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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Measurement of the t-dependence of the Beam Asymmetry of Photoproduced eta at the GlueX Experiment at Jefferson Lab

We report on the photoproduction of eta mesons studied at the GlueX experiment at Thomas Jefferson National Laboratory in Newport News, VA. A linearly polarized photon beam at energies between 8.2 and 8.8 GeV, incident on a liquid hydrogen target, produces eta dominantly through t-channel exchanges. Azimuthal angular distributions of the eta, for the direction of the polarized photon, facilitate the extraction of the beam asymmetry Sigma for the reaction gamma p -> eta p. We can understand the production mechanisms of the eta by analyzing Sigma_eta, which is sensitive to the particles exchanged. Compared to previous GlueX results [[4],[17]], we have access to five times the statistics, thereby allowing us to extend these measurements to values beyond the previous limitation of -t lte 1.1 (GeV)2. Results will be shown for events reconstructed from the decay of eta -> gamma gamma and eta -> pi^+ pi^- pi^0 Systematic checks are also made for the neutral mode decay to confirm the stability of the extracted results. We find through data binned up to a momentum transfer of 2.0 (GeV)2 that the photoproduction of eta at these beam energies is largely carried out by natural processes, with a preliminary comparison with the photoproduction of eta' suggesting possible strangeness exchanges at wider kinematic regions.

Erbora, Tolga↗
DOE OSTI2022

AI for Experimental Controls at Jefferson Lab

We report the AI for Experimental Controls project is developing an AI system to control and calibrate detector systems located at Jefferson Laboratory. Currently, calibrations are performed offline and require significant time and attention from experts. This work would reduce the amount of data and the amount of time spent calibrating in an offline setting. The first use case involves the Central Drift Chamber (CDC) located inside the GlueX spectrometer in Hall D. We use a combination of environmental and experimental data, such as atmospheric pressure, gas temperature, and the flux of incident particles as inputs to a sequential Neural Network (NN) to recommend a high voltage setting and the corresponding calibration constants in order to maintain consistent gain and optimal resolution throughout the experiment. Utilizing AI in this manner represents an initial shift from offline calibration towards near real time calibrations performed at Jefferson Laboratory.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Status of the LCLS-II-HE Project at Jefferson Lab

The Linac Coherent Light Source II High Energy (LCLS-II-HE) upgrade at the SLAC National Accelerator Laboratory is being constructed in partnership with the Thomas Jefferson National Accelerator Facility (JLab) and the Fermi National Accelerator Laboratory (FNAL). The cryomodule production scope consists of the design, procurement, construction, and acceptance testing of 24 eight-cavity, 1.3 GHz cryomodules, as well as R&D activities necessary to develop the required technology. To achieve this, JLab and FNAL are also contributing to SLAC’s effort to develop the cavity recipe and production processes necessary to meet the LCLS-II-HE goal of 20.8 MV/m and average Q₀ of 2.7·10¹⁰. This paper details the JLab scope, focusing on the project initiation phase, in particular technology development and prototyping, project development and planning, and implementation of lessons learned from LCLS-II.

Wilson, K. M.↗
DOE OSTI2024

Strong interaction physics at the luminosity frontier with 22 GeV electrons at Jefferson Lab

Here, the purpose of this document is to outline the developing scientific case for pursuing an energy upgrade to 22 GeV of the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility (TJNAF, or JLab). This document was developed with input from a series of workshops held in the period between March 2022 and April 2023 that were organized by the JLab user community and staff with guidance from JLab management (see Sec. 10). The scientific case for the 22 GeV energy upgrade leverages existing or already planned Hall equipment and world-wide uniqueness of CEBAF high-luminosity operations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Measurement of the EMC Effect of the Helium-3 Nucleus at Jefferson Lab

The MARATHON (MeAsurement of the Fn 2 /Fp 2 , d/u RAtios and A=3 EMC Effect in Deep Inelastic Scattering Off the Tritium and Helium MirrOr Nuclei) experiment ran in the Hall A Facility of the Thomas Jefferson National Accelerator Facility (JLab). The experiment used a 10.59 GeV electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF) of JLab to measure the ratio of the F2 structure functions of Helium-3 and Deuterium. Data were taken in the kinematic range of 0.195 lte x lte 0.825, 2.5 (GeV/c)2 lte Q2 lte 13 (GeV/c)2, and 3.5 (GeV/c2)^2 lte W^2 lte 13 (GeV/c2)^2. This is the first measurement of the 3He EMC effect that is purely in the Deep Inelastic Scattering region. The results of this experiment constitute an important, complimentary addition, to the limited data presently available for the EMC effect of light nuclei. The MARATHON results are compared to the world data for light, medium, and heavy nuclei. This measurement is considered an essential component to uncovering the nature of the EMC effect.

