Kent Paschke

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 aim of this study was to retire the risk of maintaining the integrity of S2-glass reinforced CTD-403 (a cyanate ester resin) that is exposed to radiation and elevated temperature over the life of the MOLLER experiment in experimental Hall A at Jefferson Lab. In this paper, the shear strength and flexural modulus of irradiated S2-glass reinforced CTD-403 specimens were measured at 65 °C (the magnets are to operate at less than 65 °C) under two scenarios: vacuum and gaseous nitrogen. The testing method is the Short-Beam Shear (SBS) test according to ASTM D2344. The specimens were exposed to neutrons and gamma-rays up to 124 MGy. The results show that specimens have excellent resistance against radiation, only 23% degradation of apparent shear strength with 124 MGy at 65 °C under vacuum. At the highest dose areas of the coils tungsten plates are used to reduce the radiation dose to the resin …

We report a high precision measurement of electron beam polarization using Compton polarimetry. The measurement was made in experimental Hall A at Jefferson Lab during the CREX experiment in 2020. A total uncertainty of d P/P= 0.36% was achieved detecting the back-scattered photons from the Compton scattering process. This is the highest accuracy in a measurement of electron beam polarization using Compton scattering ever reported, surpassing the groundbreaking measurement from the SLD Compton polarimeter. Such uncertainty reaches the level required for the future flagship measurements to be made by the MOLLER and SoLID experiments.

The PREX-2 and CREX experiments in Hall A at Jefferson Lab are precision measurements of parity violating elastic electron scattering from complex nuclei. One requirement was that the incident electron beam polarization, typically≈ 90%, be known with 1% precision. We commissioned and operated a Møller polarimeter on the beam line that exceeds this requirement, achieving a precision of 0.89% for PREX-2, and 0.85% for CREX. The uncertainty is purely systematic, accumulated from several different sources, but dominated by our knowledge of the target polarization. Our analysis also demonstrates the need for accurate atomic wave functions in order to correct for the Levchuk Effect. We describe the details of the polarimeter operation and analysis, as well as (for CREX) a comparison to results from a different polarimeter based on Compton scattering.

We are writing this letter to express our interest in pursuing an experiment at Fermilab to searchfor neutrinoless conversion of muons into electrons in the field of a nucleus, which is a leptonflavor-violating (LFV) reaction. The sensitivity goal of this experiment represents animprovement of more than a factor of 10,000 over existing limits. It would provide the mostsensitive test of LFV, a unique and essential window on new physics unavailable at the highenergy frontier. We present a conceptual scheme that would exploit the existing FermilabAccumulator and Debuncher rings to generate the required characteristics of the primary protonbeam. The proposal requires only modest modifications to the accelerator complex beyond thosealready planned for the NOvA experiment, with which this experiment would be fully compatible;however, it could also benefit significantly from possible upgrades such as the "Project X" linac.We include the conceptual design of the muon beam and the experimental apparatus, which usethe previously proposed MECO experiment as a starting point.

III. Progress since the last Long Range Plan 9 A. Searches for neutrinoless double beta decay 9 B. Searches for electric dipole moments 11 C. Parity-violating electron scattering 12 D. Precision beta decay with nuclei 12 E. Precision beta decay with neutrons 12 F. Precision Measurements with muons and mesons 13 G. Hadronic Parity and Time-Reversal Violation 13 H. Searches for neutron oscillations 13 I. Neutrino mass and sterile neutrinos 14 J. Neutrino interactions 14 K. Neutrinos in astrophysics and cosmology 14 L. Other precision measurements 15

It is currently understood that there are four fundamental forces in nature: gravitational, electromagnetic, weak and strong forces. The strong force governs the interactions between quarks and gluons, elementary particles whose interactions give rise to the vast majority of visible mass in the universe. The mathematical description of the strong force is provided by the non-Abelian gauge theory Quantum Chromodynamics (QCD). While QCD is an exquisite theory, constructing the nucleons and nuclei from quarks, and furthermore explaining the behavior of quarks and gluons at all energies, remain to be complex and challenging problems. Such challenges, along with the desire to understand all visible matter at the most fundamental level, position the study of QCD as a central thrust of research in nuclear science. Experimental insight into the strong force can be gained using large particle accelerator facilities, which are necessary to probe the very short distance scales over which quarks and gluons interact. The Long Range Plans (LRPs) exercise of 1989 and 1996 led directly to the construction of two world-class facilities: the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) that is focused on studying how the structure of hadrons emerges from QCD (cold QCD research), and the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab (BNL) that aims at the discovery and study of a new state of matter, the quark-gluon plasma (QGP), at extremely high temperatures (hot QCD research). The different collision systems used to access the incredibly rich field of hot and cold QCD in the laboratory are illustrated …

