We present the results of an extensive evaluation of strip and pixel AC-LGAD sensors tested with a 120 GeV proton beam, focusing on the influence of design parameters on the sensor temporal and spatial resolutions. Results show that reducing the thickness of pixel sensors significantly enhances their time resolution, with 20 mu m-thick sensors achieving around 20 ps. Uniform performance is attainable with optimized n+ sheet resistance, making these sensors ideal for future timing detectors. Conversely, 20-mu m-thick strip sensors exhibit higher jitter than similar pixel sensors, negatively impacting time resolution, despite reduced Landau fluctuations with respect to the 50-mu m-thick versions. Additionally, it is observed that a low resistivity in strip sensors limits signal size and time resolution, whereas higher resistivity improves performance. This study highlights the importance of tuning the n+ sheet resistance and suggests that further improvements should target specific applications like the Electron-Ion Collider or other future collider experiments. In addition, the detailed performance of four AC-LGADs sensor designs is reported as examples of possible candidates for specific detector applications. These advancements position AC-LGADs as promising candidates for future 4D tracking systems, pending the development of specialized readout electronics.

We present the design of the COmpact Network of Detectors with Orbital Range (CONDOR), a proposed high-altitude gamma-ray and cosmic-ray (CR) observatory set to become the highest of its kind. Planned for installation at Cerro Toco in the Atacama Desert, Chile, at 5300 meters above sea level (m.a.s.l.), CONDOR is optimized to operate in the 100 GeV to 1 TeV range using the extensive air-shower technique. The design prioritizes simplicity, modularity, and robustness to ensure reliable performance in a harsh environment. The CONDOR array has a fill factor of 90% and consists of 6000 plastic scintillator panels, each approximately 1 m2, read out by wavelength-shifting fibers and SiPMs. The readout electronics are based on flash ADCs, with White Rabbit technology ensuring time synchronization. We present an analysis of angular reconstruction and particle discrimination using CORSIKA-simulated CR showers, developing methods to reconstruct incident angles and distinguish between gamma-ray and proton CR events. CONDOR's exceptional altitude and compact design enable it to meet the target 100 GeV threshold, complementing other ground-based observatories and overlapping with satellite detection ranges. CONDOR has the potential to support an extensive research program in astroparticle physics and multimessenger astronomy from the Southern Hemisphere, operating in all-sky mode 24/7.

Measuring deeply virtual Compton scattering (DVCS) on the neutron is one of the necessary steps to understand the structure of the nucleon in terms of generalized parton distributions (GPDs). Neutron targets play a complementary role to transversely polarized proton targets in the determination of the GPD E. This poorly known and poorly constrained GPD is essential to obtain the contribution of the quarks' angular momentum to the spin of the nucleon. DVCS on the neutron was measured for the first time selecting the exclusive final state by detecting the neutron, using the Jefferson Lab longitudinally polarized electron beam, with energies up to 10.6 GeV, and the CLAS12 detector. The extracted beam-spin asymmetries, combined with DVCS observables measured on the proton, allow a clean quark-flavor separation of the imaginary parts of the Compton form factors H and E.

A liquid piston system (LP) is proposed to recover energy during the discharge of a liquid air energy storage (LAES) plant. The traditionally used air turbine is replaced with an LP system which will expand the evaporated air to generate power. Moreover, an NH3 and transcritical CO2 cycle are integrated to enhance heat and cold utilisation. The integrated LAES system was modelled using gPROMS. The numerical results have a maximum discrepancy of less than 6.4% from experimental data previously reported in the literature. The round-trip efficiency (RTE) was studied for various scenarios, including the sensitivity to thermal oil flow rate and heat exchanger efficiencies. Additionally, the study examined the influence of several LP configurations and concluded with a comparison to a conventional LAES system. With a liquefaction pressure of 40 bar, the highest RTE reached was 37%, surpassing the conventional LAES system’s 25% RTE at a discharge pressure of 25 bar. The heat utilisation was 96%, which doubles that of the conventional LAES system, while the cold utilisation was enhanced by 10%. Furthermore, the LP, NH3, and CO2 cycles thermal efficiencies were 88%, 19%, and 30%, respectively. A detailed energy assessment for heat and cold utilisation is presented.

