Highly boosted axion-like particles decaying into photon pairs are notoriously hard to detect at the LHC. The collimated decay photons cannot be individually reconstructed using only electromagnetic calorimeter information, making the signal less distinguishable from background. In this note we propose a search strategy to address this issue, exploiting the fact that a fraction of the decay photons convert into electron-positron pairs inside the tracking detector. The resulting tracks can be resolved with high resolution, allowing to separate the two collimated photons and resolve a displaced decay vertex. To demonstrate the effectiveness of this approach, we apply it to ALPs in the challenging MeV-GeV range produced via vector boson fusion. We find that such a search could give sensitivity to untested parameter space.
Production of axionlike particles in $PbPb$ collisions at the LHC, HE -- LHC and FCC: A phenomenological analysis
考虑到大型强子对撞机（LHC）下一轮运行的能量以及未来高能LHC（HE-LHC）和未来圆形对撞机（FCC）的能量，研究了超周边$PbPb$碰撞（UPHIC）中类轴子粒子（ALP）的产生.假设四种不同的组合ALP质量和耦合和典型的排他性削减中央和前向检测器，我们估计的横截面和不变的质量，快度，横向动量和{共面}分布与双光子的最终状态中产生的$γγ\rightarrow a \rightarrow γγ$子过程。对背景进行了详细的分析。我们表明，背景可以大大减少排他性削减和前向检测器，作为LHCb，是理想的探测小质量的ALP。最后，我们的结果表明，未来的实验分析的双光子末态在UPHIC可以探测类轴子粒子的存在和性质。
Axion-like particles (ALPs) are predicted by many extensions of the Standard Model (SM). When ALP mass lies in the range of MeV to GeV, the cosmology and astrophysics will be largely irrelevant. In this work, we investigate such light ALPs through the ALP-strahlung process $pp \to V a (\to γγ)$ at the 14 TeV LHC with an integrated luminosity of 3000 fb$^{-1}$ (HL-LHC). With the photon-jet algorithm, we demonstrate that our approach can probe the mass range of ALPs, which is inaccessible to previous LHC experiments. The obtained result can surpass the existing limits on ALP-photon coupling in t…
Axion-like particles (ALPs) appear in various new physics models with spontaneous global symmetry breaking. When the ALP mass is in the range of MeV to GeV, the cosmology and astrophysics bounds are so far quite weak. In this work, we investigate such light ALPs through the ALP-strahlung production processes $pp \to W^\pm a, Z a$ with the sequential decay $a \to γγ$ at the 14 TeV LHC with an integrated luminosity of 3000 fb$^{-1}$ (HL-LHC). Building on the concept of jet image which uses calorimeter towers as the pixels of the image and measures a jet as an image, we investigate the potential …
Non-Resonant Searches for Axion-Like Particles at the LHC
我们提出了一个新的碰撞探测器的轴子样粒子（ALP），更一般的伪戈德斯通玻色子：非共振搜索，利用其与标准模型粒子的相互作用的衍生性质。ALP可以作为离壳介体参与LHC等对撞机上$2 \to 2$散射过程的$s$通道。我们通过使用Run 2 CMS公共数据推导ALP耦合到规范玻色子的新限制来增强这种新型搜索的能力，通过过程$p p \to Z Z$，$p p \to γγ$和$p p \to j j$，探测ALP参数空间中以前未探索的区域。此外，我们提出了未来的非共振搜索涉及ALP耦合到其他电弱玻色子和/或希格斯粒子。
Constraining R-axion models through dijet searches at the LHC
在强子对撞机上寻找新的100 GeV的大质量共振，有效地耦合到色态是一个非常具有挑战性的问题，主要是由于在这个能量下存在大的QCD多喷流背景，使得在LHC上的搜索特别困难。最近，人们意识到，这些大的背景可以克服要求一个高$p_T$喷流从初始状态辐射（ISR）和通过新的喷流重建技术，通过该技术产生的强子化产品的大规模共振重建为脂肪喷流，一个独特的大半径喷流。ATLAS和CMS合作组织最近报告了对与ISR喷气机相关的单个脂肪喷气机的实验特征的搜索。动力学超对称性破缺与R对称性自发破缺的模型会产生一种称为R-轴子的伪南布-戈德斯通玻色子，它自然倾向于轻。在参数空间区域，异常的R-轴子耦合胶子的提升，这些模型可以测试对这些新的LHC dijet搜索。考虑到CMS搜索，我们将$q_μ$统计方法应用于信号事件对仅背景期望，得到95% C. L.对于特定信使扇区，即R-轴子质量$m_a$、衰减常数$f_a$和颜色信使$N$的数量，对最相关的模型参数的排除限制，这些限制适合于应用于具有轴子样粒子的更一般的模型。
