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DOE OSTI2019

RECENT DEVELOPMENTS OF Nb3Sn AT JEFFERSON LAB FOR SRF ACCELERATOR APPLICATION

The desire to reduce the construction and operating costs of future SRF accelerators motivates the search for alternative, higher-performing materials. Nb3Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. However, tests of early Nb3Sn-coated cavities encountered strong Q-slopes limiting the performance. Learnings from studies of coated materials related to cavity performance prompted significant changes to the coating process. It is now possible to routinely produce slope-free cavities having Q0 > 2×1010 at 4 K and > 4×1010 up to the accelerating gradient in excess of 15 MV/m at its best. Obtaining similar results in five-cell cavities is a current goal to test them under an accelerator environment. This contribution discusses recent developments at Jefferson Lab.

Pudasaini, Uttar↗
DOE OSTI2019

Electron-Argon Scattering Studies at Jefferson Lab

For many decades, the study of electron scattering off a nucleus has been used as a tool to probe the properties of that nucleus and its electromagnetic response. In recent years, these studies have become vital starting point in the development of neutrino-nucleus scattering physics that constitutes largest share of systematic uncertainty in the accelerator-based neutrino-oscillation experiments. With the surge of Liquid Argon Time Projection Chambers (LArTPCs) based detectors in the short- (SBN) and long-baseline (DUNE) neutrino programs, the challenges of controlling systematics related to (anti)neutrino-argon scattering are magnified considering the isospin asymmetric nature of argon nucleus and the scarcity of electron-argon scattering studies. In light of these, an electron-argon experiment, E12-14-012, was designed at Jefferson Lab Hall A to study electron scattering on argon (N = 22) and titanium (Z = 22) nuclei using high precision continuous electron beam. The experiment collected data for ( e,e′p ) and ( e,e′ ) processes on 40 Ar, 48 Ti and 12 C targets covering a broad range of energy transfers where quasielastic scattering and delta production are the dominant reaction mechanisms. In this contribution, we present a brief overview and status of the experiment.

Pandey, Vishvas↗
DOE OSTI2025

Development of Thin Gap GEM-µRWELL Hybrid Detectors at Jefferson Lab

Over the past few decades, Micro Pattern Gaseous Detector (MPGD) technologies have been increasingly adopted as tracking detector options in High Energy and Nuclear Physics experiments thanks to their good spatial resolution, high-rate capability, stability and more importantly their ability for large area coverage at a relatively low cost compared to the alternative. The thin gap GEM-µRWELL hybrid detector is the latest addition to the MPGD family, that was introduced to vastly improve the spatial resolution capability of gaseous trackers when deployed in the barrel region to cover large angular acceptance of the central tracker in a collider experiment. In this talk, I will re-introduce the concept and motivation for the development of thin gap GEM-µRWELL hybrid technology with an emphasis on the initial studies that establish the proof-of-concept of the technology. I will then discuss the more recent results from latest beam test campaign at Jefferson Lab in May 2025 to study detector efficiency performance with various gas mixtures. I will also briefly present the ongoing activities to develop large area thin gap GEM-µRWELL tracking detectors for the ePIC experiment of the future Electron Ion Collider as well as the exploration of the technology to provide large area tracking options to the muon system of experiments at a future Higgs Factory Collider such as the FCC-ee for example. Finally, I will conclude with some perspectives on new ideas under exploration to develop the next generation of thin gap MPGD technologies with enhanced timing and spatial resolution capabilities

Gnanvo, Kondo [Thomas Jefferson National Accelerat↗
DOE OSTI2017

Direct Comparison of M\o ller and Compton Polarimeters in Hall C at Jefferson Lab

Knowledge of the electron beam polarization is one of the most important systematic uncertainties in precision, parity-violating electron scattering experiments with next generation experiments aiming to measure the electron beam polarization to better than 0.5\%. At high energies, the most typical polarimetry techniques are M\o ller (polarized electron-electron) and Compton (polarized electron-photon) scattering. The use of two techniques with different systematic uncertainties provides confidence in the extracted beam polarization. Direct comparisons of the two polarimetry techniques are challenging in that Compton polarimeters typically desire maximum beam flux (high beam currents) while M\o ller polarimeters need to limit the beam current to avoid depolarization effects in the target. We have performed a direct comparison of the M\o ller and Compton polarimeters in experimental Hall C at Jefferson Lab. This test is unique in that the data were taken sequentially under identical beam conditions at ?4.5~?A. We found excellent agreement between the Hall C M\o ller and Compton polarimeters. Combined with high-current Compton data, we were also able to limit the beam current dependence of the beam polarization to 1\% or less up to a beam current of 180~?A.

