We study the longitudinal-transverse double-spin asymmetry with a $\cosϕ_S$ modulation in semi-inclusive deep inelastic scattering for charged and neutral pions production. We consider the particular case in which the transverse momentum of the final state hadron is integrated out. The corresponding asymmetry may be contributed by two parts: one is the convolution of the twist-3 distribution function $g_{T}(x)$ and the unpolarized fragmentation function $D_1(z)$, the other is related to the coupling of the transversity distribution function $h_1(x)$ and the collinear twist-3 fragmentation function $\tilde{E}(z)$. We take into account both contributions to predict the $\cosϕ_S$ asymmetry at the kinematics of CLAS12 and a future Electron Ion Collider. We find that the asymmetry of pion production at CLAS12 is sizable, and $\tilde{E}(z)$ can play an important role in the asymmetry in the large-$z$ region.
In this article, we investigate the $\cos2ϕ_t$ azimuthal asymmetry in $e ~p\rightarrow e ~J/ψ~Jet~ X$, where the $J/ψ$-jet pair is almost back-to-back in the transverse plane, within the framework of the generalized parton model(GPM). We use non-relativistic QCD(NRQCD) to calculate the $J/ψ$ production amplitude and incorporate both color singlet(CS) and color octet(CO) contributions to the asymmetry. We estimate the asymmetry using different parameterizations of the gluon TMDs in the kinematics that can be accessed at the future electron-ion collider (EIC) and also investigate the impact of t…
Semi-inclusive $J/ψ$ production in electron-proton collisions is a promising process to study gluon transverse momentum distributions (TMDs) at the future Electron-Ion Collider. In this article, we improve on previous studies of the $\cos 2 ϕ$ azimuthal asymmetry that arises from the linear polarization of gluons inside unpolarized protons by including TMD evolution. We find that in the TMD regime the asymmetry grows monotonically with increasing transverse momentum of the outgoing $J/ψ$, in contrast to tree level calculations with Gaussian TMDs. Our predictions for the asymmetry at EIC can be…
The possibilities to measure spin effects at a high-energy Electron-Ion Collider (EIC) are reviewed from a theory point of view. Various types of spin distributions and promising observables are discussed.
A high-energy Electron-Ion Collider (EIC) would offer a most promising tool to study in detail the transverse momentum distributions of gluons inside hadrons. This applies to unpolarized as well as linearly polarized gluons inside unpolarized protons, and to left-right asymmetric distributions of gluons inside transversely polarized protons, the so-called gluon Sivers effect. The inherent process dependence of these distributions can be studied by comparing to similar, but often complementary observables at LHC.
This is a brief overview of the spin physics opportunities at a high energy, high luminosity, polarized Electron-Ion Collider (EIC). It covers measurements of electroweak polarized structure functions, quark and gluon PDFs, TMDs, GPDs and GTMDs. Exploiting the many possible final states allows to probe various spin effects. Open and bound heavy quark production can be used to probe gluon TMDs, but also color-octet NRQCD long distance matrix elements. Spin-dependent fragmentation functions can be used too, but are also interesting in themselves. Especially for studies of the small-$x$ and the h…
We study the gauge link contribution to the dipole type transverse momentum dependent distributions of coherent photons, which is conventionally referred to as the Coulomb correction. We further propose to search for the evidence of the Coulomb correction in the Bethe-Heitler process in eA collisions at EIC and EicC.
