The EIC Comprehensive Chromodynamics Experiment (ECCE) detector has been designed to address the full scope of the proposed Electron Ion Collider (EIC) physics program as presented by the National Academy of Science and provide a deeper understanding of the quark-gluon structure of matter. To accomplish this, the ECCE detector offers nearly acceptance and energy coverage along with excellent tracking and particle identification. The ECCE detector was designed to be built within the budget envelope set out by the EIC project while simultaneously managing cost and schedule risks. This detector concept has been selected to be the basis for the EIC project detector.

We measure the spin-density matrix elements (SDMEs) of the Delta(++)(1232) in the photoproduction reaction gamma p -> pi(-) Delta(++)(1232) with the GlueX experiment in Hall D at Jefferson Lab. The measurement uses a linearly-polarized photon beam with energies from 8.2 to 8.8GeV and the statistical precision of the SDMEs exceeds the previous measurement by three orders of magnitude for the momentum transfer squared region below 1.4GeV(2). The data are sensitive to the previously undetermined relative sign between couplings in existing Regge-exchange models. Linear combinations of the extracted SDMEs allow for a decomposition into natural and unnatural-exchange amplitudes. We find that the unnatural exchange plays an important role in the low momentum transfer region.

The Electromagnetic Calorimeter (ECAL), consisting of 1,596 lead tungstate scintillating crystals, has been recently constructed and installed in Experimental Hall D at Jefferson Lab (JLab). The calorimeter is a key component of the JLab Eta Factory Experiment, whose main goal is to measure the decays of eta and eta ' mesons into multi-photon final states. The ECAL replaces the inner part of the former forward lead-glass calorimeter. Scintillation light from each crystal is detected using Hamamatsu R4125 photomultiplier tubes. Calorimeter modules were fabricated and tested in the lab using light from light-emitting diodes before being installed in the detector frame. The detector is currently undergoing commissioning using the light monitoring system and cosmic rays. We will present an overview of the fabrication and testing of the calorimeter modules, along with the first detector commissioning results. The ECAL was ready for data-taking in spring 2025.

We measure for the first time the differential photoproduction cross section dσ/dt of the a_2(1320) meson at an average photon beam energy of 8.5 GeV, using data with an integrated luminosity of 104 pb^-1 collected by the GlueX experiment. We fully reconstruct the γ p →ηπ^0 p reaction and perform a partial-wave analysis in the a_2(1320) mass region with amplitudes that incorporate the linear polarization of the beam. This allows us to separate for the first time the contributions of natural- and unnatural-parity exchanges. These measurements provide novel information about the photoproduction mechanism, which is critical for the search for spin-exotic states.

We have measured the flavor dependence of multiplicities for π+ and π− production in semi-inclusive deep-inelastic scattering (SIDIS) on proton and deuteron to explore a possible charge symmetry violation in fragmentation functions. The experiment used an electron beam with energies of 10.2 and 10.6 GeV at Jefferson Lab and the Hall-C spectrometers. The electron kinematics spanned the range 0.3<x<0.6, 2<Q2<5.5 GeV2, and 2.2<W<3.2 GeV. The pion fractional momentum range was 0.3<z<0.7, and the transverse momentum range was 0<pT<0.25 GeV/c. Assuming factorization and allowing for isospin breaking, the results can be described by two “favored” and two “unfavored” effective low pT fragmentation functions that are flavor-dependent. We find each pair converges to a common flavor-independent fragmentation function at the highest W, where factorization is most applicable.

High-performance scintillator materials are needed for particle identification and measurements of energy and momentum of electromagnetic particles in modern nuclear physics experiments. As an example, the US Electron-Ion Collider, a unique collider with diverse physics topics, requires electromagnetic calorimetry enabling high-quality electron identification and detection in the momentum range of 0.3 to tens of GeV. The highest resolution in electromagnetic calorimeters can be provided by homogeneous materials, e.g., lead tungstate crystals. Inorganic glass scintillators have been investigated as an attractive and cost-effective alternative to crystals, that is also easier and faster to manufacture in mass production. In this paper, we discuss progress in the fabrication and characterization of recent scintillating glass samples on both test bench and beam tests. The results are well-reproduced by simulation and are discussed in the context of the Electron-Ion Collider experimental requirements and bench-marked against lead tungstate crystals.