Gaskell, David↗
DOE OSTI2017

Deep Exclusive Pseudoscalar Meson Production at Jefferson Lab Hall C

Measurements of exclusive meson production are a useful tool in the study of hadronic structure. In particular, one can discern the relevant degrees of freedom at different distance scales through these studies. In the transition region between low momentum transfer (where a description of hadronic degrees of freedom in terms of effective hadronic Lagrangians is valid) and high momentum transfer (where the degrees of freedom are quarks and gluons), the predictive power of Quantum Chromodynamics (QCD), the theory of the strong interaction, is limited due to the absence of a complete solution. Thus, one has to rely upon experimental data from the non-perturbative intermediate-energy regime to thoroughly understand the onset of perturbative QCD (pQCD) as the momentum transfer is increased. This work involves two deep exclusive meson electroproduction experiments at Jefferson Lab (JLab). The p(e,e'pi+)n reaction is studied at fixed Q^2 and W of 2.5 GeV2 and 2.0 GeV, respectively, while varying the four momentum transfer to the nucleon -t from 0.2 to 2.1 GeV2 . As -t is increased, the hadronic interaction scale is reduced independently of the observation scale of the virtual photon, providing valuable information about the hard- scattering process in general. The data was taken at JLab Hall C in 2003, as a part of the experiment E01-004, Fpi-2, using the High Momentum Spectrometer (HMS) and Short Orbit Spectrometer (SOS), and in this work, the results of the differential cross section analysis are presented and compared to prior data, as well as two theoretical models. Using these results over a wide -t range, the transition from hard to soft QCD is also studied. In addition, the p(e,e'K+)Lambda(Sigma0) reactions are also studied. Despite their importance in elucidating the reaction mechanism underlying strangeness production, we still do not have complete understanding of these reactions above the resonance region. The experiment, E12- 09-011, intends to perform, for the first time, a full Rosenbluth (L/T/LT/TT) separation of p(e,e'K+)Lambda(Sigma0) cross sections above the resonance region using the newly upgraded standard equipment, Super High Momentum Spectrometer (SHMS) at JLab Hall C. The separated data will allow us to better understand the Kaon production reaction mechanism and the hard-soft QCD transition in exclusive processes. The kinematic settings being studied in the experiment ranges from Q^2 of 0.4 to 5.5 GeV2, W of 2.3 to 3.1 GeV, and -t of 0.06 to 0.53 GeV2. Here, the results from some pre-experimental studies with regards to estimations of singles rates as well as real and accidental coincidence rates are presented, using two different models. The implications of these projections on the runplan for the experiment are also discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Tagged DVCS on neutron with the CLAS12 Experiment and the detector BONuS12 at Jefferson Lab (USA)

Hadronic physics studies the properties of the proton and neutron. The theory of Quantum Chromodynamics (QCD) governs the structure of hadrons. Non-perturbative structure functions are used to describe the hadrons? structure. Generalized Parton Distributions (GPDs) are a set of structure functions providing access to a 3D view of the nucleon. GPDs contain information about the longitudinal momentum and transverse position of quarks and their correlation. They are related to the spin structure and play a role in solving the proton spin puzzle. They provide access to the quarks? orbital angular momentum, a crucial puzzle piece. For this, measurements on the proton, already present, and neutron are necessary. This thesis aims to explore Compton scattering on the neutron with a deuterium target by measuring the spectator proton with the CLAS12 detector and the BONuS12 RTPC at Jefferson Lab. This work first describes the implementation, which I carried out, of a Kalman filter to reconstruct spectator protons in the BONuS12 detector. The second part of the manuscript is dedicated to the work on the analysis of DVCS on the neutron with the subtraction of background noises. Two different methods for the subtraction of ?0 will be detailed. Finally, the obtained results are presented and discussed

