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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

New Results on the Nucleon Resonance Spectrum and Structure from Photo- and Electroproduction Experiments

Studies of the excited nucleon (N*) spectrum and structure offer unique information on many facets of strong QCD dynamics in the generation of resonances of different quantum numbers. Advances in nucleon resonance studies in experiments with electromagnetic probes will be presented. Experimental studies of meson photoproduction off the nucleon at the JLab/CLAS, ELSA, and MAMI facilities have provided detailed information on all exclusive meson photoproduction channels relevant in the resonance region. Analyses of these data have considerably extended our knowledge of the N* spectrum. Several candidate N* states were included in the PDG as an outcome of these efforts with critical impact of the strangeness photoproduction data from CLAS. Studies of the N*-electroexcitation amplitudes (?vpN* electrocouplings) at different photon virtualities Q2 continue their rapid progress, offering insight into N * structure. The CLAS detector at JLab has produced the dominant part of the data on meson electroproduction channels off the nucleon in the resonance region for Q2 up to 5.0 GeV2. The ?v pN *electrocouplings have become available for most N* states in the mass range up to 1.8 GeV and Q2 up to 5.0 GeV2. Physics analyses of these results have revealed the structure of N * states as a complex interplay between an inner core of three dressed quarks and an external meson-baryon cloud. A successful description of the ?(1232)3/2+ and N(1440)1/2+ electroexcitation amplitudes starting from the QCD Lagrangian was achieved within the Dyson-Schwinger Equation (DSE) approach with the same momentum dependence of the constituent quark mass, offering sound evidence for the capability of exploring the dynamics of hadron mass generation. Independent analysis of the CLAS data on N* electroexcitations within the light front quark model has supported the running quark mass concept. Extension of the resonance electroexcitation studies with the CLAS12 detector will make it possible to explore N* structure at the highest photon virtualities ever achieved, from 5.0 GeV2 to 12 GeV2, addressing the most challenging problems on the nature of hadron mass and the emergence of quark-gluon confinement. In addition, the search for hybrid-baryons with glue as an active structural component will be carried out, completing the N*spectrum exploration.

Mokeev, Viktor↗
DOE OSTI2017

JAM extractions of helicity and transversity distributions

Polarized semi-inclusive deep inelastic scattering (SIDIS) plays a crucial role in understanding sea quark contributions to the proton spin through global analyses of spin-dependent parton distribution functions (PDFs). The shape of the strange quark polarization in particular has been shown to be dramatically different between analyses that include or exclude SIDIS data. The inclusion of SIDIS data, however, requires knowledge of fragmentation functions (FFs), which up until now have been fixed in all current analyses of SIDIS data to specific parameterizations determined from single-inclusive annihilation (SIA) and other quark to hadron fragmentation processes. In this talk, I will present results from a first ever simultaneous Monte Carlo analysis of polarized PDFs and FFs using DIS, SIA, and SIDIS data. I will also discuss in detail the extent to which available pion and kaon SIDIS data can constrain the sea quark spin distributions of the proton.

Ethier, Jacob↗
DOE OSTI2017

Extracting sea quark spin distributions from a global Monte Carlo analysis of semi-inclusive DIS data

Polarized semi-inclusive deep inelastic scattering (SIDIS) plays a crucial role in understanding sea quark contributions to the proton spin through global analyses of spin-dependent parton distribution functions (PDFs). The shape of the strange quark polarization in particular has been shown to be dramatically different between analyses that include or exclude SIDIS data. The inclusion of SIDIS data, however, requires knowledge of fragmentation functions (FFs), which up until now have been fixed in all current analyses of SIDIS data to specific parameterizations determined from single-inclusive annihilation (SIA) and other quark to hadron fragmentation processes. In this talk, I will present results from a first ever simultaneous Monte Carlo analysis of polarized PDFs and FFs using DIS, SIA, and SIDIS data. I will also discuss in detail the extent to which current pion and kaon SIDIS data can distinguish between the valence and sea spin distributions of the proton.

Ethier, Jacob↗
DOE OSTI2017

Lattice calculation of the pion electromagnetic form factor at high momentum transfer

The pion electromagnetic form factor, Fn, is a fundamentally important topic for our understanding of the hadron structure and the transition from perturbative to nonperturbative QCD. JLAB?s experiment E12-06-101 proposes to extend the high quality F? data to Q2=6.0 GeV2 as a part of JLAB?s 12 GeV upgrade. Being motivated by this, we present a lattice QCD calculation of Fn using the method of distillation and the variational approach which significantly reduce the excited state contamination. We study the shape of the vector form factor in the Q2 range from zero to a few GeV2 using Wilson quark formalism on our 203×128 anisotropic lattice configuration with light (up/down) and strange quarks in the sea and 400 MeV pion mass.

