masses at the GeV scale. To illustrate this point we consider two dark sector models with light LLPs that decay hadronically: a strongly-interacting dark sector with long-lived exotic mesons, and a Higgsed dark sector with a long-lived dark Higgs boson. We study the sensitivity of an existing ATLAS search for displa…
Long-lived particles have significant enough lifetimes as to, when produced in collisions, leave a distinct signature in the detectors. Driven by increasingly higher energies, trigger and reconstruction algorithms at particle colliders are optimized for increasingly heavier particles, which in turn, tend to be short-lived. This makes searches for long-lived particles difficult, usually requiring dedicated methods and sometimes dedicated hardware top spot them. However, taking upon the challenge brings enormous potential, since new, long-lived particles feature in a variety of promising new phy…
Long-Lived Sleptons at the LHC and a 100 TeV Proton Collider
我们研究了长寿命带电粒子（LLCP）搜索在当前和未来的LHC运行和在100 TeV PP对撞机的前景，使用Drell-Yan slepton对生产为例。由于动量测量对于高能粒子变得更具挑战性，我们仔细对待预期的动量分辨率。同时，100 TeV碰撞的一个新特征是探测器中高能μ子的显著能量损失。我们用它来帮助区分μ子和LLCP。我们发现，14 TeV的LHC与3 ab $^{-1}$的积分亮度可以探测LLCP slepton质量高达1.2 TeV，和100 TeV的PP对撞机与3 ab $^{-1}$可以探测LLCP slepton质量高达4 TeV，使用飞行时间测量。这些搜索将对暗物质产生惊人的影响，LHC最终测试了slepton-neutralino共同湮灭WIMP暗物质的可能性，并且LHC和未来的强子对撞机具有在超级WIMP暗物质模型中发现LLCP的强大潜力。
In this paper, we point out a novel signature of physics beyond the Standard Model which could potentially be observed both at the Large Hadron Collider (LHC) and at future colliders. This signature, which emerges naturally within many proposed extensions of the Standard Model, results from the multiple displaced vertices associated with the successive decays of unstable, long-lived particles along the same decay chain. We call such a sequence of displaced vertices a "tumbler." We examine the prospects for observing tumblers at the LHC and assess the extent to which tumbler signatures can be d…
While the triplet-like Higgses up to a few hundred GeV masses are already excluded for a vast region of the model parameter space from the LHC searches, strikingly, there is a region of this parameter space that is beyond the reach of the existing LHC searches, and doubly/singly-charged and neutral Higgses as light as 200 GeV or even lighter are still allowed by the LHC data. We study several search strategies targeting different parts of this LHC elusive parameter space at two configurations of $e^-e^+$ colliders -- 500 GeV and 1 TeV centre of mass energies. We find that a vast region of this…
The next generation of circular high energy collider is expected to be a lepton collider, FCC-ee at CERN or CEPC in China. However, the civil engineering concepts foresee to equip these colliders with bigger detector caverns than one would need for a lepton collider, so that they can be used for a hadron collider that may be installed in the same tunnel without further civil engineering. This opens up the possibility to install extra instrumentation at the cavern walls to search for new long-lived particles at the lepton collider. We use the example of heavy neutral leptons to show that such a…
Searching for a stop-pair sample from top counting experiments at hadron colliders
如果光停止对在强子对撞机中产生，并通过可能的衰变链停止->电荷伴子+ b，然后是电荷伴子->中性伴子+ f f '衰变，则当停止的质量接近时，可以密切模拟顶夸克事件。顶夸克的。由于产生率低得多，停止事件可以被埋在顶夸克事件样本之下。为了揭示停止事件，需要应用特定的选择切割。通过蒙特卡罗模拟和适当的运动学切割，我们发现这种停止事件可以从顶夸克样品中提取出来，并在即将进行的Tevatron和LHC升级实验中被顶夸克计数实验检测到。然而，由于Tevatron的运行1的小统计，停止信号在运行1处保持隐藏。
As the planning stages for a high energy muon collider enter a more concrete era, an important question arises as to what new physics could be uncovered. A TeV-scale muon collider is also a vector boson fusion (VBF) factory with a very clean background, and as such it is a promising environment to look for new physics that couples to the electroweak (EW) sector. In this paper, we explore the ability of a future TeV-scale muon collider to search for Majorana and Dirac Heavy Neutral Leptons (HNLs) produced via EW bosons. Employing a model-independent, conservative approach, we present an estimat…
