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DOE OSTI2014

Excited Baryon Structure Using KY Exclusive Reactions with CLAS12

Studying excited nucleon structure via exclusive KY electroproduction will be an important tool for exploring the non-perturbative strong interaction. Electrocouplings for low-lying N? states (<1.7 GeV) have been determined from analyses of CLAS ?N and ??N data. This work made clear that consistency of independent analyses of exclusive channels with different couplings and non-resonant contributions is essential to have confidence in the extracted results. In terms of hadronic coupling, most high-lying N? states preferentially decay through the ??N channel instead of ?N. Data from the KY channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying N? states against those determined from the ??N channel from an already approved CLAS12 12-GeV experiment. A new experiment that will focus on N??KY decays using CLAS12 at JLab will be discussed that will measure differential cross sections to be used as input to extract the ?vNN? transition form factors for the most prominent N? states in the range of invariant energy W from 1.6 to 3~GeV in the virtually unexplored domain of momentum transfers Q2 up to 12~GeV2.

Carman, Daniel↗

DOE OSTI2014

Implications of the Q$_{\rm weak}$ Commissioning Result

The commissioning results of the Qweak experiment at Jefferson Lab, which constituted approximately 4\% of the total results obtained in that experiment, were recently published (D. Androic, {\em et al.} [Qweak Collaboration], Phys. Rev. Lett. 111, 141803 (2013)). After a brief review of the experiment, new, unpublished results derived from that publication will be presented. The sensitivity of the fit used to extract the proton's weak charge to the choice of electromagnetic form factors, to the proton radius puzzle, and to the dipole mass used for the Q2 evolution will be examined. The running of sin2(?W) and the experiment's mass reach will be discussed. The status of the ongoing effort to complete the analysis of the full experiment will also be shown.

Smith, Gregory↗

DOE OSTI2014

Excited Baryon Structure Using KY Exclusive Reactions with CLAS12

Carman, Daniel↗

DOE OSTI2015

Meson Electro-Photo-Production from QCD

In this talk I present the first determination of transition amplitudes for meson electro-/photo-production from lattice QCD. The amplitude studied is that of ?+?* to ? ?. By constraining the amplitude for a range of center of mass energies of the final state, we analytic continue said amplitude to the rho-pole and obtains the ?-to-? form factor. I discuss some of the details of the lattice QCD calculation and review the formalism needed in performing the resulting analysis.

Briceno, Raul↗

DOE OSTI2015

Excited Baryon Structure Using Exclusive Reactions with CLAS12

Studying excited nucleon structure through exclusive electroproduction reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. Electrocouplings for $N^*$ states in the mass range below 1.8~GeV have been determined from analyses of CLAS $\pi N$, $\eta N$, and $\pi \pi N$ data. This work made it clear that consistency of independent analyses of exclusive channels with different couplings and non-resonant backgrounds but the same $N^*$ electro-excitation amplitudes, is essential to have confidence in the extracted results. In terms of hadronic coupling, many high-lying $N^*$ states preferentially decay through the $\pi \pi N$ channel instead of $\pi N$. Data from the $KY$ channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying $N^*$ states against those determined from the $\pi N$ and $\pi \pi N$ channels. A program to study excited $N^*$ decays to non-strange and strange exclusive final states using CLAS12 will measure differential cross sections to be used as input to extract the $\gamma_vNN^*$ transition form factors for the most prominent $N^*$ states in the range of invariant energy $W$ up 3~GeV in the virtually unexplored domain of momentum transfers $Q^2$ up to 12~GeV$^2$.

Carman, Daniel↗

DOE OSTI2015

Model Sensitivities in the Extraction of Qw(p) from PVES Data

As the Qweak collaboration prepares to unblind our final result, studies have been performed to quantify the sensitivities of the fit used to extract the proton's weak charge Qw(p) from the body of existing parity-violating electron scattering (PVES) data. The results of these sensitivity studies will be used to freeze choices associated with the fitting procedure before unblinding. Under study are the effects of including PVES data on D2 and He targets in the fit, and restrictions on the angular and Q2 range of the data in the fit. The impact of different electromagnetic form factor (EM FF) fits, and the separate impact of the uncertainties associated with the EM FF fits themselves on the fit used to extract Qw(p) from the body of (mostly) e? p data have been studied. The impact of recent lattice QCD calculations of charge symmetry effects on our fit result will be assessed. A comparison will be made using recent lattice calculations of ?s and ?s in our Qw(p) determination, or floating these parameters in our fit. The dipole mass sensitivity in the strange and axial FFs will be assessed. The impact of floating the isoscalar and/or isovector axial FFs to theory or floating them freely in the fit will also be studied.