We report new pion electroproduction measurements in the Δ (1232) resonance, utilizing the SHMS - HMS magnetic spectrometers of Hall C at Jefferson Lab. The data focus on a region that exhibits a strong and rapidly changing interplay of the mesonic cloud and quark-gluon dynamics in the nucleon. The results are in reasonable agreement with models that employ pion cloud effects and chiral effective field theory calculations, but at the same time they suggest that an improvement is required to the theoretical calculations and provide valuable input that will allow their refinements. The data illustrate the potential of the magnetic spectrometers setup in Hall C towards the study the Δ (1232) resonance. These first reported results will be followed by a series of measurements in Hall C, that will expand the studies of the Δ (1232) resonance offering a high precision insight within a wide kinematic range from low to high momentum transfers.

Nucleon structure functions, as measured in lepton-nucleon scattering, have historically provided a critical observable in the study of partonic dynamics within the nucleon. However, at very large parton momenta it is both experimentally and theoretically challenging to extract parton distributions due to the probable onset of non-perturbative contributions and the unavailability of high precision data at critical kinematics. Extraction of the neutron structure and the d-quark distribution have been further challenging due to the necessity of applying nuclear corrections when utilizing scattering data from a deuteron target to extract free neutron structure. However, a program of experiments has been carried out recently at the energy-upgraded Jefferson Lab electron accelerator aimed at significantly reducing the nuclear correction uncertainties on the d-quark distribution function at large partonic momentum. This allows leveraging the vast body of deuterium data covering a large kinematic range to be utilized for d-quark parton distribution function extraction. We present new data from experiment E12-10-002 carried out in Jefferson Lab Hall C on the deuteron to proton cross-section ratio at large BJorken-x. These results significantly improve the precision of existing data, and provide a first look at the expected impact on quark distributions extracted from global parton distribution function fits.

This paper presents the design, performance, and results of radiation tests of an active base for a Hamamatsu 4125 photomultiplier tube. The active base was designed at Jefferson Lab and comprises a high voltage divider and an on-board amplifier. The photomultiplier with the active base is used to detect light from lead tungstate scintillating crystals of the forward electromagnetic calorimeter of the GlueX detector. The addition of the amplifier within the active base allows to operate the tube at lower high voltage, thereby limiting the photomultiplier anode current to a few microamperes even at a maximum counter rate of 1 MHz, while retaining the dynamic range of output signals. The performance of the active base and the calorimeter module assembly was studied using a bench test setup and a prototype positioned into a beam of photons. Measured key performance parameters such as linearity, high-rate capability, and the energy resolution verified that the active base design aligns with the detector specifications. Additionally, the resistance of the active base components to radiation was tested using a Caesium-137 source. Some damage observed during these tests required to make modifications to the original base design to improve its resilience.

The ECCE detector has been recommended as the selected reference detector for the future Electron-Ion Collider (EIC). A series of simulation studies have been carried out to validate the physics feasibility of the ECCE detector. In this paper, detailed studies of heavy flavor hadron and jet reconstruction and physics projections with the ECCE detector performance and different magnet options will be presented. The ECCE detector has enabled precise EIC heavy flavor hadron and jet measurements with a broad kinematic coverage. These proposed heavy flavor measurements will help systematically study the hadronization process in vacuum and nuclear medium especially in the underexplored kinematic region.

We report on the results of the first search for the production of axion-like particles (ALPs) via Primakoff production on nuclear targets, γA→aA, in the “SRC-CT” experiment using the GlueX detector at Jefferson Lab. This search uses an integrated luminosity of 100 pb⋅−1nucleon on a 12C target with a real photon beam of energies 6