Background In support of UCB pharmaceutical research programs, the aim of this research was to implement a novel process for patient involvement in a multidisciplinary research group to co-create a clinical outcome assessment strategy to accurately reflect the experience of people living with early-stage Parkinson’s. Patient experts were an integral part of the decision-making process for patient-reported outcome (PRO) research and instrument development. Methods In partnership with two patient organizations (Parkinson’s UK and the Parkinson’s Foundation), 6 patient experts were recruited into a multidisciplinary research group alongside clinical, patient engagement and involvement, regulatory science, and outcome measurement experts. The group was involved across two phases of research; the first phase identified what symptoms are cardinal to the experience of living with early-stage Parkinson’s and the second phase involved the development of PRO instruments to better assess the symptoms that are important to people living with early-stage Parkinson’s. Patient experts were important in performing a variety of roles, in particular, qualitative study protocol design, conceptual model development, and subsequent co-creation of two PRO instruments. Results Involving people with Parkinson’s in PRO research ensured that the expertise of these representatives from the Parkinson’s community shaped and drove the research; as such, PRO instruments were being developed with the patient at the forefront. Working with patient experts required considerable resource and time allocation for planning, communication, document development, and organizing meetings; however, their input enriched the development of PRO instruments and was vital in developing PRO instruments that are more meaningful for people with Parkinson’s and clinicians. Conclusions Conducting PRO research, in the context of clinical development involving pharmaceutical companies, requires balancing regulatory and scientific rigor with tight time constraints. Incorporating a multi-stakeholder perspective, which included patient experts as joint investigators, had a strong positive impact on our research, despite the logistical complexities of their involvement. Due to the input of patient experts, the innovative clinical outcome assessment strategy and the co-created novel PRO instruments were more relevant and holistic to the patient experience of early-stage Parkinson’s. Graphical abstract

This document presents the initial scientific case for upgrading the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) to 22 GeV. It is the result of a community effort, incorporating insights from a series of workshops conducted between March 2022 and April 2023. With a track record of over 25 years in delivering the world's most intense and precise multi-GeV electron beams, CEBAF's potential for a higher energy upgrade presents a unique opportunity for an innovative nuclear physics program, which seamlessly integrates a rich historical background with a promising future. The proposed physics program encompass a diverse range of investigations centered around the nonperturbative dynamics inherent in hadron structure and the exploration of strongly interacting systems. It builds upon the exceptional capabilities of CEBAF in high-luminosity operations, the availability of existing or planned Hall equipment, and recent advancements in accelerator technology. The proposed program cover various scientific topics, including Hadron Spectroscopy, Partonic Structure and Spin, Hadronization and Transverse Momentum, Spatial Structure, Mechanical Properties, Form Factors and Emergent Hadron Mass, Hadron-Quark Transition, and Nuclear Dynamics at Extreme Conditions, as well as QCD Confinement and Fundamental Symmetries. Each topic highlights the key measurements achievable at a 22 GeV CEBAF accelerator. Furthermore, this document outlines the significant physics outcomes and unique aspects of these programs that distinguish them from other existing or planned facilities. In summary, this document provides an exciting rationale for the energy upgrade of CEBAF to 22 GeV, outlining the transformative scientific potential that lies within reach, and the remarkable opportunities it offers for advancing our understanding of hadron physics and related fundamental phenomena.

The new experimental measurements of beam spin asymmetry were performed for the deeply virtual exclusive π0 production in a wide kinematic region with the photon virtualities Q2 up to 6.6 GeV2 and the Bjorken scaling variable xB in the valence regime. The data were collected by the CEBAF Large Acceptance Spectrometer (CLAS12) at Jefferson Lab with longitudinally polarized 10.6 GeV electrons scattered on an unpolarized liquid-hydrogen target. Sizable asymmetry values indicate a substantial contribution from transverse virtual photon amplitudes to the polarized structure functions. The interpretation of these measurements in terms of the Generalized Parton Distributions (GPDs) demonstrates their sensitivity to the chiral-odd GPD E¯T, which contains information on quark transverse spin densities in unpolarized and polarized nucleons and provides access to the nucleon's transverse anomalous magnetic moment. Additionally, the data were compared to a theoretical model based on a Regge formalism that was extended to the high photon virtualities.

Hadronization, which is the process by which an energetic colored quark evolves into a color-singlet hadron in Quantum Chromodynamics, can be studied both in small nuclei and large nuclei, and the comparison of the differences between those two systems provides information about the hadronization mechanisms on femtometer distance scales. It can be argued that this process is well understood for light meson production on nuclei, but data from HERMES and CLAS for baryon production present puzzling patterns that are not well described by models. Herein we suggest that this might be due to the presence of diquarks in the protons and neutrons making up these nuclei.