Hague, Tyler↗
DOE OSTI2026

Intrinsic energy and time resolution of the Jefferson Lab Hall C Neutral Particle Spectrometer

The Neutral Particle Spectrometer (NPS) is an advanced calorimeter designed to measure neutral electro- magnetic particles with high precision in energy, time, and position, under conditions of high luminosity and significant background. Integrated into the experimental setup of Hall C at Thomas Jefferson National Accelerator Facility, the NPS plays a critical role in studies of nucleon structure through exclusive and semi- inclusive reaction channels. Here, this paper presents an assessment of the detector’s performance characteristics, specifically its energy and timing resolution, derived from elastic electron–proton scattering data. We report an energy resolution between 1.2% and 1.3% in the 4.5–7.3 GeV range, and an intrinsic timing resolution better than 200 ps for energies above 500 MeV. These results serve as a reference for current and future precision measurements in hadronic physics.

Detector performance↗
DOE OSTI2026

First measurement of polarized spin-density matrix elements and differential cross sections dσ/dt in ω photoproduction off the proton for 2.7 < Eγ < 5.2 GeV using CLAS at Jefferson Lab

We report on the differential cross sections dσ/dt, the unpolarized spin-density matrix elements ρ 00 0 , ρ 1 − 1 0 , Re ρ 10 0 , and the first extraction of the polarized elements Im ρ 10 3 , Im ρ 1 − 1 3 for the reaction γp → pω using the CLAS spectrometer at Jefferson Laboratory. The ω mesons were detected in their dominant charged decay mode, ω → π + π − π 0 , and all t-dependent results are presented in a fine binning for incident photon energies between 2.73 and 5.16 GeV (corresponding to the center-of-mass energy range W ∈ [ 2.45, 3.25 ] GeV). All matrix elements are first measurements for − t > 0.6 GeV2. Moreover, differential cross sections dσ/d(cos Θ c . m . ω ) and the corresponding angle-dependent unpolarized spin-density matrix elements in the Adair frame are presented for the incident photon energy range 1.56–3.80 GeV (corresponding to W ∈ [ 1.95, 2.83 ] GeV). These new ω photoproduction data are consistent with earlier CLAS results but extend the energy range well beyond the nucleon resonance region into the Regge regime. The comparison with Regge-theory-based model predictions shows that the new data impose more stringent constraints on our understanding of ω photoproduction.

Hu, T.↗
DOE OSTI2024

Measurement of the Pion Exclusive Electro-Production Cross-Section in the E12-19-006 Experiment in Hall-C at Jefferson Lab

One of the most effective methods for exploring the transition from hadronic degrees of freedom to quark-gluon degrees of freedom in Quantum Chromodynamics (QCD) is through the investigation of \exclusive" pion and kaon electro-production reactions at various Q2 and ?t values. The E12-19-006 experiment is conducted within the confi?nes of experimental Hall C at the Thomas Jefferson National Accelerator Facility, USA, for such studies. The primary aim of the experiment is to ?first enhance our comprehension of the pion electro-production cross-section and its form factor at Q2 = 0.38 and 0.42 GeV2. This is the fi?rst run period of the E12-19-006 experiment which ran in summer 2019. A more profound understanding of the pion electro-production reaction, 1H(e,e'?+)n, at low Q2 is deemed essential to employ this electro-production reaction (an indirect technique) for the high Q2 studies, thereby delving deeper into the realm of QCD. Consequently, this dissertation presents a thorough analysis of the experimental data acquired in the ?first run period of the E12-19-006 experiment. In pursuit of precision, a series of systematic studies (target boiling correction study, the elastic reaction cross-section measurements, study for determining vari- ous kinematics o?sets, etc.) are conducted to discern the accuracy of the analyzed data, a prerequisite for the use of Rosenbluth separation technique to separate the pion electro-production cross-section terms in t bins. The separated pion electro-production cross-section through the Rosenbluth separation technique is then used to extract the pion electromagnetic form factor. In this dissertation, the pion electro-production cross-section is carefully dissected into its four constituent components: longitudinal (?L), transverse (?T ), longitudinal-transverse (?LT ), and transverse-transverse (?TT ), using the full version of Rosenbluth separation technique for the Q2 = 0.38 GeV2. The technique is simultaneously fi?tted to the unseparated pion electro-production cross-sections at the three values of polarization of the virtual photon (?), i.e., ? = 0.286, 0.629 and 0.781. An iterative process is applied to re?ne the parameters of the model cross-sections until the yield ratio of experimental and Monte Carlo simulation converges. In this study, 21 iterations are conducted to re?ne the model cross-section parameters. The fi?nal pion electro-production cross-section terms are then determined for 7 t bins using the optimized parameters of the model cross-sections.