The lead tungstate crystals are well-known radiator material for precise homogeneous electromagnetic calorimetry. In experimental nuclear physics, the typical way to read out the crystals is using conventional photomultiplier tubes (PMTs). If a magnetic field is present such a method has complications and requires a passive PMT shielding design. However, in the case of a strong field use of a PMT is almost impossible. The recent development of Silicon Photomultipliers (SiPMs) with small pixel pitch sizes and relatively small noise levels presents an alternative to conventional PMTs. The SiPM-based readout is currently considered for the instrumentation of lead tungstate calorimeters for future nuclear physics and collider experiments. We present the beam test results of a 3x3 calorimeter prototype instrumented with SiPM readout performed at Jefferson Lab. The SiPM readout performance was compared with the PMT readout measured in the same experimental conditions. The prototype was successfully tested using a beam of photons in the energy range between (2.5--11.5) GeV in experimental Hall D. The detector performance was also studied using a secondary beam of positrons provided by the Hall D pair spectrometer.

The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in B10 and B11. Previous measurements of the EMC effect in A≤12 nuclei showed an unexpected nuclear dependence; B10 and B11 were measured to explore the EMC effect in this region in more detail. Results are presented for Be9, B10, B11, and C12 at an incident beam energy of 10.6 GeV. The EMC effect in the boron isotopes was found to be similar to that for Be9 and C12, yielding almost no nuclear dependence in the EMC effect in the range A=4–12. This represents important new data supporting the hypothesis that the EMC effect depends primarily on the local nuclear environment due to the cluster structure of these nuclei.Received 8 July 2022Revised 21 April 2023Accepted 17 July 2023DOI:https://doi.org/10.1103/PhysRevC.108.035201©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLepton induced nuclear reactionsQCD in nuclear reactionsProperties6 ≤ A ≤ 19TechniquesParticle sources & targetsSpectrometers & spectroscopic techniquesNuclear Physics

The evaluation of the measurement of double-spin asymmetries for charge-separated pions and kaons produced in deep-inelastic scattering from the proton using the ECCE detector design concept is presented, for the combinations of lepton and hadron beam energies of 5 x 41 GeV2 and 18 x 275 GeV2. The study uses unpolarised simulated data that are processed through a full GEANT simulation of the detector. These data are then reweighted at the parton level with DSSV helicity distributions and DSS fragmentation functions, in order to generate the relevant asymmetries, and subsequently analysed. The performed analysis shows that the ECCE detector concept provides the resolution and acceptance, with a broad coverage in kinematic phase space, needed for a robust extraction of asymmetries. This, in turn, allows for a precise extraction of sea-quark helicity distributions.

Exclusive heavy quarkonium photoproduction is one of the most popular processes in EIC, which has a large cross section and a simple final state. Due to the gluonic nature of the exchange Pomeron, this process can be related to the gluon distributions in the nucleus. The momentum transfer dependence of this process is sensitive to the interaction sites, which provides a powerful tool to probe the spatial distribution of gluons in the nucleus. Recently the problem of the origin of hadron mass has received lots of attention in determining the anomaly contribution $M_{a}$. The trace anomaly is sensitive to the gluon condensate, and exclusive production of quarkonia such as J/$ψ$ and $Υ$ can serve as a sensitive probe to constrain it. In this paper, we present the performance of the ECCE detector for exclusive J/$ψ$ detection and the capability of this process to investigate the above physics opportunities with ECCE.

Quasi-elastic scattering on $^{12}$C$(e,e'p)$ was measured in Hall C at Jefferson Lab for space-like 4-momentum transfer squared $Q^2$ in the range of 8--14.2\,(GeV/$c$)$^2$ with proton momenta up to 8.3\,GeV/$c$. The experiment was carried out in the upgraded Hall C at Jefferson Lab. It used the existing high momentum spectrometer and the new super high momentum spectrometer to detect the scattered electrons and protons in coincidence. The nuclear transparency was extracted as the ratio of the measured yield to the yield calculated in the plane wave impulse approximation. Additionally, the transparency of the $1s_{1/2}$ and $1p_{3/2}$ shell protons in $^{12}$C was extracted, and the asymmetry of the missing momentum distribution was examined for hints of the quantum chromodynamics prediction of Color Transparency. All of these results were found to be consistent with traditional nuclear physics and inconsistent with the onset of Color Transparency.