Smith, Gregory↗

DOE OSTI2015

Momentum Distributions for 2H(e,e'p)

A primary goal of deuteron electro-disintegration is the possibility of extracting the deuteron momentum distribution. This extraction is inherently fraught with difficulty, as the momentum distribution is not an observable and the extraction relies on theoretical models dependent on other models as input. We present a new method for extracting the momentum distribution which takes into account a wide variety of model inputs thus providing a theoretical uncertainty due to the various model constituents. To test the extraction, pseudo-data was generated, and the extracted ``experimental'' distribution, which has theoretical uncertainty accounted by this extraction method, can be compared to the theoretical distribution. The calculations presented here are using a Bethe-Salpeter like formalism with a wide variety of bound state wave functions, form factors, and final state interactions. Our method takes into account the theoretical uncertainty from the various model constituents entering the calculation. In the examples we compared, the original distribution was typically within the error band of the extracted distribution. The input wave functions do contain some outliers which are discussed in the talk.

Jeschonnek, Sabine↗

DOE OSTI2023

Threshold charmonium photoproduction with GlueX

Exclusive charmonium photoproduction near threshold opens the door for studying the gluonic properties of the proton: gluonic GPDs, anomalous contribution to the mass of the proton, gravitational form factors, the mass radius of the proton. However, such an ambitious program requires precise measurements to validate the theoretical assumptions that relate the experimental results to the above quantities. The first total cross-section measurements of near-threshold exclusive J/? photoproduction (?p?J/?p) by the GlueX collaboration sparked remarkable theoretical interest, however had limited statistics. We will report new total cross-section results based on more than a four-fold increase in statistics. Even more, due to the full acceptance of the GlueX experiment for this reaction, we will present first measurements of the differential cross-sections over the whole near-threshold kinematic region. Such measurements enable more general conclusions about the reaction mechanism when compared to a wide range of theoretical predictions including GPD calculations and models with open-charm intermediate states.

Pentchev, Lubomir↗

DOE OSTI2018

Nucleon Tomography Studies at Jefferson Lab

Protons and neutrons, are the building blocks of atomic nuclei. They constitute over 99 percent of the mass of the matter in the visible universe. A fundamental challenge of modern nuclear physics is to understand the structure of these constituents. The 12 GeV Upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab and the construction of state-of-the-art detector systems make it a unique facility in the world to address this challenge. Electron scattering is a superb experimental tool to study the internal structure of nucleons at differing distance scales, as the resolving power of the probe can be varied. The CEBAF Upgrade was completed in September 2017 and the new generation of experiments has started. These experiments will enable a collaboration of scientists from around the world to perform precise experiments of exclusive processes covering a large range in kinematics to effectively engage in nuclear imaging, revealing hidden aspects of its internal structure, and providing insight into quark confinement forces in the nucleon, one of the greatest mysteries of modern physics. The Generalized Parton Distributions (GPDs) provide the theoretical framework to interpret the experimental data in terms of 3-dimensional imaging. In addition, recent development demonstrated that the GPD formalism enables access to the nucleon's Gravitational Form Factors that encode its mechanical properties. We will focus on the study of the Deeply Virtual Compton Scattering (DVCS), the most effective way to access GPDs. We will review the landscape of both theory and experiment, and discuss the latest results from Jefferson Lab at 6 GeV in comparison with results from other facilities, and present a first look at the new experiments with the 12 GeV Upgrade.

Elouadrhiri, Latifa↗

DOE OSTI2022

Integrated energy harvesting transceivers and transmitters with dual-antenna architecture for miniaturized implants and electrochemical sensors

Systems and methods for utilizing a small form-factor, wirelessly powered transceiver are disclosed. In one embodiment, a wireless powered transceiver includes a receive antenna configured to receive a receive signal, a transmit antenna configured to transmit a transmit signal, a power harvesting system including a rectifier circuit configured convert radio frequency energy from the receive signal into DC (direct current) voltage, and a power management unit (PMU) configured to set the operating mode and biasing condition of the receive and transmit circuitry blocks and provide DC voltage from the receive circuitry block to the transmit circuitry block to maintain a minimum voltage, a receiver circuitry block configured to provide energy from the receive signal to the power harvesting system, and a transmitter circuitry block including a data modulator circuit, the data modulator circuit configured to generate the transmit signal using DC voltage received from the power management unit.

