The primary goal of the GlueX experiment at Jefferson Lab is to search for and map the spectrum of light hybrid mesons. Many experiments have studied and reported evidence of exotic mesons decaying into $ηπ$ and $η'π$ final states. With a large acceptance to both charged and neutral particles, GlueX has access to both the neutral, $γp\toη^{(')}π^{0}p$, and charged, $γp\toη^{(')}π^{-}Δ^{++}$, exchanges. These proceedings will give an overview of the current studies being performed at GlueX in $η^{(')}π^{-}$ final states. It will discuss early physics goals and outline the strategy for an amplitude analysis as GlueX begins its quest to illuminate the light hybrid meson spectrum.
Photoproduction experiments are a key tool in the investigation of the spectrum of hadronic states and the way gluons contribute to this spectrum. The GlueX experiment, located at Jefferson Lab, features a linearly polarized tagged photon beam and its detector system is optimized to measure a wide range of neutral and charged final states. GlueX offers unique capabilities to study the spectrum of hadrons and is dedicated to the search for hybrid mesons, states with gluonic degrees of freedom. This talk presents first results from our initial campaign of data taking which finished in 2018.
The GlueX experiment is located at the Thomas Jefferson National Accelerator Facility (JLab) in Newport News, VA, USA. It features a hermetic 4$π$ detector with excellent tracking and calorimetry capabilities. Its 9 GeV linearly polarized photon beam is produced from the 12 GeV electron beam, delivered by JLab's Continuous Electron Beam Accelerator Facility (CEBAF), via bremsstrahlung on a thin diamond and is incident on a LH2 target. GlueX recently finished its first data taking period and published first results. The main goal of GlueX is to measure gluonic excitations of mesons. These so-ca…
A study of meson and baryon decays to strange final states with GlueX in Hall D (A proposal to the 39th Jefferson Lab Program Advisory Committee)
实验的主要动机是寻找并最终研究在γ p碰撞中产生的介子谱中的胶子激发模式。最近的格点量子色动力学计算预言了一个丰富的混合介子谱，它既有奇异的JPC，又有非奇异的JPC，对应于与胶子场耦合的q q-bar（q=u，d或s）态。对混合光谱的彻底研究，包括鉴别电荷为0和+-1的等矢量三重态，以及两个等矢量成员，|s s-bar>和|u u-bar> +| d d-bar>，对于JPC的每一个预测的混合组合，只能通过对许多不同的强子末态进行系统的振幅分析来实现。我们建议开发一个K介子识别系统，以补充现有的GSTX前向飞行时间探测器，以干净地选择介子和重子衰变通道，包括K介子。一旦这个探测器已经安装和调试，我们计划收集总共200天的物理分析数据，平均强度为每秒5 x 10^7个标记光子。这个数据样本将提供一个数量级的统计改进，在最初的GSTX数据集，并与发达的K介子识别系统，GSTX的潜力显着增加，使我们的知识的混合介子和级联重子的关键实验进展。
Hybrid mesons consist of a quark-antiquark pair bound together by a gluonic field that is in an excited state. Measuring the spectrum of these states will provide valuable information on the gluonic degrees of freedom of QCD in the quark-confinement regime. A rich spectrum of hybrid meson states has been predicted, but only a few experiments have reported evidence of their existence. The GlueX experiment at Jefferson Lab is designed to search for and measure the spectrum of light-mass hybrid mesons, and it has began its physics run in Spring 2017. For the experiment, a 12 GeV electron beam inc…
The search for hybrid mesons and the detailed study of their spectrum is the primary goal of the GlueX Experiment in Hall D at Jefferson Lab. The identification and study of hybrid mesons promises to provide unique insight into gluonic degrees of freedom in QCD and the nature of confinement. The experiment combines an intense photon beam with linear polarization peaking around 9 GeV incident on a liquid hydrogen target with a nearly hermetic spectrometer, allowing for the comprehensive study of charged and neutral particle final states. The first phase of the experiment has recently concluded,…
GlueX at Jefferson Lab aims to study the light meson spectrum with an emphasis on the search for light hybrid mesons. To this end, a linearly-polarized $9\,$GeV photon beam impinges on a hydrogen target contained within a hermetic detector with near-complete neutral and charged particle coverage. In 2016, the experiment completed its commissioning and subsequently started to take data in its design configuration. With the size of the data set so far, GlueX already exceeds previous experiments for polarized photoproduction in this energy regime. A selection of early results will be presented, f…
The GlueX experiment is located in experimental Hall D at Jefferson Lab (JLab) and provides a unique capability to search for hybrid mesons in high-energy photoproduction, utilizing a ~9 GeV linearly polarized photon beam. The initial, low-intensity phase of GlueX was recently completed and a high-intensity phase has begun in 2020 which includes an upgraded kaon identification system, known as the DIRC (Detection of Internally Reflected Cherenkov light), utilizing components from the decommissioned BaBar DIRC. The identification of kaon final states will significantly enhance the GlueX physics…
The GlueX experiment takes place in experimental Hall D at Jefferson Lab (JLab). With a linearly polarized photon beam of up to 12 GeV energy, GlueX is a dedicated experiment to search for hybrid mesons via photoproduction reactions. The low-intensity (Phase I) of GlueX was recently completed; the high-intensity (Phase II) started in 2020 including an upgraded particle identification system, known as the DIRC (Detection of Internally Reflected Cherenkov light), utilizing components from the decommissioned BaBar experiment. The identification and separation of the kaon final states will signifi…
The quality of the recent GlueX $J/ψ$ photoproduction data from Hall~D at Jefferson Laboratory, and the proximity of the data to the energy threshold, gives access to a variety of interesting physics aspects. As an example, an estimation of the $J/ψ$-nucleon scattering length $α_{J/ψp}$ is provided within the vector meson dominance model. It results in $|α_{J/ψp}| = (3.08\pm 0.55 ({\rm stat.}) \pm 0.45 ({\rm syst.}))$~mfm.