The proposed energy upgrade to the CEBAF accelerator at the Thomas Jefferson National Accelerator Facility would enable the only facility worldwide, planned or foreseen, that can address the complexity at the scientific frontier of emergent hadron structure with its high luminosity and probing precision at the hadronic scale. While high-energy facilities will illuminate the perturbative dynamics and discover the fundamental role of gluons in nucleons and nuclei, a medium energy electron accelerator at the luminosity frontier will be critical to understand the rich and extraordinary variety of non-perturbative effects manifested in hadronic structure.

It is currently understood that there are four fundamental forces in nature: gravitational, electromagnetic, weak and strong forces. The strong force governs the interactions between quarks and gluons, elementary particles whose interactions give rise to the vast majority of visible mass in the universe. The mathematical description of the strong force is provided by the non-Abelian gauge theory Quantum Chromodynamics (QCD). While QCD is an exquisite theory, constructing the nucleons and nuclei from quarks, and furthermore explaining the behavior of quarks and gluons at all energies, remain to be complex and challenging problems. Such challenges, along with the desire to understand all visible matter at the most fundamental level, position the study of QCD as a central thrust of research in nuclear science. Experimental insight into the strong force can be gained using large particle accelerator facilities, which are necessary to probe the very short distance scales over which quarks and gluons interact. The Long Range Plans (LRPs) exercise of 1989 and 1996 led directly to the construction of two world-class facilities: the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) that is focused on studying how the structure of hadrons emerges from QCD (cold QCD research), and the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab (BNL) that aims at the discovery and study of a new state of matter, the quark-gluon plasma (QGP), at extremely high temperatures (hot QCD research). These past investments have produced major advances. Nucleons and nuclei are being studied with increasing precision …

Parity-violating electron-scattering experiments represent an important focus of the nuclear physics experimental program at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. These experiments pose significant challenges because the scattering asymmetries can be very small, of the order parts-per-million and smaller. To succeed, the properties of the electron beam such as current, position, size and energy, must be very nearly identical in the two electron-polarization spin states (parallel and anti-parallel relative to the direction of beam motion at the scattering target). This paper describes the origins of unwanted helicity-correlated beam asymmetries present on the electron beam and methods to minimize them to acceptable levels.

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 …

The PREX-2 and CREX experiments in Hall A at Jefferson Lab are precision measurements of parity violating elastic electron scattering from complex nuclei. One requirement was that the incident electron beam polarization, typically 90\%, be known with 1\% precision. We commissioned and operated a M{\o}ller polarimeter on the beam line that exceeds this requirement, achieving a precision of 0.89\% for PREX-2, and 0.85\% for CREX. The uncertainty is purely systematic, accumulated from several different sources, but dominated by our knowledge of the target polarization. Our analysis also demonstrates the need for accurate atomic wave functions in order to correct for the Levchuk Effect. We describe the details of the polarimeter operation and analysis, as well as (for CREX) a comparison to results from a different polarimeter based on Compton scattering.

The Møller polarimeter in Hall A at Jefferson Lab in Newport News, VA, has provided reliable measurements of electron beam polarization for the past two decades. Past experiments have typically required polarimetry at the 1% level of absolute uncertainty which the Møller polarimeter has delivered. However, the upcoming proposed experimental program including MOLLER and SoLID have stringent requirements on beam polarimetry precision at the level of 0.4%(The MOLLER Collaboration, 2014; The SoLID collaboration, 2019), requiring a systematic re-examination of all the contributing uncertainties. Møller polarimetry uses the double polarized scattering asymmetry of a polarized electron beam on a target with polarized atomic electrons. The target is a ferromagnetic material magnetized to align the spins in a given direction. In Hall A, the target is a pure iron foil aligned perpendicular to the beam and …

We report precision determinations of the beam-normal single spin asymmetries (A n) in the elastic scattering of 0.95 and 2.18 GeV electrons off C 12, Ca 40, Ca 48, and Pb 208 at very forward angles where the most detailed theoretical calculations have been performed. The first measurements of A n for Ca 40 and Ca 48 are found to be similar to that of C 12, consistent with expectations and thus demonstrating the validity of theoretical calculations for nuclei with Z≤ 20. We also report A n for Pb 208 at two new momentum transfers (Q 2) extending the previous measurement. Our new data confirm the surprising result previously reported, with all three data points showing significant disagreement with the results from the Z≤ 20 nuclei. These data confirm our basic understanding of the underlying dynamics that govern A n for nuclei containing≲ 50 nucleons, but point to the need for further investigation to understand …