Ouillon, Mathieu↗
DOE OSTI2014

Di-hadron production at Jefferson Lab

Semi-inclusive deep inelastic scattering (SIDIS) has been used extensively in recent years as an important testing ground for QCD. Studies so far have concentrated on better determination of parton distribution functions, distinguishing between the quark and antiquark contributions, and understanding the fragmentation of quarks into hadrons. Hadron pair (di-hadron) SIDIS provides information on the nucleon structure and hadronization dynamics that complement single hadron SIDIS. Di-hadrons allow the study of low- and high-twist distribution functions and Dihadron Fragmentation Functions (DiFF). Together with the twist-2 PDFs ( f1, g1, h1), the Higher Twist (HT) e and hL functions are very interesting because they offer insights into the physics of the largely unexplored quark-gluon correlations, which provide access into the dynamics inside hadrons. The CLAS spectrometer, installed in Hall-B at Jefferson Lab, has collected data using the CEBAF 6 GeV longitudinally polarized electron beam on longitudinally polarized solid NH3 targets. Preliminary results on di-hadron beam-, target- and double-spin asymmetries will be presented.

Anefalos Pereira, Sergio↗
DOE OSTI2012

HDice, Highly-Polarized Low-Background Frozen-Spin HD Targets for CLAS experiments at Jefferson Lab

Large, portable frozen-spin HD (Deuterium-Hydride) targets have been developed for studying nucleon spin properties with low backgrounds. Protons and Deuterons in HD are polarized at low temperatures (~10mK) inside a vertical dilution refrigerator (Oxford Kelvinox-1000) containing a high magnetic field (up to 17T). The targets reach a frozen-spin state within a few months, after which they can be cold transferred to an In-Beam Cryostat (IBC). The IBC, a thin-walled dilution refrigerator operating either horizontally or vertically, is use with quasi-4{pi} detector systems in open geometries with minimal energy loss for exiting reaction products in nucleon structure experiments. The first application of this advanced target system has been used for Spin Sum Rule experiments at the LEGS facility in Brookhaven National Laboratory. An improved target production and handling system has been developed at Jefferson Lab for experiments with the CEBAF Large Acceptance Spectrometer, CLAS.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

The Search for the Color Transparency in Hall C at Jefferson Lab

Color transparency (CT) is a fundamental phenomenon of QCD postulating that at high momentum transfer hadrons fluctuate to a small color neutral transverse size in the nucleus, and final state interactions within the nuclear medium are suppressed. CT is observed experimentally as a rise in the measured nuclear transparency as a function of the momentum transferred. While CT has been observed for mesons, it remains unconfirmed in baryons. Observation of CT in baryons would provide a new handle for understanding the nuclear strong force and the first observations of hadrons fluctuating to a small size in the nucleus. An enhancement in the nuclear transparency was observed in A(p,2p) reactions at Brookhaven. This experiment seeks to confirm the measurement of proton transparency as well as to measure the onset. During the spring of 2018, this experiment was the first to run in Hall C at Jefferson Lab using the recently upgraded 12 GeV electron beam and obtained four kinematic points covering the region where Brookhaven previously observed an enhancement. This experiment used the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS) in coincidence to measure A(e,e?p). This talk will summarize the status of the experiment since the completion of data taking this spring.

Szumila-Vance, Holly↗
DOE OSTI2016

Deeply Virtual Pseudoscalar Meson Production at Jefferson Lab and Transversity GPDs

Transverse-momentum dependent parton distribution functions (TMDs) provide a description of nucleon structure in terms of the parton transverse momentum and its transverse spin. At leading twist there are eight TMDs, each offering a unique feature of quarks in a polarized or an unpolarized nucleon. The Sivers distribution is one of the most interesting TMD due to its non-universality. It has been extracted using the data from semi-inclusive deep-inelastic scattering (SIDIS), but there is no data yet from spin-dependent Drell-Yan (DY) process. Such measurement will provide a crucial test of TMD formalism which predicts an equal magnitude and opposite sign for the Sivers function extracted from SIDIS and DY process. We will discuss key future measurements of TMDs using both SIDIS and DY process with a focus on Hall A SoLID SIDIS program at Jefferson Lab.