Babakhani, Aydin↗

DOE OSTI2013

The study of excited nucleons and their structure

The nucleon excitation spectrum reflects properties of the quark-gluon system and their interaction. Quark models and Lattice QCD make predictions of masses and quantum numbers of the excited states and their internal structure according to radial, spin, and orbital transitions of the 3-quark and gluon system. Pion induced transitions revealed many nucleon states consistent with these predictions, but many predicted states have not been observed, especially at higher masses. The quest for a better understanding of the underlying symmetries and the internal structure of baryons has led to a worldwide effort to measure the nucleon excitation spectrum using electromagnetic induced processes. Jefferson Lab is playing a key role in this effort. Differential cross sections and polarization observables have been measured with unprecedented precision. Some of the data have been used in coupled-channel resonance analyses that led to new evidence for a number of excited states that were previously unobserved or lacked strong evidence. In this talk, I will discuss two directions of experimental research, the search for new nucleon states using meson photoproduction and the study of transitions form factors to understand their internal structure and the nature of excited states.

Burkert, Volker↗

DOE OSTI2013

Jefferson Laboratory Hall A SuperBigBite Spectrometer Data Acquisition System

The SuperBigBite detector is a large acceptance spectrometer which is being built for Hall A at Jefferson Laboratory and planned for completion in 2017. Several experiments are approved for this detector ranging from form factors to nucleon structure. The detector consists mainly of a large dipole magnet and several plane of Gas Electron Multiplier trackers associated with calorimeters. In order to reduce the cost of the project the electronics used will be a mix of older Fastbus and newly developed electronics. I will present the layout of the system and how we plan to handle the high background rates seen by the different detectors for the different experiments.

Camsonne, Alexandre↗

DOE OSTI2014

The Exotic Frontiers of Lattice QCD

Lattice QCD has proven to be a remarkably powerful tool for studying masses and electroweak properties of low-lying hadronic states. Extending the power of this tool to study few-body hadronic observables would impact our understanding of phenomena ranging from the inner structure of exotic mesons to the rare processes seen in particle accelerators that might shed light on possible extensions to the present paradigm of nuclear/particle physics. In this talk, I will first review the challenges associated with the studies of such systems via Lattice QCD. I will discuss recent progress towards being able to study elastic/inelastic scattering cross sections as well elastic/transition form factors for few-body systems. Finally, I will outline outstanding problems and discuss the future of the field.

Briceno, Raul↗

DOE OSTI2013

The CLAS Two Photon Exchange Experiment

There is a large discrepancy between the proton electron form factor (GEp(Q2)) measured using the Rosenbluth separation and polarization transfer methods. The most likely explanation of this discrepancy is the inclusion of two-photon exchange (TPE) amplitude contributions to the elastic electron-proton cross section. The TPE contribution can be extracted in a model-independent way from the measured ratio of the cross sections of positron-proton and electron-proton elastic scattering. This ratio was measured in Hall B at Jefferson Lab using a simultaneous mixed tertiary beam of electrons and positrons incident on a liquid hydrogen target in the center of the CLAS detector in 2010-2011. In this talk, the experimental techniques to produce e+/e- beam, the analysis techniques to identify the elastic scattering events, and some preliminary results will be presented.

Adikaram, Dasuni↗

DOE OSTI2013

PrimEx Experiments and the Prospects of Rare eta Decays at GlueX

There are two major challenges in contemporary physics: QCD confinement and new physics beyond the Standard Model. A study of not-so-rare and rare decays of light neutral pseudoscalar mesons ?0, ? and ?? provides a sensitive probe to investigate both fundamental issues. A comprehensive PrimEx experimental program at Jefferson Laboratory (Jlab) is aimed at gathering high precision measurements on the two-photon decay widths and transition form factors at low Q2 on ?0, ? and ?? via the Primakoff effect. Completed experiments on the ?0 radiative decay width at Jlab 6 GeV, and planned measurements of ? and ?? at Jlab 12 GeV will provide a rich laboratory to test chiral anomaly and to study the origin and dynamics of symmetry breaking in QCD confinement. On the other hand, measurements of branching ratios or upper limits for various rare and forbidden ? decays are about five orders of magnitude more sensitive to high order QCD contributions or new interactions, because the lowest orders are filtered out by conserved symmetries. This circumstance presents a great opportunity to test high order chiral perturbation predictions, and to search for new sources of symmetry violations (such as C and CP) and new physics beyond the Standard Model. An experimental program to study ? rare decays with the GlueX apparatus has been developed at Jlab. Simulations show that the experimental approach, which combines a state of the art PbWO4 calorimeter, a 12 GeV tagged photon beam, and recoil particle measurement, will reduce the background by almost two orders of magnitude compared to other competitors in the world. The updated result from the PrimEx experiments and the prospects of rare meson decays at GlueX will be presented.