The analysis of azimuthal correlations in multiparticle production can be useful to uncover the existence of new physics beyond the Standard Model, e.g., Hidden Valley, in $e^+e^-$ annihilation at high energies. In this paper, based on previous theoretical studies and using PYTHIA8 event generator, it is found that both azimuthal and rapidity long-range correlations are enhanced due to the presence of a new stage of matter on top of the QCD partonic cascade. Ridge structures, similar to those observed at the LHC, show up providing a possible signature of new physics at future $e^+e^-$ collider…
A new approach to long-lived particle detection at hadron colliders: the $\textsf{DELIGHT-SHIELD}$ concept
Indian Institute of Science（印度科学学院）；Indian Institute of Technology, Kanpur（坎普尔印度理工学院）；University of the Witwatersrand（威特沃特斯兰德大学）；Universität Bonn（波恩大学）
We study the pair production of the long-lived mediator particles from the decay of the SM Higgs boson and their subsequent decay into standard model particles. We compute the projected sensitivity, both model-independently and with a minimal model, of using the muon spectrometer of the CMS detector at the HL-LHC experiment for ggF, VBF, and Vh production modes of the Higgs boson and various decay modes of the mediator particle, along with dedicated detectors for LLP searches like CODEX-b and MATHUSLA. Subsequently, we study the improvement with the FCC-hh detector at the 100\,TeV collider exp…
In the context of the minimal left-right symmetric model, we study the interplay between current and future neutrinoless double beta ($0νββ$) decay experiments, long-lived particle searches at the LHC main detectors ATLAS/CMS, and the proposed far detector MATHUSLA. The heavy Majorana neutrino can be produced in association with an electron from the decay of $W$ boson for a non-zero left-right mixing and subsequently decays into another electron with the same charge and jets. Owing to the suppression of large right-handed charged gauge boson $W_R$ mass, the heavy neutrinos could be long-lived.…
We investigate the sensitivity to long-lived dark photons produced in Higgstrahlung events via the Higgs portal, $H \rightarrow γ_{D} γ_{D}$, with the Silicon Detector (SiD) at the International Linear Collider (ILC). These events provide a useful benchmark for tracking and vertex detector performance with long-lived particle decays at displaced vertices. The ILC is one of several Higgs factories proposed by the international community to study the properties of the Higgs boson at high precision.
We study a search for the charged Higgs boson via $e^+e^- \to H^+H^- \to c\bar{b}\bar{c}b$ at the 500 GeV ILC. In a general two Higgs doublet model without $Z_2$ symmetry, extra Yukawa couplings $ρ_{tt}$ and $ρ_{tc}$ can drive baryogenesis, but searches at the HL-LHC may still go empty-handed if the couplings are relatively weak. Taking $m_{H^+ } \simeq m_H \simeq m_A \simeq 200$ GeV, with $ρ_{tt}$, $ρ_{tc}\sim 0.1$ and no $h(125)$-$H$ mixing, $H^+ \to c\bar b$ decay is dominant, and the $c\bar{b}\bar{c}b$ final state is likely overwhelmed by QCD background at the LHC. We show that the electro…
Searching for the minimal Seesaw models at the LHC and beyond
I型Seesaw模型是标准模型的最简单的推广，用Majorana型SM规范单重右手中微子（RHN）可以很自然地解释中微子质量和味混合的存在。如果RHN在电弱（EW）标度附近与SM轻中微子有相当大的混合，它们可以在高能对撞机如大型强子对撞机（LHC）和未来的$100$ TeV质子-质子（pp）对撞机上通过具有相同符号的双轻子引入轻子数违反（LNV）的特征信号产生。另一方面，具有小LNV参数的Seesaw模型，即逆Seesaw模型，在满足中微子振荡数据的同时，可以容纳EW尺度的赝Dirac中微子与SM轻中微子的大量混合.由于模型的LNV参数很小，同号双轻子的“烟枪”特征被抑制了，因为模型中的RHN将在LHC和未来的$100$ TeV pp对撞机上主要通过具有丢失横向能量（MET）的轻子数守恒（LNC）三轻子末态出现。通过研究这类RHN的各种产生通道，我们给出了13 TeV LHC和未来100 TeV pp对撞机上轻重中微子混合参数的最新上限。
Electromagnetic dipole moment and time reversal invariance violating interactions for high energy short-lived particles in bent and straight crystals at Large Hadron Collider
QCD instantons are arguably the best motivated yet unobserved nonperturbative effects predicted by the Standard Model. A discovery and detailed study of instanton-generated processes at colliders would provide a new window into the phenomenological exploration of QCD and a vastly improved fundamental understanding of its non-perturbative dynamics. Building on the optical theorem, we numerically calculate the total instanton cross-section from the elastic scattering amplitude, also including quantum effects arising from resummed perturbative exchanges between hard gluons in the initial state, t…