Kubarovsky, Valery P.↗
DOE OSTI2019

Preliminary results searching for the onset of color transparency in A(e,e'p) in Hall C at Jefferson Lab

Color transparency (CT) is a fundamental phenomenon of QCD postulating that at high momentum transfer, one can preferentially measure hadrons that fluctuate to a small color neutral transverse size in the nucleus, and final state interactions within the nuclear medium are sup- pressed. CT is observed experimentally as a rise in the measured nuclear transparency as a function of the momentum transferred. While CT has been observed for mesons, it remains unconfirmed in baryons. Observation of CT in baryons would provide a new means to study the nuclear strong force and would be the first clear observation of hadrons fluctuating to a small size in the nucleus. An enhancement in the nuclear transparency was observed in A(p,2p) reactions at Brookhaven. This experiment, E1206107, seeks to confirm the measurement of pro- ton transparency as well as to measure the onset. During the spring of 2018, this experiment was the first to run in Hall C at Jefferson Lab using the recently upgraded 12 GeV electron beam and obtained four kinematic points at momentum transfer Q^2 from 8-14.3 GeV^2, overlapping the same region where Brookhaven previously observed an enhancement. This ex- periment used the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS) in coincidence to measure A(e,e'p) on a carbon target. This talk will summarize the motivation to measure the onset of color transparency in baryons and will present preliminary results from this experiment. DOE Grant Number: DE-FG02-07ER41528

Szumila-Vance, Holly↗
DOE OSTI2024

First Measurement of the Isospin-Dependence of Nuclear Structure Functions at 12 GeV Jefferson Lab

The structure functions of protons and neutrons provide crucial insight into how the strong nuclear force, as described by Quantum Chromodynamics (QCD), manifests at everyday energies, allowing us to better understand precisely how quarks and gluons interact to form the basic building blocks of almost all visible mass in our universe. Despite more than 40 years of experimental and theoretical effort, the EMC effect – the observation that nuclear structure functions appear to be modified from those of free nucleons – is still not fully understood. One open question that remains is whether or not the modification of quark distributions is the same for all quark flavors. Determining the flavor (isospin) dependence of the EMC effect, which is predicted by several models, is essential for coming to a complete understanding of how QCD manifests in nuclei. To this end, inclusive electron Deep Inelastic Scattering (DIS) from nuclei with approximately constant atomic mass number A and variable proton-to-neutron ratio N/Z was measured in Jefferson Lab experiment E12-10-008 to look for isospin-dependent modification of nuclear structure functions. The preliminary EMC ratios presented here cover a kinematic range of 2.8 < Q2 < 8.1 GeV2 and 0.18 < xBj < 1.0. The size of the EMC effect in these nuclei is extracted by calculating the slope of the EMC ratio as a function of Bjorken x (xBj ) over the ranges 0.3 < xBj < 0.6 and 0.3 < xBj < 0.7; these slopes then are compared with existing world data. Our preliminary results do not appear to indicate significant isospin-dependence of the EMC effect, though a more careful study is needed once all results are confirmed.

Cotton, Cameron William [Univ. of Virginia, Charlo↗
DOE OSTI2014

Potential for a Tensor Asymmetry Azz Measurement in the x > 1 Region at Jefferson Lab

The tensor asymmetry A(zz) in the quasi-elastic region through the tensor polarized D(e, e')X channel is sensitive to the nucleon-nucleon potential. Previous measurements of A(zz) have been used to extract b(1) in the DIS region and T(20) in the elastic region. In the quasielastic region, A(zz) can be used to compare light cone calculations with variation nucleon- nucleon calculations, and is an important quantity to determine for understanding tensor effects, such as the dominance of pn correlations in nuclei. In the quasi-elastic region, A(zz) was first calculated in 1988 by Frankfurt and Strikman using the Hamada-Johnstone and Reid soft-core wave functions [1]. Recent calculations by M. Sargsian revisit A(zz) in the x > 1 range using virtual-nucleon and light-cone methods, which differ by up to a factor of two [2]. Discussed in these proceedings, a study has been completed that determines the feasibility of measuring A(zz) in the quasi-elastic x > 1 region at Jefferson Lab's Hall C.

