A future Electron-Ion Collider (EIC) will deliver luminosities of $10^{33} - 10^{34}$ cm$^{-2}$s$^{-1}$ for collisions of polarized electrons and protons and heavy ions over a wide range of center-of-mass energies (40 $\mathrm{GeV}$ to 145 $\mathrm{GeV}$). One of its promising physics programs is to study the partonic structure of quasi-real photons. Measuring di-jet in photoproduction events, one can effectively access the underlying parton dynamics of the photons through the selection of the resolved photon processes. In this paper, we discuss the feasibility of tagging resolved photon processes and measuring the di-jet cross section as a function of jet transverse momentum in ranges of $x_γ^{rec}$ at an EIC. These studies show that parton distributions in the photon can be extracted at an EIC.
The dark photon is widely predicted in many new physics beyond the Standard Model. In this work, we propose to utilize the polarized lepton cross section in neutral current DIS process at the HERA and upcoming Electron-Ion Collider (EIC) to probe the properties of the dark photon. It shows that we can constrain the mixing parameter $ε<0.02$ when the dark photon mass $m_{A_D}<10 ~{\rm GeV}$ at the HERA with polarized lepton beam and this bound is comparable to the limit from the unpolarized HERA data. With the help of high integrated luminosity and high electron beam polarization of the EIC, th…
We present a detailed phenomenological study of polarized inclusive jet production in electron-proton collisions at a future Electron-Ion Collider (EIC). Our analysis is performed at next-to-leading order in perturbative QCD using the numerical code DISTRESS and includes all relevant partonic channels and resolved photon contributions. We elucidate the role of different kinematic regions in probing different aspects of proton and photon structure and study the impact of the EIC collision energy on the measurement of polarized parton distribution functions.
Studying Maximal Entanglement and Bell Nonlocality at an Electron-Ion Collider
The Chinese University of Hong Kong (Shenzhen)（香港中文大学（深圳））；The Ohio State University（俄亥俄州立大学）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）
The axion-like particle (ALP) is a well motivated new particle candidate of beyond the Standard Model. In this work, we propose to probe the ALP through the photon fusion scattering at the upcoming Electron-Ion Collider (EIC) with electron and proton energy $E_e=20~{\rm GeV}$ and $E_p=250~{\rm GeV}$. It shows that we could constrain the effective coupling strength between ALP and photons to be $0.2~{\rm TeV}^{-1}$ at $2σ$ confidence level with the integrated luminosity of $300~{\rm fb}^{-1}$ for the mass range $m_a\in [5,40]~{\rm GeV}$. Such bound could be much improved if we consider the nucl…
We study the inclusive J/psi production at large transverse momenta at lepton-hadron colliders in the limit when the exchange photon is quasi real, also referred to as photoproduction. Our computation includes the leading-P_T leading-v next-to-leading alpha_s corrections. In particular, we consider the contribution from J/psi plus another charm quark, by employing for the first time in quarkonium photoproduction the variable-flavour-number scheme. We also include a QED-induced contribution via an off-shell photon which remained ignored in the literature and which we show to be the leading cont…
A future Electron Ion Collider (EIC) will be able to provide collisions of polarized electrons with protons and heavy ions over a wide range of center-of-mass energies (20 $\mathrm{GeV}$ to 140 $\mathrm{GeV}$) at an instanteous luminosity of $10^{33} - 10^{34}$ cm$^{-2}$s$^{-1}$. One of its promising physics programs is the study of the partonic structure of quasi-real photons. Measuring di-jets in quasi-real photoproduction events, one can effectively access the underlying parton dynamics of the photons. In this paper, we discuss the feasibility of tagging resolved photon processes and measur…
The recent exclusive backward-angle electroproduction of omega from Jefferson Lab Hall C electron-proton fixed-target scattering experiments above the resonance region hints at a new domain of applicability of QCD factorization in a unique u-channel kinematics regime. Thanks to this effort, the interest in studying nucleon structure through u-channel meson production observables has grown significantly. In the fixed target configuration, the u-channel meson electroproduction observables feature a unique interaction picture: the target proton absorbs nearly all momentum induced by virtual photo…