Chakraborty, Bipasha↗
DOE OSTI2017

New insights into sea quark asymmetries from global PDF analysis

We present results from the most recent global QCD analysis by the CTEQ-Jefferson Lab (CJ) Collaboration on the flavour content of the nucleon sea quark distributions. Constraints from LHC, Fermilab and Jefferson Lab data on the SU(2) flavour asymmetry, dbar - ubar, as well as on the strange asymmetry s - sbar will be discussed.

Melnitchouk, Wolodymyr↗
DOE OSTI2016

Lattice studies of hyperon spectroscopy

I describe recent progress at studying the spectrum of hadrons containing the strange quark through lattice QCD calculations. I emphasise in particular the richness of the spectrum revealed by lattice studies, with a spectrum of states at least as rich as that of the quark model. I conclude by prospects for future calculations, including in particular the determination of the decay amplitudes for the excited states.

Richards, David↗
DOE OSTI2013

The Excited Baryon Spectrum in Lattice QCD

I describe recent progress at understanding the excited baryon spectrum of QCD from lattice gauge simulations. I begin by outlining the recipe for spectroscopy calculations. I compare lattice calculations of the spectrum of the baryons containing the light (u,d) and strange quarks for pion masses in excess of 400 MeV, and compare with expectations from QCD-inspired descriptions of the spectrum, before addressing the issue of unstable resonances in lattice QCD. I conclude by describing the prospects for examining the electromagnetic properties of baryon excited states from lattice gauge calculations.

Richards, David↗
DOE OSTI2013

The 1/Nc Expansion for Excited Baryons

I describe recent progress at understanding the excited baryon spectrum of QCD from lattice gauge simulations. I begin by outlining the recipe for spectroscopy calculations. I compare lattice calculations of the spectrum of the baryons containing the light (u,d) and strange quarks for pion masses in excess of 400 MeV, and compare with expectations from QCD-inspired descriptions of the spectrum, before addressing the issue of unstable resonances in lattice QCD. I conclude by describing the prospects for examining the electromagnetic properties of baryon excited states from lattice gauge calculations.

Goity, Jose↗
DOE OSTI2013

High-Resolution Hypernuclear Spectroscopy at JLab Hall A. Results and perspectives

Hypernuclear spectroscopy via electromagnetic induced reactions is a valuable and powerful way to study hypernuclei, hadronic systems with non-zero strangeness content, providing an alternative to the hadron induced reactions mainly studied so far. Electron-induced hypernuclear spectroscopy has been studied in Hall A at Je!erson Lab [1] on three nuclei, 12C, 16O, and 9Be with unprecedented resolution and with an improved particle identification system, using a RICH detector, in order to unambiguously identify kaons, thus allowing the measurement of high-quality, almost backgroundfree, hypernuclear spectra. Two superconducting septum magnets were added to the existing apparatus in order to permit particle detection at very forward angle providing a reasonable counting rate. These studies have provided the first quantitative information on core-excited states in hypernuclei. In the case of oxygen, a waterfall target has been employed allowing for the simultaneous measurement of hypernuclear production on oxygen and of elementary kaon-? electro-production on protons: a crucial measurement to disentangle the contribution of the elementary reaction from the measured hypernuclear production cross section, yielding direct access to the nucleus-hypernucleus transition structure. A ? binding energy value for 16 ?N calibrated against the elementary (e, e?K+) reaction on hydrogen, has been obtained. Final results for 12C, 16O, 9Be will be presented [1-3]. Results of Hall C experiments will be presented in another talk in this Conference. Since it is essential for further theoretical study of hypernuclei to collect enough information about L production on nucleons and about excitation spectra of a wide variety of ? hypernuclei, a continuation of the successful hypernuclear program at JLab is very desirable. For these reasons Hall A and Hall C Jefferson Lab hypernuclear collaborations decided to merge and propose a new layout for the 12 GeV Jefferson Lab era that has the advantages of both the experimental setups. In fact the new experimental design not only widens and deepens the physics range but also dramatically improves production yield and efficiency allowing to study both mass spectroscopy on a wide range of nuclei (from few body to 208Pb) and pion decay spectroscopy at the same time [4]. Figs.1, 2 show the results obtained for 12C and 16O. Fig. 3 shows the new layout.

Garibaldi, Franco↗
DOE OSTI2011

Generalised parton distributions: low-energy nucleon structure in pp collisions at LHC

The study of the electro-magnetic form factors (EMFF) of the nucleon has been strongly revitalized a decade ago with the ever improving quality of polarized electron beams, polarized targets and recoil polarimeters. The biggest surprise yielded by that innovative instrumentation was the observed linear decrease with Q2 of the ratio of the proton charge and form factors. The present data set on all EMFFs and its interpretation will be reviewed. All experiments so far using parity violation have measured the contribution of the strange quark to be negligibly small. Neglecting this contribution, the new measurements of the charge form factor of the neutron have now made it possible to extract the form factors of the up and the down quarks. A status and outlook will be given of two-photon exchange effects. Finally, the broad research on nucleon form factors presently approved with the 12 GeV upgrade will be discussed.

