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Register a new userAccessing quark GPDs in diffractive events at an electron-ion collider
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We discuss two collider processes which combine a diffractively produced $rho$ meson separated by a large rapidity gap from a hard exclusive scattering of a Pomeron on a nucleon, giving rise to a lepton pair or to a second meson. These two processes probe the nucleon quark content described by generalized parton distributions in a very specific way.
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In high energy electron-ion colliders, a new way to probe nucleon structure becomes available through diffractive reactions, where the incident particle produces a very energetic almost forward particle. QCD describes these reactions as due to the exchange of a Pomeron which may be perturbatively described as a dressed two-gluon state, provided a hard scale allows the factorization of the amplitude in terms of two impact factors convoluted with a Pomeron propagator. We consider here a process where such a description allows to access hadronic structure in terms of the generalized parton distributions, namely the electroproduction of a forward $rho$ meson and a timelike deeply virtual photon, separated by a large rapidity gap. We explore the dependence of the cross section on the kinematic variables and study the dependence on the non-perturbative inputs (generalized parton distributions, distribution amplitude). Our leading order studies show the cross section is mainly sensitive to the GPD model input, but the small size of the cross sections could prohibit straightforward analysis of this process at planned facilities.
We consider the one-parameter family of jet substructure observables known as angularities using the specific case of inclusive jets arising from photoproduction events at an Electron-Ion Collider (EIC). We perform numerical calculations at next-to-leading logarithmic accuracy within perturbative QCD and compare our results to PYTHIA 6 predictions. Overall, we find good agreement and conclude that jet substructure observables are feasible at the EIC despite the relatively low jet transverse momentum and particle multiplicities. We investigate the size of subleading power corrections relevant at low energies within the Monte Carlo setup. In order to establish the validity of the Monte Carlo tune, we also perform comparisons to jet shape data at HERA. We further discuss detector requirements necessary for angularity measurements at an EIC, focusing on hadron calorimeter energy and spatial resolutions. Possible applications of precision jet substructure measurements at the EIC include the tuning of Monte Carlo event generators, the extraction of nonperturbative parameters and studies of cold nuclear matter effects.
We study all the possible spin asymmetries that can arise in back-to-back electron-jet production, $eprightarrow e+text{jet}+X$, as well as the associated jet fragmentation process, $eprightarrow e+ text{jet} (h)+X$, in electron-proton collisions. We derive the factorization formalism for these spin asymmetries and perform the corresponding phenomenology for the kinematics relevant to the future electron ion collider. In the case of unpolarized electron-proton scattering, we also give predictions for azimuthal asymmetries for the HERA experiment. This demonstrates that electron-jet production is an outstanding process for probing unpolarized and polarized transverse momentum dependent parton distribution functions and fragmentation functions.
We propose to use transverse momentum $p_T$ distribution of $J/psi$ production at the future Electron Ion Collider (EIC) to explore the production mechanism of heavy quarkonia in high energy collisions. We apply QCD and QED collinear factorization to the production of a $cbar{c}$ pair at high $p_T$, and non-relativistic QCD factorization to the hadronization of the pair to a $J/psi$. We evaluate $J/psi$ $p_T$-distribution at both leading and next-to-leading order in strong coupling, and show that production rates for various color-spin channels of a $cbar{c}$ pair in electron-hadron collisions are very different from that in hadron-hadron collisions, which provides a strong discriminative power to determine various transition rates for the pair to become a $J/psi$. We predict that the $J/psi$ produced in electron-hadron collisions is likely unpolarized, and the production is an ideal probe for gluon distribution of colliding hadron (or nucleus). We find that the $J/psi$ production is dominated by the color-octet channel, providing an excellent probe to explore the gluon medium in large nuclei at the EIC.
The feasibility for a measurement of the exclusive production of a real photon, a process although known as Deeply Virtual Compton Scattering (DVCS) at an Electron Ion Collider (EIC) has been explored. DVCS is universally believed to be a golden measurement toward the determination of the Generalized Parton Distribution (GPDs) functions. The high luminosity of the machine, expected in the order of 10^34 cm^-2 s^-1 at the highest center-of-mass energy, together with the large resolution and rapidity acceptance of a newly designed dedicated detector, will open a opportunity for very high precision measurements of DVCS, and thus for the determination of GPDs, providing an important tool toward a 2+1 dimensional picture of the internal structure of the proton and nuclei.
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