We are developing gaseous photon detectors for Cherenkov imaging applications in the experiments at the future Electron Ion Collider. CsI, converting photons in the far ultraviolet range, is, so far, the only photoconverter compatible with the operation of gaseous detectors. It is very delicate to handle due to its hygroscopic nature: the absorbed water vapour decomposes the CsI molecule. In addition, its quantum efficiency degrades under ion bombardment. These are the key reasons to quest for novel, less delicate materials for photocathodes adequate for gaseous photon detectors. Layers of hyd…
Massachusetts Institute of Technology（麻省理工学院）；University of Regina（里贾纳大学）
Imaging Cherenkov detectors form the backbone of particle identification (PID) at the future Electron Ion Collider (EIC). Currently all the designs for the first EIC detector proposal use a dual Ring Imaging CHerenkov (dRICH) detector in the hadron endcap, a Detector for Internally Reflected Cherenkov (DIRC) light in the barrel, and a modular RICH (mRICH) in the electron endcap. These detectors involve optical processes with many photons that need to be tracked through complex surfaces at the simulation level, while for reconstruction they rely on pattern recognition of ring images. This proce…
We reinterpret jet clustering as an axis-finding procedure which, along with the proton beam, defines the virtual-photon transverse momentum $q_T$ in deep inelastic scattering (DIS). In this way, we are able to probe the nucleon intrinsic structure using jet axes in a fully inclusive manner, similar to the Drell-Yan process. We present the complete list of azimuthal asymmetries and the associated factorization formulae at leading power for deep-inelastic scattering of a nucleon. The factorization formulae involve both the conventional time-reversal-even (T-even) jet function and the T-odd one,…
Particle IDentification (PID) is a central requirement of the experiments at the future EIC. Hadron PID at high momenta by RICH techniques requires the use of low density gaseous radiators, where the challenge is the limited length of the radiator region available at a collider experiment. By selecting a photon wavelength range in the far UV domain, around 120 nm, the number of detectable photons can be increased. Ideal sensors are gaseous Photon Detectors (PD) with CsI photocathode, where the status of the art is represented by the MPGD-based PDs at COMPASS RICH. Detector optimization is requ…
Producing and Studying Rare Isotopes in $e+A$ Collisions at the Electron-Ion Collider
Texas Southern University（德克萨斯南方大学）；Michigan State University（密歇根州立大学）；Stony Brook University（石溪大学）；Brookhaven National Laboratory（布鲁克海文国家实验室）；Mississippi State University（密西西比州立大学）；University of South Carolina（南卡罗来纳大学）；Morgan State University（摩根州立大学）
The quantitative knowledge of heavy nuclei's partonic structure is currently limited to rather large values of momentum fraction $x$ -- robust experimental constraints below $x \sim 10^{-2}$ at low resolution scale $Q^2$ are particularly scarce. This is in sharp contrast to the free proton's structure which has been probed in deep inelastic scattering (DIS) measurements down to $x \sim 10^{-5}$ at perturbative resolution scales. The construction of an Electron-Ion Collider (EIC) with a possibility to operate with a wide variety of nuclei, will allow one to explore the low-$x$ region in much gr…
Based on rare fluctuations in strong interactions, we argue that there is a strong physical resemblance between the high multiplicity events in photo-nuclear collisions and those in $pA$ collisions, in which interesting long range collective phenomena are discovered. This indicates that the collectivity can also be studied in certain kinematic region of the upcoming Electron-Ion Collider (EIC) where the incoming virtual photon has a sufficiently long lifetime. Using a model in the Color Glass Condensate formalism, we first show that the initial state interactions can explain the recent ATLAS a…
Coherent exclusive vector meson electroproduction is a key physics channel at an electron-ion collider. It probes the gluon structure of nuclei over a wide range of $Q^2$, and can be used to measure nuclear shadowing and to search for gluon saturation and/or the colored glass condensate. In this paper, we present calculations of the kinematic distributions for a variety of exclusive vector meson final states: the $ρ$, $ϕ$, J/$ψ$, $ψ'$ and the $Υ$ states. The cross-sections for light and $c\overline c$ mesons are large, while $Υ$ states should be produced in moderate numbers at a medium energy …