The high accuracy $ϕ$-meson photoproduction data from the CLAS experiment in Hall~B of Jefferson Laboratory allow us to determine the near-threshold total cross section of the $γp\toϕp$ reaction and use it for evaluating the $ϕp$ scattering length $α_{ϕp}$. These data result in an absolute value of $|α_{ϕp}| = (0.063\pm 0.010)$~fm, which is smaller than the typical hadron size. A comparative analysis of $α_{ϕp}$ with the previously determined scattering lengths for $ωp$ and $J/ψp$ from the A2 and GlueX experiments is performed.
The GlueX experiment, located in experimental Hall D of Jefferson Lab, seeks to map the spectrum of light mesons in search of exotic hybrid mesons, a predicted class of hadronic states with explicit gluonic degrees of freedom. GlueX is a photoproduction experiment utilizing a linearly polarized photon beam at $E_γ=$ 8-9 GeV and a large acceptance spectrometer. The experiment has already collected orders of magnitude more data than previous experiments at similar energies. We show results on asymmetry measurements in the production of pseudoscalars mesons, which refine our understanding of prod…
Search for the $Y(2175)$ in the photoproduction cross section measurement of $γp \to ϕπ^{+} π^{-} p$ at GlueX
Ruhr-Universität-Bochum（波鸿鲁尔大学）；Thomas Jefferson National Accelerator Facility（托马斯·杰斐逊国家加速器设施）；Old Dominion University（老道明大学）；William & Mary（威廉与玛丽学院）；Florida International University（佛罗里达国际大学）；Carnegie Mellon University（卡内基梅隆大学）；Springfield College（斯普林菲尔德学院）；Florida State University（佛罗里达州立大学）；Indiana University（印第安纳大学）
The GlueX experiment at Jefferson Lab aims to study the light meson spectrum with an emphasis on the search for hybrid mesons. To this end, a linearly-polarized $9\,$GeV photon beam impinges on a hydrogen target contained within a detector with near-complete neutral and charged particle coverage. In 2018, the experiment completed its first phase of data taking in its design configuration and the quantity of analyzed data already exceed that of previous experiments for polarized photoproduction in this energy regime by orders of magnitude. Polarization observables such as spin-density matrix el…
We briefly review and expand our recent analysis for all three invariant A,B,D gravitational form factors of the nucleon in holographic QCD. They compare well to the gluonic gravitational form factors recently measured using lattice QCD simulations. The holographic A-term is fixed by the tensor $T=2^{++}$ (graviton) Regge trajectory, and the D-term by the difference between the tensor $T=2^{++}$ (graviton) and scalar $S=0^{++}$ (dilaton) Regge trajectories. The B-term is null in the absence of a tensor coupling to a Dirac fermion in bulk. A first measurement of the tensor form factor A-term is…
Baryon - anti-baryon photoproduction off a proton target is being studied in detail at Jefferson Lab with the GlueX Experiment. We observe $p\bar{p}$ and, for the first time, $Λ\barΛ$ photoproduction (with $Λ\rightarrow π^- p$, $\barΛ \rightarrow π^+ \bar{p}$) from thresholds up to $E_γ = 11.4$ GeV. Preliminary spectra from data accumulated during the GlueX Phase-I period are shown. Angular distributions of the photoproduced hyperons indicate more than one production mechanism in the reaction channel $γp \rightarrow Λ\barΛp$. A Monte Carlo simulation with four mechanisms, tested through compar…
High-accuracy $Υ$-meson photoproduction data from EIC and EicC experiments will allow the measurement of the near-threshold total cross section of the reaction $γp\toΥp$, from which the absolute value of the $Υp$ scattering length, $|α_{Υp}|$, can be extracted using a Vector-Meson Dominance model. For this evaluation, we used $Υ$-meson photoproduction quasi-data from the QCD approach (the production amplitude can be factorized in terms of gluonic generalized parton distributions and the quarkonium distribution amplitude). A comparative analysis of $|α_{Υp}|$ with the recently determined scatte…