Kumar, Vijay↗
DOE OSTI2021

Nuclear Transparency from Quasi-elastic ¹²C(e, e'p) scattering reaction up to Q2 = 14.2 (GeV/c)2 in Hall C at Jefferson Lab

Color Transparency (CT) is a unique prediction of Quantum Chromodynamics (QCD) where the final (and/or initial) state interactions of hadrons with the nuclear medium are suppressed for exclusive processes at high momentum transfers. While this phenomenon has been observed for mesons, there has never been a conclusive observation for baryons. A clear signal of CT for baryons would be the first evidence of baryons fluctuating to a small size in the nucleus, and the onset would show the transition from nucleon-meson picture to quark-gluon degrees of freedom. The experiment E1206107, searching for the onset of CT in protons was completed in Hall C at Jefferson Laboratory (JLab) using the upgraded 12 GeV e- beam. It used the High Momentum Spectrometer (HMS) and the new Super High Momentum spectrometer (SHMS) in coincidence to measure the e- + ¹²C ? e-' + p + X reaction in quasi-elastic kinematics. Data were collected on a ¹²C target over the range of Q2 = 8 - 14.3 (GeV/c)2, covering the region where a previous p + A ? p' + p + X experiment at Brookhaven National Laboratory (BNL) had observed an enhancement. Proton Transparency (PT) was extracted from these data. A rise in the PT as a function of Q2 (defined as the square of the negative of the 4-momentum transfer by the scattered electron) is predicted to be a signature of the onset of CT. Our data showed no significant increase and consistent with the traditional nuclear physics calculation. This dissertation discusses the theory and implementation of the CT experiment, summarizes the data analysis and presents results on hydrogen normalization and nuclear transparency.

Bhetuwal, Deepak↗
DOE OSTI2024

Measurement of the Photoproduction Cross-Section of f1(1285) in the Exclusive Reactions p¿ p'K±KSp± AT 7.5 < E¿ < 11.5 GeV with GlueX at Jefferson Lab

The f1(1285) meson is commonly understood to belong to the axial-vector nonet as the low-mass isoscalar partner to the f1(1420) but has been suggested as a candidate for a KK?+c.c molecule. A nearly mass-degenerate 0?+ state has been observed in ? p scattering that calls into question the established branching ratios of the f1(1285) decays. Recently, the differential cross-section for the photoproduction of f1(1285) was measured by the CLAS experiment and the results disagreed with theoretical predictions. Additionally, the CLAS experiment did not observe a mass-degenerate 0?+ state. We present the results of the first photoproduction cross-section measurement d?/dt of f1(1285) at 7.5 < E? < 11.5 GeV from the GlueX experiment at Thomas Jefferson National Accelerator Facility in the reactions ? p ? p?K?Ks?+ and ? p ? p?K+Ks??. We find that the production mechanism of f1(1285) is consistent with t-channel exchange. We also observe a difference in the differential cross-section of f1(1285) as a function of ?t as measured in the charge conjugated K?Ks?± decay modes that we hypothesize to be due to baryonic N? interference. The observed distributions of M(KK) and M(K?) are consistent with both a q ¯ q state and predictions for a KK?+c.c molecular state. Additionally, we find that the cross-section at low M(KK?) is dominated by the 1++ state.

Viducic, Tyler↗
DOE OSTI2024

Timelike Compton Scattering from a longitudinally polarised target with CLAS12 at Jefferson Lab