We consider transverse momentum dependent gluon distributions inside both unpolarized and transversely polarized protons and show how they can be probed by looking at azimuthal modulations in $e \, p \to e \, J/ψ\, \mathrm{jet} \, X$. We find that the contribution due to quark induced subprocesses is always suppressed in the considered kinematic regions, accessible in principle at a future Electron-Ion Collider. Our model-independent estimates of the maximal values of these asymmetries allowed by positivity bounds suggest the feasibility of their measurement. In addition, by adopting the McLer…
We explore the feasibility of direct measurements of nuclear gluon densities using heavy-quark production (open charm, beauty) at a future Electron-Ion Collider (EIC). We focus on the regions x > 0.3 (EMC effect) and x ~ 0.05-0.1 (antishadowing), where the nuclear modifications of the gluon density offer insight into non-nucleonic degrees of freedom and the QCD structure of nucleon-nucleon interactions. We describe the charm production rates and momentum distributions in nuclear deep-inelastic scattering (DIS) at large x_B, and comment on the possible methods for charm reconstruction using nex…
In this paper we consider a small-$x$ model for gluon GTMDs that we fit to data on diffractive dijet production in electron-proton collisions obtained by HERA's H1 Collaboration. Assuming a small number of free parameters, each with a physical motivation, we are able to describe those data fairly well and with this model we obtain predictions for the EIC for both electroproduction and photoproduction which may allow to further test the underlying GTMD description. In the general discussion of the impact parameter dependence we recall some subtle issues related to localization of states, choice…
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…
Gluon Generalized TMD signatures at the EIC from exclusive heavy (axial-)vector meson production
University of Connecticut（康涅狄格大学）；Shandong University（山东大学）；Shandong Institute of Advanced Technology（山东高等技术研究院）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）
The exclusive $π^0$ electroproduction is analyzed within the handbag approach based on Generalized Parton Distributions (GPDs) factorization. We consider the leading-twist contribution together with the transversity effects. It is shown that the transversity, $H_T$ and $\bar E_T$ GPDs are essential in the description of $π^0$ cross section. Predictions for future Electron-Ion Collider of China (EicC) energy range are done. It is found that transversity dominance $σ_T\ggσ_L$, observed at low energies is valid up to EicC energy range.
Baryon-to-meson Transition Distribution Amplitudes extend both the concepts of generalized parton distributions and baryon distribution amplitudes encoding valuable complementary information on the 3-dimensional hadronic structure. The recent analysis of backward meson electroproduction at JLab supports the hope to perform femto-photography of hadrons from a brand new perspective.and in particular opens a new domain for EIC experiments.
We study the potential of dijet photoproduction measurements at a future electron-ion collider (EIC) to better constrain our present knowledge of the nuclear parton distribution functions. Based on theoretical calculations at next-to-leading order and approximate next-to-next-to-leading order of perturbative QCD, we establish the kinematic reaches for three different EIC designs, the size of the parton density function modifications for four different light and heavy nuclei from He-4 over C-12 and Fe-56 to Pb-208 with respect to the free proton, and the improvement of EIC measurements with res…
We investigate the potential of inclusive-jet production in deep-inelastic scattering (DIS) at a future Electron-Ion Collider (EIC) to improve our current knowledge of nuclear parton density functions (PDFs). We demonstrate that the kinematic reach is extended similarly to inclusive DIS, but that the uncertainty of the nuclear PDFs, in particular of the gluon density at low Bjorken-x, is considerably reduced, by up to an order of magnitude compared to the present situation. Using an approximate next-to-next-to-leading order (aNNLO) calculation implemented in the program JetViP, we also make pr…
We propose to utilize the average jet charge weighted single-spin asymmetry $A_e^{bQ}$ in the neutral current DIS scattering with one $b$-tagged jet produced at the EIC to probe the $Zb\bar{b}$ interactions. This novel observable is sensitive to the axial-vector component of the $Zb\bar{b}$ coupling and is complementary to the single-spin asymmetry measurement at the EIC and the $gg\to Zh$ cross section measurement at the HL-LHC in the determination of the $Zb\bar{b}$ couplings. We show that the apparent degeneracy of the $Zb\bar{b}$ couplings, implied by the LEP and SLC precision electroweak …
