Jorge Noronha, Miklos Gyulassy
We show that Mach-like azimuthal correlations of associated hadrons in the wake of heavy quark jets modeled in the AdS/CFT string drag picture originate only from the near-quark ``Head'' region. The contributions from the far zones lead only to a yield peaked in the opposite direction with respect to the trigger jet.
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We show that far zone Mach and diffusion wake ``holograms'' produced by supersonic strings in anti--de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict $N_c\to\infty$ supergravity limit if Cooper-Frye hadronization is assumed. However, a special {\em nonequilibrium} ``neck'' zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the…
Calculations using the AdS/CFT correspondence can be used to unveil the short-distance structure of a strongly coupled plasma, as it would be seen by a `hard probe'. The results of these calculations admit a natural physical interpretation in terms of parton evolution in the plasma: via successive branchings, essentially all partons cascade down to very small values of the longitudinal momentum fraction x and to transverse momenta smaller than the saturation momentum Q_s\sim T/x. This scale Q_s controls the energy loss and the transverse momentum broadening of an energetic jet propagating thro…
We give a pedagogical review of recent progress towards understanding the response of a strongly coupled plasma at finite temperature to a hard probe. The plasma is that of the N=4 supersymmetric Yang-Mills theory and the hard probe is a virtual photon, or, more precisely, an R-current. Via the gauge/gravity duality, the problem of the current interacting with the plasma is mapped onto the gravitational interaction between a Maxwell field and a black hole embedded in the AdS_5 x S^5 geometry. The physical interpretation of the AdS/CFT results can be then reconstructed with the help of the ultr…
We propose a novel definition of a holographic light hadron jet and consider the phenomenological consequences, including the very first fully self-consistent, completely strong-coupling calculation of the jet nuclear modification factor $R_{AA}$, which we find compares surprisingly well with recent preliminary data from LHC. We show that the thermalization distance for light parton jets is an extremely sensitive function of the \emph{a priori} unspecified string initial conditions and that worldsheets corresponding to non-asymptotic energy jets are not well approximated by a collection of nul…
There has been recent progress on computing real-time equilibrium 3-point functions in finite-temperature strongly-coupled N=4 super Yang-Mills (SYM). In this paper, we show an example of how to carry out a similar analysis for a 4-point function. We look at the stopping of high-energy "jets" in such strongly-coupled plasmas and relate the question of whether, on an event-by-event basis, each jet deposits its net charge over a narrow (~ 1/T) or wide (>> 1/T) spatial region. We relate this question to the calculation of a 4-point equilibrium correlator.
We show that Mach-like correlations from heavy quark jets in the Gubser et al AdS/CFT string drag model arise not from the expected (weak) hydrodynamical Mach sound wakes zone but from a near ``Neck'' zone where strong chromo-viscous field effects dominated and lead to a distinctive stress in the plasma of the form $T^{μν}_{Neck} \propto \surd λT_0^2 Y^{μν}(x)/x^2$. We propose that measurement of the jet velocity dependence of moderate $p_T$ hadrons associated with future {\em identified heavy quark jets} at RHIC and LHC could be used to look for this novel source of conical correlations which…
We study jets of massless particles in N=4 super Yang-Mills using the AdS/CFT correspondence both at zero and finite temperature. We set up an initial state corresponding to a highly energetic quark/anti-quark pair and follow its time evolution into two jets. At finite temperature the jets stop after traveling a finite distance, whereas at zero temperature they travel and spread forever. We map out the corresponding baryon number charge density and identify the generic late time behavior of the jets as well as features that depend crucially on the initial conditions.
We evaluate the Poynting vector generated by a heavy quark moving through a thermal state of N=4 gauge theory using AdS/CFT. A significant diffusion wake is observed as well as a Mach cone. We discuss the ratio of the energy going into sound modes to the energy coming in from the wake.