Explorations into the internal dynamics of hadrons are constantly evolving, and the requirement for experimental results to verify theoretical models of hadron structure is paramount. A key area in this field is the study of Generalised Parton Distributions (GPDs), which are functions used to model the momenta of quarks and gluons within hadrons, and the methods to access GPDs experimentally. One such scattering process that allows access to these is Timelike Compton Scattering. TCS complements existing Deeply Virtual Compton Scattering experiments and allows investigation into the universality of GPDs through access to the real and imaginary parts of the parton helicity independent GPD Hq via beam spin asymmetries (BSA), and it provides novel access to the real and imaginary parts of the parton helicity dependent GPD ˜Hq through target polarisation asymmetries (TSA). This thesis work presents a comparative study with the first published BSA for TCS at the Thomas Jefferson National Accelerator Facility (JLab), alongside a first time extraction of a Target Spin Asymmetry with the Summer 2022 data taking run. JLab hosts the Continuous Electron Beam Accelerator Facility (CEBAF) which provides a 12 GeV electron beam to four experimental halls. Hall-B contains the CEBAF Large Acceptance Spectrometer, which took data across three run periods on a longitudinally polarised NH3 and ND3 fixed target from 2022-2023, to extract measurements of electron-proton scattering, from which a TCS signal could be extracted. The thesis discusses work done to understand and eliminate contributions from the non-/low-polarised nuclear background, testing pre-established cuts to eliminate pion background from a dilepton (e+e-) final state and modifying them as needed for the new experimental run, and attempts to hone in on a clean TCS signal from which to extract the two asymmetry observables. A comparison with existing BSA results was performed; however, the statistical errors are too large to draw a significant conclusion as to whether there is agreement across each bin. More data is needed for a multidimensionally binned extraction. A proof of principle was achieved in the TSA measurements, with two out of four kinematic bins showing preliminary agreement in shape with theoretical values. Again, the errors are significant due to the contributions from the nuclear background. To support these conclusions, a further study was done, which takes into account an estimate of the asymmetries with the full available dataset (this thesis is based only on data taken in the summer set; at the time of writing processing was still being conducted for the final two datasets), as well as an estimate including additional future experiment days that were awarded in July 2024. Additional work was done on a secondary project exploring the feasibility of measuring TCS at the upcoming Electron Ion Collider, supporting the design proposal for the detector for the first interaction region and giving a positive outlook for the future of these types of measurements beyond JLab.

Gates, Kayleigh [Univ. of Glasgow, Scotland (Unite↗
DOE OSTI2020

Deeply Virtual Compton Scattering at Hall A, Jefferson Lab

The Standard Model of particle physics de?nes quarks and leptons as the basic building blocks of all matter. The interaction between them are mediated by force carrying gauge bosons. Quantum Chromo Dynamics (QCD), the theory that explains the strong interaction is still not complete enough to derive the physical observables of a Quark-Gluon system from the fundamental degrees of freedom of its constituents. Experimentally observable single particle densities provide important insights into our understanding of the quark-gluon system and hence help fill in the gaps of QCD. Generalized Parton Distributions (GPDs) provide simultaneous information of both spacial and longitudinal momentum distributions of constituents of a quark-gluon system. Deeply Virtual Compton Scattering (DVCS) is understood to be the simplest and cleanest process to access GPDs. Even though the exclusive DVCS is simple to understand, the experimental process however, is complex with the Bethe-Heitler and e + p ? e + ? + N? being in the mix of the electron proton scattering e+p ? e+?+X. Over the years, 3 generations of DVCS experiments have been conducted in the Experimental Hall-A of Thomas Jefferson National Accelerator Facility (JLab). This thesis presents the extraction of DVCS cross section in 9 total kinematic points from the 3rd generation experiment (DVCS3) conducted after the 12 GeV upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) of JLab during Fall 2014 - Fall 2016.

Hashir Rashad, Mohamed Nuhman↗
DOE OSTI2023

Search for a Singly Strange Hexaquark Using Polarization Data From CLAS12 at Jefferson Lab Virginia

Recently hadron spectroscopy has seen a lot of success. There has been a large number of baryon and meson resonances discovered over the last two decades. There have also been several tetra and pentaquark candidates with experimental evidence but not confirmed. The first serious candidate was the X(3872), a potential tetraquark, leading to this rise in success for exotic hadron physics. This has brought about improvements in Quantum Chromo Dynamics (QCD), our current best description of interactions between quarks and gluons. QCD predicts the existence of hexaquark states, and then the d*(2380) was discovered. This thesis explores the rest of the d* Jp =3+ anti-decuplet by searching for experimental evidence of the ds hexaquark. This is the first analysis of the e'd ¿e'K+d0 s ¿e'K+¿n channel using the Py' measurements of the ¿ as a lens to perform this search. This observable was extracted from ¿ electroproduction events off a liquid deuterium target. From this an upper limit of the Breit-Wigner peak strength was extracted. This was done with the use of the CLAS12 detector system housed at Thomas Jefferson Laboratory in Virginia, USA. These polarization measurements are the first to be made on this data, and this is the first time the ds has been searched for in such a way.