A simple, scalable, and efficient method is proposed to extract energy from a pressurised gas flow to generate electrical power. The proposed liquid piston system is fed continuously with air into the piston chamber, which is filled with water. The water is driven by the gas’s expansion, and their interaction enables an isothermal expansion. A dynamic model was developed in gPROMS and validated against 300 W and 4 kW experimental data. The accuracy of the power output predictions has a maximum discrepancy of less than 6.4% from the experimental values. Subsequently, a sensitivity analysis and optimisation using the height to diameter piston geometry ratio was performed to study the variation in the thermal efficiency. The simulations were performed for energy systems from 300 kW to 100 MW and for several intake gas temperatures. The study shows that lower piston geometry ratios of 4 are preferred for 300 kW and 1 MW case studies. Because of reduced heat transfer between water and air, these systems reach 92.5% thermal efficiency. Moreover, the predicted thermal efficiencies for high power ratings were as high as 82%. The power output values obtained were constant in time. Finally, an energy and exergy assessment and worst-case scenario with decreased turbo machinery efficiency are presented. The proposed method matches the specific power of traditional power cycles and has potential uses for energy recovery in cryogenic plants.

We report the first measurements of deep inelastic scattering spin-dependent azimuthal asymmetries in back-to-back dihadron electroproduction in the deep inelastic scattering process. In this reaction, two hadrons are produced in opposite hemispheres along the z axis in the virtual photon-target nucleon center-of-mass frame, with the first hadron produced in the current-fragmentation region and the second in the target-fragmentation region. The data were taken with longitudinally polarized electron beams of 10.2 and 10.6 GeV incident on an unpolarized liquid-hydrogen target using the CLAS12 spectrometer at Jefferson Lab. Observed nonzero sinΔϕ modulations in ep→e^{'}pπ^{+}X events, where Δϕ is the difference of the azimuthal angles of the proton and pion in the virtual photon and target nucleon center-of-mass frame, indicate that correlations between the spin and transverse momenta of hadrons produced in the target- and current-fragmentation regions may be significant. The measured beam-spin asymmetries provide a first access in dihadron production to a previously unexplored leading-twist spin- and transverse-momentum-dependent fracture function. The fracture functions describe the hadronization of the target remnant after the hard scattering of a virtual photon off a quark in the target particle and provide a new avenue for studying nucleonic structure and hadronization.

AC-LGADs, also referred to as resistive silicon detectors, are a recent development of low-gain avalanche detectors (LGADs), based on a sensor design where the multiplication layer and n+ contact are continuous, and only the metal layer is patterned. In AC-LGADs, the signal is capacitively coupled from the continuous, resistive n+ layer over a dielectric to the metal electrodes. Therefore, the spatial resolution is not only influenced by the electrode pitch, but also the relative size of the metal electrodes. Signal propagation between the metallized areas and charge sharing between electrodes plays a larger role in these detectors than in conventional silicon sensors read out in DC mode. AC-LGADs from two manufacturers were studied in beam tests and with infrared laser scans. The impact of n+ layer resistivity and metal electrode pitch on the charge sharing and achievable position resolution is shown. For strips with 100 μm pitch, a resolution of ¡ 5 μm can be reached. The charge sharing between neighboring strips is investigated in more detail, indicating the induction of signal charge and subsequent re-sharing over the n+ layer. Furthermore, an approach to identify signal sharing over large distances is presented.

We present the first beam test results with centimeter-scale AC-LGAD strip sensors, using the Fermilab Test Beam Facility and sensors manufactured by the Brookhaven National Laboratory. Sensors of this type are envisioned for applications that require large-area precision 4D tracking coverage with economical channel counts, including timing layers for the Electron Ion Collider (EIC), and space-based particle experiments. A survey of sensor designs is presented, with the aim of optimizing the electrode geometry for spatial resolution and timing performance. Several design considerations are discussed towards maintaining desirable signal characteristics with increasingly larger electrodes. The resolutions obtained with several prototypes are presented, reaching simultaneous 18 micron and 32 ps resolutions from strips of 1 cm length and 500 micron pitch. With only slight modifications, these sensors would be ideal candidates for a 4D timing layer at the EIC.

The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized 8.5 GeV photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson rho(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. We confirm a high degree of s-channel helicity conservation at small squared four-momentum transfer t and are able to extract the t dependence of natural and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full t range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced rho(770) differ by two units are negligible for -t < 0.5 GeV2/c(2).