Probing High-Momentum Protons and Neutrons in Neutron-Rich Nuclei

The atomic nucleus is one of the densest and most complex quantum-mechanical systems in nature. Nuclei account for nearly all the mass of the visible Universe. The properties of individual nucleons (protons and neutrons) in nuclei can be probed by scattering a high-energy particle from the nucleus and detecting this particle after it scatters, often also detecting an additional knocked-out proton. Analysis of electron- and proton-scattering experiments suggests that some nucleons in nuclei form close-proximity neutron–proton pairs with high nucleon momentum, greater than the nuclear Fermi momentum. However, how excess neutrons in neutron-rich nuclei form such close-proximity pairs remains unclear. In this study we measure protons and, for the first time, neutrons knocked out of medium-to-heavy nuclei by high-energy electrons and show that the fraction of high-momentum protons increases markedly with the neutron excess in the nucleus, whereas the fraction of high-momentum neutrons decreases slightly. This effect is surprising because in the classical nuclear shell model, protons and neutrons obey Fermi statistics, have little correlation and mostly fill independent energy shells. These high-momentum nucleons in neutron-rich nuclei are important for understanding nuclear parton distribution functions (the partial momentum distribution of the constituents of the nucleon) and changes in the quark distributions of nucleons bound in nuclei (the EMC effect). They are also relevant for the interpretation of neutrino-oscillation measurements and understanding of neutron-rich systems such as neutron stars

First Measurement of the EMC Effect in 10^{10}B and 11^{11}B

The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in $^{10}$B and $^{11}$B. Previous measurements of the EMC effect in $A \leq 12$ nuclei showed an unexpected nuclear dependence; $^{10}$B and $^{11}$B were measured to explore the EMC effect in this region in more detail. Results are presented for $^9$Be, $^{10}$B, $^{11}$B, and $^{12}$C at an incident beam energy of 10.6~GeV. The EMC effect in the boron isotopes was found to be similar to that for $^9$Be and $^{12}$C, 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.Comment: Submitted to PR

Probing high-momentum protons and neutrons in neutron-rich nuclei

The atomic nucleus is one of the densest and most complex quantum-mechanical systems in nature. Nuclei account for nearly all the mass of the visible Universe. The properties of individual nucleons (protons and neutrons) in nuclei can be probed by scattering a high-energy particle from the nucleus and detecting this particle after it scatters, often also detecting an additional knocked-out proton. Analysis of electron- and proton-scattering experiments suggests that some nucleons in nuclei form close-proximity neutron-proton pairs1-12 with high nucleon momentum, greater than the nuclear Fermi momentum. However, how excess neutrons in neutron-rich nuclei form such close-proximity pairs remains unclear. Here we measure protons and, for the first time, neutrons knocked out of medium-to-heavy nuclei by high-energy electrons and show that the fraction of high-momentum protons increases markedly with the neutron excess in the nucleus, whereas the fraction of high-momentum neutrons decreases slightly. This effect is surprising because in the classical nuclear shell model, protons and neutrons obey Fermi statistics, have little correlation and mostly fill independent energy shells. These high-momentum nucleons in neutron-rich nuclei are important for understanding nuclear parton distribution functions (the partial momentum distribution of the constituents of the nucleon) and changes in the quark distributions of nucleons bound in nuclei (the EMC effect)1,13,14. They are also relevant for the interpretation of neutrino-oscillation measurements15 and understanding of neutron-rich systems such as neutron stars3,16

Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab

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.Comment: Updates to the list of authors; Preprint number changed from theory to experiment; Updates to sections 4 and 6, including additional figure

The present and future of QCD

This White Paper presents an overview of the current status and future perspective of QCD research, based on the community inputs and scientific conclusions from the 2022 Hot and Cold QCD Town Meeting. We present the progress made in the last decade toward a deep understanding of both the fundamental structure of the sub-atomic matter of nucleon and nucleus in cold QCD, and the hot QCD matter in heavy ion collisions. We identify key questions of QCD research and plausible paths to obtaining answers to those questions in the near future, hence defining priorities of our research over the coming decades

The present and future of QCD

This White Paper presents an overview of the current status and future perspective of QCD research, based on the community inputs and scientific conclusions from the 2022 Hot and Cold QCD Town Meeting. We present the progress made in the last decade toward a deep understanding of both the fundamental structure of the sub-atomic matter of nucleon and nucleus in cold QCD, and the hot QCD matter in heavy ion collisions. We identify key questions of QCD research and plausible paths to obtaining answers to those questions in the near future, hence defining priorities of our research over the coming decades

Optimal operation of distributed energy storage systems to improve distribution network loand and generational hosting capablilty

This paper proposes a strategy for optimal integration of battery energy storage systems (BESSs) to improve the load and DG hosting ability of the utility grid. An effective tool that determines the optimal location, capacity and day-ahead operation strategy for deployment of distribution network operator (DNO) owned and controlled BESSs is presented. It is a cost based multi-objective optimization strategy that considers two primary factors; distribution system cost and battery linear cycling cost. Quantitative analyses on the benefits and trade-offs of BESS installations and management are carried out considering different service options. The performance of the proposed multi-objective control is also compared with single-objective optimization strategies that target the exclusive control of voltage regulation, loss reduction or demand curtailment and peak reduction. Results show optimal integration of BESS can realize maximum operational and cost benefits while effectively elevating the load and distributed generation (DG) hosting capability of the network. The single- and multi-objective control methods are developed using a predictive optimization approach using an improved interior-point algorithm. Simulations are conducted for an LV distribution network in Western Australia studied during the Perth Solar city Trial

A Rapid and Satisfactory Outcome with Combined Immunosuppressive Therapy in Acquired Haemophilia A with Underlying Tuberculosis

Acquired haemophilia A (AHA) is a rare disorder with an incidence of 1.5 cases per million per year in the United Kingdom. The incidence could be underestimated due to difficulty in diagnosis and also due to the fact that people with low titre inhibitor levels are asymptomatic. It is usually a disease affecting elderly but a disease peak in the younger population is known. The common underlying diseases are autoimmune disorders, malignancies, infections, and drugs. However, approximately 50% of the cases do not have a specific aetiology and about 10% will not have bleeding manifestations. Therefore, an isolated prolongation of APTT should be evaluated, especially prior to any haemostatic challenges. We report a case of a middle-aged man who presented with bleeding due to AHA associated with high inhibitory titres and active pulmonary tuberculosis. He was treated with both antituberculous and combined-aggressive immunosuppressive therapy which resulted in satisfactory disease remission

First Measurement of the EMC effect in ¹⁰B and ¹¹B

The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in 10B and 11B. Previous measurements of the EMC effect in A ≤ 12 nuclei showed an unexpected nuclear dependence; 10B and 11B were measured to explore the EMC effect in this region in more detail. Results are presented for 9Be, 10B, 11B, and 12C at an incident beam energy of 10.6 GeV. The EMC effect in the boron isotopes was found to be similar to that for 9Be and 12C, 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