Long, Elena↗
DOE OSTI2020

MEASUREMENT OF Fn 2 /Fp 2 FROM DEEP INELASTIC ELECTRON SCATTERING OFF A=3 MIRROR NUCLEI AT JEFFERSON LAB

This research is part of the Je?erson Lab MARATHON experiment (MeAsurement of the Fn 2 /Fp 2 , d/u RAtios and A = 3 EMC E?ect in Deep Inelastic Electron Scattering Off the Tritium and Helium MirrOr Nuclei). MARATHON is an experiment on electron deep inelastic scattering off the 3H, 3He mirror nuclei. It has extracted, from the measured deep inelastic scattering cross section ratio o? 3H and 3He, the ratio of the neutron to proton inelastic structure functions Fn 2 /Fp 2 . The extraction has taken advantage of the isospin symmetry of the A = 3 mirror nuclei within a novel technique, which avoids the theoretical uncertainties that are present in the SLAC experiments of the 1970s, which used hydrogen and deuterium targets. The experiment was performed using the upgraded 11 GeV beam of the Jefferson Lab electron accelerator, the Hall A Experimental Facility, and a newly designed cryogenic, high-pressure gas target system containing 3H and 3He cells. Electrons scattered o? the gas targets were detected in the two superconducting, high-resolution magnetic spectrometers of Hall A. The cross section data cover the four-momentum transfer squared range 2.0 < Q2 < 14.0 (GeV/c)2, and the Bjorken x scaling variable range 0.19 < x < 0.83. The experiment also measured, for calibration purposes, electron deep inelastic scattering off hydrogen and deuterium at selected kinematics.

Su, Tong↗
DOE OSTI2023

Measuring the Neutron Spin Asymmetry A1n in the Valence Quark Region in Hall C at Jefferson Lab

The quest to understand how the nucleon spin is decomposed into its constituent quark and gluon spin and orbital angular momentum (OAM) components has been at the forefront of nuclear physics for decades. Due to the non-perturbative nature of Quantum Chromodynamics (QCD) - the theory describing how quarks and gluons bind together to form protons and neutrons - making absolute predictions of nucleon spin structure is generally difficult, especially as a function of its quark and gluon longitudinal momentum fraction x. Measurements involving nucleon spin structure serve as a sensitive test for QCD, including ab-initio lattice QCD calculations due to the advent of the quasi-PDF formalism, and various predictions that diverge at large-x. The neutron spin asymmetry An 1 at high?x is a key observable for probing nucleon spin structure. In the valence domain (x > 0.5), sea effects are expected to be negligible, and so the total nucleon spin is considered to be carried by the valence quarks. The valence region can therefore enable us to study the role of quark OAM and other non-perturbative effects of the strong force. An 1 was measured in the deep inelastic scattering region of 0.40 < x < 0.75 and 6 < Q2 < 10 GeV2 in Hall C at Jefferson Lab using a 10.4 GeV longitudinally polarized electron beam, upgraded polarized 3He target, and the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS). E12- 06-110 provides the first precision data in the valence quark region above x = 0.60, and its preliminary results proved consistent with earlier data disqualifying a pQCD model that excluded quark OAM. Combined with previous world proton data, the ratio of the polarized-to-unpolarized up quark momentum distribution (?u + ?u)/(u + u) remained positive at large-x, and the down quark (?d + ?d)/(d + d) remained negative.

