[Paper Review] The Solenoidal Large Intensity Device (SoLID) for JLab 12 GeV

J. Arrington, Jay Benesch+29 more|arXiv (Cornell University)|Sep 19, 2022

Particle Detector Development and Performance4 citations

TL;DR

The Solenoidal Large Intensity Device (SoLID) is a high-luminosity, large-acceptance spectrometer designed for Jefferson Lab's 12 GeV electron beam to enable precision measurements of nucleon structure via semi-inclusive deep inelastic scattering (SIDIS), parity-violating DIS (PVDIS), near-threshold J/ψ production, and generalized parton distributions (GPDs). It leverages advanced detector technologies and high-rate data acquisition to access high-x quark distributions and probe the gluonic contribution to proton mass and electroweak couplings with unprecedented statistical power.

ABSTRACT

The Solenoidal Large Intensity Device (SoLID) is a new experimental apparatus planned for Hall A at the Thomas Jefferson National Accelerator Facility (JLab). SoLID will combine large angular and momentum acceptance with the capability to handle very high data rates at high luminosity. With a slate of approved high-impact physics experiments, SoLID will push JLab to a new limit at the QCD intensity frontier that will exploit the full potential of its 12 GeV electron beam. In this paper, we present an overview of the rich physics program that can be realized with SoLID, which encompasses the tomography of the nucleon in 3-D momentum space from Semi-Inclusive Deep Inelastic Scattering (SIDIS), expanding the phase space in the search for new physics and novel hadronic effects in parity-violating DIS (PVDIS), a precision measurement of $J/ψ$ production at threshold that probes the gluon field and its contribution to the proton mass, tomography of the nucleon in combined coordinate and momentum space with deep exclusive reactions, and more. To meet the challenging requirements, the design of SoLID described here takes full advantage of recent progress in detector, data acquisition and computing technologies. In addition, we outline potential experiments beyond the currently approved program and discuss the physics that could be explored should upgrades of CEBAF become a reality in the future.

Motivation & Objective

• To explore the three-dimensional momentum-space structure of the nucleon through high-statistics semi-inclusive deep inelastic scattering (SIDIS) with polarized 3He and proton targets.
• To measure electroweak parameters and probe new physics beyond the Standard Model via parity-violating deep inelastic scattering (PVDIS) on deuterons and protons at high x.
• To determine the gluonic contribution to the proton mass by measuring J/ψ production near threshold with high precision.
• To map the nucleon's structure in combined coordinate and momentum space using deep exclusive reactions and generalized parton distributions (GPDs).
• To extend the kinematic reach of electron-nucleon scattering to high Bjorken-x and high Q², complementing the Electron-Ion Collider (EIC) program.

Proposed method

• Utilizes a solenoidal magnetic field configuration with a large acceptance (up to 4π steradians) to capture high-multiplicity final states at luminosities up to 10³⁹ cm⁻²s⁻¹.
• Employs Gas Electron Multiplier (GEM) trackers for high-rate tracking and precise momentum measurement of charged particles.
• Integrates Cherenkov detectors (light and heavy gas) for particle identification of pions, kaons, and protons in high-rate environments.
• Uses an electromagnetic calorimeter and scintillator pad detectors for energy and timing measurements of photons and hadrons.
• Deploys a multi-gap resistive plate chamber (MRPC) system for precise timing and triggering in high-rate conditions.
• Applies advanced data acquisition and computing systems with real-time processing, machine learning, and unfolding techniques to handle high event rates and extract physics observables.

Experimental results

Research questions

• RQ1 What is the three-dimensional momentum-space structure of the nucleon, particularly the transversity and tensor charge distributions, as revealed by transverse-spin-dependent SIDIS?
• RQ2 What are the electroweak couplings of quarks to electrons, and can deviations from the Standard Model be observed in the asymmetry A^{e+e-} in deep inelastic scattering?
• RQ3 What is the role of the gluonic field in generating the proton mass, as probed by near-threshold J/ψ production?
• RQ4 How do parton distribution functions (PDFs) and generalized parton distributions (GPDs) evolve in coordinate and momentum space, and what is their role in nucleon spin and structure?
• RQ5 What is the isospin dependence of the EMC effect, and how does it vary with x and Q² in the high-x region?

Key findings

• SoLID enables a 1000-fold increase in figure-of-merit over existing facilities for high-x SIDIS, allowing precision extraction of transverse-momentum-dependent parton distributions (TMDs) in the valence quark region.
• The PVDIS program on deuterons can measure the electroweak coupling combination 2g_{AA}^{eu} - g_{AA}^{ed} with a precision that surpasses previous muon-beam experiments, reaching a target uncertainty of ~0.15 in the 20+ GeV upgrade scenario.
• Near-threshold J/ψ production measurements at SoLID will probe the gluonic gravitational form factor G_G(0) with a sensitivity of ~10% on the gluon contribution to the proton mass.
• The GPD program with deep exclusive meson production will access the 3D structure of the nucleon in coordinate and momentum space, with kinematic reach extending to x_Bj > 0.6, a region previously inaccessible at high luminosity.
• SoLID’s high-luminosity capability allows the first direct measurement of the d/u PDF ratio at x > 0.6, with statistical uncertainty below 1% for the first time.
• The instrument is designed to handle event rates exceeding 10⁷ Hz, with a data acquisition system capable of real-time event reconstruction and selection using AI/ML-based algorithms.