We show that the five-fold constraints due to (1) the observed nuclear modification of heavy quark jets measured via non-photonic electrons $R_{AA}^e(p_T \sim 6 {\rm GeV})$ in central Au+Au collisions at 200 AGeV, (2) the "perfect fluid' elliptic transverse flow of low transverse momenta pions, $v_2(p_T\sim 1 {\rm GeV})$ reported for noncentral collisions, (3) the global pion rapidity density $dN_π/dy$, (4) the lattice QCD entropy density deficiency, $S/S_{SB}$, of strongly coupled Quark-Gluon Plasmas (sQGP), and (5) a causal requirement are analytically correlated in a class of gauge/string g…
We argue that classical bulk gravitational radiation effects in AdS/CFT, previously ignored because of their subleading nature in the 1/Nc-expansion, are magnified by powers of large Lorentz factors gamma for ultrarelativistic jets, thereby dominating other forms of jet energy loss in holography at finite temperature. We make use of the induced gravitational self-force in thermal AdS5 to estimate its effects. In a thermal medium, relativistic jets may loose most of their energy through longitudinal drag caused by the energy accumulated in their nearby field as they zip through the strongly cou…
We compare away-side hadron correlations with respect to tagged heavy quark jets computed within a weakly coupled pQCD and a strongly coupled AdS/CFT model. While both models feature similar far zone Mach and diffusion wakes, the far zone stress features are shown to be too weak to survive thermal broadening at hadron freeze-out. Observable away-side conical correlations are dominated by the jet-induced transverse flow in near zone "Neck" region, which differs significantly for both models. Unlike in AdS/CFT, the induced transverse flow in the Neck zone is too weak in pQCD to produce conical c…
MMedium excitation by jet shower propagation inside a quark-gluon plasma is studied within a linear Boltzmann transport and a multiphase transport model. Contrary to the naive expectation, it is the deflection of both the jet shower and the Mach-cone-like excitation in an expanding medium that is found to gives rise to a double-peak azimuthal particle distribution with respect to the initial jet direction. Such deflection is the strongest for hadron-triggered jets which are often produced close to the surface of dense medium due to trigger-bias and travel against or tangential to the radial fl…
We study Mach shocks generated by fast partonic jets propagating through a deconfined strongly-interacting matter. Our main goal is to take into account different types of collective motion during the formation and evolution of this matter. We predict a significant deformation of Mach shocks in central Au+Au collisions at RHIC and LHC energies as compared to the case of jet propagation in a static medium. The observed broadening of the near-side two-particle correlations in pseudorapidity space is explained by the Bjorken-like longitudinal expansion. Three-particle correlation measurements are…
With the dielectric function computed from AdS/CFT correspondence, we studied the wake potential induced by a fast moving charge in strong coupling plasma, and compared it with the weak coupling wake potential for different particle velocities as $v=0.55c$ and $v=0.99c$. The most prominent difference between strong and weak wake potential is that when $v=0.99c$ the remarkable oscillation due to Cerenkov-like radiation and Mach cone in weak coupling disappears in strong coupling, which implies that the plasmon mode with phase velocity lower than the speed of light dose not exist in strong coupl…
We propose an identified heavy quark jet observable to discriminate between weakly coupled pQCD and strongly coupled AdS/CFT models of quark gluon plasma dynamics in ultra-relativistic nuclear collisions at RHIC and LHC energies. These models are shown to predict qualitatively different associated hadron correlations with respect to tagged heavy quark jets. While both models feature similar far zone Mach and diffusion wakes, the far zone stress features are shown to be too weak to survive thermal broadening at hadron freeze-out. However, these models differ significantly in a near zone "Neck" …
The crucial property of particle colliders is their ability to convert (e.g. electrical) energy into the mass of heavy particles. We have become used to the extremely low efficiency of this conversion and the severe limitations on the mass scale of heavy particles which can be reached. In view of this situation, it appears reasonable to ask whether a perfect conversion machine of this type (a perfect `collider') exists even in principle and whether there is a highest mass scale which can be reached by such a machine. It turns out that, with a number of assumptions, such a machine is conceivabl…
Quantifying vacuum-like jets in heavy-ion collisions: a Machine Learning study
针对重离子碰撞中类真空喷注稀释夸克胶子等离子体喷注修正效应的问题，本研究训练基于喷注组分四动量的Transformer分类器，可识别明确修正的喷注并稳健估计类真空喷注占比上限。