Rehfuss, Melanie↗
DOE OSTI2024

Probing the Isospin Composition of Short-Range Correlated Pairs at Jefferson Lab Hall B

Nucleons in short-range correlated (SRC) pairs, due to their close proximity and high relative momentum, can provide insight into the short-range part of the strong nuclear interaction. In particular, the prevalence of np pairs is due to the dominance of a tensor term for correlated nucleons with momenta of approximately 400?600 MeV/c. This dissertation comprises two studies advancing the community?s understanding of the isospin composition of SRC pairs. First, I performed a study of proton and neutron knockout from initially low-momentum and high-momentum states in 3He. Previous work has shown that protons are disproportionately represented in high-momentum states in neutron-rich nuclei. I demonstrate that spectral functions for the proton-rich nucleus 3He predict, in agreement with data, that neutrons are disproportionately represented in high-momentum states, but that 3He does not display the same strong prevalence of np pairs that is observed in larger nuclei. Second, Generalized Contact Formalism (GCF), a well-supported theory for predicting SRC behavior, predicts the transition from an isospin-dependent, tensor-dominant interaction at intermediate distances to a scalar-dominant, isospin-independent interaction at very short distances. This dissertation uses data from the CLAS12 Nuclear Targets Experiments in Hall B at Jefferson Lab to measure the relative abundances of pp and pn pairs for increasing relative momentum and decreasing separation. I provide an independent confirmation of the previously-observed increase in pp pairs at increasing momentum of the struck nucleon. I also contribute to the application of the new CLAS12 Central Neutron Detector by precisely measuring the neutron detection efficiency and developing a machine learning model for rejecting charged particle background.

Seroka, Erin↗
DOE OSTI2012

Physics Opportunities with the 12 GeV Upgrade at Jefferson Lab

We are at the dawn of a new era in the study of hadronic nuclear physics. The non-Abelian nature of Quantum Chromodynamics (QCD) and the resulting strong coupling at low energies represent a significant challenge to nuclear and particle physicists. The last decade has seen the development of new theoretical and experimental tools to quantitatively study the nature of confinement and the structure of hadrons comprised of light quarks and gluons. Together these will allow both the spectrum and the structure of hadrons to be elucidated in unprecedented detail. Exotic mesons that result from excitation of the gluon field will be explored. Multidimensional images of hadrons with great promise to reveal the dynamics of the key underlying degrees of freedom will be produced. In particular, these multidimensional distributions open a new window on the elusive spin content of the nucleon through observables that are directly related to the orbital angular momenta of quarks and gluons. Moreover, computational techniques in Lattice QCD now promise to provide insightful and quantitative predictions that can be meaningfully confronted with, and elucidated by, forthcoming experimental data. In addition, the development of extremely high intensity, highly polarized and extraordinarily stable beams of electrons provides innovative opportunities for probing (and extending) the Standard Model, both through parity violation studies and searches for new particles. Thus the 12 GeV upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab will enable a new experimental program with substantial discovery potential to address these and other important topics in nuclear, hadronic and electroweak physics.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Light Baryon Spectroscopy at Jefferson Lab: What have we learned about excited baryons?

Nucleons are complex systems of confined quarks and gluons and exhibit the characteristic spectra of excited states. These states serve as an excellent probe of quantum chromodynamics (QCD), the fundamental theory of strong interaction. Highly-excited states are sensitive to the details of quark confinement, which is only poorly understood within QCD. This is the regime of non-perturbative QCD and it is one of the key issues in hadronic physics to identify the corresponding relevant degrees of freedom and the effective forces between them. In recent years, lattice-QCD has made significant progress toward understanding the spectra of hadrons. On the experimental side, high-energy electrons and photons are a remarkably clean probe of hadronic matter, providing a microscope for examining atomic nuclei and the strong nuclear force. For more than a decade, laboratories worldwide have accumulated data for such investigations, resulting in a number of surprising discoveries and contributing to our understanding of the nucleon, its underlying quark structure, and the dynamics of the strong interaction. Current experimental efforts utilize highly-polarized frozen-spin (butanol) targets and deuterium targets in combination with polarized photon beams. These are important steps toward so-called complete experiments that will allow us to unambiguously determine the scattering amplitudes in the underlying reactions and to identify resonance contributions. In my talk, I will give an overview of the excited baryon program at Jefferson Lab and I will discuss recent results from (double-)polarization experiments.

Crede, Volker↗