Session KQ: Mini-Symposium: U.S.-based Electron-Ion Collider: Physics and Detectors I

The electron-ion collider: A collider to unravel the mysteries of visible matter

Understanding the properties of nuclear matter and its emergence through the underlying partonic structure and dynamics of quarks and gluons requires a new experimental facility in hadronic physics known as the Electron-Ion Collider (EIC). The EIC will address some of the most profound questions concerning the emergence of nuclear properties by precisely imaging gluons and quarks inside protons and nuclei such as the distribution of gluons and quarks in space and momentum, their role in building the nucleon spin and the properties of gluons in nuclei at high energies. In January 2020 the EIC received CD-0 and Brookhaven National Laboratory was chosen as site. This presentation will highlight the capabilities of an EIC and discuss the accelerator design and the concepts for the experimental equipment.   

Optimizing the EIC for future PDF phenomenology

The recent approval of CD-0 for the Electron-Ion Collider (EIC) has set in motion an aggressive Yellow-Report Initiative to optimize the design of the EIC to guarantee the highest-impact physics program. A crucial aspect of this process has been a focus on the EIC's potential impact on the collinear parton distribution functions (PDFs) of the nucleon and nuclei as well as the resulting phenomenological implications, including at higher energies. In this talk, I will survey a number of PDF-driven activities that have played out in support of the EIC Yellow Report throughout 2020. Special attention will be paid to the ability for the EIC to disentangle the flavor dependence of the unpolarized PDFs, which generally require a diversity of experimental measurements and channels to constrain.   

Impact of EIC on the collinear gluon helicity distribution (Δ𝑔)

We assess the impact of the future Electron-Ion Collider on the collinear gluon helicity distribution ($\Delta g$). In particular, we study the constraining power of longitudinally polarized inclusive deep-inelastic scattering on $\Delta g$ using the $Q^2$ range covered by the EIC kinematics.   

Measuring gluon polarization in the nucleon via open charm production at the EIC.

To understand gluon polarization inside a polarized nucleon is one of the most important physics goals of the future EIC proposed at Brookhaven National Laboratory. In addition to the extraction of such information by a QCD fit on the polarized g1 structure functions, another direct measurement on gluon polarization via double spin asymmetries in the open charm production through photon-gluon fusion process is proposed. In this talk, the idea of such measurement and simulation studies at the EIC will be presented.   

Small-x Helicity Phenomenology

One of the key components to solving the proton spin problem is understanding the small-x asymptotics of the helicity parton distribution functions (hPDFs). Several years ago, novel, small-$x$ evolution equations were derived using the shock-wave/Wilson line formalism, designed for calculating the $x$-dependence of the quark and gluon hPDFs and the proton $g_1$ structure function. These equations can be used to predict the contribution to the spin of the proton coming from the helicities of the small-$x$ quarks and gluons. In this talk we will present the first-ever attempt to describe the world data on the $g_1$ structure function at small $x$ using the evolution equations derived the novel evolution equations within the JAM global analysis framework. Our results serve as a prediction for future measurements at the EIC and can be used to estimate the net amount of quark spin at small-$x$, ultimately bringing us one step closer to understanding the proton spin.   

Probing gluon distributions with heavy quark pairs at the EIC

Heavy quark production in deep inelastic scattering proceeds via the Boson Gluon Fusion process and thus provides constraints to the gluon distributions inside the nucleon/ion probed. Measurements of semi-inclusive deep inelastic scattering events with tagged charm and anti-charm hadron pair in the final state and the pair transverse momentum and azimuthal distributions can therefore be used to probe the spin-dependent gluon transverse momentum distribution functions in the nucleon/ion. In this talk we will discuss open charm hadron reconstruction studies with an all silicon detector design for a future Electron Ion Collider (EIC) experiment and the impact on the reconstructed open charm hadron pair signal significance for different particle identification and secondary vertex resolution capabilities. Statistical uncertainty projections for physics observables in both polarized and unpolarized collisions at the EIC will be discussed.   

The spin of the proton at small-x: Emergent axion dynamics and spin diffusion

The worldline representation of quantum field theory is a powerful framework for the computation of perturbative multi-leg Feynman amplitudes. In particular, in gauge theories, it provides an efficient way, via point particle Grassmann functional integrals, to compute spinor and color traces in these amplitudes. We show how it can be applied to the problem of computation of the polarized deeply inelastic structure function $g_1$. In particular, we discuss a relation between $g_1$ and the physics of the axial (or chiral) anomaly responsible for the explicit breaking of the $U_A(1)$ symmetry of QCD.