Clash, Geraint↗
DOE OSTI2023

νBDX: a Coherent Elastic Neutrino Nucleus Scattering (CEνNS) experiment at Jefferson Lab

Particle physics is an ever-changing field seeking to explain phenomena that lie at the limits of our current knowledge. Among discovered and hypothesized interactions, Coherent Elastic Neutrino-Nucleus Scattering (CE?NS) stands out as a fascinating and elusive phenomenon, offering a unique window into the nature of neutrinos and their interactions with matter. CE?NS, a process predicted by the Standard Model, represents one of the subtle ways in which neutrinos can interact with atomic nuclei. Unlike other neutrinonucleus interactions, CE?NS occurs coherently, meaning that the entire nucleus collectively responds to the neutrino-mediated weak force, resulting in small energy transfers to the nucleus as a whole. The extremely rare nature of CE?NS events presents a formidable challenge to experimenters seeking to detect and study these interactions. Recent advances in detector technologies and the implementation of large-scale experiments, such as coherent neutrino scattering experiments at research facilities around the world, have opened up new avenues for exploring this elusive phenomenon. These experiments aim not only to observe CE?NS directly but also to extract valuable information on neutrino properties, nuclear structure, and potential deviations from the Standard Model. This thesis aims to study the feasibility of an experiment to study CE?NS at The Thomas Jefferson National Accelerator Facility, Newport News, VA, USA. This would be an experiment that exploits the production of neutrinos by an electron beam dumped on a thick target (the beam dump). The large quantity of neutrinos produced and their energy profile are well suited to the purpose of studying the CE?NS. In my thesis, I will start from previous studies on CE?NS and from theoretical considerations regarding the process, then quantify the expected events for a hypothetical experiment and possible backgrounds through simulations aimed at optimizing the geometry of the future detector. I will also show some tests on selected detector components that will be part of a first prototype.

Grazzi, Stefano↗
DOE OSTI2021

Realization of a high luminosity muon beam at the Jefferson Lab

The proton is the major component of the visible matter of our universe, so being able to determine its fundamental properties, such as its charge radius, is of vital importance. In recent years, several experiments have been performed for the accurate measurement of the proton radius with different experimental techniques. The main and most common are based on two different techniques: ep scattering and Lamb shift spectroscopy of regular hydrogen atoms. The latter can also be performed on muonic hydrogen atoms with a significant improvement in accuracy. Recent measurements that use this method have highlighted a discrepancy between the results obtained with the diffusion of electrons and those obtained with the spectroscopic technique leading to the so-called ?proton radius puzzle?. The explanation of why this difference between the measured values exists is still a matter of discussion. The last attempt to address the puzzle was the PRad Experiment. It was performed with a unique experimental setup that gave the scientists an excellent control on the systematic errors that are usually present in electron-proton scattering experiments. This has significantly increased the precision of the measurement, bringing it in the same area as the spectroscopic ones done on muonic hydrogen atoms, which are considered the most precise. However, to solve the puzzle once and for all, even more precise electron scattering measurements are needed. Alternatively, new methods can be used, such as eg. muon-proton scattering at low transferred momenta in order to lower the systematic errors that comes with the measurement. This thesis tries to address this problem by studying the set up of an intense muon beam at the Jefferson Laboratory (JLab) that can be used to carry out a high-precision m ? p scattering experiment. Using Montecarlo simulations I studied the muon production resulting from the interaction of the primary electron beam with the beam-dump at JLab Hall-A. The simulations were performed using the FLUKA package via the FLAIR graphical interface. In this study, I modified an existing geometry (built for the ?Beam Dump eXperiment?) and performed several studies in order to optimize the muon beam parameters. In order to estimate the beam intensity, I studied the muon generation and transportation through the concrete bunker surrounding the Hall-A beam-dump. Detailed studies on muon attenuation and dispersion at different depth allowed me to track the beam profile in space and momentum as a function of the distance from the beam-dump. Last, but not least, I studied a possible tagging system for the muon beam. The tagging system will allow us to know with good precision (O(1=1000)) the energy of each muon of the beam. Based on the results obtained, I created an event generator that incorporates the detailed description of the muon beam (energy, position, emittance) useful to define and optimize the experimental setup for a future measurement of the proton radius at the JLab.

Fulci, Antonino↗
DOE OSTI2020

Nb 3 Sn multicell cavity coating system at Jefferson Lab

Superconducting radio frequency niobium cavities are the building blocks of modern accelerators for scientific applications. Lower surface resistance, higher fields, and high operating temperatures advance the reach of the future accelerators for scientific discovery as well as potentially enabling cost-effective industrial solutions. We describe the design and performance of an Nb 3 Sn coating system that converts the inner surface of niobium cavities to an Nb 3 Sn film. The niobium surface, heated by radiation from the niobium retort, is exposed to Sn and SnCl 2 vapor during the heat cycle, which results in about 2 μm Nb 3 Sn film on the niobium surface. Film composition and structure as well as radio frequency properties with 1-cell R&D cavities and 5-cell practical accelerator cavities are presented.

47 OTHER INSTRUMENTATION↗