ATHENA detector proposal — a totally hermetic electron nucleus apparatus proposed for IP6 at the Electron-Ion Collider - IOPscience This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy. Close this notification Skip to content IOP Science home Accessibility Help Search Journals Journals list Browse more than 100 science journal titles Subject collections Read the very best research published in IOP journals Publishing partners Partner organisations and publications Open access IOP Publishing open access policy guide IOP Conference Series Read open access proceedings from science conferences worldwide Books Publishing Support Login IOPscience login / Sign Up Click here to close this panel. Search Primary search Search all IOPscience content Article Lookup Select journal (required) Volume number: Issue number (if …

In the version of this article initially published, Stephanie L. Bailey’s name was listed as Stephen J. Bailey. The author’s name has been corrected in the HTML and PDF versions of the article.

This report describes the physics case, the resulting detector requirements, and the evolving detector concepts for the experimental program at the Electron-Ion Collider (EIC). The EIC will be a powerful new high-luminosity facility in the United States with the capability to collide high-energy electron beams with high-energy proton and ion beams, providing access to those regions in the nucleon and nuclei where their structure is dominated by gluons. Moreover, polarized beams in the EIC will give unprecedented access to the spatial and spin structure of the proton, neutron, and light ions. The studies leading to this document were commissioned and organized by the EIC User Group with the objective of advancing the state and detail of the physics program and developing detector concepts that meet the emerging requirements in preparation for the realization of the EIC. The effort aims to provide the basis for …

We report the first measurement of the parity-violating elastic electron scattering asymmetry on Al 27. The Al 27 elastic asymmetry is A PV= 2.16±0.11 (stat)±0.16 (syst) ppm, and was measured at⟨ Q 2⟩= 0.02357±0.00010 GeV 2,⟨ θ lab⟩= 7.6 1±0.0 2, and⟨ E lab⟩= 1.157 GeV with the Q weak apparatus at Jefferson Lab. Predictions using a simple Born approximation as well as more sophisticated distorted-wave calculations are in good agreement with this result. From this asymmetry the Al 27 neutron radius R n= 2.89±0.12 fm was determined using a many-models correlation technique. The corresponding neutron skin thickness R n− R p=− 0.04±0.12 fm is small, as expected for a light nucleus with a neutron excess of only 1. This result thus serves as a successful benchmark for electroweak determinations of neutron radii on heavier nuclei. A tree-level approach was used to extract the Al 27 weak radius R w= 3 …

We report a precise measurement of the parity-violating (PV) asymmetry A PV in the elastic scattering of longitudinally polarized electrons from Ca 48. We measure A PV= 2668±106 (stat)±40 (syst) parts per billion, leading to an extraction of the neutral weak form factor F W (q= 0.8733 fm− 1)= 0.1304±0.0052 (stat)±0.0020 (syst) and the charge minus the weak form factor F ch− F W= 0.0277±0.0055. The resulting neutron skin thickness R n− R p= 0.121±0.026 (exp)±0.024 (model) fm is relatively thin yet consistent with many model calculations. The combined CREX and PREX results will have implications for future energy density functional calculations and on the density dependence of the symmetry energy of nuclear matter.

MOLLER is a future experiment designed to measure parity violation in Moller scattering to extremely high precision. MOLLER will measure the right-left scattering differential cross-section parity-violating asymmetry APV , in the elastic scattering of polarized electrons off an unpolarized LH2 target to extreme ppb precision. To make this measurement, the polarized electron source, generated with a circularly polarized laser beam, must have the ability to switch quickly between right and left helicity polarization states. The polarized source must also maintain minimal right-left helicity correlated beam asymmetries, including energy changes, position changes, intensity changes, or spot-size changes. These requirements can be met with appropriate choice and design of the Pockels cell used to generate the circularly polarized light. Rubidium Titanyl Phosphate (RTP) has been used in recent years for ultra-fast Pockels cell switches due to its lack of piezo-electric resonances at frequencies up to several hundred MHz. However, crystal non-uniformity in this material leads to poorer extinction ratios than in commonly used KD*P Pockels cells when used in hald-wave configuration. It leads to voltage dependent beam steering when used in quarter-wave configuration. Here we present an innovative RTP Pockels cell design which uses electric field gradients to counteract crystal non-uniformities and control beam steering down to the nm-level. We demonstrate this RTP Pockels cell design is capable of producing precisely controlled polarized electron beam at Jefferson Laboratory, a national accelerator facility, for current experiments, including the recent …