We propose a novel way of studying the gluon number density (the so-called Weizsäcker-Williams gluon distribution) using the planned Electron Ion Collider. Namely, with the help of the azimuthal correlations between the total transverse momentum of the dijet system and the scattered electron, we examine an interplay between the effect of the soft gluon emissions (the Sudakov form factor) and the gluon saturation effects. The kinematic cuts are chosen such that the dijet system is produced in the forward direction in the laboratory frame, which provides an upper bound on the probed longitudinal…
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…
A simulation study of measurements of neutral current structure functions of the nucleon at the future high-energy and high-luminosity polarized electron-ion collider (EIC) is presented. A new series of $γ-Z$ interference structure functions, $F_1^{γZ}$, $F_3^{γZ}$, $g_1^{γZ}$, $g_5^{γZ}$ become accessible via parity-violating asymmetries in polarized electron-nucleon deep inelastic scattering (DIS). Within the context of the quark-parton model, they provide a unique and, in some cases, yet-unmeasured combination of unpolarized and polarized parton distribution functions. The uncertainty proje…
We present a calculation of the $cos (2 ϕ_h)$ asymmetry in $J/ψ$ production in electron-proton collision at the future electron-ion collider (EIC), a useful channel to probe the gluon TMDs. We calculate the asymmetry at next-to-leading order (NLO) in $α_s$ in the framework of generalized factorization. The dominating sub-process is $γ^* +g \rightarrow J/ψ+g$. The production of $J/ψ$ is calculated in the non-relativistic QCD(NRQCD) framework with the inclusion of both color singlet and color octet contributions. Numerical estimates of the $cos(2ϕ_h)$ asymmetry are given in the kinematical regio…
We propose a new measurement of the heavy flavor hadron double spin asymmetry in deep-inelastic scattering at a future Electron-Ion Collider (EIC) to constrain the polarized gluon distribution function inside the proton. Statistical projection on $D^0$ meson double spin asymmetry is calculated with an EIC central detector using an all-silicon tracker and vertexing subsystem. A first impact study was done by interpreting pseudo-data at next-to-leading order in QCD. The sensitivity of the experimental observable in constraining gluon helicity distribution in a wide range of parton momentum fract…
We discuss the measurement of gluon transverse momentum distribution (TMD) in dijet and heavy hadron pair (HHP) production in semi-inclusive deep inelastic scattering. The factorization of these processes in impact parameter space shows the appearance of a specific new soft factor matrix element on top of angular a complex valued anomalous dimensions. We show in detail how these features can be treated consistently and we discuss a scale prescription for the evolution kernel of the dijet soft function. As a result we obtain phenomenological predictions for unpolarized and angular modulated cro…
We calculate cross sections for the exclusive diffractive leptoproduction of $ρ$-mesons, $γ^*~p~\to~ρ~p$, within the framework of high-energy factorization. Cross sections for longitudinally and transversally polarized mesons are shown. We employ a wide variety of unintegrated gluon distributions available in the literature and compare to HERA data. The resulting cross sections strongly depend on the choice of unintegrated gluon distribution. We also present predictions for the proton target in the kinematics of the Brookhaven EIC.
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.
Recently unpolarized and polarized $J/ψ\,(Υ)$ production at the Electron-Ion Collider (EIC) has been proposed as a new way to extract two poorly known color-octet NRQCD long-distance matrix elements: $\langle0\vert{\cal O}_{8}^{J/ψ}(^{1}S_{0})\vert0\rangle$ and $\langle0\vert{\cal O}_{8}^{J/ψ}(^{3}P_{0})\vert0\rangle$. The proposed method is based on a comparison to open heavy-quark pair production ideally performed at the same kinematics. In this paper we analyze this proposal in more detail and provide predictions for the EIC based on the available determinations of the color-octet matrix el…
We show how transverse momentum dependent gluon distributions could be probed at a future Electron-Ion Collider through the analysis of transverse momentum spectra and azimuthal asymmetries in the inclusive electroproduction of $J/ψ$ and $Υ$ mesons. The maximum values of these asymmetries, obtained in a model-independent way by imposing the positivity bounds of the polarized gluon distributions, suggest the feasibility of the proposed measurements.