We propose a new search for Axion-Like Particles (ALPs), targeting Vector Boson Scattering (VBS) processes at the LHC. We consider nonresonant ALP-mediated VBS, where the ALP participates as an off-shell mediator. This process occurs whenever the ALP is too light to be produced resonantly, and it takes advantage of the derivative nature of ALP interactions with the electroweak Standard Model bosons. We study the production of $ZZ$, $Zγ$, $W^\pm γ$, $W^\pm Z$ and $W^\pm W^\pm$ pairs with large diboson invariant masses in association with two jets. Working in a gauge-invariant framework, upper l…
We present a new calculation of axion-like particle (ALP) production in the semi-exclusive photon-initiated (PI) channel, that is either with intact outgoing protons or rapidity gaps present in the final state, and with no colour flow between the colliding LHC protons. This is the first full treatment of this process, accounting for both the possibility of proton dissociation and the survival factor probability of no additional proton-proton interactions, including its kinematic and process dependence. We present the expected event yields in the case that either one or both protons are require…
This article describes a search for low-mass axion-like particles (ALPs) at the Large Hadron Collider (LHC). If ALPs were produced at the LHC via gluon-gluon fusion and decayed to bosons, the energy dependence of the measured diboson cross-sections would differ from the Standard Model expectation. Measurements of $WW$ and $Zγ$ differential cross-sections by the ATLAS collaboration are interpreted to constrain ALP couplings to $W$-, $Z$-bosons and photons assuming gluon-gluon-fusion production.
Probing the Axion--Photon--Dark Photon Interaction with LHC Mono-Photons and Fermi-LAT Gamma-Ray Lines
National Taiwan Normal University（台湾师范大学）；Sichuan University（四川大学）；National Center for Theoretical Sciences, National Taiwan University（台湾大学理论科学中心）；Phenikaa Institute for Advanced Study, Phenikaa University（菲尼亚卡大学先进研究院）
We propose the use of FASER as a light-shining-through-walls experiment to search for axions and axion-like particles (ALPs). LHC collisions generate a high intensity and high energy photon flux in the forward direction which can oscillate into ALPs in the magnetic fields that are used to confine the beam. These ALPs then pass through about 100~m of rock before reaching the magnetic fields of FASER, where they can convert back into photons and be detected by an electromagnetic calorimeter. In the next years, FASER and its successor FASER2 at the Forward Physics Facility will be able to explore…
We discuss how LHC di-muon data collected to study $B_q \to μμ$ can be used to constrain light particles with flavour-violating couplings to $b$-quarks. Focussing on the case of a flavoured QCD axion, $a$, we compute the decay rates for $B_q \to μμa$ and the SM background process $B_q \to μμγ$ near the kinematic endpoint. These rates depend on non-perturbative $B_q \to γ^{(*)}$ form factors with on- or off-shell photons. The off-shell form factors -- relevant for generic searches for beyond-the-SM particles -- are discussed in full generality and computed with QCD sum rules for the first time.…
Experimental searches for Axion-Like Particles (ALPs) which couple to the electroweak bosons span over a wide range of ALP masses, from MeV searches at beam-dump experiments, to TeV searches at the LHC. Here we examine an interesting range of parameter space in which the ALP couples only to hypercharge. In the GeV to hundreds of GeV mass range, the contribution of an ALP to light by light scattering can be significant. By making simple kinematic cuts, we show that the ILC running at $\sqrt{s} = 250\,\rm{GeV}$ or $\sqrt{s} = 500\,\rm{GeV}$ can discover ALPs in this range of masses with signific…