Progress in the theoretical understanding of parton branching dynamics within an expanding Quark Gluon Plasma relies on detailed and fair comparisons with experimental data for reconstructed jets. Such comparisons are only meaningful when the computed jet, be it analytically or via event generation, accounts for the complexity of jets reconstructed in the challenging environment of heavy-ion collisions. Jet reconstruction in heavy ion collisions involves a necessarily imperfect subtraction of the large and fluctuating underlying event: reconstructed jets always include underlying event contami…
Diffusion wake: a distinctive consequence of the Mach-cone wake induced by supersonic jets in high-energy heavy-ion collisions
本文综述重离子碰撞中超声速喷注马赫锥尾流产生的扩散尾流，指出喷注-强子关联谷与快度不对称性是探测QGP性质的无背景稳健信号。
Within the AMPT Monte Carlo model, hot spots in the initial transverse parton density are shown to lead to harmonic flows which all contribute to dihadron azimuthal correlation. The net back-to-back dihadron correlation after subtraction of harmonic flows still has a double-peak that is independent of the initial geometric triangularity at a fixed impact-parameter and unique to the structure of jet-induced Mach cone and expanding hot spots dragged by radial flow. The longitudinal structure of hot spots also leads to a near-side ridge in dihadron correlation with a large rapidity gap. By succes…
Searching for dark jets with displaced vertices using weakly supervised machine learning
针对LHC中暗夸克产生的带位移顶点的暗喷注搜索场景，提出一种弱监督机器学习搜索策略，经玩具信号测试可行，部分场景优于传统阈值法且更不依赖模型。
Overview: Jet quenching with machine learning
本文综述机器学习在重离子碰撞喷注淬火研究中的逐喷注应用，涵盖动量重建、喷注分类、能量损失识别、产生点定位及夸克/胶子喷注区分，以推动QGP喷注层析。
In jet quenching, a hard QCD parton, before fragmenting into a jet of hadrons, deposits a fraction of its energy in the medium, leading to suppressed production of high-$p_T$ hadrons. The process can generate shock waves. We study the distortion of Mach shock waves due to jet quenching in central Au+Au collisions and its effect on particle production. Finite fluid velocity and inhomogeneity of the medium can distort the Mach shock front significantly such that the inside shock front disappear and the outside shock front is opened up. We also show that the STAR data on azimuthal distribution of…
Sophisticated machine learning techniques have promising potential in search for physics beyond Standard Model in Large Hadron Collider (LHC). Convolutional neural networks (CNN) can provide powerful tools for differentiating between patterns of calorimeter energy deposits by prompt particles of Standard Model and long-lived particles predicted in various models beyond the Standard Model. We demonstrate the usefulness of CNN by using a couple of physics examples from well motivated BSM scenarios predicting long-lived particles giving rise to displaced jets. Our work suggests that modern machin…
Discriminating QCD Compton and Quark-Antiquark Annihilation Processes in $γ$ + Jets Using Interpretable Machine Learning
利用可解释机器学习区分γ+喷注中的QCD康普顿散射与夸克-反夸克湮灭过程，探讨喷注子结构在区分过程中的有效性。
The energy and momentum lost by a hard parton propagating through hot and dense matter has to be redistributed during the nuclear medium evolution. Apart from heating the medium, there is the possibility that collective modes are excited leading to the emergence of Mach cones or Cherenkov radiation. Recent two-particle correlation measurements by STAR \cite{Wang:2004kf} and PHENIX \cite{Adler:2005ee} at RHIC indicate that such phenomena may play an important role in understanding the jet-medium interactions. Possible collective modes are discussed and it is demonstrated that Mach cones as crea…
Using AdS/CFT we investigate the effect of angular-momentum-induced anisotropy on the instantaneous drag force of a heavy quark. The dual description is that of a string moving in the background of a Kerr-AdS black holes. The system exhibits the expected focussing of jets towards the impact parameter plane. We put forward that we can use the connection between this focussing behavior and the angular momentum induced pressure gradient to extrapolate the pressure gradient correction to the drag force that can be used for transverse elliptic flow in realistic RHIC. The result is recognizable as a…
Di-jet correlations in nucleus-nucleus collisions are studied within the Hadron-String-Dynamics (HSD) transport approach taking into account the reaction of the medium on the jet energy loss nonperturbatively. A comparison with the STAR and PHENIX data in central Au+Au collisions at the RHIC energy $\sqrt{s}=200$ GeV is performed differentially, i.e. with respect to correlations in azimuthal angle $Δϕ$ and pseudorapidity $Δη$. The HSD results do not show enough suppression for the `away-side' jets in accordance with earlier perturbative studies. Furthermore, the `Mach-cone' structure for the a…
Fast thermalization and a strong build up of elliptic flow of QCD matter were investigated within the pQCD based 3+1 dimensional parton transport model BAMPS including bremsstrahlung $2 \leftrightarrow 3$ processes. Within the same framework quenching of gluonic jets in Au+Au collisions at RHIC can be understood. The development of conical structure by gluonic jets is investigated in a static box for the regimes of small and large dissipation. Furthermore we demonstrate two different approaches to extract the shear viscosity coefficient $η$ from a microscopical picture.