Quark-antiquark pair (or dijet) production at the electron-ion collider (EIC) has been argued to be one of most important processes that allowing to access the Weizsäcker-Williams (WW) gluon distributions at small $x$ limit. Within the framework of Color Glass Condensate (CGC) effective field theory (EFT), we calculated the dijet cross sections and the azimuthal correlations by including the Sudakov resummations, numerical results shown that the back-to-back correlations are significantly suppressed when the Sudakov resummations are taken into account. In addition, by using the solutions of ru…
Institute for Nuclear Theory, University of Washington（华盛顿大学核理论研究所）；Northwestern University（西北大学）；KEK Theory Center, IPNS, KEK（高能加速器研究机构理论中心）；Theoretical Division, Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室理论部）
Electro-production of several pentaquark states is investigated in this paper. eSTARlight package is adapted to study the electro-production of $J/ψ$ and $Υ(1S)$ via pentaquark $P_c$ and $P_b$ resonance channels in $e p \to e eJ/ψp$ and $e p \to eΥ(1S) p$ scattering processes at proposed electron-ion colliders (EICs). The results in this paper are compared to the non-resonance $t$-channels, which is described in pomeron exchange model in our studies. Some pseudo-rapidity distributions rapidity distributions of $J/ψ$ and $Υ(1S)$ are presented for proposed EICs including EicC and EIC-US. It is f…
An Electron-Ion Collider (EIC) would enable next-generation measurements of deep-inelastic scattering (DIS) on the deuteron with detection of a forward-moving nucleon (p, n) and measurement of its recoil momentum ("spectator tagging"). Such experiments offer full control of the nuclear configuration during the high-energy process and can be used for precision studies of the neutron's partonic structure and its spin dependence, nuclear modifications of partonic structure, and nuclear shadowing at small x. We review the theoretical description of spectator tagging at EIC energies (light-front nu…
We investigate all the possible spin asymmetries that can occur in back-to-back electron-jet production with hadron observed inside a jet in electron-proton collisions. We derive the factorization formalism for all spin asymmetries and perform phenomenological studies for the future electron ion collider kinematics. We illustrate that the back-to-back electron-jet production opens up new opportunities to study transverse momentum dependent fragmentation functions and distribution functions.
Understanding various fundamental properties of nucleons and nuclei are among the most important scientific goals at the upcoming Electron-Ion Collider (EIC). With the unprecedented opportunity provided by the next-generation machine, the EIC might provide definitive answers to many standing puzzles and open questions in modern nuclear physics. Here we investigate one of the golden measurements proposed at the EIC, which is to obtain the spatial gluon density distribution within a lead ($Pb$) nucleus. The proposed experimental process is the exclusive $J/ψ$ vector-meson production off the $Pb$…
We calculate azimuthal asymmetries in back-to-back production of $J/ψ$ and a photon in electron-proton scattering process at the future electron-ion collider (EIC) using TMD factorization framework. We consider the cases where the proton is unpolarized or transversely polarized. For the formation of $J/ψ$, non-relativistic QCD (NRQCD) is used. We find that the cross-section gets contribution from only one color octet state, as a result, the azimuthal modulations become independent of the long-distance matrix elements (LDMEs), and thus can be used to probe, in particular the gluon TMDs which ar…
Leading neutron (LN) production in $ep$ collisions at high energies is investigated using the color dipole formalism and taking into account saturation effects. We update the treatment of absorptive effects and estimate the impact of these effects on LN spectra in the kinematical range that will be probed by the Electron Ion Collider (EIC) and by the Large Hadron electron Collider (LHeC). We demonstrate that Feynman scaling, associated to saturation, is not violated by the inclusion of absorptive effects. Moreover, our results indicate that the LN spectrum is strongly suppressed at small photo…