Gan, Liping↗

DOE OSTI2023

Systems and methods lattice spray substrates for mass spectrometry

The present disclosure relates to a lattice substrate adapted for use in direct ionization mass spectrometry. The substrate may have a plurality of tessellated unit cells forming an integral structure. Each tessellated unit cell may have a dimension of no more than about 1.5 mm and may include a plurality of pores arranged in an ordered pattern. The substrate may further include a form factor suitable for use with a direct ionization mass spectrometry system.

Prieto Conaway, Maria C.↗

DOE OSTI2023

Precise Measurement of the Neutron Skin Thicknesses of 208Pb and 48Ca

Despite great leaps of development in nuclear physics over the past century, we still do not have a comprehensive understanding of nuclear structure. This is mainly due to the lack of precise knowledge of the neutron distribution inside nucleus. Electromagnetic probes are ineffective in probing neutrons, unlike their charged partners, the protons. Therefore, it is of great importance to constrain the neutron distributions experimentally. Heavy nuclei have more neutrons than protons in order to balance the repulsion between protons. In such neutron-rich nuclei, the extra neutrons are pushed out to the surface by the nuclear symmetry energy, forming the so-called ?neutron skin?. The neutron skin can be probed with a well-established experimental technique ? parity-violating electron scattering (PVES). Using the scattering of longitudinally polarized electrons by an unpolarized target, PREX-II and CREX measure the small parity-violating asymmetry in cross sections. Employing electrons with opposite helicities the weak form factor, the neutron distribution and the neutron skin thickness of the target nucleus are extracted. With excellent beam qualities and dedicated instrumentation at Jefferson Lab, the asymmetry measurements are statistics-limited. We report the results of these two high-precision measurements and their implications on broad topics, from the nuclear structures to the neutron stars.

Zhang, Weibin↗

DOE OSTI2023

J/ψ Near-Threshold Photoproduction off the Proton and Neutron with CLAS12

In recent years, J/? photoproduction in the near-threshold region has seen a renewed theoretical interest due to the wealth of information it has to offer. Near-threshold J/? photopro-duction proceeds through the exchange of gluons in the t-channel and is expected to provide unique insight about the nucleon gluonic gravitational form factors (GFFs). Previous studies at the Thomas Jefferson National Accelerator Facility (JLab) in Virginia, USA, have already measured the total and differential cross section of J/? near-threshold photoproduction on the free proton. This thesis presents the first measurements of J/? near-threshold photoproduction on the bound proton and bound neutron in a deuteron target. The CEBAF Large Acceptance Spectrometer at 12 GeV (CLAS12) based at JLab?s Hall B uses a 11 GeV electron beam impinging on a fixed liquid deuteron target. J/? is then produced via the exchange of a quasi-real photon and decays to a lepton pair which is detected along-side the recoil nucleon by CLAS12. Analysis procedures and in particular machine learning based techniques were developed in order to correctly identify final state particles and select J/? photoproduction events. The total and differential cross section of J/? near-threshold photoproduction on the bound proton and bound neutron were then measured from the detected J/? photoproduction events. The measurements of the cross sections on the bound proton and bound neutron agree well within their statistical uncertainty. This is consistent with the assumed two-gluon exchange production mechanism which is isospin invariant. Overall a first measurement of the J/? near-threshold photoproduction cross sections on the bound proton and bound neutron was achieved. A better understanding of the mechanical properties of the nucleon, such as pressure and mass distributions, can be obtained by relating J/? production to the nucleon GFFs. This opens the way for exciting new insights into the internal structure of the nucleon, and in particular of the nucleon?s gluonic content. An upcoming overhaul of the CLAS12 reconstruction will increase the reconstruction efficiency and the statis- tical precision of the preliminary measurements described in this thesis, with an expected gain in statistics of at least 50%. Future upgrades at JLab will allow to test some of the theoretical assumptions made in relating J/? near-threshold photoproduction to the nucleon GFFs

Tyson, Richard↗