Weiss, Christian↗
DOE OSTI2023

Online Monitoring of Medium Voltage Cable Systems with Spread Spectrum Time Domain and Frequency Domain Reflectometry

In-service failures of wave energy convertor (WEC) cable systems can have a significant cost and power availability impact. Close parallel research 2019 data showed > 1B£ and 9 Terra-Watt-Hours associated with global off-shore wind (OSW) cable failures (Strang-Moran 2020). OSW is a closely related technology but currently is significantly cheaper than WEC technology. For wave energy to compete, the problem of reliable cable transmission must be mitigated. This project develops isolation technology to allow online high frequency reflectometry testing of medium voltage cables (1 to 10 kV and higher) without arcing or damage to the test instrument. Online spread spectrum time domain reflectometry (SSTDR) testing has been established for low voltage cable systems in the aircraft and rail industry and the ability to detect and locate cable flaws of interest is well understood. Extending reflectometry testing to medium voltage systems could enable detection of cable damage before failures occur thereby allowing repair and replacement of damaged cable segments to be scheduled and managed. The seedling project succeeded to pass and receive high frequency SSTDR signals onto a cable up to 1 kV using a parallel trace isolation circuit board that can be connected onto the test cable. The approach used a novel circuit design for which an invention disclosure has been filed. A proposed sapling project would extend the technology toward the higher operating voltages used by WEC systems, thereby enabling online SSTDR cable monitoring. The goal of the seedling project was to extend the capability of the ARENA cable/motor test bed to address medium voltages and to develop a high pass filter isolation architecture to protect the reflectometry instrument from the low frequency (DC – 60 Hz) line voltage while allowing the high frequency diagnostic signal to pass to and from the test instrument to the live line. Initial efforts focused on passive LCR filter circuits to reduce 60 Hz levels below 10 volts from a 10 kV line while allowing the MHz high frequency chirps to pass onto the cables and for mV signals to be detected. We discovered that the parasitic loss behavior of real high voltage components precluded this approach from working. An alternate approach was adapted for the electric field to couple between two parallel traces on a printed circuit board much like a radio-frequency coupler. The challenge here was and is to have the parallel traces close enough to each other to effectively pass the high frequency chirp onto the live line and receive any reflected signal from any encountered impedance change along the cable. This reflected signal will be in the mV range. The traces however must be far enough apart to not allow arcing on the board. A design with 3 mm spacing was determined to allow the high frequency signal to pass onto the live line and receive the mV signal back into the instrument while reducing the 60 Hz voltage amplitude by >80 dB (more than a factor of 10,000) without allowing arcing from across the parallel traces. This was confirmed by simulation and test.

16 TIDAL AND WAVE POWER↗
DOE OSTI2023

Emergent Quantum Magnetism and Cryogenic Spin-Memory in Twisted Bilayer Graphene

Recently developed techniques for assembling moiré heterostructures have enabled unprecedented control of the interlayer interactions within the heterostructure, allowing for the realization of strongly correlated electronic states. The experimentally realized states, to date, include a variety of topological states, superconductivity, and strange metal behavior. However, the phenomenology varies significantly from sample to sample. Here we will present microscopy techniques for further characterization of both the progenitor exfoliated materials and the composite moiré heterostructure. The application of these techniques has allowed for an unprecidented degree of characterization in ambient conditions. Additionally we will explore the use of resistively detected electron spin resonance (ESR) as a novel probe for spin order in moirés. While our results do not show clearly dispersive features that would unambiguously evince spin excitations within the sample, the technique is still promising.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Diagrammatic Monte Carlo Approach to Real‐frequency Response Functions and the Spin‐Fermion Model of Hot Spots (Final Report)

This three‐year research project was focused on two outstanding condensed matter problems (i) Real‐frequency response functions in Coulomb systems at finite temperature, and Fermi surface (FS) reconstruction in the Spin-Fermion (SF) model. The uniform electron gas (jellium) model, describing electrons interacting via long‐range Coulomb forces on positive neutralizing background, is fundamentally important both for understanding the physics of correlated electrons and for formulation of the time‐dependent density functional theory (TDDFT). The spin-fermion model has found a wide range of applications in the physics of cuprates and iron‐based superconductors to explain the “strange metal" behavior and to suggest a possible pairing mechanism for high‐temperature superconductivity. The project’s goals were development and application of the Diagrammatic Monte Carlo (DiagMC) techniques for solving the above problems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Spin-Density Matrix Elements in K∗(892) Photoproduction with Recoiling Λ at GlueX