Toward Precision Helicity PDFs from Global DIS and SIDIS Fits with Projected EIC Measurements
AGH University（AGH科技大学）；School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM)（基本科学研究所粒子与加速器学院）；Institut für Theoretische Physik, Universität Münster（明斯特大学理论物理研究所）；Istituto Nazionale di Fisica Nucleare, Gruppo collegato di Cosenza（意大利国家核物理研究所科森扎协作组）；Helmholtz-Institut für Strahlen-und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn（波恩大学斯特拉斯曼和核物理亥姆霍兹研究所及贝特理论物理中心）；Institute for Advanced Simulation (IAS-4), Forschungszentrum Jülich（于利希研究中心先进模拟研究所（IAS-4））；Peng Huanwu Collaborative Center for Research and Education, International Institute for Interdisciplinary and Frontiers, Beihang University（北京航空航天大学国际交叉前沿研究院彭桓武教研合作中心）
Deeply virtual meson production at HERA and at the EIC within the Color Glass Condensate EFT
CPHT, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris（巴黎综合理工学院）；Dipartimento di Fisica, Università della Calabria（卡塔尼亚大学物理系）；INFN, Gruppo Collegato di Cosenza（意大利国家核物理研究所科森扎协作组）；National Centre for Nuclear Research (NCBJ)（波兰国家核研究中心）；Université Paris-Saclay, CNRS/IN2P3, IJCLab（巴黎萨克雷大学）
We analyze the possibility of extracting a clear signal of non-linear parton saturation effects from future measurements of nuclear structure functions at the Electron-Ion Collider (EIC), in the small-x region. Our approach consists in generating pseudodata for electron-gold collisions, using the running-coupling Balitsky-Kovchegov evolution equation, and in assessing the compatibility of these saturate pseudodata with existing sets of nuclear parton distribution functions (nPDFs), extrapolated if necessary. The level of disagreement between the two is quantified by applying a Bayesian reweigh…
Deeply-inelastic scattering (DIS) stands to enter a golden age with the prospect of precision programs at the Electron-Ion Collider (EIC) and Large Hadron-electron Collider (LHeC). While these programs will be of considerable importance to resolving longstanding issues in (non)perturbative QCD as well as hadronic and nuclear structure, they will also have valuable implications for a wider range of physics at the Energy and Intensity Frontiers, including at the High-Luminosity LHC (HL-LHC) and future $νA$ facilities. In this plenary contribution, we highlight a number of salient examples of the…
We investigate the $\sin (ϕ_Λ-ϕ_S)$ single-spin asymmetry in the transversely polarized $Λ$ production in semi-inclusive deeply inelastic scattering process within the framework of the transverse momentum dependent~(TMD) factorization. The asymmetry is contributed by the convolution of the polarizing TMD fragmentation function $D_{1T}^\perp$ of the $Λ$ hyperon and the unpolarized TMD distribution function $f_1$ of the target nucleon. We apply two sets of $D_{1T}^{\perp,Λ^\uparrow/q}$, the spectator diquark model result and available parametrization, to numerically estimate the $\sin (ϕ_Λ-ϕ_S)$…
We provide a comprehensive overview of transversely polarized $Λ$ production at the future Electron-Ion Collider (EIC). In particular, we study both spontaneous transverse $Λ$ polarization as well as the transverse spin transfer within the Transverse Momentum Dependent (TMD) factorization region. To describe spontaneous $Λ$ polarization, we consider the contribution from the TMD Polarizing Fragmentation Function (TMD PFF). Similarly, we study the contribution of the transverse spin transfer originating from the transversity TMD Fragmentation Function (TMD FF). We provide projections for the st…
The exclusive vector meson production in electron-ion collisions for the energies of the future colliders is investigated. We present predictions for the coherent and incoherent $ϕ$ and $J/ψ$ production in $eAu$ collisions considering the possible states of nucleon configurations in the nuclear wave function and taking into account of the non-linear corrections to the QCD dynamics. The cross sections and transverse momentum distributions are estimated assuming the energies of the Electron-Ion Collider (EIC), Large Hadron Electron Collider (LHeC) and Future Circular Collider (FCC-$eh$). Our res…