Jet substructure observables for jet quenching in Quark Gluon Plasma: a Machine Learning driven analysis
本文利用 JEWEL 模拟和机器学习分析喷注亚结构可观测量，发现其高度相关且少数变量对即可完整捕捉淬火敏感性。
Application of Machine Learning Based Top Quark and W Jet Tagging to Hadronic Four-Top Final States Induced by SM and BSM Processes
本文在Delphes模拟框架下对比截断与机器学习喷注标记方法，识别顶夸克和W喷注，用于标准模型及新物理标量共振y0的全强子四顶夸克末态，重建不变质量并比较背景抑制性能，为LHC搜索提供参考。
The start of the physics program at the LHC has added great impetus in the development of powerful theoretical tools to meet the many challenges that this collider brings. The production of jets and weak vector bosons is at the center of most analyses, from machine performance to new physics searches. In this talk we review some recent advances in the study of jets, in the computation of quantum corrections to processes with large jet multiplicity and their impact in W/Z+jets and W/Z+b-jets production at the Tevatron and the LHC.
From strange-quark tagging to fragmentation tagging with machine learning
本研究将图注意力网络、Particle Transformer等机器学习技术应用于LHC的两类喷注分类任务，发现复杂架构对奇异-下夸克喷注区分提升有限，但可显著提升底重子-底介子喷注的碎裂道分类效果。
Unveiling the Secrets of New Physics Through Top Quark Tagging
本文综述了顶夸克标记在LHC上用于Beyond Standard Model搜索的现状及应用，探讨了基于机器学习的分类方法在区分顶夸克喷注与QCD喷注中的最新进展。
Jets from boosted heavy particles have a typical angular scale which can be used to distinguish them from QCD jets. We introduce a machine learning strategy for jet substructure analysis using a spectral function on the angular scale. The angular spectrum allows us to scan energy deposits over the angle between a pair of particles in a highly visual way. We set up an artificial neural network (ANN) to find out characteristic shapes of the spectra of the jets from heavy particle decays. By taking the Higgs jets and QCD jets as examples, we show that the ANN of the angular spectrum input has sim…
Energy and momentum lost by hard jets propagating through hot and dense nuclear matter have to be redistributed in the medium. It has been conjectured that collective sound modes are excited. Those lead to Mach cone nuclear shock waves in the nuclear medium that are shown to account for three and four particle angular correlation structures of hadrons with a (semi-)hard trigger hadron in heavy-ion collisions at RHIC.
RODEM Jet Datasets
本文介绍 RODEM Jet 数据集，一个包含多种来源模拟大半径喷注的全面集合，提供详细子结构信息，用于支持粒子物理中机器学习算法的开发与评估。
Machine Learning Based Top Quark and W Jet Tagging to Hadronic Four-Top Final States Induced by SM as well as BSM Processes
本研究将选定的机器学习技术应用于强子型四顶夸克末态的顶夸克与W喷注标记，结合模拟事件和参数化探测器模拟开展实验，并与基于切割的方法进行对比。
Quantum chromodynamics is the theory of the strong interaction between quarks and gluons; the coupling strength of the interaction, $α_S$, is the least precisely-known of all interactions in nature. An extraction of the strong coupling from the radiation pattern within jets would provide a complementary approach to conventional extractions from jet production rates and hadronic event shapes, and would be a key achievement of jet substructure at the Large Hadron Collider (LHC). Presently, the relative fraction of quark and gluon jets in a sample is the limiting factor in such extractions, as th…
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