We report on the measurement of spin-density matrix elements for the K∗(892) → K+π0 photoproduction process with a recoiling Λ hyperon. The measurement used high-statistics GlueX data from photoproduction off a proton target at photon energies between 8.2 and 8.8 GeV, in a kinematic regime dominated by t-channel exchange processes. GlueX is a fixed-target experiment with a linearly polarized photon beam and a nearly 4π hermetic detector, allowing extraction of the full spin observ- ables from both the K+π0 and Λ → π−p systems. The GlueX data show clear evidence of the K∗(892) resonance in the K+π0 mass spectrum, along with additional structures at higher masses that may correspond to K∗0 or K∗2 resonances. The precise measurement of the spin-density matrix elements of the K∗(892) could serve as a standard candle for con- tinuing studies of higher-mass excited K∗ states. In addition, t-channel K∗ photoproduction differs from previous measurements of non-strange vector meson photoproduction, as it is free from Pomeron exchange and is virtually unexplored in this energy regime. Furthermore, the unprece- dented data collected by GlueX allow for investigations of correlations between the Λ polarization and the spin-density matrix elements of K∗ production, paving the way for future partial-wave analyses with full spin information involving the recoil hyperon.

Li, Hao [College of William and Mary, Williamsburg↗
DOE OSTI2026

Final Technical Report for U.S.-Japan Hadronic Physics Exchange Program for Studies of Hadron Structure and QCD

Nuclear physics explores the fundamental properties of matter -- how protons and neutrons emerge as quantum systems of elementary particles, how they form the atomic nuclei, and how they give rise to the wide variety of phenomena and applications at biological, technical, and astronomical scales. It is a global scientific effort centered around large-scale experimental user facilities (particle accelerators and detectors), advanced theoretical methods and concepts, and computational techniques and resources. Exchange of knowledge and ideas, scientific collaboration, and workforce development on a global scale are essential for the future of the field. The nuclear physics program envisaged in the 2023 DOE/NSF NSAC Long-Range Plan and pursued at the U.S. National Labs has strong synergies with programs at other facilities worldwide and will realize significant benefits from international collaboration. Nuclear physics is also recognized for promoting international cooperation in the broadest sense through joint construction and operation of experimental equipment, personal contacts between scientists, and education and training. The U.S.-Japan Hadronic Physics Exchange Program (USJPHE) supported collaborative scientific research in hadronic physics and quantum chromodynamics. USJHPE focused on subject areas related to the programs at current and future experimental facilities in the U.S.\ and Japan and supported both experimental and theoretical studies. USJHPE particularly aimed to realize synergies between the hadronic physics programs at Jefferson Lab 12 GeV and J-PARC resulting from the complementarity of electromagnetic and hadronic probes in the multi-GeV energy range. Subject areas of common interest included the quark-gluon structure of hadrons and nuclei, meson and baryon spectroscopy, strangeness and hypernuclear physics, and other related topics. USJHPE also supported research in hadronic physics and nuclear-physics-enabled tests of fundamental symmetries related to the programs at Brookhaven National Lab, Fermilab, KEK, Spring-8, and university-based facilities in the U.S. and Japan. USJHPE especially promoted collaboration between the U.S. and Japanese nuclear physics communities in developing the physics program and instrumentation for the future Electron-Ion Collider. USJHPE was intended to provide travel grants to U.S.-based scientists (primary institutional affiliation with a U.S.\ university, national laboratory, or other research center) to visit Japanese institutions and conduct collaborative research there. The program supported senior researchers, postdoctoral fellows, and students. Continuing the setup of the preceding grant period, J-PARC served as the Japanese “hub” for U.S. physicists for short- and long-term visits, and JLab served as the corresponding U.S. “hub”. The program was officially managed through the U. of Connecticut in Storrs, CT. Support for Japanese physicists visiting the U.S. was provided through funds from Japanese funding agencies. The USJHPE program promoted the scientific exchange and the collaborative spirit in hadronic physics between the two countries.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

First Measurement of Charged Current Muon Neutrino-Induced Kaon Production on Argon using the MicroBooNE Detector

MicroBooNE is an 85-tonne active mass liquid argon time projection chamber (LArTPC) neutrino detector exposed to the Booster Neutrino Beamline (BNB) at Fermilab. One of the key physics goals is the precise measurement of neutrino interactions on argon in the 1 GeV energy regime. The study of strange and heavier meson production in neutrino interactions, in particular final states containing $K^{+}$, will help to improve the background estimates for future nucleon decay searches in experiments such as DUNE, provide valuable input for improving neutrino generator models, and will allow the development of techniques to enhance the particle identification capabilities of LArTPCs. In this work, we present the first-ever cross-section measurements of charged current muon neutrino-induced kaon production on argon at MicroBooNE.

Rodriguez Rondon, Jairo H. [South Dakota Sch. Mine↗