Separating coherent and incoherent photoproduction at an Electron-Ion Collider: Comparing lead, gold and silver beams
Nuclear Science Division, Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室核科学部）；Department of Physics and Astronomy, University of California, Davis（加州大学戴维斯分校物理与天文学系）
A future Electron-Ion Colllider (EIC) is the ideal laboratory for studying the gluon distributions in both nucleons and nuclei for $\sqrt{s}$ = 63 - 158 (40 - 110) GeV/A for e+p (e+A) collisions. Whilst gluon distributions have been studied extensively in nucleons at HERA, there is very little information on them for $x <$ 0.1 in nuclei. The rapid increase in the gluon momentum distribution at low-$x$ in nucleons found at HERA, if not tamed, leads to the violation of the Froissart Unitarity Bound at small-$x$. This can be achieved in non-linear QCD by allowing for the recombination of low-$x$ …
Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High Intensity heavy-ion Accelerator Facility (HIAF) which is currently under construction, together with a new electron ring. The proposed collider will provide highly polarized electrons (with a polarization of $\sim$80%) and protons (with a polarization of $\sim$70%) with variable center o…
We study the inclusive photoproduction of $T_{{\bar c}{\bar c}}(3875)^-$ mesons (which are the antiparticles of the doubly charmed tetraquarks $T_{cc}(3875)^+$ discovered recently by the LHCb Collaboration) from nuclei in the near-threshold energy region within the nuclear spectral function approach by considering incoherent direct ($γp(n) \to D^+(D^0){T_{{\bar c}{\bar c}}(3875)^-}Λ^+_c$) photon--nucleon $T_{{\bar c}{\bar c}}(3875)^-$ creation processes as well as five possible different scenarios for their internal structure with the main goal of clarifying the possibility to decipher this st…
Unpolarized electron-proton elastic scattering cross-section measurements at high $Q^2$ allow for improved extractions of the proton electromagnetic form factors as well as provide constraints on possible hard two-photon exchange effects. We present a detailed study of the feasibility of making these high $Q^2$ e-p elastic measurements at the future Electron-Ion Collider (EIC). The results show that e-p elastic cross sections can be obtained in the momentum transfer range of $6~(GeV/c)^2 < Q^2 < 40~(GeV/c)^2$, which would be the highest-ever $Q^2$ values measured. These data will all be at vir…
Charged-particle spectra associated with direct photon ($γ_{dir} $) and $π^0$ are measured in $p$+$p$ and Au+Au collisions at center-of-mass energy $\sqrt{s_{_{NN}}}=200$ GeV with the STAR detector at RHIC. A hower-shape analysis is used to partially discriminate between $γ_{dir}$ and $π^0$. Assuming no associated charged particles in the $γ_{dir}$ direction (near side) and small contribution from fragmentation photons ($γ_{frag}$), the associated charged-particle yields opposite to $γ_{dir}$ (away side) are extracted. At mid-rapidity ($|η|<0.9$) in central Au+Au collisions, charged-particle y…
The past few years has seen tremendous progress in our understanding of short-range correlated (SRC) pairing of nucleons within nuclei, much of it coming from electron scattering experiments leading to the break-up of an SRC pair. The interpretation of these experiments rests on assumptions about the mechanism of the reaction. These assumptions can be directly tested by studying SRC pairs using alternate probes, such as real photons. We propose a 30-day experiment using the Hall D photon beam, nuclear targets, and the GlueX detector in its standard configuration to study short-range correlatio…
A picoammeter system has been developed and engineering. It consists in a current-voltage converter, based on an operational amplifier with very low input current, a high precision ADC, a radio controlled data acquisition unit and the computer-based control, visualization and storage. The precision is of the order of a tenth of picoampers and it can measure currents between electrodes at potentials up to 8 kV. The system is battery powered and a number of strategies have been implemented to limit the power consumption. The system is designed for multichannel applications, up to 256 parallel ch…