The Electron-Ion Collider (EIC) is a cutting-edge accelerator facility that will study the nature of the "glue" that binds the building blocks of the visible matter in the universe. The proposed experiment will be realized at Brookhaven National Laboratory in approximately 10 years from now, with detector design and R D currently ongoing. Notably, EIC is one of the first large-scale facilities to leverage Artificial Intelligence (AI) already starting from the design and R D phases. The EIC Comprehensive Chromodynamics Experiment (ECCE) is a consortium that proposed a detector design based on a 1.5T solenoid. The EIC detector proposal review concluded that the ECCE design will serve as the reference design for an EIC detector. Herein we describe a comprehensive optimization of the ECCE tracker using AI. The work required a complex parametrization of the simulated detector system. Our approach dealt with an optimization problem in a multidimensional design space driven by multiple objectives that encode the detector performance, while satisfying several mechanical constraints. We describe our strategy and show results obtained for the ECCE tracking system. The AI-assisted design is agnostic to the simulation framework and can be extended to other sub-detectors or to a system of sub-detectors to further optimize the performance of the EIC detector.

The recently approved Electron-Ion Collider (EIC) will provide a unique new opportunity for searches of charged lepton flavor violation (CLFV) and other new physics scenarios. In contrast to the $e \leftrightarrow \mu$ CLFV transition for which very stringent limits exist, there is still a relatively large discovery space for the $e \to \tau$ CLFV transition, potentially to be explored by the EIC. With the latest detector design of ECCE (EIC Comprehensive Chromodynamics Experiment) and projected integral luminosity of the EIC, we find the $\tau$-leptons created in the DIS process $ep\to \tau X$ are expected to be identified with high efficiency. A first ECCE simulation study, restricted to the 3-prong $\tau$-decay mode and with limited statistics for the Standard Model backgrounds, estimates that the EIC will be able to improve the current exclusion limit on $e\to \tau$ CLFV by an order of magnitude.

We are presenting a new readout circuit developed for the PbWO4 scintillation detectors for the Electron Ion Collider (EIC) EEEMCAL. The design is centered around a 4 x 4 matrix of fast silicon photomultiplier (SiPM) sensors which are directly coupled to a preamplification stage, and which cover an area of 20 mm x 20 mm. The architecture allows for a small footprint where the signal extraction, summation and amplification are performed in addition to the SiPM bias supply and a gain and offset adjustment circuit with settings saved in local memory. The SiPM overvoltage is temperature compensated to provide additional gain stability to the unit. Adjustments to gain and offset are done remotely through a communication port. The design was optimized for spectral resolution, fast response and large dynamic range with a small footprint and low energy consumption/heat dissipation that does not require active cooling for stable operation. These features are very important for future implementation at EIC where thousands of modules will be assembled in a compact manner for the Electron Endcap Electromagnetic Calorimeter. In addition, this readout development presents many features and performance capabilities that make it an excellent choice for scintillation detectors in other research and industrial applications. The signal output can be adjusted for negative amplitude with 0V baseline like that of a PMT to mate to existing pulse acquisition infrastructure. A detector prototype was constructed with a 3x3 array of 20 mm x 20 mm x 200 mm PbWO4 crystals coupled to individual sensor arrays and readouts. The detector was tested at the Thomas Jefferson National Accelerator Facility with 5GeV positrons. We will present the results of these detector characterization measurements.

Quasielastic scattering on 12C(e, e'p) was measured in Hall C at Jefferson Lab for spacelike four-momentum transfer squared Q2 in the range of 8-14.2 (GeV/c)2 with proton momenta up to 8.3 GeV/c. The experiment was carried out in the upgraded Hall C at Jefferson Lab. It used the existing high-momentum spectrometer and the new super-high-momentum spectrometer to detect the scattered electrons and protons in coincidence. The nuclear transparency was extracted as the ratio of the measured yield to the yield calculated in the plane wave impulse approximation. Additionally, the transparency of the 1s1/2 and 1p3/2 shell protons in 12C was extracted, and the asymmetry of the missing momentum distribution was examined for hints of the quantum chromodynamics prediction of color transparency. All of these results were found to be consistent with traditional nuclear physics and inconsistent with the onset of color transparency.